About this Author
College chemistry, 1983
The 2002 Model
After 10 years of blogging. . .
Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases.
To contact Derek email him directly: firstname.lastname@example.org
Snake Oil |
The Central Nervous System
The Dark Side
July 22, 2014
The Broad Institute seems to have gone through a bit of rough funding patch some months ago, but things are looking up: they've received a gift of $650 million to do basic research in psychiatric disorders. Believe it, that'll keep everyone busy, for sure.
I enjoyed Eric Lander's characterization of much of the 1990s work on the genetic basis of mental illness as "pretty much completely useless", and I don't disagree one bit. His challenge, as he and the rest of the folks at the Broad well know, is to keep someone from being able to say that about them in the year 2034. CNS work is the ultimate black box, which makes a person nervous, but on the other hand, anything solid that gets discovered will be a real advance. Good luck to them.
You might also be interested to know where the Stanley Foundation, the benefactors here, came up with over half a billion dollars to donate to basic medical research (and more to come, apparently). You'd never guess: selling collectibles. Sports figurines. Small replicas of classic cars, trucks, and tractors. Miniature porcelain versions of popular dolls. Leather-bound sets of great (public domain) novels. Order now for the complete set of Presidential Coins - that sort of thing. It looks to be a lot more lucrative than discovering drugs (!)
+ TrackBacks (0) | Category: General Scientific News | The Central Nervous System
June 3, 2014
Alex (Sasha) Shulgin has died at the age of 88. Among some groups of people, he was the most famous chemist in the world - I refer specifically to people with a strong interest in psychedelic drugs. Shulgin was, of course, the author of PIHKAL and TIHKAL, books whose titles resolve to, respectively, Phenethylamines/Tryptamines I Have Known And Loved, which should tell you where he was coming from.
But his days were different from these days. When Shulgin was doing his earlier work, these compounds were (for the most part) not illegal. Even after their legal status changed, Shulgin had cordial relations with the DEA (up until the early 1990s, that is, when things went downhill). He was certainly not interested in becoming a drug lord, or coming up with the most efficient backyard synthesis of some profitable amphetamine. Shulgin was interested in the human brain and what happened to it when you messed around with its balance of neurotransmitters, and he was his own test subject (along with a circle of friends). The papers he published on this work read now like documents from another planet - there in the Journal of Organic Chemistry would be a paper on the SAR of some series of compounds, with an experimental section that looked normal until you got to the in vivo part. It would read something like "Six subjects with experience in psychoactive substances ingested doses ranging from. . .", and it would go on to detail their responses on the Shulgin Rating Scale. (A complete publication list can be found at Shulgin's Wikipedia entry).
He actually inspired a number of people to become organic chemists. I wasn't one of them (I didn't hear about him until I was already in grad school), but I do know of others. And even though I'm about as far from him as possible in my willingness to experiment with psychoactive substances (never touched any, never plan to), I always had a lot of sympathy for him. He wanted to find out what such things did, and he was willing to do what it took to find out. We disagree in philosophy as well - Shulgin felt (as have many people who've experienced such compounds) that they provided a window into a more complicated reality. I don't put much stock in that myself - it seems to me like hearing a snarl of static after pouring a cup of coffee into the back of a radio and then deciding that it was a new kind of radio station. I think that exposing oneself to these agents risks brain damage, and since I discount the experiences they provide, it's never seemed worthwhile to me. But never having taken any such substances myself, I realize that my authority to speak about them may be limited. Many people seem to have benefited from exposure to psychedelics, while others appear to have been permanently damaged. An inability to tell which group I might fall into does not increase my desire to try anything in this line, either.
Shulgin was a very unusual person, but he was also a pioneer and a real scientist. If he has imitators, psychedelic self-experimenters who are not interested in making money, they're keeping quiet. Instead, we have plenty of folks who don't mind experimenting on others, as long as the money comes in. Many of these people probably see themselves as Shulgin's heirs, and I wonder if he thought of them as such or not. Risking your own neurons in your isolated farmhouse can be plausibly thought of as your own business - selling piles of untested compounds to partygoers is (at least to me) a different matter.
+ TrackBacks (0) | Category: Chemical News | The Central Nervous System
April 8, 2014
Here's an article by Steve Perrin, at the ALS Therapy Development Institute, and you can tell that he's a pretty frustrated guy. With good reason.
That chart shows why. Those are attempted replicates of putative ALS drugs, and you can see that there's a bit of a discrepancy here and there. One problem is poorly run mouse studies, and the TDI has been trying to do something about that:
After nearly a decade of validation work, the ALS TDI introduced guidelines that should reduce the number of false positives in preclinical studies and so prevent unwarranted clinical trials. The recommendations, which pertain to other diseases too, include: rigorously assessing animals' physical and biochemical traits in terms of human disease; characterizing when disease symptoms and death occur and being alert to unexpected variation; and creating a mathematical model to aid experimental design, including how many mice must be included in a study. It is astonishing how often such straightforward steps are overlooked. It is hard to find a publication, for example, in which a preclinical animal study is backed by statistical models to minimize experimental noise.
All true, and we'd be a lot better off if such recommendations were followed more often. Crappy animal data is far worse than no animal data at all. But the other part of the problem is that the mouse models of ALS aren't very good:
. . .Mouse models expressing a mutant form of the RNA binding protein TDP43 show hallmark features of ALS: loss of motor neurons, protein aggregation and progressive muscle atrophy.
But further study of these mice revealed key differences. In patients (and in established mouse models), paralysis progresses over time. However, we did not observe this progression in TDP43-mutant mice. Measurements of gait and grip strength showed that their muscle deficits were in fact mild, and post-mortem examination found that the animals died not of progressive muscle atrophy, but of acute bowel obstruction caused by deterioration of smooth muscles in the gut. Although the existing TDP43-mutant mice may be useful for studying drugs' effects on certain disease mechanisms, a drug's ability to extend survival would most probably be irrelevant to people.
A big problem is that the recent emphasis on translational research in academia is going to land many labs right into these problems. As the rest of that Nature article shows, the ways for a mouse study to go wrong are many, various, and subtle. If you don't pay very close attention, and have people who know what to pay attention to, you could be wasting time, money, and animals to generate data that will go on to waste still more of all three. I'd strongly urge anyone doing rodent studies, and especially labs that haven't done or commissioned very many of them before, to read up on these issues in detail. It slows things down, true, and it costs money. But there are worse things.
+ TrackBacks (0) | Category: Animal Testing | The Central Nervous System
March 28, 2014
Huntington's is a terrible disease. It's the perfect example of how genomics can only take you so far. We've known since 1993 what the gene is that's mutated in the disease, and we know the protein that it codes for (Huntingtin). We even know what seems to be wrong with the protein - it has a repeating chain of glutamines on one end. If your tail of glutamines is less than about 35 repeats, then you're not going to get the disease. If you have 36 to 39 repeats, you are in trouble, and may very well come down with the less severe end of Huntington's. If there are 40 or more, doubt is tragically removed.
So we can tell, with great precision, if someone is going to come down with Huntington's, but we can't do a damn thing about it. That's because despite a great deal of work, we don't really understand the molecular mechanism at work. This mutated gene codes for this defective protein, but we don't know what it is about that protein that causes particular regions of the brain to deteriorate. No one knows what all of Huntingtin's functions are, and not for lack of trying, and multiple attempts to map out its interactions (and determine how they're altered by a too-long N-terminal glutamine tail) have not given a definite answer.
But maybe, as of this week, that's changed. Solomon Snyder's group at Johns Hopkins has a paper out in Nature that suggests an actual mechanism. They believe that mutant Huntingtin binds (inappropriately) a transcription factor called "specificity protein 1", which is known to be a major player in neurons. Among other things, it's responsible for initiating transcription of the gene for an enzyme called cystathionine γ-lyase. That, in turn, is responsible for the last step in cysteine biosynthesis, and put together, all this suggests a brain-specific depletion of cysteine. Update: this could have numerous downstream consequences - this is the pathway that produces hydrogen sulfide, which the Snyder group has shown is an important neurotransmitter (one of several they've discovered), and it's also involved in synthesizing glutathione. Cysteine itself is, of course, often a crucial amino acid in many protein structures as well.)
Snyder is proposing this as the actual mechanism of Huntington's, and they have shown, in human tissue culture and in mouse models of the disease, that supplementation with extra cysteine can stop or reverse the cellular signs of the disease. This is a very plausible theory (it seems to me), and the paper makes a very strong case for it. It should lead to immediate consequences in the clinic, and in the labs researching possible therapies for the disease. And one hopes that it will lead to immediate consequences for Huntington's patients themselves. If I knew someone with the Huntingtin mutation, I believe that I would tell them to waste no time taking cysteine supplements, in the hopes that some of it will reach the brain.
+ TrackBacks (0) | Category: Biological News | The Central Nervous System
March 14, 2014
Here's a brave attempt to look for genetic markers of bipolar disorder. The authors studied 388 Old Order Amish sufferers, doing thorough SNP analysis on the lot and total sequencing on fifty of them. There were many parent-child relationships in the set, which gave a chance for further discrimination. And the result:
. . .despite the in-depth genomic characterization of this unique, large and multigenerational pedigree from a genetic isolate, there was no convergence of evidence implicating a particular set of risk loci or common pathways. The striking haplotype and locus heterogeneity we observed has profound implications for the design of studies of bipolar and other related disorders.
If you look around the literature, you'll find numerous smaller studies also trying to find genetic markers for bipolar disorder, and many of these propose possible candidate loci. But very few of them seem to agree, and this new study doesn't seem to confirm any of them. The authors hold out some hope for still larger cohorts and more comprehensive sequencing, and that's certainly the way to go. But if there were anything close to a simple genetic sequence for bipolar disorder, it would have been found by now. Like many other diseases (and not just those of the central nervous system), it's probably a phenotype that can be realized by a whole range of mechanisms, an alternate state of physiology that the system can slip into through a combination of genetic and environmental effects. And while there there may not be a thousand ways to get there, there sure aren't just a couple.
Dealing with these "network diseases" is going to keep us busy for quite a while to come. The best hope, as far as I can see, is for less complexity downstream. Maybe these various susceptibilities and tendencies all slide towards a similar disease process which can be modified. Looking back to the genetic causes for understanding sure hasn't worked out so far; maybe advances in studying brain function and patterns of neurotransmission will shed some light. Although if you're having to look to that area to bail you out. . .
+ TrackBacks (0) | Category: The Central Nervous System
December 5, 2013
I've been meaning to link to this piece by Lauren Wolf in C&E News on the connections between Parkinson's disease and environmental exposure to mitochondrial toxins. (PDF version available here). Links between environmental toxins and disease are drawn all the time, of course, sometimes with very good reason, but often when there seems to be little evidence. In this case, though, since we have the incontrovertible example of MPTP to work from, things have to be taken seriously. Wolf's article is long, detailed, and covers a lot of ground.
The conclusion seems to be that some people may well be genetically more susceptible to such exposures. A lot of people with Parkinson's have never really had much pesticide exposure, and a lot of people who've worked with pesticides never show any signs of Parkinson's. But there could well be a vulnerable population that bridges these two.
+ TrackBacks (0) | Category: The Central Nervous System | Toxicology
December 3, 2013
The New Yorker has an article about Merck's discovery and development of suvorexant, their orexin inhibitor for insomnia. It also goes into the (not completely reassuring) history of zolpidem (known under the brand name of Ambien), which is the main (and generic) competitor for any new sleep drug.
The piece is pretty accurate about drug research, I have to say:
John Renger, the Merck neuroscientist, has a homemade, mocked-up advertisement for suvorexant pinned to the wall outside his ground-floor office, on a Merck campus in West Point, Pennsylvania. A woman in a darkened room looks unhappily at an alarm clock. It’s 4 a.m. The ad reads, “Restoring Balance.”
The shelves of Renger’s office are filled with small glass trophies. At Merck, these are handed out when chemicals in drug development hit various points on the path to market: they’re celebrations in the face of likely failure. Renger showed me one. Engraved “MK-4305 PCC 2006,” it commemorated the day, seven years ago, when a promising compound was honored with an MK code; it had been cleared for testing on humans. Two years later, MK-4305 became suvorexant. If suvorexant reaches pharmacies, it will have been renamed again—perhaps with three soothing syllables (Valium, Halcion, Ambien).
“We fail so often, even the milestones count for us,” Renger said, laughing. “Think of the number of people who work in the industry. How many get to develop a drug that goes all the way? Probably fewer than ten per cent.”
I well recall when my last company closed up shop - people in one wing were taking those things and lining them up out on a window shelf in the hallway, trying to see how far they could make them reach. Admittedly, they bulked out the lineup with Employee Recognition Awards and Extra Teamwork awards, but there were plenty of oddly shaped clear resin thingies out there, too.
The article also has a good short history of orexin drug development, and it happens just the way I remember it - first, a potential obesity therapy, then sleep disorders (after it was discovered that a strain of narcoleptic dogs lacked functional orexin receptors).
Mignot recently recalled a videoconference that he had with Merck scientists in 1999, a day or two before he published a paper on narcoleptic dogs. (He has never worked for Merck, but at that point he was contemplating a commercial partnership.) When he shared his results, it created an instant commotion, as if he’d “put a foot into an ants’ nest.” Not long afterward, Mignot and his team reported that narcoleptic humans lacked not orexin receptors, like dogs, but orexin itself. In narcoleptic humans, the cells that produce orexin have been destroyed, probably because of an autoimmune response.
Orexin seemed to be essential for fending off sleep, and this changed how one might think of sleep. We know why we eat, drink, and breathe—to keep the internal state of the body adjusted. But sleep is a scientific puzzle. It may enable next-day activity, but that doesn’t explain why rats deprived of sleep don’t just tire; they die, within a couple of weeks. Orexin seemed to turn notions of sleep and arousal upside down. If orexin turns on a light in the brain, then perhaps one could think of dark as the brain’s natural state. “What is sleep?” might be a less profitable question than “What is awake?”
There's also a lot of good coverage of the drug's passage through the FDA, particularly the hearing where the agency and Merck argued about the dose. (The FDA was inclined towards a lower 10-mg tablet, but Merck feared that this wouldn't be enough to be effective in enough patients, and had no desire to launch a drug that would get the reputation of not doing very much).
few weeks later, the F.D.A. wrote to Merck. The letter encouraged the company to revise its application, making ten milligrams the drug’s starting dose. Merck could also include doses of fifteen and twenty milligrams, for people who tried the starting dose and found it unhelpful. This summer, Rick Derrickson designed a ten-milligram tablet: small, round, and green. Several hundred of these tablets now sit on shelves, in rooms set at various temperatures and humidity levels; the tablets are regularly inspected for signs of disintegration.
The F.D.A.’s decision left Merck facing an unusual challenge. In the Phase II trial, this dose of suvorexant had helped to turn off the orexin system in the brains of insomniacs, and it had extended sleep, but its impact didn’t register with users. It worked, but who would notice? Still, suvorexant had a good story—the brain was being targeted in a genuinely innovative way—and pharmaceutical companies are very skilled at selling stories.
Merck has told investors that it intends to seek approval for the new doses next year. I recently asked John Renger how everyday insomniacs would respond to ten milligrams of suvorexant. He responded, “This is a great question.”
There are, naturally, a few shots at the drug industry throughout the article. But it's not like our industry doesn't deserve a few now and then. Overall, it's a good writeup, I'd say, and gets across the later stages of drug development pretty well. The earlier stages are glossed over a bit, by comparison. If the New Yorker would like for me to tell them about those parts sometime, I'm game.
+ TrackBacks (0) | Category: Clinical Trials | Drug Development | Drug Industry History | The Central Nervous System
November 8, 2013
So Bristol-Myers Squibb did indeed re-org itself yesterday, with the loss of about 75 jobs (and the shifting around of 300 more, which will probably result in some job losses as well, since not everyone is going to be able to do that). And they announced that they're getting out of two therapeutic areas, diabetes and neuroscience.
Those would be for very different reasons. Neuro is famously difficult and specialized. There are huge opportunities there, but they're opportunities because no one's been able to do much with them, for a lot of good reasons. Some of the biggest tar pits of drug discovery are to be found there (Alzheimer's, chronic pain), and even the diseases for which we have some treatments are near-total black boxes, mechanistically (schizophrenia, epilepsy and seizures). The animal models are mysterious and often misleading, and the clinical trials for the biggest diseases in this area are well-known to be expensive and tricky to run. You've got your work cut out for you over here.
Meanwhile, the field of diabetes and metabolic disorders is better served. For type I diabetes, the main thing you can do, short of finding ever more precise ways of dosing insulin, is to figure out how to restore islet function and cure it, and that's where all the effort seems to be going. For type II diabetes, which is unfortunately a large market and getting larger all the time, there are a number of therapeutic options. And while there's probably room for still more, the field is getting undeniably a bit crowded. Add that to the very stringent cardiovascular safety requirements, and you're looking at a therapeutic that's not as attractive for new drug development as it was ten or fifteen years ago.
So I can see why a company would get out of these two areas, although it's also easy to think that it's a shame for this to happen. Neuroscience is in a particularly tough spot. The combination of uncertainly and big opportunities would tend to draw a lot of risk-taking startups to the area, but the massive clinical trials needed make it nearly impossible for a small company to get serious traction. So what we've been seeing are startups that, even more than other areas, are focused on getting to the point that a larger company will step in to pay the bills. That's not an abnormal business model, but it has its hazards, chief among them the temptation to run what trials you can with a primary goal of getting shiny numbers (and shiny funding) rather than finding out whether the drug has a more solid chance of working. Semi-delusional Phase II trials are a problem throughout the industry, but more so here.
+ TrackBacks (0) | Category: Business and Markets | Diabetes and Obesity | Drug Development | The Central Nervous System
October 29, 2013
Medicinal chemists talk a lot more about residence time and off rate than they used to. It's become clear that (at least in some cases) a key part of a drug's action is its kinetic behavior, specifically how quickly it leaves its binding site. You'd think that this would correlate well with its potency, but that's not necessarily so. Binding constants are a mix of on- and off-rates, and you can get to the same number by a variety of different means. Only if you're looking at very similar compounds with the same binding modes can you expect the correlation your intuition is telling you about, and even then you don't always get it.
There's a new paper in J. Med. Chem. from a team at Boehringer Ingelheim that takes a detailed look at this effect. The authors are working out the binding to the muscarinic receptor ligand tiotropium, which has been around a long time. (Boehringer's efforts in the muscarinic field have been around a long time, too, come to think of it). Tiotropium binds to the m2 subtype with a Ki of 0.2 nM, and to the m3 subtype with a Ki of 0.1 nM. But the compound has a much slower off rate on the m3 subtype, enough to make it physiologically distinct as an m3 ligand. Tiotropium is better known by its brand name Spiriva, and if its functional selectivity at the m3 receptors in the lungs wasn't pretty tight, it wouldn't be a drug. By carefully modifying its structure and introducing mutations into the receptor, this group hoped to figure out just why it's able to work the way it does.
The static details of tiotropium binding are well worked out - in fact, there's a recent X-ray structure, adding to the list of GPCRs that have been investigated by X-ray crystallography. There are plenty of interactions, as those binding constants would suggest:
The orthosteric binding sites of hM3R and hM2R are virtually identical. The positively charged headgroup of the antimuscarinic agent binds to (in the class of amine receptors highly conserved) Asp3.32 (D1483.32) and is surrounded by an aromatic cage consisting of Y1493.33, W5046.48, Y5076.51, Y5307.39, and Y5347.43. In addition to that, the aromatic substructures of the ligands dig into a hydrophobic region close to W2004.57 and the hydroxy groups, together with the ester groups, are bidentally interacting with N5086.52, forming close to optimal double hydrogen bonds. . .
The similarity of these binding sites was brought home to me personally when I was working on making selective antagonists of these myself. (If you want a real challenge, try differentiating m2 and m4). The authors point out, though, and crucially, that if you want to understand how different compounds bind to these receptors, the static pictures you get from X-ray structures are not enough. Homology modeling helps a good deal, but only if you take its results as indicators of dynamic processes, and not just swapping out residues in a framework.
Doing point-by-point single changes in both the tiotropium structure and the the receptor residues lets you use the kinetic data to your advantage. Such similar compounds should have similar modes of dissociation from the binding site. You can then compare off-rates to the binding constants, looking for the ones that deviate from the expected linear relationship. What they find is that the first event when tiotropium leaves the binding site is the opening of the aromatic cage mentioned above. Mutating any of these residues led to a big effect on the off-rate compared to the effect on the binding constant. Mutations further up along the tunnel leading to the binding site behaved in the same way: pretty much identical Ki values, but enhanced off-rates.
These observations, the paper says with commendable honesty, don't help the medicinal chemists all that much in designing compounds with better kinetics. You can imagine finding a compound that takes better advantage of this binding (maybe), but you can also imagine spending a lot of time trying to do that. The interaction with the asapragine at residue 508 is more useful from a drug design standpoint:
Our data provide evidence that the double hydrogen interaction of N5086.52 with tiotropium has a crucial influence on the off-rates beyond its influence on Ki. Mutation of N5086.52 to alanine accelerates the dissociation of tiotropium more than 1 order of magnitude than suggested by the Ki. Consequently, tiotropium derivatives devoid of the interacting hydroxy group show overproportionally short half-lives. Microsecond MD simulations show that this double hydrogen bonded interaction hinders tiotropium from moving into the exit channel by reducing the frequency of tyrosine-lid opening movements. Taken together, our data show that the interaction with N5086.52 is indeed an essential prerequisite for the development of slowly dissociating muscarinic receptor inverse agonists. This hypothesis is corroborated by the a posteriori observation that the only highly conserved substructure of all long-acting antimuscarinic agents currently in clinical development or already on the market is the hydroxy group.
But the extracellular loops also get into the act. The m2 subtype's nearby loop seems to be more flexible than the one in m3, and there's a lysine in the m3 that probably contributes some electrostatic repulsion to the charged tiotropium as it tries to back out of the protein. That's another effect that's hard to take advantage of, since the charged region of the molecule is a key for binding down in the active site, and messing with it would probably not pay dividends.
But there are some good take-aways from this paper. The authors note that the X-ray structure, while valuable, seems to have large confirmed the data generated by mutagenesis (as well it should). So if you're willing to do lots of point mutations, on both your ligand and your protein, you can (in theory) work some of these fine details out. Molecular dynamics simulations would seem to be of help here, too, also in theory. I'd be interested to hear if people can corroborate that with real-world experience.
+ TrackBacks (0) | Category: Drug Assays | In Silico | Pharmacokinetics | The Central Nervous System
October 23, 2013
G-protein coupled receptors are one of those areas that I used to think I understood, until I understood them better. These things are very far from being on/off light switches mounted in drywall - they have a lot of different signaling mechanisms, and none of them are simple, either.
One of those that's been known for a long time, but remains quite murky, is allosteric modulation. There are many compounds known that clearly are not binding at the actual ligand site in some types of GPCR, but (equally clearly) can affect their signaling by binding to them somewhere else. So receptors have allosteric sites - but what do they do? And what ligands naturally bind to them (if any)? And by what mechanism does that binding modulate the downstream signaling, and are there effects that we can take advantage of as medicinal chemists? Open questions, all of them.
There's a new paper in Nature that tries to make sense of this, and trying by what might be the most difficult way possible: through computational modeling. Not all that long ago, this might well have been a fool's errand. But we're learning a lot about the details of GPCR structure from the recent X-ray work, and we're also able to handle a lot more computational load than we used to. That's particularly true if we are David Shaw and the D. E. Shaw company, part of the not-all-that-roomy Venn diagram intersection of quantitative Wall Street traders and computational chemists. Shaw has the resources to put together some serious hardware and software, and a team of people to make sure that the processing units get frequent exercise.
They're looking at the muscarinic M2 receptor, an old friend of mine for which I produced I-know-not-how-many antagonist candidates about twenty years ago. The allosteric region is up near the surface of the receptor, about 15A from the acetylcholine binding site, and it looks like all the compounds that bind up there do so via cation/pi interactions with aromatic residues in the protein. (That holds true for compounds as diverse as gallamine, alcuronium, and strychnine), and the one shown in the figure. This is very much in line with SAR and mutagenesis results over the years, but there are some key differences. Many people had thought that the aromatic groups of the ligands the receptors must have been interacting, but this doesn't seem to be the case. There also don't seem to be any interactions between the positively charged parts of the ligands and anionic residues on nearby loops of the protein (which is a rationale I remember from my days in the muscarinic field).
The simulations suggest that the two sites are very much in communication with each other. The width and conformation of the extracellular vestibule space can change according to what allosteric ligand occupies it, and this affects whether the effect on regular ligand binding is positive or negative, and to what degree. There can also, in some cases, be direct electrostatic interactions between the two ligands, for the larger allosteric compounds. I was very glad to see that the Shaw group's simulations suggested some experiments: one set with modified ligands, which would be predicted to affect the receptor in defined ways, and another set with point mutations in the receptor, which would be predicted to change the activities of the known ligands. These experiments were carried out by co-authors at Monash University in Australia, and (gratifyingly) seem to confirm the model. Too many computational papers (and to be fair, too many non-computational papers) don't get quite to the "We made some predictions and put our ideas to the test" stage, and I'm glad this one does.
+ TrackBacks (0) | Category: Biological News | In Silico | The Central Nervous System
October 21, 2013
The orphan-drug model is a popular one in the biopharma business these days. But like every other style of business, it has something-for-nothing artists waiting around it. Take a look at this article by Adam Feuerstein on Catalyst Pharmaceuticals, and see what category you think they belong in.
They're developing a compound called Firdapse for Lambert-Eaton Myasthenic Syndrome (LEMS), a rare neuromuscular disorder. It's caused by an autoimmune response to one set of voltage-gated calcium channels in the peripheral nervous system. Right now, the treatments for the condition that seem to provide much benefit are intravenous immunoglobin and 3,4-diaminopyridine (DAP). That latter compound is a potassium channel blocker that allows calcium to accumulate intracellularly in neurons and thus counteracts some of the loss of function in the system.
DAP is not an FDA-approved treatment, but it's officially under study at a number of medical centers, and the FDA is allowing it to be given to patients under a compassionate-use protocol. It's supplied, free of charge, by a small company in New Jersey, Jacobus Pharmaceuticals, who got into the area through a request from the Muscular Dystrophy Association. So how well does Firdapse work compared to this existing drug? Pretty much the same, because it's the same damn compound.
Yep, this is another one of those unexpected-regulatory-effects stories, such as happened with colchicine and with hydroxyprogesterone. The FDA has wanted to get as many therapies as possible through the actual regulatory process, and has provided a marked-exclusivity incentive for companies willing to do the trials needed. But if you're going to offer incentives, you need to think carefully about what you're giving people an incentive to do. In this case, the door is open for a company to step in, pick up an existing drug that is being given away to patients for free, a compound that it has spent no money discovering and no money developing, run the fastest trial possible with it, and then jack the price up to whatever the insurance companies might be able to pay. Now, pricing drugs at what the market will pay for them is fine by me. But that's supposed to be a reward for taking on the risk of discovering them and getting them through the approval process. This Catalyst case is another short-circuit in the system, a perverse incentive that some people seem to have no shame about taking advantage of. A similar situation has taken place in the EU with DAP and Biomarin Pharmaceuticals.
The LEMS patient community is not a large one, and they seem to be getting the word out for people to not sign up for Catalyst's clinical trials. Jacobus themselves have realized what's going on, and are running a trial of their own, hoping to file before Catalyst does and pick up the market exclusivity for themselves, so they can continue to supply the compound at the current price: nothing.
It's worth taking a minute to contrast this situation with Biogen's Tecfidera. That's another very small molecule (dimethyl fumarate) being given to patients with a neurological disease. It's also expensive. But in this case, MS patients had not been taking dimethyl fumarate for years (to the best of my knowledge). It was not already in the medical literature as an effective treatment (the way DAP is already there for LEMS). Biogen bought the company with the rights (Fumapharm) and took on the expense of the clinical trials, taking the risk that things might not work out at all. A lot of stuff doesn't. And they're pricing their drug according to what the market will pay, because they also have to fund the many other projects they're working on, most of which can be expected to wipe out at some point.
So how does a situation like Catalyst and DAP affect the drug companies who actually do research? Not too much, you might think, and they apparently think so, too, because I don't recall any statements about any of these cases so far from that end of the industry. They may not want to take any stands that call into question the ability of a company to set the price of its drugs according to what it thinks the market will bear. But since we are not, last I saw, living in some sort of radical libertarian free-for-all, it would be worth remembering that the ability to set such prices is not some sort of inalienable right. It can be restricted or even abrogated entirely by governments all around the world. And one way to get that to happen is for these governments and (in the democratic states, their constituents) to feel as if they're being taken advantage of by a bunch of cynical manipulators.
+ TrackBacks (0) | Category: Drug Prices | Regulatory Affairs | The Central Nervous System
October 11, 2013
The British press (and to a lesser extent, the US one) was full of reports the other day about some startling breakthrough in Alzheimer's research. We could certainly use one, but is this it? What would an Alzheimer's breakthrough look like, anyway?
Given the complexity of the disease, and the difficulty of extrapolating from its putative animal models, I think that the only way you can be sure that there's been a breakthrough in Alzheimer's is when you see things happening in human clinical trials. Until then, things are interesting, or suggestive, or opening up new possibilities, what have you. But in this disease, breakthroughs happen in humans.
This latest news is nowhere close. That's not to say it's not very interesting - it certainly is, and it doesn't deserve the backlash it'll get from the eye-rolling headlines the press wrote for it. The paper that started all this hype looked at mice infected with a prion disease, which led inexorably to neurodegeneration and death. They seem to have significantly slowed that degenerative cascade (details below), and that really is a significant result. The mechanism behind this, the "unfolded protein response" (UPR) could well be general enough to benefit a number of misfolded-protein diseases, which include Alzheimer's, Parkinson's, and Huntington's, among others. (If you don't have access to the paper, this is a good summary).
The UPR, which is a highly conserved pathway, senses an accumulation of misfolded proteins inside the endoplasmic reticulum. If you want to set it off, just expose the cells you're studying to Brefeldin A; that's its mechanism. The UPR has two main components: a shutdown of translation (and thus further protein synthesis), and an increase in chaperones to try to get the folding pathways back on track. (If neither of these do the trick, things will eventually shunt over to apoptosis, so the UPR can be seen as an attempt to avoid having the apoptotic detonator switch set off too often.
Shutting down translation causes cell cycle arrest, as well it might, and there's a lot of evidence that it's mediated by PERK, the Protein kinase RNA-like Endoplasmic Reticulum Kinase. The team that reported this latest result had previously shown that two different genetic manipulations of this pathway could mediate prion disease in what I think is the exact same animal model. If you missed the wild excited headlines when that one came out, well, you're not alone - I don't remember there being any. Is it that when something comes along that involves treatment with a small molecule, it looks more real? We medicinal chemists should take our compliments where we can get them.
That is the difference between that earlier paper and this new one. It uses a small-molecule PERK inhibitor (GSK2606414), whose discovery and SAR is detailed here. And this pharmacological PERK inhibition recapitulated the siRNA and gain-of-function experiments very well. Treated mice did show some behavioralthis really does look quite solid, and establishes the whole PERK end of the UPR as a very interesting field to work in.
The problem is, getting a PERK inhibitor to perform in humans will not be easy. That GSK inhibitor, unfortunately, has side effects that killed it as a development compound. PERK also seems to be a key component of insulin secretion, and in this latest study, the team did indeed see elevated blood glucose and pronounced weight loss, to the point that that treated mice eventually had to be sacrificed. Frustratingly, PERK inhibition might actually be a target to treat insulin resistance in peripheral tissue, so if you could just keep an inhibitor out of the pancreas, you might be in business. Good luck with that. I can't imagine how you'd do it.
But there may well be other targets in the PERK-driven pathways that are better arranged for us, and that, I'd think, is where the research is going to swing next. This is a very interesting field, with a lot of promise. But those headlines! First of all, prion disease is not exactly a solid model for Alzheimer's or Parkinson's. Since this pathway works all the way back at the stage of protein misfolding, it might be just the thing to uncover the similarities in the clinic, but that remains to be proven in human trials. There are a lot of things that could go wrong, many of which we probably don't even realize yet. And as just detailed above, the specific inhibitor being used here is strictly a tool compound all the way - there's no way it can go into humans, as some of the news stories got around to mentioning in later paragraphs. Figuring out something that can is going to take significant amount of effort, and many years of work. Headlines may be in short supply along the way.
+ TrackBacks (0) | Category: Press Coverage | The Central Nervous System
August 29, 2013
As someone who will not be seeing the age of 50 again, I find a good deal of hope in a study out this week from Eric Kandel and co-workers at Columbia. In Science Translational Medicine, they report results from a gene expression study in human brain samples. Looking at the dentate gyrus region of the hippocampus, long known to be crucial in memory formation and retrieval, they found several proteins to have differential expression in younger tissue samples versus older ones. Both sets were from otherwise healthy individuals - no Alzheimer's, for example.
RbAp48 (also known as RBBP4 and NURF55), a protein involved in histone deacetylation and chromatin remodeling, stood out in particular. It was markedly decreased in the samples from older patients, and the same pattern was seen for the homologous mouse protein. Going into mice as a model system, the paper shows that knocking down the protein in younger mice causes them to show memory problems similar to elderly ones (object recognition tests and the good old Morris water maze), while overexpressing it in the older animals brings their performance back to the younger levels. Overall, it's a pretty convincing piece of work.
It should set off a lot of study of the pathways the protein's involved in. My hope is that there's a small-molecule opportunity in there, but it's too early to say. Since it's involved with histone coding, it could well be that this protein has downstream effects on the expression of others that turn out to be crucial players (but whose absolute expression levels weren't changed enough to be picked up in the primary study). Trying to find out what RbAp48 is doing will keep everyone busy, as will the question of how (and/or why) it declines with age. Right now, I think the whole area is wide open.
It is good to hear, though, that age-related memory problems may not be inevitable, and may well be reversible. My own memory seems to be doing well - everyone who knows me well seems convinced that my brain is stuffed full of junk, which detritus gets dragged out into the sunlight with alarming frequency and speed. But, like anyone else, I do get stuck on odd bits of knowledge that I think I should be able to call up quickly, but can't. I wonder if I'm as quick as I was when I was on Jeopardy almost twenty years ago, for example?
(If you don't have access to the journal, here's the news writeup from Science, and here's Sharon Begley at Bloomberg).
+ TrackBacks (0) | Category: Aging and Lifespan | The Central Nervous System
August 12, 2013
The New York Times had a rather confusing story the other day about the PTEN gene, autism, and cancer. Unfortunately, it turned into a good example of how not to explain a subject like this, and it missed out (or waited too long) to explain a number of key concepts. Things like "one gene can be responsible a lot of different things in a human phenotype", and "genes can have a lot of different mutations, which can also do different things", and "autism's genetic signature is complex and not well worked out, not least because it's such a wide-ranging diagnosis", and (perhaps most importantly, "people with autism are not doomed to get cancer".
Let me refer you to Emily Willingham at Forbes, who does a fine job of straightening things out here. I fear that what can happen at the Times (and other media outlets as well) is that when a reporter scrambles a science piece, there's no one else on the staff who's capable of noticing it. So it just runs as is.
+ TrackBacks (0) | Category: Cancer | The Central Nervous System
July 25, 2013
Ben Cravatt is talking about this work on activity-based protein profiling of serine hydrolase enzymes. That's quite a class to work on - as he says, up to 2% of all the proteins in the body fall into this group, but only half of them have had even the most cursory bit of characterization. Even among the "known" ones, most of their activities are still dark, and only 10% of them have useful pharmacological tools.
He's detailed a compound (PF-3845) that Pfizer found as a screening hit for FAAH, which although it looked benign, turned out to be a covalent inhibitor due to a reactive arylurea. Pfizer, he says, backed off when this mechanism was uncovered - they weren't ready at the time for covalency, but he says that they've loosened up since then. Studying the compound in various tissues, including the brain, showed that it was extremely selective for FAAH.
Another reactive compound, JZL184, is an inhibitor of monoacylglycerol hydrolase (MAGL). Turns out that its carbamate group also reacts with FAAH, but there's a 300-fold window in the potency. The problem is, that's not enough. In mouse models, hitting both enzymes at the same time leads to behavioral problems. Changing the leaving group to a slightly less reactive (and nonaromatic) hexafluoroisopropanol, though, made the compound selective again. I found this quite interesting - most of the time, you'd think that 300x is plenty of room, but apparently not. That doesn't make things any easier, does it?
In response to a question (from me), he says that covalency is what makes this tricky. The half-life of the brain enzymes is some 12 to 14 hours, so by the time the next once-a-day dose comes in, there's still 20 or 30% of the enzyme still shut down, and things get out of hand pretty soon. For a covalent mechanism, he recommends 2000-fold or 5000-fold. On the other hand, he says that when they've had a serine hydrolase-targeted compound, they've never seen it react out of that class (targeting cysteine residues, though, is a very different story). And the covalent mechanism gives you some unique opportunities - for example, deliberate engineering a short half-life, because that might be all you need.
+ TrackBacks (0) | Category: Chemical Biology | The Central Nervous System
May 9, 2013
Want to be weirded out? Study the central nervous system. I started off my med-chem career in CNS drug discovery, and it's still my standard for impenetrability. There's a new paper in Science, though, that just makes you roll your eyes and look up at the ceiling.
The variety of neurotransmitters is well appreciated - you have all these different and overlapping signaling systems using acetylcholine, dopamine, serotonin, and a host of lesser-known molecules, including such oddities as hydrogen sulfide and even carbon monoxide. And on the receiving end, the various subtypes of receptors are well studied, and those give a tremendous boost to the variety of signaling from a single neurotransmitter type. Any given neuron can have several of these going on at the same time - when you consider how many different axons can be sprawled out from a single cell, there's a lot of room for variety.
That, you might think, is a pretty fair amount of complexity. But note also that the density and population of these receptors can change according to environmental stimuli. That's why you get headaches if you don't have your accustomed coffee in the morning (you've made more adenosine A2 receptors, and you haven't put any fresh caffeine ligand into them). Then there are receptor dimers (homo- and hetero-) that act differently than the single varieties, constituitively active receptors that are always on, until a ligand turns them off (the opposite of the classic signaling mechanism), and so on. Now, surely, we're up to a suitable level of complex function.
Har har, says biology. This latest paper shows, by a series of experiment in rats, that a given population of neurons can completely switch the receptor system it uses in response to environmental cues:
Our results demonstrate transmitter switching between dopamine and somatostatin in neurons in the adult rat brain, induced by exposure to short- and long-day photoperiods that mimic seasonal changes at high latitudes. The shifts in SST/dopamine expression are regulated at the transcriptional level, are matched by parallel changes in postsynaptic D2R/SST2/4R expression, and have pronounced effects on behavior. SST-IR/TH-IR local interneurons synapse on CRF-releasing cells, providing a mechanism by which the brain of nocturnal rats generates a stress response to a long-day photoperiod, contributing to depression and serving as functional integrators at the interface of sensory and neuroendocrine responses.
This remains to be demonstrated in human tissue, but I see absolutely no reason what the same sort of thing shouldn't be happening in our heads as well. There may well be a whole constellation of these neurotransmitter switchovers that can take place in response to various cues, but which neurons can do this, involving which signaling regimes, and in response to what stimuli - those are all open questions. And what the couplings are between the environmental response and all the changes in transcription that need to take place for this to happen, those are going to have to be worked out, too.
There may well be drug targets in there. Actually, there are drug targets everywhere. We just don't know what most of them are yet.
+ TrackBacks (0) | Category: The Central Nervous System
April 2, 2013
Let us take up the case of Tecfidera, the new Biogen/Idec drug for multiple sclerosis, known to us chemists as dimethyl fumarate. It joins the (not very long) list of industrial chemicals (the kind that can be purchased in railroad-car sizes) that are also approved pharmaceuticals for human use. The MS area has seen this before, interestingly.
A year's supply of Tecfidera will set you (or your insurance company) back $54,900. That's a bit higher than many analysts were anticipating, but that means "a bit higher over $50,000". The ceiling is about $60,000, which is what Novartis's Gilenya (fingolomod) goes for, and Biogen wanted to undercut them a bit. So, 55 long ones for a year's worth of dimethyl fumarate pills - what should one think about that?
Several thoughts come to mind, the first one being (probably) "Fifty thousand dollars for a bunch of dimethyl fumarate? Who's going to stand for that?" But we have an estimate for the second part of that question - Biogen thinks that quite a few people are going to stand for it, rather than stand for fingolomod. I'm sure they've devoted quite a bit of time and effort into thinking about that price, and that it's their best estimate of maximum profit. How, exactly, do they get away with that? Simple. They get away with it because they were willing to take the compound through clinical trials in MS patients, find out if it's tolerated and if it's efficacious, figure out the dosing regimen, and get it approved for this use by the FDA. If you or I had been willing to do that, and had been able to round up the money and resources, then we would also have the ability to charge fifty grand a year for it (or whatever we thought fit, actually).
What, exactly, gave them the idea that dimethyl fumarate might be good for multiple sclerosis? As it turns out, a German physician described its topical use for psoriasis back in 1959, and a formation of the compound as a cream (along with some monoesters) was eventually studied clinically by a small company in Switzerland called Fumapharm. This went on the market in Germany in the early 1990s, but the company did not have either the willingness or desire to extend their idea outside that region. But since dimethyl fumarate appears to work on psoriasis by modulating the immune system somehow, it did occur to someone that it might also be worth looking at in multiple sclerosis. Biogen began developing dimethyl fumarate for that purpose with Fumapharm, and eventually bought them outright in 2006 as things began to look more promising.
In other words, the connection of dimethyl fumarate as a possible therapy for MS had been out there, waiting to be made, since before many of us were born. Generations of drug developers had their chances to see it. Every company in the business had a chance to get interested in Fumapharm back in the late 80s and early 90s. But Biogen did, and in 2013 that move has paid off.
Now we come to two more questions, the first of which is "Should that move be paying off quite so lucratively?" But who gets to decide? Watching people pay fifty grand for a year's supply of dimethyl fumarate is not, on the face of it, a very appealing sight. At least, I don't find it so. But on the other hand, cost-of-goods is (for small molecules) generally not a very large part of the expense of a given pill - a rule of thumb is that such expenses should certainly be below 5% of a drug's selling price, and preferably less than 2%. It's just that it's even less in this case, and Biogen also has fewer worries about their supply chain, presumably. The fact this this drug is dimethyl fumarate is a curiosity (and perhaps an irritating one), but that lowers Biogen's costs by a couple of thousand a year per patient compared to some other small molecule. The rest of the cost of Tecfidera has nothing to do with what the ingredients are - it's all about what Biogen had to pay to get it on the market, and (most importantly) what the market will bear. If insurance companies believe that paying fifty thousand a year for the drug is a worthwhile expense, the Biogen will agree with them, too.
The second question is divorced from words like "should", and moves to the practical question of "can". The topical fumarate drug in Europe apparently had fairly wide "homebrew" use among psoriasis patients in other countries, and one has to wonder just a bit about that happening with Tacfidera. Biogen Idec certainly has method-of-use patents, but not composition-of-matter, so it's going to be up to them to try to police this. I found the Makena situation more irritating than this one (and the colchicine one, too), because in those cases, the exact drugs for the exact indications had already been on the market. (Dimethyl fumarate was not a drug for MS until Biogen proved it so, by contrast). But KV Pharmaceuticals had to go after people who were compounding the drug, anyway, and I have to wonder if a secondary market in dimethyl fumarate might develop. I don't know the details of its formulation (and I'm sure that Biogen will make much of it being something that can't be replicated in a basement), but there will surely be people who try it.
+ TrackBacks (0) | Category: Drug Development | Drug Prices | The Central Nervous System
March 21, 2013
If you looked at the timelines of a clinical trial, you'll notice that there's often a surprisingly long gap between when the trial actually ends and when the results of it are ready to announce. If you've ever been involved in working up all that data, you'll know why, but it's usually not obvious to people outside of medical research why it should take so long. (I know how they'd handle the scene in a movie, were any film to ever take on such a subject - it would look like the Oscars, with someone saying "And the winner is. . ." within the first few seconds after the last patient was worked up).
The Danish company NeuroSearch unfortunately provided everyone with a lesson in why you want to go over your trial data carefully. In February of 2010, they announced positive results in a Phase III trial of a drug (pridopidine, Huntexil) for Huntington's (a rare event, that), but two months later they had to take it back. This move cratered their stock price, and investor confidence in general, as you'd imagine. Further analysis, which I would guess involved someone sitting in front of a computer screen, tapping keys and slowly turning pale and sweaty, showed that the drug actually hadn't reached statistical significance after all.
It came down to the varying genetic background in the patients being studied, specifically, the number of CAG repeats. That's the mutation behind Huntington's - once you get up to too many of those trinucleotide repeats in the middle of the gene sequence, the resulting protein starts to behave abnormally. Fewer than 36 CAGs, and you should be fine, but a good part of the severity of the disease has to do with how many repeats past that a person might have. NeuroSearch's trial design was not predicated on such genetic differences, at least not for modeling the primary endpoints. If you took those into account, they reached statistical significance, but if you didn't, you missed.
That's unfortunate, but could (in theory) be worse - after all, their efficacy did seem to track with a clinically relevant measure of disease severity. But you'll have noticed that I'm wording all these sentences in the past tense. The company has announced that they're closing. It's all been downhill since that first grim announcement. In early 2011, the FDA rejected their New Drug Application, saying that the company needed to provide more data. By September of that year, they were laying off most of their employees to try to get the resources together for another Phase III trial. In 2012, the company began shopping Huntexil around, as it became clear that they were not going to be able to develop it themselves, and last September, Teva purchased the program.
This is a rough one, because for a few weeks there in 2010, NeuroSearch looked like they had made it. If you want to see the fulcrum, the place about which whole companies pivot, go to clinical trial design. It's hard to overstate just how important it is.
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
January 18, 2013
Here's another one to file under "What we don't know about brain chemistry". That's a roomy category for sure, which (to be optimistic about it) leaves a lot of room for discovery. In that category are the observations that ketamine seems to dramatically help some people with major depression. It's an old drug, of course, still used in some situations as an anesthetic, and also used (or abused) by people who wish to deliberately derange themselves in dance clubs. Chemists will note the chemical resemblance to phencyclidine (PCP), a compound whose reputation for causing derangement is thouroughly deserved. (Ketamine was, in fact, a "second-generation" version of PCP, many years on).
Both of these compounds are, among other things, NMDA receptor antagonists. That had not been considered a high-priority target for treating depression, but you certainly can't argue with results (not, at least, when you know as little about the mechanisms of depression as we do). There are better compounds around, fortunately:
AZD6765, an inhibitor of the N-methyl-D-aspartate (NMDA) receptor, a glutamate signaling protein involved in cellular mechanisms for learning and memory, was originally developed as a treatment for stroke. It was shelved in 2000 by the drug's manufacturer, AstraZeneca, after phase 2 trials failed to show signs of efficacy. In the decade that followed, however, small clinical reports started to emerge showing that ketamine, an analgesic that also blocks the NMDA receptor, produced rapid responses in people who didn't benefit from any other antidepressants. And unlike most therapies for major depression, which usually take weeks to kick in, ketamine's mood-lifting effects could be seen within two hours, with a therapeutic boost that often lasted for weeks following a single infusion. Ketamine treatment also came with a number of debilitating side effects, though, including psychosis and detachment from reality. Fortunately for AstraZeneca, the company had a cleaner drug on its shelves that could harness ketamine's benefits with fewer problems.
Note that AZD6765 (lanicemine) has a rather simple structure, further confirmation (if anyone needed any) that things this size can be very effective drugs. Here's the clinical study that Nature Medicine news item refers to, and it makes clear that this was a pretty tough patient cohort:
This double-blind, placebo-controlled, proof-of-concept study found that a single intravenous infusion of a low-trapping nonselective NMDA channel blocker in patients with treatment-resistant MDD rapidly (within minutes) improved depressive symptoms without inducing psychotomimetic effects. However, this improvement was transitory. To our knowledge, this is the first report showing rapid antidepressant effects associated with a single infusion of a low-trapping nonselective NMDA channel blocker that did not induce psychotomimetic side effects in patients with treatment-resistant MDD.
More specifically, patient depression scores improved significantly more in patients receiving AZD6765 than in those receiving placebo, and this improvement occurred as early as 80 min. This difference was statistically significant for the MADRS, HDRS, BDI, and HAM-A. These findings are particularly noteworthy, because a large proportion of study participants had a substantial history of past treatment that was not efficacious. The mean number of past antidepressant trials was seven, and 45% of participants had failed to respond to electroconvulsive therapy.
The problem is the short duration. By one evaluation scale, the effects only lasted about two hours (by another less stringent test, some small effect could still be seen out to one or two days). Ketamine lasts longer, albeit at a cost of some severe side effects. This doesn't seem to be a problem with high clearance of AZD6765 (its PK had been well worked out when it was a candidate for stroke). Other factors might be operating:
These differences could be due to subunit selectivity and trapping blockade. It is also possible that the metabolites of ketamine might be involved in its relatively sustained antidepressant effects, perhaps acting on off-site targets; a recent report described active ketamine metabolites that last for up to 3 days. It is also important to note that, although trapping blockade or broadness of antagonist effects on the NMDA subunit receptors might be key to the robustness of antidepressant effects, these same properties might be involved in the dissociative and perceptual side effects of ketamine. Notably, these side effects were not apparent at the dose of AZD6765 tested.
If that last part is accurate, this is going to be a tricky target to work with. I doubt if AZD6765 itself has a future as an antidepressant, but if it can help to understand that mode of action, what the downstream effects might be, and which ones are important, it could lead to something very valuable indeed. The time and effort that will be needed for that is food for thought, particularly when you consider the patients in this study. What must it be like to feel the poison cloud of major depression lift briefly, only to descend again? The Nature Medicine piece has this testimony:
(David) Prietz, 48, a scheduling supervisor at a sheet-metal manufacturer in Rochester, New York, who has been on disability leave for several years, started to feel his head clear from the fog of depression within days of receiving AZD6765. After his second infusion, he vividly began noticing the fall foliage of the trees outside his doctor's office—something he hadn't previously appreciated in his depressed state. “The greens seemed a lot greener and the blue sky seemed a lot bluer,” he says. Although the lift lasted only a couple months after the three-week trial finished and the drug was taken away, the experience gave Prietz hope that he might one day get better. “I can't recall feeling as well I did at the time,” he says.
Fall foliage for Algernon? I hope we can do something for these people, because as it is, a short-duration effect is scientifically fascinating but emotionally cruel.
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
January 10, 2013
There's a paper out in Nature with the provocative title of "Automated Design of Ligands to Polypharmcological Profiles". Admittedly, to someone outside my own field of medicinal chemistry, that probably sounds about as dry as the Atacama desert, but it got my attention.
It's a large multi-center contribution, but the principal authors are Andrew Hopkins at Dundee and Bryan Roth at UNC-Chapel Hill. Using James Black's principle that the best place to find a new drug is to start with an old drug, what they're doing here is taking known ligands and running through a machine-learning process to see if they can introduce new activities into them. Now, those of us who spend time trying to take out other activities might wonder what good this is, but there are a some good reasons: for one thing, many CNS agents are polypharmacological to start with. And there certainly are situations where you want dual-acting compounds, CNS or not, which can be a major challenge. And read on - you can run things to get selectivity, too.
So how well does their technique work? The example they give starts with the cholinesterase inhibitor donepezil (sold as Aricept), which has a perfectly reasonable med-chem look to its structure. The groups' prediction, using their current models, was the it had a reasonable chance of having D4 dopaminergic activity, but probably not D2 (which numbers were borne out by experiment, and might have something to do with whatever activity Aricept has for Alzheimer's). I'll let them describe the process:
We tested our method by evolving the structure of donepezil with the dual objectives of improving D2 activity and achieving blood–brain barrier penetration. In our approach the desired multi-objective profile is defined a priori and then expressed as a point in multi-dimensional space termed ‘the ideal achievement point’. In this first example the objectives were simply defined as two target properties and therefore the space has two dimensions. Each dimension is defined by a Bayesian score for the predicted activity and a combined score that describes the absorption, distribution, metabolism and excretion (ADME) properties suitable for blood–brain barrier penetration (D2 score = 100, ADME score = 50). We then generated alternative chemical structures by a set of structural transformations using donepezil as the starting structure. The population was subsequently enumerated by applying a set of transformations to the parent compound(s) of each generation. In contrast to rules-based or synthetic-reaction-based approaches for generating chemical structures, we used a knowledge-based approach by mining the medicinal chemistry literature. By deriving structural transformations from medicinal chemistry, we attempted to mimic the creative design process.
Hmm. They rank these compounds in multi-dimensional space, according to distance from the ideal end point, filter them for chemical novelty, Lipinski criteria, etc., and then use the best structures as starting points for another round. This continues until you reach close enough to the desired point, or until you dead-end on improvement. In this case, they ended up with fairly active D2 compounds, by going to a lactam in the five-membered ring, lengthening the chain a bit, and going to an arylpiperazine on the end. They also predicted, though, that these compounds would hit a number of other targets, which they indeed did on testing.
How about something a bit more. . .targeted? They tried taking these new compounds through another design loop, this time trying to get rid of all the alpha-adrenergic activity they'd picked up, while maintaining the 5-HT1A and dopamine receptor activity they now had. They tried it both ways - running the algorithms with filtration of the alpha-active compounds at each stage, and without. Interestingly, both optimizations came up with very similar compounds, differing only out on the arylpiperazine end. The alpha-active series wanted ortho-methoxyphenyl on the piperazine, while the alpha-inactive series wanted 2-pyridyl. These preferences were confirmed by experiment as well. Some of you who've worked on adrenergics might be saying "Well, yeah, that's what the receptors are already known to prefer, so what's the news here?" But keep in mind, what the receptors are known to prefer is what's been programmed into this process, so of course, that's what it's going to recapitulate. The idea is for the program to keep track of all the known activities - the huge potential SAR spreadsheet - so you don't have to try to do it yourself, with you own grey matter.
The last example asks whether, starting from donezepil, potent and selective D4 compounds could be evolved. I'm going to reproduce the figure from the paper here, to give an idea of the synthetic transformations involved:
So, donezepil (compound 1) is 614 nM against D4, and after a few rounds of optimization, you get structure 13, which is 9 nM. Not bad! Then if you take 13 as a starting point, and select for structural novelty along the way, you get 18 (five micromolar against D4), 20, 21, and (S)-27 (which is 90 nM at D4). All of these compounds picked up a great deal more selectivity for D4 compared to the earlier donezepil-derived scaffolds as well.
Well, then, are we all out of what jobs we have left? Not just yet. You'll note that the group picked GPCRs as a field to work in, partly because there's a tremendous amount known about their SAR preferences and cross-functional selectivities. And even so, of the 800 predictions made in the course of this work, the authors claim about a 75% success rate - pretty impressive, but not the All-Seeing Eye, quite yet. I'd be quite interested in seeing these algorithms tried out on kinase inhibitors, another area with a wealth of such data. But if you're dwelling among the untrodden ways, like Wordsworth's Lucy, then you're pretty much on your own, I'd say, unless you 're looking to add in some activity in one of the more well-worked-out classes.
But knowledge piles up, doesn't it? This approach is the sort of thing that will not be going away, and should be getting more powerful and useful as time goes on. I have no trouble picturing an eventual future where such algorithms do a lot of the grunt work of drug discovery, but I don't foresee that happened for a while yet. Unless, of course, you do GPCR ligand drug discovery. In that case, I'd be contacting the authors of this paper as soon as possible, because this looks like something you need to be aware of.
+ TrackBacks (0) | Category: Drug Assays | In Silico | The Central Nervous System
December 20, 2012
Tiny Allon Therapeutics had an ambitious plan to go after progressive supranuclear palsy, a kind of progressive brain deterioration, and thence (they hoped) to other neurodegenerative disorders. The lead compound was davunetide, an oligopeptide derived from activity-dependent neuroprotective protein, ADNP.
It was a reasonable idea, but neurodegeneration is not a reasonable area. The drug has now completely wiped out in the clinic, failing both primary endpoints in its pivotal trial. This is one example of the sort of research that most people don't ever hear about, from a small company that most people will never have heard of at all. But this is the background activity of drug research (with an all-too-common outcome), and if more people were aware of it, perhaps that would be a good thing (see today's other post).
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
November 23, 2012
I wanted to mention that the crowdfunded CNS research that I mentioned here is now in its final 48 hours for donations. Money seems to be picking up, but it'll be close to see if they can make their target. If you're interested, donations can be made here.
+ TrackBacks (0) | Category: The Central Nervous System
October 18, 2012
One of the questions I get asked most often, by people outside of the drug industry, is whether generic medications really are the same as the original branded ones. My answer has always been the same: that yes, they are. And that's still my answer, but I'll have to modify it a bit, because we're seeing an exception right now. Update: more exceptions are showing up in the comments section.
Unfortunately, "right now" turns out, in this case, to mean "over the last five years". The problem here is bupropion (brand name Wellbutrin), the well-known antidepressant. A generic version of it came on the market in 2006, and it went through the usual FDA review. For generic drugs, the big question is bioequivalence: do they deliver the same ingredient in the same way as the originally approved drug and formulation? The agency requires generic drug applications to show proof of this for their own version.
For bupropion/Wellbutrin, the case is complicated by the two approved doses, 150mg and 300mg. The higher dose is associated with a risk of seizures, which made the FDA grant a waiver for its testing - they extrapolated from the 150mg data instead. And right about here is where the red flags began to go up. The agency began to receive reports, almost immediately, of trouble with the 300mg generic dose. In many cases, these problems (lack of efficacy and/or increased side effects) resolved when patients switched back to the original branded formulation. That link also shows the pharamacokinetic data comparing the two 150mg dosages (branded and generic), which turned out to have some differences, mostly in the time it took to reach the maximum concentration (the generic came on a bit faster).
At the time, though, as that link shows, the FDA decided that because of the complicated clinical course of depression (and antidepressant therapy) that they couldn't blame the reported problems on a difference between the two 300mg products. A large number of patients were taking each one, and the number of problems reported could have been explained by the usual variations:
The FDA considers the generic form of bupropion XL 300 mg (Teva Pharmaceuticals) bioequivalent and therapeutically equivalent to (interchangeable with) Wellbutrin XL 300 mg. Although there are small differences in the pharmacokinetic profiles of these two formulations, they are not outside the established boundaries for equivalence nor are they different from other bupropion products known to be effective. The recurrent nature of (major depression) offers a scientifically reasonable explanation for the reports of lack of efficacy following a switch to a generic product. The adverse effects (e.g., headache, GI disorder, fatigue and anxiety) reported following a switch were relatively few in number and typical of adverse drug events reported in drug and placebo groups in most clinical trials. . .
But they seem to have changed their minds about this. It appears that reports continued to come in, and were associated most frequently with the generic version marketed by Teva (and produced by Impax Pharmaceuticals). That FDA page I've quoted above is not dated, but appears to come from late 2007 or so. As it turns out, the agency was at that time asking Teva to conduct that missing bioequivalence study with their 300mg product. See Q12 on this page:
FDA continued to review postmarketing reports throughout 2007. In November 2007, taking into consideration reports of lack of efficacy, FDA requested that Impax/Teva conduct a bioequivalence study directly comparing Budeprion XL 300 mg to Wellbutrin XL 300 mg. The study protocol stipulated the enrollment of patients who reported problems after switching from Wellbutrin XL 300 mg to Budeprion XL 300 mg. Impax/Teva began the study, but terminated it in late 2011, reporting that despite efforts to enroll patients, Impax/Teva was unable to recruit a significant number of affected patients.
The agency apparently was continuing to receive reports of problems, because they ended up deciding to run their own study, which is an uncommon move. This got underway before Teva officially gave up on their study, which gives one the impression that the FDA did not expect anything useful from them by that point:
In 2010, because of the public health interest in obtaining bioequivalence data, FDA decided to sponsor a bioequivalence study comparing Budeprion XL 300 mg to Wellbutrin XL 300 mg. The FDA-sponsored study enrolled 24 healthy adult volunteers and examined the rate and extent of absorption of the two drug products under fasting conditions. In that study, the results of which became available in August 2012, Budeprion XL 300 mg failed to demonstrate bioequivalence to Wellbutrin XL 300 mg.
That FDA-sponsored study is what led to the recent decision to pull the Imapax/Teva 300mg product from the market. Their 150mg dosage is still approved, and doesn't seem to have been associated with any increased reports of trouble (despite the small-but-real PK differences noted above). And it's also worth noting that there are four other generic 300mg bupropion/Wellbutrin products out there, which do not seem to have caused problems.
How big a difference are we talking about here? There are several measurements that are used for measuring blood levels of a drug. You have Cmax, the maximum concentration that is seen at a given dosage, and there's also Tmax, the time at which that maximum concentration occurs. And if you plot blood levels versus time, you also get AUC (area under the curve), which is a measure of the total exposure that a given dose provides. There are a lot of ways these measurements can play out: a very quickly absorbed drug will have an early Tmax and a large Cmax, for example, but that concentration might come back down quickly, too, which could lead to a lower AUC than a formulation of the same drug (at the same nominal dose) that came on more slowly and spread out over a longer time period. To add to the fun, some drugs have efficacy that's more driven by how high their Cmax values can get, while others are more driven by how large the AUCs are. And in the case of bupropion/Wellbutrin, there's an additional complication: some of the drug's efficacy is due to a metabolite, a further compound produced in the liver after dosing, and such metabolites have their own PK profiles, too.
So in this case, it turns out that the AUC just missed on the low side. The FDA wants the statistical 90% confidence interval to fall between 80 and 125% compared to the original drug, and in this case the 90% CI was 77-96%. The Cmax was definitely lower, too - 90% CI was 65-87% of the branded product. And while the agency doesn't provide numbers for the metabolite, they also state that it missed meeting the standards as well. There are drugs, it should be said, that would still be effective at these levels, but Wellbutrin clearly isn't one of them.
My own take is that the FDA was willing to consider the adverse reports as just the usual noisy clinical situation with an antidepressant until the other generics were approved, at which point it became clear that the problems were clustering around the Impax/Teva product. Here's how the FDA addresses the "Why didn't we find out about this earlier?" question:
Q17. In retrospect, were FDA’s decisions regarding the approval and ongoing monitoring of Budeprion XL 300 mg appropriate?
A17. A less cautious approach in studying the bioequivalence of Budeprion XL 300 mg could have brought the data to light earlier. The FDA-sponsored study was completed only weeks ago, which is a very short time for data from a clinical experiment to be announced to the public.
Bupropion is associated with a risk for seizures, which was the basis of the Agency's cautious approach with regard to the early Budeprion XL bioequivalence studies, in which data were extrapolated from Budeprion XL 150 mg in patients to the projected consequences of exposure to Budeprion 300 mg. In retrospect, it is clear that this extrapolation did not provide the right conclusion regarding bioequivalence of Budeprion XL 300 mg. FDA also has much more knowledge today of the seizure-associated risk of bupropion-containing drugs. The trial design of the sponsor-initiated study of 2007 could have been successful, had it been replaced by the trial design employed in the recent FDA-sponsored study.
Of course, the trial design in the sponsor-initiated study of 2007 was that requested by the FDA. But Teva, for their part, does not appear to have been a ball of fire in getting that study recruited and completed, either. It's quite possible, though, that they couldn't round up enough patients who'd had trouble with the generic switch and were also willing to go back and experience that again in the cause of science. Overall, I think that the FDA is more on the hook here for letting things go on as long as they did, but there's plenty of blame to go around.
Still, I find this post at Forbes to be full of unnecessary hyperventilation. You wouldn't know, from reading it, that the FDA initially waived the requirement for 300mg testing in this case because of the risk of seizures. There's a line in there about how the agency is making patients their guinea pigs by not testing at the higher dose, but you could have scored the same debating points after a 300mg study that harmed its patients, which is what it looked at the time would happen. You also wouldn't know that the other generic 300mg formulations don't seem to have been associated with increased adverse-event reports, either.
And that post makes much of the way that these bioequivalence tests are left up the manufacturers. That they are: but if you want to change that, you're going to have to (1) fund the FDA at a much higher level, and (2) wait longer for generic switches to occur. The generic manufacturers will run these tests at the absolute first possible moment, since they want to get onto the market. The FDA will run them when they get around to it; they don't have the same incentives at all. Their incentives, in fact, oscillate between "Don't approve - there might be trouble" and "Definitely approve - we might be missing out on benefit". The winds of fortune blow the line between those two around all the time.
In this case, I think the FDA should have exercised its court-of-last-resort function earlier and more forcefully. But that's easy for me to say, sitting where I am. I don't have to see the mass of noisy adverse event reports coming in over the transom day after day. If the agency acted immediately and forcefully on every one, we'd have no drugs on the market at all. There's a middle ground, but boy, is it hard to find.
+ TrackBacks (0) | Category: Clinical Trials | Regulatory Affairs | The Central Nervous System
October 8, 2012
It hasn't been good over at Targacept. They had a big antidepressant failure a while back, and last month ended development of an ADHD drug, the nicotinic acetylcholine receptor ligand TC-5619.
They cut back staff back in the spring, and the CEO departed. Now the expected has happened: the company has apparently laid off everyone in research, and is conserving what cash it has to try to get something to the deal-making point. A sad, but familiar story in this business. . .sometimes companies come back after this point, and sometimes the event horizon turns out to have been passed.
+ TrackBacks (0) | Category: Business and Markets | The Central Nervous System
October 5, 2012
Ethan Perlstein at Princeton is the main author of this research on sertraline that I blogged about earlier this year. Now he's looking to crowdfund his next research project, on the neuronal effects of amphetamines. He's trying to raise $25,000 to do radiolabeling and electron microscopy studies, which would make this the largest crowdfunding experiment in the sciences so far (but still, I might add, small change compared to the sorts of grants that much of academia spends its time trying to line up).
What he's looking at is 2 to 3 months of work for one MS-level scientist. In this post he describes some of the reactions he's had to the idea so far, and lists the benefits that donors will receive, according to the amounts they contribute. That list is a real eye-opener, let me tell you - it's a different world we're entering, or trying to enter, at any rate. For example: "$100 or higher – You’ll get a hearty thanks in person, and the opportunity to talk science over a round of beer or glass of wine at a NYC watering hole one night after work, or when you visit NYC within the next 6 months." Or how about this one: "$1,000 or higher – Attend up to 2 lab meetings during the project and 1 publication brainstorming session at the end of the project. You will also receive access to a Google Doc during the manuscript writing stage. Supporters who contribute substantially to the final manuscript may receive co-authorship."
Needless to say, I'm going to watch this with great interest. The projects that can be funded at this level (with some expectation of producing something useful) are, perhaps, special cases, but it's the principle of the thing that intrigues me the most. That's why I'm also putting this one in the "Business and Markets" category, because asking for donations like this is a pure market activity. As a person with a pronounced free-market bias, I'm very much wondering how this will all play out. Thoughts?
Update: Wavefunction has a post on this here.
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September 20, 2012
Swamped with all sorts of stuff today - when science marches on, you have to make sure that it's not leaving its bootprints on your back. But I do have some interesting links:
The bluest of blue-sky brain research, funded by Paul Allen. Fascinating stuff, on several levels - here's a big publication that came out this week. I find the phenomenon of tech-billionaire funding for things like this, asteroid mining, low-cost orbital access and the like very encouraging. (And of course, the Gates Foundation is doing a lot in more earthbound pursuits).
The Wall Street Journal reveals what is apparently a rather ill-kept secret: most firms funded by venture capital fail. "Most", as in about 3 out of 4. That's a loose definition, though - as the article says, if you're talking total wipeout of capital, then that's about one third of them. If you're talking about failing to see the projected return in the projected time, well, that's over 90%. But it's all about the ones that succeed, just like the drug business.
The Royal Society of Chemistry, in a rather self-congratulatory press release, pledges money to help authors publish their work open-access in RSC journals. The UK government is putting money into this, but no one's sure if it'll be enough.
Do you want to make this compound? No? Neither do I. Especially not when they turn around and stick three more nitro groups onto it.
+ TrackBacks (0) | Category: Business and Markets | The Central Nervous System | The Scientific Literature
August 31, 2012
Eli Lilly has been getting shelled with bad news recently. There was the not-that-encouraging-at-all failure of its Alzheimer's antibody solanezumab to meet any of its clinical endpoints. But that's the good news, since that (at least according to the company) it showed some signs of something in some patients.
We can't say that about pomaglumetad methionil (LY2140023), their metabotropic glutamate receptor ligand for schizophrenia, which is being halted. The first large trial of the compound failed to meet its endpoint, and an interim analysis showed that the drug was unlikely to have a chance of making its endpoints in the second trial. It will now disappear, as will the money spent on it so far. (The first drug project I ever worked on was a backup for an antipsychotic with a novel mechanism, which also failed to do a damned thing in the clinic, and which experience perhaps gave me some of the ideas I have now about drug research).
This compound is an oral prodrug of LY404039, which has a rather unusual structure. The New York Times did a story about the drug's development a few years ago, which honestly makes rather sad reading in light of the current news. It was once thought to have great promise. Note the cynical statement in that last link about how it really doesn't matter if the compound works or not - but you know what? It did matter in the end. This was the first compound of its type, an attempt at a real innovation through a new mechanism to treat mental illness, just the sort of thing that some people will tell you that the drug industry never gets around to doing.
And just to round things off, Lilly announced the results of a head-to-head trial of its anticoagulant drug Effient versus (now generic) Plavix in acute coronary syndrome. This is the sort of trial that critics of the drug industry keep saying never gets run, by the way. But this one was, because Plavix is the thing to beat in that field - and Effient didn't beat it, although there might have been an edge in long-term followup.
Anticoagulants are a tough field - there are a lot of patients, a lot of money to be made, and a lot of room (in theory) for improvement over the existing agents. But just beating heparin is hard enough, without the additional challenge of beating cheap Plavix. It's a large enough patient population, though, that more than one drug is needed because of different responses.
There have been a lot of critics of Lilly's research strategy over the years, and a lot of shareholders have been (and are) yelling for the CEO's head. But from where I sit, it looks like the company has been taking a lot of good shots. They've had a big push in Alzheimer's, for example. Their gamma-secretase inhibitor, which failed in terrible fashion, was a first of its kind. Someone had to be the first to try this mechanism out; it's been a goal of Alzheimer's research for over twenty years now. Solanezumab was a tougher call, given the difficulties that Elan (and Wyeth/Pfizer, J&J, and so on) have had with that approach over the years. But immunology is a black box, different antibodies do different things in different people, and Lilly's not the only company trying the same thing. And they've been doggedly pursuing beta-secretase as well. These, like them or not, are still some of the best ideas that anyone has for Alzheimer's therapy. And any kind of win in that area would be a huge event - I think that Lilly deserves credit for having the nerve to go after such a tough area, because I can tell you that I've been avoiding it ever since I worked on it in the 1990s.
But what would I have spent the money on instead? It's not like there are any low-risk ideas crowding each other for attention. Lilly's portfolio is not a crazy or stupid one - it's not all wild ideas, but it's not all full of attempts to play it safe, either. It looks like the sort of thing any big (and highly competent) drug research organization could have ended up with. The odds are still very much against any drug making it through the clinic, which means that having three (or four, or five) in a row go bad on you is not an unusual event at all. Just a horribly unprofitable one.
+ TrackBacks (0) | Category: Cardiovascular Disease | Clinical Trials | Drug Development | Drug Industry History | The Central Nervous System
August 14, 2012
I wrote here about Ampyra, the multiple sclerosis drug from Acorda Therapeutics, one that came close to the record for "simplest chemical matter in a marketed drug". (As it happens, Biogen Idec is making sure that it doesn't even have the title of "simplest drug for multiple sclerosis", and the shadow of valproic acid looms over this entire competition).
That post mentioned some doubts that had been expressed about how effective Ampyra is for its target: improving gait in MS patients. And now those doubts are increasing, because the company has been asked to conduct a trial of a lower 5 mg dose of the drug along with the approved 10 mg one (which was associated with seizures in some patients). And neither one of them met the primary endpoint. As that link shows, the company has several explanations - different endpoint than used before, higher placebo response than usual, wider variety of patients - but those are all ex post facto. Acorda wouldn't have set up the trial like this in the first place if they didn't think that the approved dose would work, and it didn't.
For a drug with a rather narrow symptomatic indication, that's not good news. And it comes as Acorda is still trying to get the compound approved in Europe. The cost/benefit ratio usually can't stand a big hit to the "benefit" term.
+ TrackBacks (0) | Category: Clinical Trials | Regulatory Affairs | The Central Nervous System
August 9, 2012
The British Medical Journal says that the "widely touted innovation crisis in pharmaceuticals is a myth". The British Medical Journal is wrong.
There, that's about as direct as I can make it. But allow me to go into more detail, because that's not the the only thing they're wrong about. This is a new article entitled "Pharmaceutical research and development: what do we get for all that money?", and it's by Joel Lexchin (York University) and Donald Light of UMDNJ. And that last name should be enough to tell you where this is all coming from, because Prof. Light is the man who's publicly attached his name to an estimate that developing a new drug costs about $43 million dollars.
I'm generally careful, when I bring up that figure around people who actually develop drugs, not to do so when they're in the middle of drinking coffee or working with anything fragile, because it always provokes startled expressions and sudden laughter. These posts go into some detail about how ludicrous that number is, but for now, I'll just note that it's hard to see how anyone who seriously advances that estimate can be taken seriously. But here we are again.
Light and Lexchin's article makes much of Bernard Munos' work (which we talked about here), which shows a relatively constant rate of new drug discovery. They should go back and look at his graph, because they might notice that the slope of the line in recent years has not kept up with the historical rate. And they completely leave out one of the other key points that Munos makes: that even if the rate of discovery were to have remained linear, the costs associated with it sure as hell haven't. No, it's all a conspiracy:
"Meanwhile, telling "innovation crisis" stories to politicians and the press serves as a ploy, a strategy to attract a range of government protections from free market, generic competition."
Ah, that must be why the industry has laid off thousands and thousands of people over the last few years: it's all a ploy to gain sympathy. We tell everyone else how hard it is to discover drugs, but when we're sure that there are no reporters or politicians around, we high-five each other at how successful our deception has been. Because that's our secret, according to Light and Lexchin. It's apparently not any harder to find something new and worthwhile, but we'd rather just sit on our rears and crank out "me-too" medications for the big bucks:
"This is the real innovation crisis: pharmaceutical research and development turns out mostly minor variations on existing drugs, and most new drugs are not superior on clinical measures. Although a steady stream of significantly superior drugs enlarges the medicine chest from which millions benefit, medicines have also produced an epidemic of serious adverse reactions that have added to national healthcare costs".
So let me get this straight: according to these folks, we mostly just make "minor variations", but the few really new drugs that come out aren't so great either, because of their "epidemic" of serious side effects. Let me advance an alternate set of explanations, one that I call, for lack of a better word, "reality". For one thing, "me-too" drugs are not identical, and their benefits are often overlooked by people who do not understand medicine. There are overcrowded therapeutic areas, but they're not common. The reason that some new drugs make only small advances on existing therapies is not because we like it that way, and it's especially not because we planned it that way. This happens because we try to make big advances, and we fail. Then we take what we can get.
No therapeutic area illustrates this better than oncology. Every new target in that field has come in with high hopes that this time we'll have something that really does the job. Angiogenesis inhibitors. Kinase inhibitors. Cell cycle disruptors. Microtubules, proteosomes, apoptosis, DNA repair, metabolic disruption of the Warburg effect. It goes on and on and on, and you know what? None of them work as well as we want them to. We take them into the clinic, give them to terrified people who have little hope left, and we watch as we provide with them, what? A few months of extra life? Was that what we were shooting for all along, do we grin and shake each others' hands when the results come in? "Another incremental advance! Rock and roll!"
Of course not. We're disappointed, and we're pissed off. But we don't know enough about cancer (yet) to do better, and cancer turns out to be a very hard condition to treat. It should also be noted that the financial incentives are there to discover something that really does pull people back from the edge of the grave, so you'd think that we money-grubbing, public-deceiving, expense-padding mercenaries might be attracted by that prospect. Apparently not.
The same goes for Alzheimer's disease. Just how much money has the industry spent over the last quarter of a century on Alzheimer's? I worked on it twenty years ago, and God knows that never came to anything. Look at the steady march, march, march of failure in the clinic - and keep in mind that these failures tend to come late in the game, during Phase III, and if you suggest to anyone in the business that you can run an Alzheimer's Phase III program and bring the whole thing in for $43 million dollars, you'll be invited to stop wasting everyone's time. Bapineuzumab's trials have surely cost several times that, and Pfizer/J&J are still pressing on. And before that you had Elan working on active immunization, which is still going on, and you have Lilly's other antibody, which is still going on, and Genentech's (which is still going on). No one has high hopes for any of these, but we're still burning piles of money to try to find something. And what about the secretase inhibitors? How much time and effort has gone into beta- and gamma-secretase? What did the folks at Lilly think when they took their inhibitor way into Phase III only to find out that it made Alzheimer's slightly worse instead of helping anyone? Didn't they realize that Professors Light and Lexchin were on to them? That they'd seen through the veil and figured out the real strategy of making tiny improvements on the existing drugs that attack the causes of Alzheimer's? What existing drugs to target the causes of Alzheimer are they talking about?
Honestly, I have trouble writing about this sort of thing, because I get too furious to be coherent. I've been doing this sort of work since 1989, and I have spent the great majority of my time working on diseases for which no good therapies existed. The rest of the time has been spent on new mechanisms, new classes of drugs that should (or should have) worked differently than the existing therapies. I cannot recall a time when I have worked on a real "me-too" drug of the sort of that Light and Lexchin seem to think the industry spends all its time on.
That's because of yet another factor they have not considered: simultaneous development. Take a look at that paragraph above, where I mentioned all those Alzheimer's therapies. Let's be wildly, crazily optimistic and pretend that bapineuzumab manages to eke out some sort of efficacy against Alzheimer's (which, by the way, would put it right into that "no real medical advance" category that Light and Lexchin make so much of). And let's throw caution out the third-floor window and pretend that Lilly's solanezumab actually does something, too. Not much - there's a limit to how optimistic a person can be without pharmacological assistance - but something, some actual efficacy. Now here's what you have to remember: according to people like the authors of this article, whichever of these antibodies that makes it though second is a "me-too" drug that offers only an incremental advance, if anything. Even though all this Alzheimer's work was started on a risk basis, in several different companies, with different antibodies developed in different ways, with no clue as to who (if anyone) might come out on top.
All right, now we get to another topic that articles like this latest one are simply not complete without. That's right, say it together: "Drug companies spend a lot more on marketing than they do on research!" Let's ignore, for the sake of argument, the large number of smaller companies that spend all of their money on R&D and none on marketing, because they have nothing to market yet. Let's even ignore the fact that over the years, the percentage of money being spent on drug R&D has actually been going up. No, let's instead go over this in a way that even professors at UMDNJ and York can understand it:
Company X spends, let's say, $10 a year on research. (We're lopping off a lot of zeros to make this easier). It has no revenues from selling drugs yet, and is burning through its cash while it tries to get its first on onto the market. It succeeds, and the new drug will bring in $100 dollars a year for the first two or three years, before the competition catches up with some of the incremental me-toos that everyone will switch to for mysterious reasons that apparently have nothing to do with anything working better. But I digress; let's get back to the key point. That $100 a year figure assumes that the company spends $30 a year on marketing (advertising, promotion, patient awareness, brand-building, all that stuff). If the company does not spend all that time and effort, the new drug will only bring in $60 a year, but that's pure profit. (We're going to ignore all the other costs, assuming that they're the same between the two cases).
So the company can bring in $60 dollars a year by doing no promotion, or it can bring in $70 a year after accounting for the expenses of marketing. The company will, of course, choose the latter. "But," you're saying, "what if all that marketing expense doesn't raise sales from $60 up to $100 a year?" Ah, then you are doing it wrong. The whole point, the raison d'etre of the marketing department is to bring in more money than they are spending. Marketing deals with the profitable side of the business; their job is to maximize those profits. If they spend more than those extra profits, well, it's time to fire them, isn't it?
R&D, on the other hand, is not the profitable side of the business. Far from it. We are black holes of finance: huge sums of money spiral in beyond our event horizons, emitting piteous cries and futile streams of braking radiation, and are never seen again. The point is, these are totally different parts of the company, doing totally different things. Complaining that the marketing budget is bigger than the R&D budget is like complaining that a car's passenger compartment is bigger than its gas tank, or that a ship's sail is bigger than its rudder.
OK, I've spend about enough time on this for one morning; I feel like I need a shower. Let's get on to the part where Light and Lexchin recommend what we should all be doing instead:
What can be done to change the business model of the pharmaceutical industry to focus on more cost effective, safer medicines? The first step should be to stop approving so many new drugs of little therapeutic value. . .We should also fully fund the EMA and other regulatory agencies with public funds, rather than relying on industry generated user fees, to end industry’s capture of its regulator. Finally, we should consider new ways of rewarding innovation directly, such as through the large cash prizes envisioned in US Senate Bill 1137, rather than through the high prices generated by patent protection. The bill proposes the collection of several billion dollars a year from all federal and non-federal health reimbursement and insurance programmes, and a committee would award prizes in proportion to how well new drugs fulfilled unmet clinical needs and constituted real therapeutic gains. Without patents new drugs are immediately open to generic competition, lowering prices, while at the same time innovators are rewarded quickly to innovate again. This approach would save countries billions in healthcare costs and produce real gains in people’s health.
One problem I have with this is that the health insurance industry would probably object to having "several billion dollars a year" collected from it. And that "several" would not mean "two or three", for sure. But even if we extract that cash somehow - an extraction that would surely raise health insurance costs as it got passed along - we now find ourselves depending on a committee that will determine the worth of each new drug. Will these people determine that when the drug is approved, or will they need to wait a few years to see how it does in the real world? If the drug under- or overperforms, does the reward get adjusted accordingly? How, exactly, do we decide how much a diabetes drug is worth compared to one for multiple sclerosis, or TB? What about a drug that doesn't help many people, but helps them tremendously, versus a drug that's taken by a lot of people, but has only milder improvements for them? What if a drug is worth a lot more to people in one demographic versus another? And what happens as various advocacy groups lobby to get their diseases moved further up the list of important ones that deserve higher prizes and more incentives?
These will have to be some very, very wise and prudent people on this committee. You certainly wouldn't want anyone who's ever been involved with the drug industry on there, no indeed. And you wouldn't want any politicians - why, they might use that influential position to do who knows what. No, you'd want honest, intelligent, reliable people, who know a tremendous amount about medical care and pharmaceuticals, but have no financial or personal interests involved. I'm sure there are plenty of them out there, somewhere. And when we find them, why stop with drugs? Why not set up committees to determine the true worth of the other vital things that people in this country need each day - food, transportation, consumer goods? Surely this model can be extended; it all sounds so rational. I doubt if anything like it has ever been tried before, and it's certainly a lot better than the grubby business of deciding prices and values based on what people will pay for things (what do they know, anyway, compared to a panel of dispassionate experts?)
Enough. I should mention that when Prof. Light's earlier figure for drug expense came out that I had a brief correspondence with him, and I invited him to come to this site and try out his reasoning on people who develop drugs for a living. Communication seemed to dry up after that, I have to report. But that offer is still open. Reading his publications makes me think that he (and his co-authors) have never actually spoken with anyone who does this work or has any actual experience with it. Come on down, I say! We're real people, just like you. OK, we're more evil, fine. But otherwise. . .
+ TrackBacks (0) | Category: "Me Too" Drugs | Business and Markets | Cancer | Drug Development | Drug Industry History | Drug Prices | The Central Nervous System | Why Everyone Loves Us
August 8, 2012
There doesn't seem to be any mention of it on their web site, but the Neurosciences Institute in San Diego/La Jolla may be closing up shop. A reader received an e-mail about a lab equipment auction at that address, and sure enough, there's an "online lab liquidation auction" being held by BioSurplus. They mention in passing that ". . .The Institute is now shutting down its lab spaces", but I can't find any other mention of what's happened.
+ TrackBacks (0) | Category: The Central Nervous System
July 27, 2012
One of the hazards of medicinal chemistry - or should I say, one of the hazards of long experience in medicinal chemistry - is that you start to think that you know more than you do. Specifically, after a few years and a few projects, you've seen plenty of different compounds and their activities (or lack thereof). Human brains categorize things and seek patterns, so it's only natural that you develop a mental map of the chemical space you've encountered. Problem is, any such map has to be incomplete, grievously incomplete, and if you start making too many decisions based on it (rather than on actual data), you can miss out on some very useful things.
Here's a case in point: an assay against cancer stem cells, which have been a hot research area for some time now. It may well be that some classes of tumor are initiated and then driven by such cells, in which case killing them off or inactivating them would be a very good thing indeed. This was an interesting assay, because it included control stem cells to try to differentiate between compounds that would have an effect on the neoplasm-derived cells while leaving the normal ones alone.
And what did they find? Thioridiazine is what - an old-fashioned phenothiazine antipsychotic drug. For reasons unknown, it's active against these cancer stem cells. When the authors did follow-up screening, two other compounds of this class also showed up active: fluphenazine and prochlorperazine, so I'd certainly say that this is real.
And it appears that it might actually be the compounds' activity against dopamine receptors that drives this assay. The authors found that there's a range of dopamine receptor expression in such cells, and that this correlates with the activity of the phenothiazine compounds. That's quite interesting, but it complicates life quite a bit for running assays:
Our observations of differential DR expression between normal and neoplastic patient samples strongly suggest human CSCs are heterogeneous and drug targeting should be based on molecular pathways instead of surrogate phenotypic markers.
Working out molecular pathways is hard; a lot more progress might be made at this stage of the game by running phenotypic assays - but not if they're against a heterogeneous cell population. That way lies madness.
Interesting, the phenothiazines had been reported to show some anti-cancer effects, and schizophrenic patients receiving such drugs had been reported to show lower incidences of some forms of cancer. These latest observations might well be the link between all these things, and seem to represent the only tractable small-molecule approach (so far) targeting human cancer stem cells.
But you have to cast your net wide to find such things. Dopamine receptors aren't the most obvious thing to suspect here, and ancient antipsychotics aren't the most obvious chemical matter to screen. Drop your preconceptions at the door, is my advice.
+ TrackBacks (0) | Category: Cancer | Drug Assays | The Central Nervous System
June 25, 2012
Here's another reminder that we don't know what a lot of existing drugs are doing on the side. This paper reports that the kinase inhibitor Nexavar (sorafenib) is actually a pretty good ligand at 5-HT (serotinergic) receptors, which is not something that you'd have guessed at all.
The authors worked up a binding model for the 5-HT2a receptor and ran through lists of known drugs. Sorafenib was flagged, and was (experimentally) a 2 micromolar antagonist. As it turns out, though, it's an even strong ligand for 5-HT2b (57 nM!) and 5-HT2c (417 nM), with weaker activity on a few other subtypes. This makes a person wonder about the other amine GPCR receptors, since there's often some cross-reactivity with small molecule ligands. (Those, though, often have good basic tertiary amines in them, carrying a positive charge under in vivo conditions. Sorafenib lacks any such thing, so it'll be interesting to see the results of further testing). It's also worth wondering if these serotinergic activities help or hurt the drug in oncology indications. In case you're wondering, the compound does get into the brain, although it's significantly effluxed by the BCRP transporter.
What I also find interesting is that this doesn't seem to have been picked up by some of the recent reports on attempts to predict and data-mine potential side effects. We still have a lot to learn, in case anyone had any doubts.
+ TrackBacks (0) | Category: Cancer | Drug Assays | The Central Nervous System | Toxicology
May 29, 2012
Update: Immune Response Biopharma CEO David Buswell has left a detailed comment to this point, pointing out that it was his company that ended talks with GSK, and not the other way around. See here for the details.
GlaxoSmithKline has decided not to pursue further development of a potential vaccine therapy for multiple sclerosis, dumping former partner Immune Response BioPharma. We get that sort of headline all the time in this business - deals come, and deals go. What we don't get are press releases like these. The full unaltered text:
"Immune Response BioPharma, Inc. has the first MS Vaccine a first in class and best in class multiple sclerosis drug which restores deficient FOXP3+ T-Regs. GSK has no approved MS drug and probably will never have one they are busy wasting their shareholders money on HGSI and a Lupus drug with poor sales, we don't need them or to give away our blockbuster drug for MS to them which we believe will become treatment of choice" IRBP CEO Mr. Buswell
"IRBP values NeuroVax north of a billion dollar of annual sales once approved. We will find a solid partner or raise capital on our own, we don't need GSK which has zer0 experience in multiple sclerosis or auto-immune diseases. GSK is a joke and seems very ignorant on how multiple sclerosis drugs work and how to develop one, we gave them a chance to develop NeuroVax but their management appears to be very poor. We have decided to terminate any collaboration or development with GSK. GSK is a loser in the MS market and will continue to be a loser" IRBP CEO Mr. Buswell
Y'know, in his way, this CEO is a breath of fresh air. Everyone thinks these things in such situations, but not many people put them out on the PR wires. This release seems to have transcribed directly from Mr. Buswell's (no doubt heated) statements at the time, which I'm sure accounts for the take-a-breath grammar. I'll follow NeuroVax's progress with interest to see who has the last laugh this time. . .
+ TrackBacks (0) | Category: Business and Markets | The Central Nervous System
May 16, 2012
How much do we really know about what small drug molecules do when they get into cells? Everyone involved in this sort of research wonders about this question, especially when it comes to toxicology. There's a new paper out in PLoS One that will cause you to think even harder.
The researchers (from Princeton) looked at the effects of the antidepressant sertraline, a serotonin reuptake inhibitor. They did a careful study in yeast cells on its effects, and that may have some of you raising your eyebrows already. That's because yeast doesn't even have a serotonin transporter. In a perfect pharmacological world, sertraline would do nothing at all in this system.
We don't live in that world. The group found that the drug does enter yeast cells, mostly by diffusion, with a bit of acceleration due to proton motive force and some reverse transport by efflux pumps. (This is worth considering in light of those discussions we were having here the other day about transport into cells). At equilibrium, most (85 to 90%) of the sertaline that makes it into a yeast cell is stuck to various membranes, mostly ones involved in vesicle formation, either through electrostatic forces or buried in the lipid bilayer. It's not setting off any receptors - there aren't any - so what happens when it's just hanging around in there?
More than you'd think, apparently. There's enough drug in there to make some of the membranes curve abnormally, which triggers a local autophagic response. (The paper has electron micrographs of funny-looking Golgi membranes and other organelles). This apparently accounts for the odd fact, noticed several years ago, that some serotonin reuptake inhibitors have antifungal activity. This probably applies to the whole class of cationic amphiphilic/amphipathic drug structures.
The big question is what happens in mammalian cells at normal doses of such compounds. These may well not be enough to cause membrane trouble, but there's already evidence to the contrary. A second big question is: does this effect account for some of the actual neurological effects of these drugs? And a third one is, how many other compounds are doing something similar? The more you look, the more you find. . .
+ TrackBacks (0) | Category: Drug Assays | Pharmacokinetics | The Central Nervous System | Toxicology
April 23, 2012
We should expect to see more of this sort of thing. The Wall Street Journal headline says it all: "Frustrated ALS Patients Concoct Their Own Drug". In this case, the drug appears to be sodium chlorite, which is under investigation as NP001 by Neuraltus Pharmaceuticals in Palo Alto. (Let's hope that isn't one of their lead structures at the top of their web site).
It is an accepted part of scientific lore that scientists sometimes use themselves in experiments, and cancer patients and others with life-threatening illnesses are known to self-medicate using concoctions of vitamins, special teas, and off-label medications. But the efforts of patients with ALS to come up with a home-brewed version of a drug still in early-stage clinical trials and not approved by the FDA is one of the most dramatic examples of how far the phenomenon of do-it-yourself science has gone.
A number of patients who have been involved in the Phase II trials of NP001 have been sharing information about it, and they and others have dug into the literature enough to be pretty sure that what Neuraltus is investigating is, indeed, some formulation of sodium chlorite. Here's one of them:
Mr. Valor first read about NP001 in a news release. He tracked down published papers that led him to believe the compound was sodium chlorite, a chemical that in various forms is used in municipal water treatment plants. A friend found online the scientists' patent filings. He also consulted an engineer in water treatment to learn more and read environmental reports to get insight into toxicity levels. The chemical is easy to order online and is inexpensive. He estimates he has spent less than $150 total.
Mixed in distilled water, the sodium chlorite is delivered through Mr. Valor's feeding tube three days a week, one week per month. He says he cautions participants that the chemical isn't as efficacious as NP001 and "that this is only to buy time until NP001 is available to all."
This case is the prefect situation for something like this to happen: a terrible disease, with an unfortunately fast clinical course, rare enough for a good fraction of the patient population to be very organized, along with an easily-available active agent. If NP001 were some sort of modified antibody, we wouldn't be having this discussion (although eventually, who knows?) And as much as I agree that Phase II and Phase III trials are necessary to find out if something really works or not, if I had ALS myself, I'd be doing what these people are doing, and if it were a family member affected, I'd be helping them mix the stuff up. With a condition like ALS, honestly, the risk/benefit ratio is pretty skewed.
If NP001 progresses, look for comment along the lines of "How can this little company get a patent on the use of this common chemical for this dread disease?" But as the WSJ article reports, the sodium chlorite mixtures that people are whipping up in their kitchens don't seem to be as effective as whatever NP001 is, for one thing. And Neuraltus is basically much of their existence on whether it works or not; they're taking on the risk and trouble of a proper investigation, and good for them. But it's true that many people who have ALS right now will not be around to see the end of a Phase III trial, and I can't blame them at all for doing whatever they can to try to get some of the benefits of this research in the interim.
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
March 2, 2012
I (and many of the readers here) have long thought that stem cells are perhaps the most overhyped medical technology out there - at least for now. I definitely agree that the possibilities for their use are staggering, and I very much hope that some of these pan out, but the gap between those possibilities and the current reality is just as huge. And it's a gap that really shows how hard medical progress is compared to how hard it is in the public imagination.
Nature has an article that bears on this, and on some other important topics. They've found that stem cell treatments are being sold to patients in Texas.
(The investigation) suggests that (Celltex Therapeutics) has supplied adult stem cells to Texas doctors who offer unproven treatments to patients, and that the company is involved in these treatments. One doctor claims that the treatments are part of a clinical study run by Celltex and that the company pays him US$500 a time to inject the cells into patients, who are charged up to $25,000 for a course. The US Food and Drug Administration (FDA) considers it to be a crime to inject unapproved adult stem cells into patients. David Eller, chief executive of Celltex, denies that the company is involved in treatment procedures, but would not comment on Nature's findings about how its cells are used or answer questions about them.
This makes me wonder about what is going on down there in Texas (and I can tell you, as an Arkansan, I'm willing to believe just about anything in that department). This latest business reminds me of the Burzynski cancer treatment stuff, in the way that definitions of "clinical trial" are stretched like rubber bands. Personally, I think that clinical trials are supposed to follow something very much like Yog's Law in publishing ("Money flows towards the writer"). If you're being asked to put up all kinds of money to get your book edited and published, you're very likely being scammed. And if you're being asked to pay thousands of dollars to be in a "clinical trial", well. . .you're being sold something. Real clinical trials reimburse their patients for time and effort, with money and/or medical care. They do not bill them for 25 long ones at the end of the dosing schedule
I should mention here that Slate also had an article up on Celltex, but there have been some problems. They've taken the piece down, citing editorial problems, but (as you'd figure), the cherchez le lawsuit rule applies here. Nature, though, doesn't seem to be getting sued for what they've written.
Now, back to the stem cell treatments. Among other things, Nature mentions a blog by a woman in Texas, who's written about her experiences being treated with adult stem cells from Celltex. It appears that she's receiving these treatments for multiple sclerosis, and was told that "This method has been successful with auto immune diseases such as Parkinson’s, arthritis, Multiple Sclerosis as well as others." She had apparently had a similar procedure done earlier in Mexico, but then:
". . .a friend told Larry about a doctor in Houston who went to South Korea two years ago for a stem cell transplant to treat the debilitating effects of psoriatic arthritis. He is now able to continue his medical practice, perform surgeries, and live without pain. Because our friends had noticed progress from my first stem cell transplant, they wanted us to know that Dr. Jones was now licensed to perform the procedure in Houston. To say the least, we were both excited about the possibilities and timing."
As that extract illustrates, at no point (that I have found) does this patient mention the phrase "clinical trial". One gets the strong impression, actually, that she believes that she is paying to undergo a new medical procedure, the latest thing, rather than participating in any kind of investigational study for a therapy that has not yet been reviewed by the FDA. The Nature writer, David Cyranoski, was able to speak with the physician involved, who says he's treated a number of people with cells from Celltex:
Lotfi says that most of his patients claim to get better after the treatment, but he admits that there is no scientific evidence that the cells are effective. “The scientific mind is not convinced by anecdotal evidence,” he acknowledges. “You need a controlled, double-blind study. But for many treatments, that's not possible. It would take years, and some patients don't have years.”
“The worst-case scenario is that it won't work,” he adds. “But it could be a panacea, from cosmetics to cancer.” He says that Celltex is conducting a trial in which patients “will be their own control”. “If you can compare before and after and show improvement, there's no need for a placebo,” he explains. “How can you charge people, and then give them a placebo?”
Indeed! Maybe you could try not charging them, and not making them spend their own money to find out whether your treatment is any good. Maybe you could get a large, statistically significant number of people together, who've been given thorough diagnostic workups, and give half of them the best standard of care for multiple sclerosis and half of them the stem cell treatment - at your expense - and see if they get better. How about that? (Oh, and just a little note - the worst case is not that nothing happens at all. It might be good for the people involved to think about that a bit).
This gets back to the discussions we've had around here about rethinking clinical trials. One of the things I'll say for the FDA is that they do force people to be rigorous, and to put new medical ideas to well-controlled tests. My worry about the "sell, then test" ideas was summed up in the first link in this paragraph: "I fear that there are any number of entrepreneurial types who would gladly stretch things out, as long as someone else is paying, in the hopes of finally seeing something useful. No one will - or should - pay for extending fishing expeditions." Read that Celltex article and see if that sounds familiar.
+ TrackBacks (0) | Category: Clinical Trials | Regulatory Affairs | The Central Nervous System | The Dark Side
February 10, 2012
Everyone who's done drug discovery has encountered this situation: you get what looks like a hit in a screening assay, but when you re-check it with fresh material, it turns out to be inactive. So you go back to the original batch, but it's still active. There are several possibilities: if that original batch was a DMSO solution, perhaps the compound has done something funny on standing, and you don't have what you thought you had. Maybe the DMSO stock was made from the wrong compound, or was mislabeled somehow - in which case, good luck figuring out what's really in there. If the original batch was a solid, the first thing to do is a head-to-head analysis (NMR, LC-mass spec) between the two. (That sort of purity check is actually the first thing you should do with interesting screening hits in general, as experienced chemists will have had several chances to learn).
But if those assay numbers repeat for both batches, you're in the realm of the Infinitely Active Impurity. The thinking is, and it's hard to find fault with it, that there must be something in Batch One that's causing the assay to light up, something that's not present in Batch Two. I found myself in this situation one time where the problem turned out to be that Batch One had the right structure, except it was a zinc complex, a fact the original submitters apparently hadn't appreciated. (We had to send out for metals analysis to confirm that one). In that case, the assay could be made to show a hit by adding zinc to most any compound you wanted, which wasn't too useful.
Most of the time, chasing after these things proves futile, which is frustrating for everyone involved. But not always. There's a recent example of a successful impurity hunt in ACS Medicinal Chemistry Letters, from a group at Pfizer searching for inhibitors of kynurenine aminotransferase II.
One of the hits was that compound 6 shown in the figure, but a second batch of it showed no activity at all. They dug into the original sample, and found that there was a touch of the N-hydroxy compound in it, and that was the reason for all the activity. Interestingly, it turns out that the amino group was involved in a covalent interaction with the enzyme's cofactor, pyridoxal-5′-phosphate (PLP). That's one of the things you probably want to suspect when you find such tiny amounts of a compound having such a large effect.
It's not a deal-breaker, but it's something to keep in mind. The whole topic of irreversible inhibitors has come up around here before, but it's worth another post soon, in light of the recent acquisition of Avila Pharmaceuticals, who specialized in this field. In this case, the compound isn't covalently attached to the protein, but rather to its bound cofactor, which would make people breath a bit easier. (And the group responsible for the covalency, an amine, isn't something to worry about, either).
Still, it's interesting to see this part of the paper:
"Although irreversible inhibition was not one of our lead criteria at the outset of the program, maintaining this attribute of 7 was a high priority through our optimization efforts. The potential advantages of irreversible inhibitors include low dose requirements and reduced off-target toxicity."
I say that because increased off-target toxicity has always been the worry with covalent drugs. But there's been a real revival of interest in the last few years - more on this next week.
+ TrackBacks (0) | Category: Drug Assays | The Central Nervous System
December 21, 2011
Not exactly a load of happy holiday news from AstraZeneca here - they're already facing one of the nastiest patent cliffs in the industry (second only, and arguably, to Eli Lilly), and now they've had still more development compounds crash out on them.
There's olaparib (AZN-), which is an inhibitor of the DNA repair pathway enzyme PARP, Poly-ADP ribose polymerase. There are a number of PARP inhibitors making their way through the clinic, but olaparib's performance can't be giving comfort to anyone else in the field. It looked promising a couple of years ago in an ovarian cancer trial, but that, folks, was only progression-free survival. As time went on, it became clear that there wasn't going to be any benefit in overall survival, and that's what the world cares about, as it should. The compound's still in trials against other forms of cancer, and who knows, it might have better effects there. Oncology is a crap shoot if ever there was one. But ovarian cancer was the big first hope for AZ, and that's been written off.
The other compound that's hit the skids recently was TC-5214, mecamylamine, a nicotinic antagonist, which would have been a new mechanism for depression. But not if it doesn't work, and the compound missed its primary endpoint in the clinic, as I wrote about here last month. That one came in from Targacept, as olaparib came in from KuDOS, and these results have people wondering in the press about what this says about AstraZeneca's whole inlicensing strategy.
The problem is, these are two fields (cancer and depression) that have very high failure rates no matter who's doing the inlicensing. And while it's true that AZ seems to have had a lot of bad luck, some of that might just be the normal course of events if you're targeting these conditions. Having it happen while your other patents are expiring is bad, of course, but being in a position to have to depend on these therapeutic areas is a tough place to be to start with. (Not that there are a lot of safe places to work, true, but these are especially tricky). And it leads to things like this:
“AstraZeneca seems to have had more than its fair share of misfortune when it comes to the development pipeline,” analysts at Barclays Capital in London wrote in a note to investors today. “Additional development failures increase the probability that management will reassess the likely return on investment from additional R&D investment and cut costs further.”
Well, that'll really make R&D more productive. . .
+ TrackBacks (0) | Category: Business and Markets | Cancer | The Central Nervous System
December 6, 2011
Neuroscience is a long-established graveyard for drug discovery - there are a lot of serious disorders there, but it's very hard to do anything about them. So the "unmet medical need" is being exacerbated by both of those factors at once.
And if you need some empirical proof of those assertions, look no farther than the press releases. GlaxoSmithKline and AstraZeneca have already bailed out of the field, and now it looks like Novartis is joining them. That doesn't leave too many big players, and there are two effects to that which come immediately to mind: that progress may slow down, because there's not as much money and effort going on, but that this leaves the door open for smaller organizations who can take advantage of any new discoveries and/or get lucky.
I spent the first eight or nine years of my med-chem career doing CNS, and am not overwhelmed by the desire to do it again - at least, not under standard drug-discovery conditions. But the rewards are still out there - on a high, high shelf - for those who want to try.
+ TrackBacks (0) | Category: Business and Markets | The Central Nervous System
December 5, 2011
You may remember Rexahn Pharmaceuticals being mentioned here in 2010. They're the company whose lead antidepressant drug Serdaxin showed no significance versus placebo in Phase IIa trials, and whose CEO (Dr. Ahn himself) then calmed the investment community by saying that the trial was never designed to show any statistical significance, anyway, and was therefore a success. You know, because it showed that patients could benefit from the drug, even though it didn't show that patients could benefit from the drug. You may think I'm exaggerating, but go back and read Ahn's statement and see if you still think that.
And when you do, you'll discover that Serdaxin is nothing else than clavulinic acid, the beta-lactamase inhibitor, and not the first thing you'd think of as a CNS agent. But Rexahn has pushed on to Phase IIb with it, and this time they seem to actually have been going all the way, looking for a statistically meaningful effect and everything. That hasn't gone so well, although the press release does what it can:
The randomized, double-blind, placebo-controlled study compared two doses of Serdaxin, 0.5 mg and 5 mg, to placebo over an 8-week treatment period. Results from the study did not demonstrate Serdaxin’s efficacy compared to placebo measured by the Montgomery-Asberg Depression Rating Scale (MADRS). All groups showed an approximate -14 point improvement in the protocol defined primary endpoint of MADRS. All groups had a substantial number of patients who demonstrated a meaningful clinical improvement from baseline. The study showed Serdaxin to be safe and well tolerated.
What really attracts me to this follow-up is another quote from Dr. Ahn: "These results contradict findings from previous studies of Serdaxin in depression, which is disappointing", he stated. Those previous studies, of course, are the ones that didn't reach significance, either, so I'd say that the latest results are right in line. But then, I have a different outlook on life. Serdaxin doesn't look like it'll do much for me, though.
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
November 22, 2011
I've been doing drug research since 1989 myself, which means that I'm fairly experienced. But Regeneron started in this business a year or two before I did, and they're just now getting their first major drug, Eylea (aflibercept) onto the market. To be fair, they did get approval for Araclyst (rilonacept) in 2008, but that one pays the electric bill and not much more - although that might be changing (see below).
As Andrew Pollack at the New York Times points out, the company has run through over two billion dollars over the years. I remember when they were working on nerve growth factors for ALS and other diseases, back in the early 1990s (I worked in the area briefly myself, to no good effect whatsoever). There are not a lot of nerve growth factor drugs on the market, although it seemed like a perfectly plausible mechanism for one back then.
That work shaded into another indication, ciliary neurotrophic factor for obesity. Regeneron spent a lot of time and money developing a modified form of that protein called Axokine, but in 2003 that project ran into the rocks. Some patients did lose weight on the drug (with daily injections), but too many of them developed antibodies to it, which raised the possibility of cross-reactivity with their own CNF, which would surely not have been a good thing. So much for Axokine.
But Eylea, a VEGF-based therapy for macular degeneration (entering the same space as Lucentis and Avastin), has now made it. And the company has another use for Arcalyst in preventative gout therapy coming along, and some interesting cholesterol work targeting PCSK9 in collaboration with Sanofi. So welcome, Regeneron, to the ranks of profitable biotech companies (well, pretty soon) who've developed their own products. It's taken a lot of time, a lot of patience - yours and your investors' - and a lot of cash. But you're still here, and how many other bioctech startups from the late 1980s can say that?
+ TrackBacks (0) | Category: Cardiovascular Disease | Diabetes and Obesity | Drug Industry History | Regulatory Affairs | The Central Nervous System
November 17, 2011
Just how different is one brain cell from another? I mean, every cell in our body has the same genome, so the differences in type (various neurons, glial cells) must be due to expression during development. And the differences between individual members of a class must be all due to local environment and growth - right?
Maybe not. I wasn't aware of this myself, but there's a growing body of evidence that suggests that neurons might actually differ more at the genomic level than you'd imagine. A lot of this work has come from the McConnell lab at the Salk Institute, where they've been showing that mouse precursor cells can develop into neurons with various chromosomal changes along the way. And instead of a defect (or an experimental artifact), he's hypothesized that this is a normal feature that helps to form the huge neuronal diversity seen in brain tissue.
His latest work used induced pluripotent cells transformed into neurons. Taking these cells from two different people, he found that the resulting neurons had highly variable sequences, with all sorts of insertions, deletions, and transpositions. (The precursor cells had some, too, but different ones, suggesting that the neural cell changes happened along the way). And this recent paper suggests that neurons have an unusual number of transposons in their DNA, which fits right in with McConnell's results.
The implication is that human brains are mosaics of mosaics, at the cell and sequence levels. And that immediately makes you wonder if these processes are involved in disease states (hard to imagine how they wouldn't be). The problem is, it's not too easy to get ahold of well-matched and well-controlled human brain tissue samples to check these ideas. But that's the obvious next step - take several similar-looking neurons and sequence them all the way. Obvious, but very difficult: single-cell sequencing is not so easy, to start with, and how exactly do you grab those single neurons out of the tangle of nerve tissue to sequence them? Someone's going to do this, but it's going to be a chore. (Note: McConnell's group was able to do the pluripotent-cell-derived stuff a bit more easily, since those come out clonal and give you more to work with).
Now, the idea that neurons are taking advantage of chromosomal instability to this degree is a little unnerving. That's because when you think of chromosomal instability, you think of cancer cells (See also the link in that last paragraph. It's interesting, as an aside, to see that those last two are to posts from this blog in 2002 - next year will mark ten years of this stuff! And I also enjoy seeing my remark from back then about "With headlines like this, I can't think why I'm not pulling in thousands of hits a day", since these days I'm running close to 20K/day as it is).
So, on some level, are our brains akin to tumor tissue? You really wonder why brain cancer isn't more common than it is, if these theories are correct. There may well be ways to get "controlled chromosomal instability", though, as opposed to the wild-and-woolly kind, but even the controlled kind is a bit scary. And all this makes me think of a passage from an old science fiction story by James Blish, "This Earth of Hours". The Earthmen have encountered a bizarre civilization that seems to involve many of the star systems toward the interior of the galaxy, and a captured human has informed them that these aliens apparently have no brains per se:
"No brains," the man from the Assam Dragon insisted. "Just lots of ganglia. I gather that's the way all of the races of the Central Empire are organized, regardless of other physical differences. That's what they mean when they say we're all sick - hadn't you realized that?"
"No," 12-Upjohn said in slowly dawning horror. "You had better spell it out."
"Why, they say that's why we get cancer. They say that the brain is the ultimate source of all tumors, and is itself a tumor. They call it 'hostile symbiosis.' "
"In the long run. Races that develop them kill themselves off. Something to do with solar radiation; animals on planets of Population II stars develop them, Population I planets don't."
The things you pick up reading 1950s science fiction. Blish, by the way, was an odd sort. He had a biology degree, and a liking for James Joyce, Oswald Spengler, and Richard Strauss. All of these things worked their ways into his stories, which were often much better and more complex than they strictly needed to be. Here's a PDF of "This Earth of Hours", if you're interested - it's not a perfect transcription, though; you'll have to take my word for it that the original has no grammatical errors. It's a good illustration of Blish's style - what appears at first to be a pulpy space-war story turns out to have a lot of odd background dropped into it, along with speculations like the above. And for someone who didn't always write a lot of descriptive prose, preferring to let philosophical points drive his plots, I find Blish's stories strangely vivid, particularly the relatively actionless ones like "Beep" or "Common Time". He's pretty thoroughly out of print these days, but you can find the paperbacks used, and in many cases as e-books. Now if you're looking for someone who always lets philosophical points drive his stores, then you'll be wanting some Borges. (As it happens, I've had occasion to discuss that particular translation with an Argentine co-worker. But this is not a literary blog, not for the most part, so I'll stop there!)
+ TrackBacks (0) | Category: Biological News | Book Recommendations | Cancer | The Central Nervous System
November 8, 2011
Bad news yesterday from Targacept, a small company that's been developing an antidepressant with AstraZeneca. TC-5214 (the S enantiomer of the nicotinic ligand mecamylamine) missed its endpoints in a trial of 295 patients in Europe who had not responded to standard drug therapy - the trial started with more like 700 patients, who received open-label therapy with one of the usual agents, and then they picked out the tough cases for the real trial, adding this compound to the standard regimens.
Seeing results in such a population is a very tall order, but that's why AZ and others were excited about the earlier Targacept data. The Phase II numbers were extraordinary. A compound that followed through on that promise would be huge. This piece by Adam Feuerstein gets across the excitement - people really couldn't believe what they were seeing.
And maybe they shouldn't have. The grumbling today, though, is taking an interesting turn. What you might not realize from reading about those Phase II results is that they were the result of a clinical trial in India. That's added an extra layer of can-we-trust-this-stuff to the usual despairing comments about Phase II/Phase III disconnects. This is an unusually brutal disconnect, because the earlier data were unusually good. So the muttering is not going to go away any time soon.
AstraZeneca says that they're committed to further studies of TC-5214, so we'll see what happens then. Depression is a tricky illness, and getting solid clinical data isn't easy. It's possible that this latest study just had some confounding variable that messed up the numbers - but then, it's possible that the earlier one did, too, and that, sad to say, is probably the way to bet. This is bad news for AZ, a company that needs all the help it can get, and downright catastrophic news for Targacept, as I'm sure their stock price will reflect. And it might even be bad news for India, and Indian clinical research.
Update: to drive the point home, Adam Feuerstein has posted this under the heading of "My punishment for getting TRGT wrong".
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
November 2, 2011
What is the deal with multiple sclerosis and small off-the-shelf molecules? Last year I wrote about Ampyra, which is 4-aminopyridine. Now Biogen is showing what looks like good results with BG-12, which is. . .dimethyl fumarate. See the Haystack blog for more. The same comments I made earlier about Ampyra's intellectual property situation apply here - it's just interesting to see that Biogen has a hand in both of these. What's next? Toluene?
+ TrackBacks (0) | Category: The Central Nervous System
October 18, 2011
Under the "Who'da thought?" category, put this news about cyclodextrin. For those outside the field, that's a ring of glucose molecules, strung end to end like a necklace. (Three-dimensionally, it's a lot more like a thick-cut onion ring - see that link for a picture). The most common form, beta-cyclodextrin, has seven glucoses. That structure gives it some interesting properties - the polar hydroxy groups are mostly around the edges and outside surface, while the inside is more friendly to less water-soluble molecules. It's a longtime additive in drug formulations for just that purpose - there are many, many examples known of molecules that fit into the middle of a cyclodextrin in aqueous solution.
But as this story at the Wall Street Journal shows, it's not inert. A group studying possible therapies for Niemann-Pick C disease (a defect in cholesterol storage and handling) was going about this the usual way - one group of animals was getting the proposed therapy, while the other was just getting the drug vehicle. But this time, the vehicle group showed equivalent improvement to the drug-treatment group.
Now, most of the time that happens when neither of them worked; that'll give you equivalence all right. But in this case, both groups showed real improvement. Further study showed that the cyclodextrin derivative used in the dosing vehicle was the active agent. And that's doubly surprising, since one of the big effects seen was on cholesterol accumulation in the central neurons of the rodents. It's hard to imagine that a molecule as big (and as polar-surfaced) as cyclodextrin could cross into the brain, but it's also hard to see how you could have these effects without that happening. It's still an open question - see that PLoS One paper link for a series of hypotheses. One way or another, this will provide a lot of leads and new understanding in this field:
Although the means by which CD exerts its beneficial effects in NPC disease are not understood, the outcome of CD treatment is clearly remarkable. It leads to delay in onset of clinical signs, a significant increase in lifespan, a reduction in cholesterol and ganglioside accumulation in neurons, reduced neurodegeneration, and normalization of markers for both autophagy and neuro-inflammation. Understanding the mechanism of action for CD will not only provide key insights into the cholesterol and GSL dysregulatory events in NPC disease and related disorders, but may also lead to a better understanding of homeostatic regulation of these molecules within normal neurons. Furthermore, elucidating the role of CD in amelioration of NPC disease will likely assist in development of new therapeutic options for this and other fatal lysosomal disorders.
Meanwhile, the key role of cholesterol in the envelope of HIV has led to the use of cyclodextrin as a possible antiretroviral. This looks like a very fortunate intersection of a wide-ranging, important biomolecule (cholesterol) with a widely studied, well-tolerated complexing agent for it (cyclodextrin). It'll be fun to watch how all this plays out. . .
+ TrackBacks (0) | Category: Biological News | Infectious Diseases | The Central Nervous System | Toxicology
October 17, 2011
I've had some problems over the years with the Singularity-Is-Near line of thought, and some problems with the "If we can build a new generations of microchips in five years, we ought to be able to cure cancer in ten" idea. Here's an article by Paul Allen in Technology Review that takes aim at both of these simultaneously:
The complexity of the brain is simply awesome. Every structure has been precisely shaped by millions of years of evolution to do a particular thing, whatever it might be. It is not like a computer, with billions of identical transistors in regular memory arrays that are controlled by a CPU with a few different elements. In the brain every individual structure and neural circuit has been individually refined by evolution and environmental factors. The closer we look at the brain, the greater the degree of neural variation we find. Understanding the neural structure of the human brain is getting harder as we learn more. Put another way, the more we learn, the more we realize there is to know, and the more we have to go back and revise our earlier understandings. We believe that one day this steady increase in complexity will end—the brain is, after all, a finite set of neurons and operates according to physical principles. But for the foreseeable future, it is the complexity brake and arrival of powerful new theories, rather than the Law of Accelerating Returns, that will govern the pace of scientific progress required to achieve the singularity.
Very true. Imagine a fiendishly complex chip diagram, but with not a single component of it standardized. It's one bespoke piece of hardware after another, billions of them, and the wiring between them was put together the same idiosyncratic way. And it's altering while you study it - in fact, it may be altering because you're studying it. Glorious stuff, and understanding it is going to give us extraordinary powers. But that's not happening soon, or on anyone's schedule.
+ TrackBacks (0) | Category: General Scientific News | The Central Nervous System
October 6, 2011
That's what this paper in Molecular Psychiatry is suggesting. The authors injected material from human Alzheimer's patients into the brains of normal mice, and saw what appears to be the induction of amyloid pathlology. This didn't happen in control animals, got worse with time, and wasn't just noted at the point of injection. Their hypothesis is that Alzheimer's might be a prion-type disease of protein misfolding, and possibly capable of being spread by infectious particles. I recall ideas like this being advanced in the past, but this is the first time I've seen evidence like this (hasn't this sort of experiment been run before?) It's simultaneously fascinating and alarming, and I would very much like to see it repeated and confirmed.
This comes as broadly similar ideas are being advanced in Parkinson's disease, where recent work has shown misfolded alpha-synuclein protein (long known as a key factor) spreading slowly through infected neurons. No one has ever seen evidence of transmissible Parkinson's between humans, but it does seem to move between neurons like an internal epidemic.
And that comes as broadly similar ideas are being advanced in ALS. A recent paper in PNAS suggests that a mutant form of superoxide dismutase 1 (which had already been found to be associated with the disease) can be spread by the injection of precursor cells that express it. That makes you think that the SOD1 mutant (G93A, which is not the most common mutation in humans) may also have prion-like properties, and can induce other proteins to misfold along with it. What's especially interesting (and again, rather alarming) is that it apparently can recruit normal SOD1 into this state. (In this study, though, the effects were confined to the region around the introduction of the cells, so the spread was not that fast). It's important to note again that, as in the case of Parkinson's, no one has ever seen evidence that ALS is transmissible from person to person - in fact, I don't think that anyone has ever seen ALS in anyone without the mutation in their genome. But this does shed some light on what happens internally.
So taken together, the spreading-protein-misfolding mechanism seems to have a lot of momentum behind it. The big question is whether it can result in human-to-human transmission. Even in the cases where we've confirmed prion-based disease, transmission seems (fortunately) rather difficult, although this is a very active field of research, and definitely something to keep an eye on. The possible Alzheimer's connection is especially interesting, since that one is simultaneously more common and does not have a strong genetic component. It occurs (as far as we can tell) mostly sporadically. The amyloid hypothesis for its cause has been taking some hits in recent years, but the other side of the story is still very much alive. . .
+ TrackBacks (0) | Category: The Central Nervous System
August 8, 2011
A couple of weeks ago, we had this discussion about the cost-effectiveness of drugs for multiple sclerosis. It was pointed out that Novartis's new Gilenya (fingolimod) is priced even higher than the drugs in the study that found that MS drugs are among the priciest in the world for their medical benefit.
Now the United Kingdom's NICE has said that Gilenya has not (so far) shown enough efficacy to justify its price. There's going to be a lot of emotionally engaged comment on both sides of this issue, but people should have been able to see this coming. And by "people", yes, I also mean Novartis.
+ TrackBacks (0) | Category: General Scientific News | The Central Nervous System
August 1, 2011
If you haven't been reading carefully, you might have had trouble figuring out Teva's oral therapy for multiple sclerosis, laquinimod. After all, earlier this year, the company was blowing the horn for the compound at neurology meetings, touting how safe and effective it was, its advantages over existing therapies, and its potential in the market. You'd hardly know that the compound actually didn't perform as well as many people were hoping. And of course, that very article does mention, near the end, that the company was going to have some more results later in the year. . .
. . .and that day has arrived. Unfortunately. Laquinimod missed its primary endpoint of reducing relapses in MS patients, and unless Teva and its
Israeli Swedish partner company (Active Biotech) have some real surprises to unveil, you'd have to presume that the compound is dead. Or if not dead, destined to never make much of an impact in the market, for sure. This program has had a long history, with an earlier version of the structure (roquinimex) running into severe cardiovascular issues ten or twelve years ago.
Teva is a huge player in the generic world, and in recent years has been trying to break into the research end of the drug business. (Their first was Copaxone (glatiramer acetate), also for MS, a compound with a tangled history). Enjoy the experience, guys. If you're used to dealing with compounds whose value has already been proven, this sort of thing must come as even more of a shock than usual.
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
July 21, 2011
Now this is an uncomfortable study, if you're in the business of treating multiple sclerosis. An article in Neurology looks at the cost-effectiveness of several disease-modifying therapies: the two interferon-beta-1as (Avonex and Rebif), interferon-beta-1b (Betaseron) Copaxone, Betaseron and the immune modulator Copaxone (glatiramer acetate). The authors tracked ten-year quality of life, including lost time at work, overall time without relapses, and so on, and compared that with the cost of treatment.
The final figure is in dollars per quality-adjusted life year (QALY). That's not the most exact calculation in the world, but if you're going to try to rank cost-effectiveness, no measure is going to be without controversy. There's been a lot of debate about this in the UK, where the NICE explicitly uses these figures in its recommendations, and if you haven't heard much about the concept over here, well, you're definitely going to. What's considered a good figure? To give you an idea, the NICE starts raising an eyebrow at about $40K to $50K (based on 1.62 dollars to the pound). Here, we'll stand for 100K to 150K.
And how do the MS drugs compare? Closer to $1 million/QALY than any of those figures. All of them were above $800,000/QALY. In other words, the benefits of these drugs are real (although Copaxone's were less impressive compared to the interferons), but are they real enough to justify their prices? It'll be quite interesting to see where Gilenya (fingolimod) will land once it gets more of a track record in the real world. Note that the price of all these drugs has gone up since the study's calculations (while their effectiveness has presumably not budged) and that Gilenya, I believe, costs even more than the rest of them.
This naturally brings up all the usual questions about drug pricing. In no particular order, and with no priority given to those that I agree with, we have: Who says you can put a price on quality of life? Well, if you can't, then why can't drug companies just charge whatever the market will bear? What market - drug pricing is about the worst example of a free market you could ask for! Well, what if people want to pay out of their own pockets - shouldn't they be free to? Right, sure, who does that, and how much would sales fall if everyone had to? But still, shouldn't people be able to get what therapies are available - who's the person who gets to tell patients that they can't have what's out there? OK, but since a lot of this is Medicare and the like, are we supposed to pay for everything to be done to everyone forever? And why should these drugs cost so much, anyway? Well, because insurance companies apparently will pay for them - why don't you go complain to them? And so on. I honestly have no idea what the end to these arguments might be, but studies like this one are going to force us to have them again. Here's more from the New York Times and from Bloomberg, with a hat tip to FiercePharma.
+ TrackBacks (0) | Category: Drug Prices | The Central Nervous System
June 23, 2011
Multiple sclerosis therapy has been changing a lot in recent years, and one of the biggest events was the introduction of Gilenya (fingolimod). That's the first non-injectable for MS, and it's quite a story (as well as being quite a weird compound from a chemistry perspective).
Novartis has been racing ahead in selling that one, because they knew the Merck KgGa (Merck-Darmstadt) had another oral compound in the works, cladribine. That's a nucleoside analog with a different mechanism (targeting some lymphoctye subtypes and thus changing immune response), and it was already used in treatment of some forms of leukemia. It did show promising results in the clinic for relapsing MS, and there were high hopes.
Not now. Word has come that the company that they're withdrawing their application in Europe and the US, and taking the drug off the market in the only two countries (Russia and Australia) where it had been approved. The FDA had already said that it would not approve cladribine without more safety information, and Merck KgGa has decided that (1) the ongoing trials won't do the job, and (2) it's not worth it (risk/reward) to try new ones.
So that leaves the field open for Novartis, and German Merck (who have had several disappointments in recent years) in some trouble. . .
+ TrackBacks (0) | Category: Regulatory Affairs | The Central Nervous System
March 31, 2011
After my post the other day on the NIH neurological disease effort, I heard from Rebecca Farkas there, who's leading the medicinal chemistry effort on the program. She's glad to get feedback from people in the industry, and in fact is inviting questions and comments on the whole program. Contact her at farkasr-at-ninds-dot-nih-dotgov (perhaps putting the address in that form will give the spam filters at NIH a bit less to do than otherwise).
She also sends word that they'll be advertising soon for a Project Manager position for this effort, and is looking for suggestions on how to reach the right audience for a good selection of candidates. This post might help a bit, but she's interesting in suggestions on where to advertise and who to contact for good leads.
+ TrackBacks (0) | Category: Drug Development | The Central Nervous System
March 29, 2011
Here's an interesting funding opportunity from NIH:
Recent advances in neuroscience offer unprecedented opportunities to discover new treatments for nervous system disorders. However, most promising compounds identified through basic research are not sufficiently drug-like for human testing. Before a new chemical entity can be tested in a clinical setting, it must undergo a process of chemical optimization to improve potency, selectivity, and drug-likeness, followed by pre-clinical safety testing to meet the standards set by the Food and Drug Administration (FDA) for clinical testing. These activities are largely the domain of the pharmaceutical industry and contract research organizations, and the necessary expertise and resources are not commonly available to academic researchers.
To enable drug development by the neuroscience community, the NIH Blueprint for Neuroscience Research is establishing a ‘virtual pharma’ network of contract service providers and consultants with extensive industry experience. This Funding Opportunity Announcement (FOA) is soliciting applications for U01 cooperative agreement awards from investigators with small molecule compounds that could be developed into clinical candidates within this network. This program intends to develop drugs from medicinal chemistry optimization through Phase I clinical testing and facilitate industry partnerships for their subsequent development. By initiating development of up to 20 new small-molecule compounds over two years (seven projects were launched in 2011), we anticipate that approximately four compounds will enter Phase 1 clinical trials within this program.
My first thought is that I'd like to e-mail that first paragraph to Marcia Angell and to all the people who keep telling me that NIH discovers most of the drugs on the market. (And as crazy as that sounds, I still keep running into people who are convinced that that's one of those established facts that Everyone Knows). My second thought is that this is worth doing, especially for targeting small or unusual diseases. There could well be interesting chemical matter or assay ideas floating around out there, looking for the proper environment to have something made of them.
My third thought, though, is that this could well end up being a real education for some of the participants. Four Phase I compounds out of twenty development candidates - it's hard to say if that's optimistic or not, because the criteria for something to be considered a development candidate can be slippery. And that goes for the drug industry too, I hasten to add. Different organizations have different ideas about what kinds of compounds are worth taking to the clinic, and those criteria vary by disease area, too. (Sad to say, they can also vary by time of the year and the degree to which bonuses are tied to hitting number-of-clinical-candidate goals, and anyone who's been around the business a while will have seen that happen, to their regret).
It'll be interesting to see how many people apply for this; the criteria look pretty steep to me:
Applicants must have available small-molecule compounds with strong evidence of disease-related activity and the potential for optimization through iterative medicinal chemistry. Applicants must also be able to conduct bioactivity and efficacy testing to assess compounds synthesized in the development process and provide all pre-clinical validation for the desired disease indication. . .This initiative is not intended to support development of new bioactivity assays, thus the applicant must have in hand well-characterized assays and models.
Hey, there are small companies out there that don't come up to that standard. To clarify, though, the document does say that "Evaluation of the approach should focus primarily on the rationale and strengths/weaknesses of proposed bioactivity studies and compound "druggability," since all other drug development work (e.g., medicinal chemistry, PK/tox, phase I clinical testing) will be designed and implemented by NIH-provided consultants and contractors after award", which must come as something of a relief.
What's interesting to me, though, is that the earlier version of this RFA (from lsat year) had the following language:
The ultimate goals of this Neurotherapeutics Grand Challenge are to produce at least one novel and effective drug for a nervous system disorder that is currently poorly treated and to catalyze industry interest in novel disease targets by demonstrating early-stage success.
That's missing this time around, which is a good thing. If they're really hoping for a drug to come out of four Phase I candidates in poorly-treated CNS disorders, then I'd advise them to keep that thought well hidden. The overall attrition rate in the clinic in CNS is somewhere around (and maybe north of) 90%, and if you're going to go after the tough end of that field it's going to be even steeper.
+ TrackBacks (0) | Category: Academia (vs. Industry) | Drug Development | The Central Nervous System
February 14, 2011
I wrote here the other day about the NIH's new translational medicine plans. The New York Times article that brought this to wide attention didn't go over well with director Francis Collins, who ended up trying to disabuse people of the idea that the NIH was going to set up its own drug company.
But there's been an overwhelming negative response from the academic research community, largely driven (it seems) by worries about funding. Given the state of the budget, flat funding would be seen as a victory by NIH, so this isn't the best environment to be talking about putting together a great new institute. The money for it will, after all, have to come out of someone else's pile. Collins spends most of that statement linked above denying this, but it's hard to see how there won't be problems.
I think, though, that there's an even more fundamental problem here. In the latest BioCentury, there's an interesting sidelight on all this:
In comments submitted to NIH, Joseph Zaia, associate director of the Center for Biomedical Mass Spectrometry at the Boston University School of Medicine, argued against setting timetables for research results. “I do not believe that running medical science on a short sighted business time schedule will produce more cures faster. It will, however, deplete NIH resources very rapidly and possibly tear down an infrastructure of knowledge that took decades to create.”
Zaia complained that the NCATS “process seems to be driven by the FasterCures movement sponsored by Michael Milken,” which he said has “been masterful in manipulating the political system for their purposes, and forcing NIH into this reorganization.”
FasterCures’ Margaret Anderson, executive director of the non-profit group that advocates for accelerating medical innovation, submitted a letter strongly endorsing NCATS, which she said “will provide a significant stimulus to moving ideas out of the lab and into the clinic.”
And that's the problem. Over the last few years, an idea has taken hold that there are all kinds of great ideas for all kinds of diseases that no one is doing anything with. Now, I'm not going to claim that everyone is trying every single thing that could possibly be tried, but I really don't see how there's this treasure chest of great discoveries that aren't being followed up on. Drug companies of all sizes are always watching for such opportunities - I've been a part of many such efforts to jump on these as they show up.
My guess is that many of these advocates have a different definition of what a "great discovery" is than I do. There are all kinds of things that come out in the literature, often with breathless press releases from the university PR office, that make it sound like the latest JBC paper has the cure for cancer in it. But the huge majority of these things don't pan out, generally because they're just part of a much, much larger (and more complicated) story. And that's why things tend to fail on the way to (and through) the clinic.
Am I exaggerating? Well, many advocates in this area have taken to using the phrase "valley of death" to describe the gap between basic research and success in the clinic. Here's Amy Rick of the Parkinson's Action Network:
Rick said patient groups are concerned that the valley of
death is growing, and they want government to help bridge it. The prospect that there are “good discoveries that are basically collecting dust” is “terrifying to patients,” she said.
“What we are finding from a patient perspective is that discoveries that are being made in very exciting basic research are not being acted upon,” Rick told BioCentury This Week. “They are not moving through the pipeline. So the patient community is pushing very hard — if private money isn’t filling that space, the government should be moving some of its funding into that space.”
I have a great deal of sympathy for the patient population - they're our customers in this business, after all, and any one of us could join their ranks at any time. (Drug company researchers come down with all the maladies that everyone else does). But the patient population is not the group of people discovering and developing drugs. What looks like agonizingly slow progress from outside is often just the best that can be done. It can be hard to imagine how crazy, complex, and frustrating medical research can be unless you've tried doing it. Nothing else quite compares.
I worry that some of these people have an unrealistic view of how things work (or should work). This all reminds me of Andrew Grove, ex-Intel, and his complaints that the drug research business wasn't moving as fast as the semiconductor industry. It sure isn't. That's because it's a lot harder.
The Biocentury article is right in line with my thinking here:
FASEB’s Talman argues that patient groups and the public are overly optimistic about the breakthroughs that could be made by shifting resources to translational science. He believes basic scientists are partly to blame because “there is too much of a tendency for basic or clinical scientists to sell our work.” In the process, he said, “we can come across as saying that the newest discovery can lead to a cure.”
Senior NIH officials have contributed to the belief that cures are around the corner by dangling the prospect of quick payoffs in front of congressional appropriators. For example, in 1999, Gerald Fischbach, then director of the National Institute of Neurological Diseases and Stroke, told a Senate committee that with sufficient funding it was reasonable to expect a cure for Parkinson’s disease within five years. The NINDS budget has increased from $902 million in FY99 to $1.6 billion in FY10, but PD hasn’t been cured.
Starting in 2004, National Cancer Institute Director Andrew von Eschenbach claimed in numerous public speeches that it would be possible to “end suffering and death from cancer by 2015,” a claim that current NCI Director Harold Varmus has repudiated.
When he led the human genome sequencing effort, NIH Director Collins himself made comments that the press, public and politicians interpreted as promising that it would directly and quickly lead to new medicines for common diseases.
“There is a real danger of over-promising,” Keith Yamamoto, executive vice dean of the University of California San Francisco School of Medicine, told BioCentury. “Scientists too often take an intellectual short cut. They think they will not be able to explain the nuances of why basic discovery takes so long, so they just say if you give me the money we are about to cure the disease.”
He added: “That’s thin ice — it is our responsibility to explain why things are as difficult as they are.”
It sure is. I know that patients and the general public get tired of hearing about how it's hard, how discoveries take time, all that sort of thing, while the diseases just keep marching on and on. But it's all true. I honestly don't think that most people realize, despite that huge amounts of knowledge we've managed to accumulate, just how little we know about what we're doing.
+ TrackBacks (0) | Category: Academia (vs. Industry) | Cancer | Drug Development | The Central Nervous System
February 9, 2011
Poker players in the audience may remember the old story of the guy who lost three cars over the years by drawing to try to fill inside straights - the first two when he came up empty, and the last time when he made his hand. You can have the same experience in drug development, too, for higher stakes.
Remember Fanapt (iloperidone)? That's the antipsychotic compound that bounced around from company to company during the 1990s, and nearly sank Vanda Pharmaceuticals a few years ago when the FDA gave them a "Not Approvable" letter. I predicted at the time that we'd never hear from them again, but to my surprise (and to Vanda's, I'd guess), the FDA reversed itself and let the compound through in 2009.
Novartis signed up to market the drug, and it was launched early last year. Some analysts predicted about $100 million in sales, growing to two or three times that number - not a blockbuster, but very welcome indeed for Vanda (and for earlier developer Titan, who still retained some rights). And now, reports Adam Feuerstein, we have the full-year numbers: $31 million, most of which appears to have been initial inventory stocking. Not good.
I've already tried to teach my kids not to draw to the inside straight. The more advanced player needs to try to work out if the pot offers a payout consistent with the risks, and to figure out what the chances of that payout might be, even if the hand comes through. . .
+ TrackBacks (0) | Category: Business and Markets | The Central Nervous System
January 17, 2011
Some time ago, I took nominations for Least Useful Animal Models. There were a number of good candidates, many of them from the CNS field. A recent report makes me think that these are even stronger contenders than I thought.
The antidepressant reboxetine (not approved in the US, but sold in a number of other countries by Pfizer) was recently characterized by a German meta-analysis of the clinical data as "ineffective and potentially harmful". Its benefits versus placebo (and SSRI drugs) have been overestimated, and its potential for harm underestimated. It was approved in Europe in 1997, and provisionally by the FDA in 1999, although that was later rolled back when more studies came in that showed lack of efficacy.
Much has been made of the fact that Pfizer had not published many of the studies they conducted on the drug. These do seem, however, to have been available to regulatory authorities, and were the basis for the FDA's decision not to grant full approval. As that BMJ link discusses, though, there's often not a clear pathway, especially in the EU, for a regulatory agency to go back and re-examine a previous decision based on efficacy (as opposed to safety).
So the European regulatory agencies can be faulted for not revisiting their decision on this drug in a better (and quicker) fashion, and Pfizer can certainly be faulted for letting things stand (in the face of evidence that the drug was not effective). All this is worrisome, but these are problems that are being dealt with. Since 2007, for example, trials for the FDA have been required to be posted at clinicaltrials.gov, although the nontranparency of older data can make it hard to compare newer and older treatments in the same area.
What's not being dealt with as well is an underlying scientific problem. As this piece over at Scientific American makes plain, reboxetine, although clinically ineffective, works just fine in all the animal models:
And this is a rough moment for scientists studying depression. Why? Because reboxetine works beautifully in our animal models. It’s practically a poster-child antidepressant. It produces acute effects in tests such as forced-swim tests and tail-suspension tests (which use changes in struggle as a measure of antidepressant efficacy). It produces neurogenesis in the hippocampus, which is thought to be correlated with antidepressant effects. When behavioral pharmacologists are doing comparisons between older antidepressants and newer ones, reboxetine is often used as a positive control, a drug known to have an effect in the behavioral test of choice.
But it doesn’t work in patients. And patients are what matters. Now, scientists are stuck with a difficult question: What went wrong?
A very good question, and one without any very good answers. And this certainly isn't the first CNS drug to show animal model efficacy but do little good in people. So, how much is the state of the art advancing? Are we getting anywhere, or just doing the same old thing?
+ TrackBacks (0) | Category: Animal Testing | Clinical Trials | Regulatory Affairs | The Central Nervous System | The Dark Side
January 14, 2011
Everyone in this industry wants to have good, predictive biomarkers for human diseases. We've wanted that for a very long time, though, and in most cases, we're still waiting. [For those outside the field, a biomarker is some sort of easy-to-run test that for a factor that correlates with the course of the real disease. Viral titer for an infection or cholesterol levels for atherosclerosis are two examples. The hope is to find a simple blood test that will give you advance news of how a slow-progressing disease is responding to treatment]. Sometimes the problem is that we have markers, but that no one can quite agree on how relevant they are (and for which patients), and other times we have nothing to work with at all.
A patient's antibodies might, in theory, be a good place to look for markers in many disease states, but that's some haystack to go rooting around in. Any given person is estimated, very roughly, to produce maybe ten billion different antibodies. And in many cases, we have no idea of what ones to look for since we don't really know what abnormal molecules they've been raised to recognize. (It's a chicken-and-egg problem: if we knew what those antigens were, we'd probably just look for them directly with reagents of our own).
So if you don't have a good starting point, what to do? One approach has been to go straight into tissue samples from patients and look for unusual molecules, in the belief that these might well be associated with the disease. (You can then do just as above to try to use them as a biomarker - look for the molecules themselves, if they're easy to assay, or look for circulating antibodies that bind to them). This direct route has only become feasible in recent years, with advanced mass spec and data handling techniques, but it's still a pretty formidable challenge. (Here's a review of the field).
A new paper in Cell takes another approach. The authors figured that antigen molecules would probably look like rather weirdly modified peptides, so they generated a library of several thousand weirdo "peptoids". (These are basically poly-glycines with anomalous N-substituents). They put these together as a microarray and used them as probes against serum from animal models of disease.
Rather surprisingly, the idea seems to have worked. In a rodent model of multiple sclerosis (the EAE, or experimental autoimmune encephalitis model), they found several peptoids that pulled down antibodies from the model animals and not from the controls. A time course showed that these antibodies came on at just the speed expected for an immune response in the animal model. As a control, another set of mice were immunized with a different (non-disease-causing) protein, and a different set of peptoids pulled down those resulting antibodies, with little or no cross-reactivity.
Finally, the authors turned to a real-world case: Alzheimer's disease. They tried out their array on serum from six Alzheimer's patients, versus six age-matched controls, and six Parkinson's patients as another control, and found three peptoids that seems to have about a 3-fold window for antibodies in the AD group. Further experimentation (passing serum repeated over these peptoids before assaying) showed that two of them seem to react with the same antibody, while one of them has a completely different partner. These experiments also showed that they are indeed pulling down the same antibodies in each of the patients, which is an important thing to make sure of.
Using those three peptoids by themselves, they tried a further 16 AD patient samples, 16 negative controls, and 6 samples from patients with lupus, all blinded, and did pretty well: the lupus patients were clearly distinguished as weak binders, the AD patients all showed strong binding, and 14 out of the 16 control patients showed weak binding. Two of the controls, though, showed raised levels of antibody detection, up to the lowest of the AD patients.
So while this isn't good enough for a diagnostic yet, for a blind shot into the wild blue immunological yonder, it's pretty impressive. Although. . .there's always the possibility that this is already good enough, and that the test picked up presymptomatic Alzheimer's in those two control patients. I suppose we're going to have to wait to find that out. As you'd imagine, the authors are extending these studies to wider patient populations, trying to make the assay easier to run, and trying to find out what native antigens these antibodies might be recognizing. I wish them luck, and I hope that it turns out that the technique can be applied to other diseases as well. This should keep a lot of people usefully occupied for quite some time!
+ TrackBacks (0) | Category: Analytical Chemistry | Biological News | The Central Nervous System
January 7, 2011
I wrote here about a Wall Street Journal article covering illegal street-drug labs in Europe. Well, maybe that should be not-quite-illegal, because the people involved were deliberately making compounds that the law hadn't caught up with yet.
The article mentioned David Nichols at Purdue as someone whose published work on CNS compounds had been followed/ripped off/repurposed by the street drug folks. Now Nature News has a follow-up piece by him, and he's not happy at all with the way things have been turning out:
We never test the safety of the molecules we study, because that is not a concern for us. So it really disturbs me that 'laboratory-adept European entrepreneurs' and their ilk appear to have so little regard for human safety and human life that the scant information we publish is used by them to push ahead and market a product designed for human consumption. Although the testing procedure for 'safety' that these people use apparently determines only whether the substance will immediately kill them, there are many different types of toxicity, not all of which are readily detectable. For example, what if a substance that seems innocuous is marketed and becomes wildly popular on the dance scene, but then millions of users develop an unusual type of kidney damage that proves irreversible and difficult to treat, or even life-threatening or fatal? That would be a disaster of immense proportions. This question, which was never part of my research focus, now haunts me.
Well, that's absolutely right, and it's not terribly implausible, either. The MPTP story is as good an example as you could want of what happens when you just dose whoever shows up on the street corner with that cool stuff you made in your basement lab. All we need is a side effect like that, which comes on a bit more slowly, and there you'd have it. That's one of the reasons I have such disgust for the people who are making and selling these things - they show a horrifying and stupid disregard for human life, all for the purpose of making a few bucks.
At the same time, I think that Nichols himself should try not to blame himself. His article comes across rather anguished; I have a lot of sympathy for him. But the actions of other people, especially scum, are outside of his control, and I think he's taking every reasonable precaution on his end while he does some valuable work.
Homo homini lupus: the sorts of people who see basement drugs as a fun business opportunity would likely be doing something equally stupid and destructive otherwise. Dr. Nichols, you have nothing to be ashamed of, nothing to apologize for - and, honestly, nothing to keep you up at night. You're the responsible member of the human race in this story.
+ TrackBacks (0) | Category: The Central Nervous System | The Dark Side | Toxicology
November 1, 2010
This article reminds me of the "designer drug" era in the 1980s. The Wall Street Journal profiles one of the many European chemical entrepreneurs making a fortune by synthesizing and selling new psychoactive drugs. And they're all labeled "Not For Human Consumption", so hey, everything's perfectly legal. Until the authorities ban the specific substance, naturally, and then he moves on to another one down the list.
As someone who doesn't see a new chemical structure go into humans until years of testing have been done, you can imagine what I think of this. The small amount of amazement I feel is completely overwhelmed by contempt for anyone who would dose people with an untried CNS drug. Oh, but he's not dosing anyone, is he? All he's doing is selling them little vials of white powdery stuff for $30/gram, and it says right on the label that they're not supposed to take it. Right? How people like this sleep at night is a continuing mystery to me.
Making new psychoactive drugs is not that hard. There are plenty of chemotypes out there that will drop you right into the CNS receptors. In many cases, it looks like this guy and his ilk are hanging single-atom changes off of existing drugs. They also monitor the chemical literature, specifically mentioning papers by David Nichols of Purdue, who's well aware of what's going on (and has the same reaction I do). No, there are plenty of small changes to ring on known scaffolds; it's not like anyone's having to invent any new chemical classes here.
So, how do they make these things in quantity? The article treats a rota-vap as an exotic piece of equipment, so we're not going to learn too much from it. But I imagine that there's a lot of used lab equipment floating around, which must help. But the article also mentions that this particular business has labs in the Netherlands and Scotland, outfitted with custom stainless-steel gear made by a welder, so as to not draw attention by buying standard chemistry apparatus. (This is as good a time as any to mention that one of the things that irritates me about these people is the way they make owning any kind of chemistry equipment at home instantly suspicious in the eyes of the law).
That takes a back seat, though, to my feelings about the other aspects of this business. I'm not, admittedly, a good person to ask about recreational drug use, because I don't use any. I have what I think are well-justified reasons for avoiding the whole spectrum, from alcohol on up. The more I've learned about brain chemistry, the less inclined I am to mess around with it.
But even if you take a more lenient attitude, I don't see how the sort of business that this article details can be excused. Advocates for decriminalized various drugs often make the point that we know what their effects are, and that society would be better off dealing with them than dealing with the effects of trying to suppress the drugs themselves. They may be right, actually - I haven't made up my mind about that one yet - but this line of thought can't extend to the new-drug-of-the-month-club. We don't know what the effects of these substances are, what neurological damage they might do, and what other side effects they might have. That's for the customers to find out! Here's the safety testing method this moron uses:
Mr. Llewellyn, meanwhile, is unfazed. He boasts that his safety testing method is foolproof: He and several colleagues sit in a room and take a new product "almost to overdose levels" to see what happens. "We'll all sit with a pen and a pad, some good music on, and one person who's straight who's watching everything," he says.
Well, fine, then. Foolproof! This sort of thing shows that nothing is foolproof, because fools are just too ingenious. I'm ashamed to share a phylum with these people, much less a scientific discipline.
+ TrackBacks (0) | Category: The Central Nervous System | The Dark Side
October 21, 2010
There's a headline I've never written before, for sure. A new paper in PNAS describes an assay in nematodes to look for compounds that have an effect on nerve regeneration. That means that you have to damage neurons first, naturally, and doing that on something as small (and as active) as a nematode is not trivial.
The authors (a team from MIT) used microfluidic chips to direct single nematodes into a small chamber where they're held down briefly by a membrane. Then an operator picks out one of its neurons on an imagining screen, whereupon a laser beam cuts it. The nematode is then released into a culture well, where it's exposed to some small molecule to see what effect that has on the neuron's regrowth. It takes about 20 seconds to process a single C. elegans, in case you're wondering, and I can imagine that after a while you'd wish that they weren't streaming along quite so relentlessly.
The group tried about 100 bioactive molecules, targeting a range of known pathways, to see what might speed up or slow down nerve regeneration. As it happens, the highest hit rates were among the kinase inhibitors and compounds targeting cytoskeletal processes. (By contrast, nothing affecting vesicle trafficking or histone deacetylase activity showed any effect). The most significant hit was an old friend to kinase researchers, staurosporine. Interestingly, this effect was only seen on particular subtypes of neurons, suggesting that they weren't picking up some sort of broad-spectrum regeneration pathway.
The paper acknowledges that staurosporine has a number of different activities, but treats it largely as a PKC inhibitor. I'm not sure that that's a good idea, personally - I'd be suspicious of pinning any specific activity to that compound without an awful lot of follow-up, because it's a real Claymore mine when it comes to kinases. The MIT group did check to see if caspases (and apoptotic pathways in general) were involved, since those are well-known effects of staurosporine treatment, and they seem to have ruled those out. And they also followed up with some other PKC inhibitors, chelerythrine and Gö 6983, and these showed similar effects.
So they may be right about this being a PKC pathway, but that's a tough one to nail down. (And even if you do, there are plenty of PKC isoforms doing different things, but there aren't enough selective ligands known to unravel all those yet). Chelerythrine inhibits alanine aminotransferase, has had some doubts expressed about it before in PKC work, and also binds to DNA, which may be responsible for some of its activity in cells. Gö 6983 seems to be a better tool, but it's is in the same broad chemical class as staurosporine itself, so as a medicinal chemist I still find myself giving it the fishy eye.
This is very interesting work, nonetheless, and it's the sort of thing that no one's been able to do before. I'm a big fan of using the most complex systems you can to assay compounds, and living nematodes are a good spot to be in. I'd be quite interested in a broader screen of small molecules, but 20 seconds per nematode surgery is still too slow for the sort of thing a medicinal chemist like me would like to run - a diversity set of, say, ten or twenty thousand compounds, for starters. And there's always the problem we were talking about here the other day, about how easy it is to get compounds into nematodes at all. I wonder if there were some false negatives in this screen just because the critters had no exposure?
+ TrackBacks (0) | Category: Biological News | Drug Assays | The Central Nervous System
August 25, 2010
Emily Yoffe at Slate has a very accurate piece up on just how hard it is to make progress against things like Alzheimer's, Parkinson's, and other neurodegenerative diseases. The contrast with the hopes of patients - and the hype often surrounding the initial discoveries - is painful.
And we're back to that optimism/realism tightrope. On the one hand, I don't see any reason why we shouldn't be able - eventually - to stop such conditions in their tracks, or to keep them from starting in the first place. (Reversing the damage once it's done, though, is much more of a stretch, to me). But on the other hand - sheesh, we really, really have a lot to learn about these things. The likelihood of any one discovery being the key breakthrough is small - nonzero, but small. So in the long term, I'm an optimist, but in the short term, well. . .every little bit helps, and most of the bits are going to be little.
That's not the sort of news you want to give to someone suffering from these conditions, of course. That desire for encouraging news, along with plenty of other good intentions (and a few not-so-good-ones) leads to the cycles of hype that we've seen over and over. Stem cell research is a perfect example. There really are huge possibilities there, extraordinary ones. But our level of ignorance is also extraordinary. And to go out and make claims that we're going to be able to cure X and reverse Y soon, based on our present knowledge, is just plain irresponsible.
But plenty of people do just that - politicians, headline writers, and others. And then people who only know what they see in the news wonder where things went wrong, and how come these wonderful cures haven't arrived yet. It all makes explaining the real situation that much harder.
It's not like the real situation is even all that terrible. As I said above, I really do think that these diseases - and many others - are eventually going to be treatable. No one likes that word "eventually", though.
+ TrackBacks (0) | Category: Press Coverage | The Central Nervous System
August 23, 2010
Ray Kurzweil has responded to the criticism of his Singularity Summit comments on reverse-engineering the brain, a chorus to which I added my voice here. He says that he was misquoted on the timeline and on the importance of genomic data for doing it.
His plan, he says, is to understand what level of complexity will be needed in order for a system to organize and adapt the way the brain does to stimuli, and the modular nature of its organization gives him hope that this can be realized:
For example, the cerebellum (which has been modeled, simulated and tested) — the region responsible for part of our skill formation, like catching a fly ball — contains a module of four types of neurons. That module is repeated about ten billion times. The cortex, a region that only mammals have and that is responsible for our ability to think symbolically and in hierarchies of ideas, also has massive redundancy. It has a basic pattern-recognition module that is considerably more complex than the repeated module in the cerebellum, but that cortex module is repeated about a billion times. There is also information in the interconnections, but there is massive redundancy in the connection pattern as well.
Fine. But even that argument triggers the reaction in me that Kurzweil's statements often do. I wasn't aware that we had "modeled, simulated, and tested" a cerebellum yet, for one thing. If that's so well worked out, where is it? Why aren't industrial robots a lot more coordinated? I assume that one reason is that we haven't done it with four billion processing modules yet. But if not, does that really qualify as something that's been tested? Will it all really just be a matter of scaling up, or will more subtle features become important along the way?
He also goes on to say that "We have sufficiently high-resolution in-vivo brain scanners now that we can see how our brain creates our thoughts and see our thoughts create our brain." I'd disagree with that statement. The resolution of brain imaging techniques has been improving steadily, but it's still crude compared to what we're going to need. Every time we improve it, we find that things are more complicated than we thought.
If any of Kurzweil's exponential-growth predictions are to come true, though, it'll be the ones that involve computing power most directly, since that's where this sort of growth has come most reliably and spectacularly. I just don't think that our understanding increases at the same rate - and not every problem will find a solution through our ability to throw more processing power at it.
How do I reconcile this attitude of mine with my reasons-for-optimism post of the other day? Well, as I've said, we don't need miracles in drug discovery (although I'll welcome any that might show up). We just need to do things a little bit better than we do already - it's that young a field, and we're that poor at it. Compared to what we could know, and what we might be able to do, we're still way back on the curve. When your clinical failure rate is 90%, anything you can do better is an improvement. I'm not asking to (or claiming that we will) figure out predictive human toxicology in ten years. I just want to fail miserably eight out of ten times, instead of nine. And thus double the number of drugs coming to market. . .
+ TrackBacks (0) | Category: The Central Nervous System
August 18, 2010
News like today's gamma-secretase failure makes me want to come down even harder on stuff like this. Ray Kurzweil, whom I've written about before, seems to be making ever-more-optimistic predictions with ever-more-shortened timelines. This time, he's saying that reverse-engineering the human brain may be about a decade away.
I hope he's been misquoted, or that I'm not understanding him correctly. But some of his other statements from this same talk make me wonder:
Here's how that math works, Kurzweil explains: The design of the brain is in the genome. The human genome has three billion base pairs or six billion bits, which is about 800 million bytes before compression, he says. Eliminating redundancies and applying loss-less compression, that information can be compressed into about 50 million bytes, according to Kurzweil.
About half of that is the brain, which comes down to 25 million bytes, or a million lines of code.
This is hand-waving, and at a speed compatible with powered flight. It would be much less of a leap to say that the Oxford English Dictionary and a grammar textbook are sufficient to write the plays that Shakespeare didn't get around to. And while I don't believe that the brain is a designed artifact like The Tempest (or Tempest II: The Revenge of Caliban), I do most certainly believe that it is an object whose details will keep us busy for more than ten years.
Saying that its entire design is in the genome is deeply silly, mistaken, and misleading. The information in the genome takes advantage of so much downstream processing and complexity in a way that no computer program ever has, and that makes comparing it to lines of code laughable. I mean, lines of code have basically one level of reality to them: they're instructions to deal with data. But the genomic code is a set of instructions to make another set of instructions (RNA), which tells how to make another even more complex pile of multifunctional tools (proteins), which go on to do a bewildering variety of other things. And each of these can feed back on themselves, co-operate with and modulate the others in real time, and so on. Billions of years of relentless pressure (work well, or die) have shaped every intricate detail. The result makes the most complex human designs look like toys.
So here I am, absolutely stunned and delighted when I can make tiny bits of this machinery alter their course in a way that doesn't make the rest of it fall to pieces - a feat that takes years of unrelenting labor and hundreds of millions of dollars. And Ray Kurzweil is telling me that it's all just code. And not that much code, either. Have it broken down soon we will, no sweat. Sure.
I see that PZ Myers has come to the same conclusion. I don't see how anyone who's ever worked in molecular biology, physiology, cell biology, or medicinal chemistry could fail to, honestly. . .
+ TrackBacks (0) | Category: Biological News | The Central Nervous System
July 23, 2010
One big story from the last week was the FDA advisory panel's "No" decision on Qnexa, the drug-combo obesity therapy developed by Vivus. This is the one that's a combination of phentermine and topiramate, both of which have been around for a long time. And clinical trials showed that patients could indeed lose weight on the drug (with the required diet and exercise) - but also raised a lot of questions about safety.
And it's safety that's going to always be a worry with any obesity drug, even once you get past the (rather large) hurdle of showing efficacy. That's what took the Fen-Phen combination off the market, and what torpedoed Acomplia (rimonabant) and the other CB-1 compounds before they'd even been property launched. The FDA panel basically agreed that Qnexa helps with weight loss, but couldn't decide how bad the side effects might be in a wider patient population, and whether they'd be worth it:
But the drug has side effects, both known and theoretical. It may cause birth defects, it may increase suicide risk, it can cause a condition called metabolic acidosis that speeds bone loss, it increases risk of kidney stones, and may have other serious effects.
"It is difficult if not impossible to weigh these issues as the clinical trials went on only for a year, and patients will use this drug for lifetime," (panel chair Kenneth) Burman said. "It is impossible to extrapolate the trial data to the wider population."
That's a problem, all right, and it's not just Vivus that has to worry about it. When the potential number of patients is so large, well, any nasty side effects that are out there will show up eventually. How do you balance all these factors? Is it possible at all? As that WebMD article correctly points out, a new obesity drug will come on the market with all kinds of labeling about how it's only for people over some nasty BMI number, the morbidly obese, people with other life-threatening complications, and so on. But that's not how it's going to be prescribed. Not after a little while. Not with all the pent-up demand for an obesity drug.
Although that's probably the worst situation, this problem isn't confined to obesity therapies - any other drug that requires long-term dosing has this hanging over it (think diabetes, for one prominent example). That brings up the question that anyone looking over clinical trial data inevitably has to face: how much are the trials telling us about the real world? After all, the only way to be sure about how a drug will perform in millions of people for ten years is to dose millions of people for ten years. No one's going to want to pay for any drugs that have been through that sort of testing, I can tell you, so that puts us right where we are today, making judgment calls based on the best numbers we can get.
The FDA itself still has that call to make on Qnexa, and they could still approve it with all kinds of restrictive labeling and follow-up requirements. What about the other obesity compound coming along, then? A lot of people are watching Arena's lorcaserin (which I wrote about negatively here and followed up on here). Arena's stock seems to have climbed on the bad news for Vivus, but I have to say that I think that's fairly stupid. Lorcaserin may well show a friendlier side-effect profile than Qnexa, but if the FDA is going to play this tight, they could just let no one through at all - or send everyone back to the clinic for bankrupting.
As the first 5-HT2C compound to make it through, lorcaserin still worries me. A lot of people have tried that area out and failed, for one thing. And being first-to-market with a new CNS mechanism, in an area where huge masses of people are waiting to try out your drug. . .well, I don't see how you can not be nervous. I said the same thing about rimonabant, for the same reasons, and I haven't changed my opinion.
Since I got a lot of mail the last time I wrote about Arena, I should mention again that I have no position in the stock - or in any of the other companies in this space. But I could change my mind about that. If Arena runs up in advance of their FDA advisory panel in the absence of any new information, I'd consider going short (with money I could afford to lose). If I do that, I'll say so immediately.
+ TrackBacks (0) | Category: Clinical Trials | Diabetes and Obesity | Regulatory Affairs | The Central Nervous System | Toxicology
June 21, 2010
I haven't commented on the controversy over Boehringer Ingleheim's drug for female libido, flibanserin. An FDA advisory panel voted it down on Friday, and it wasn't close: 10-1 against whether the drug showed efficacy, and unanimously against its side effect profile. I really don't see how the drug is going to make it back from that kind of reception.
The press coverage of this compound has not been good. Far too many headlines have called it "Female Viagra", which is ridiculously off-base. Viagra, for its part, does absolutely nothing for the libido; it's plumbing, a pure cardiovascular effect. The assumption (a reasonable one, for many men) is that the desire is already there. Meanwhile, flibanserin is a central nervous system agent, affecting the mental state of sexual satisfaction, not any cardiovascular sequelae. The drugs are completely different.
And the FDA panel's problem (one of their problems) with the drug was that it doesn't seem to do much for desire, either. We can argue all day about whether low desire is a disease or not, but even if someone does want to do something about it, flibanserin doesn't seem to be the answer.
Boehringer is taking a lot of criticism for bringing the drug this far, actually. It was originally developed as an antidepressant, but during the trials reports came in of the sexual effects in female patients, so they repurposed it - taking the drug out of a crowded field and into completely new territory. You can admire that as showing flexibility, or you can worry that the company found a possible drug and then went shopping for a disease, with a willingness to invent one if it didn't quite exist.
I don't know where I stand on that latter point; I've no idea what the statistics are on low sexual desire as a problem (and I'm willing to bet that what numbers might exist have whopping error bars on them). But I think that we're not going to be revisiting this topic any time soon. The FDA panel officially encouraged Boehringer to continue research, but the vote tallies are not the sort of thing that would encourage anyone.
+ TrackBacks (0) | Category: Drug Development | Regulatory Affairs | The Central Nervous System
June 9, 2010
For a long time now, people have been searching for a way to raise HDL levels (the so-called "good cholesterol"). Statins will lower your LDL, while raising HDL just a pinch, but no one has a good, robust way to do it. (Niacin is probably the closest thing, but not everyone can take it). Many have tried, and failed, with Pfizer's CETP inhibitor torcetrapib being the most notably horrendous.
Now there's a completely new way to regulate HDL, and it comes from a direction you might not expect: the brain. A new paper in Nature Neuroscience demonstrates that melanocortin signaling, ghrelin and GLP-1 change HDL levels, through both altered cholesterol synthesis and uptake. Since these are involved in a number of ways in food intake and metabolism, it makes sense (in retrospect) that there would be a lipoprotein connection, but this does seem to be a dramatically direct one. (More and more, it appears that many metabolic processes that were thought to be more peripheral are under some sort of central control, actually). As the authors put it:
An integrated neuroendocrine control of food intake, body weight and glucose homeostasis, as well as cholesterol metabolism and cardiovascular lipid exposure, would connect all of the hallmarks of the metabolic syndrome. Therapies promoting the increase of HDL levels have been proposed for the prevention of atherosclerosis in humans. . . We speculate that modulation of neuroendocrine circuits may offer therapeutic opportunities to prevent cardiovascular disease.
Yes, indeed. It's not going to be easy, though. Ghrelin and GLP-1 have already been looked at for diabetes and obesity therapy, and they're tricky to deal with. Small-molecule ghrelin antagonists are known - as I should know - and there have been many reports of melanocortin receptor ligands as well. Of course, the question will be how many other things you might mess with at the same time, but it's going to be very interesting and worthwhile to unravel these.
+ TrackBacks (0) | Category: Cardiovascular Disease | The Central Nervous System
June 4, 2010
Now here's one that I certainly didn't expect: there's a mouse model of obsessive-compulsive disorder, where the animals have a mutation in the Hoxb8 gene. These animals spend huge amounts of time repetitively grooming themselves (and their cagemates), and eventually remove so much hair that they give themselves lesions. From what I can see, they're doing the usual moves that mice do, but spending a lot more time doing them. And it doesn't seem to be something due to insensitivity to pain; the animals have some sensory alterations, but disrupting Hoxb8 in the spinal cord only doesn't lead to the grooming phenotype.
A new paper from a group at University of Utah reports that the brain signature of Hoxb8 mutation is found only in a population of microglia, one variety of the support cells that surround neurons. Hoxb8 was already known to affect the formation of blood cells, so this cohort of microglia (about 40% of the total in the mouse brain) look to be derived from the same precursors. So this study went the direct route: they did bone-marrow transplants on the mutant mice so that normal Hoxb8 cells would be produced. And over a time scale of weeks,most of the mice stopped their overgrooming. Meanwhile, the group also transplanted mutant bone marrow into normal mice, whereupon some of these mice began obsessively removing hair. (Here's the Nature News article on all this).
This seems to be the first time that anyone's linked microglia with behavior. The focus, naturally enough, has been on the neurons themselves and their connections, but it looks like we're all going to have to broaden our outlook. There are some things that need to be cleared up here, though. For one thing, it's not certain that these mice are truly an analog of human OCD - even the form of it that involves obsessive hair-pulling. Other obsessive mice types are known, and it'll be quite interesting to see what shape their microglia are in. At the same time, it would be worth going the other way, and seeing if the pharmacological agents used for OCD have any affect in the Hoxb8 mice, too.
Another thing that this study demonstrates is that at least one population of microglia are being continually renewed in the brain from the bone marrow. What the different roles are of this group versus the "resident" microglia is yet to be figured out. My mental picture of the brain has always been this protected zone, with very little allowed to cross in or out, but that's clearly incorrect.
But it looks as if we can say that someone has drawn a direct link between the immune/blood cell system and behavior in an animal model. Such things had long been suspected, but they've been very difficult to prove. Whether these mice have OCD or not, they've illustrated something new. This makes me wonder if various immunosuppressive drugs could have psychological and behavioral side effects that we haven't been picking up on - anyone who knows that field care to comment?
+ TrackBacks (0) | Category: The Central Nervous System
May 17, 2010
I've been meaning to write about this paper from a recent issue of Science. They've been studying the differences between young (3-month) mice and old (16-month) mice - their ability to learn, and to remember. Markers of neuronal plasticity and the like are pretty similar between the groups, although the older mice definitely show some impairments in spatial learning and recall. Looking down at the genetic level, for effects on chromatin handling, didn't seem to show much, either - the young and old mice have similar levels of histone deacetylase and histone acyltransferase enzymes.
But a look at the real levels of acetylated histones showed something different: the older mice seemed to be deficient in one particular type of acetylation, H4K12. That particular lysine residue was acetylated much more readily in the younger animals in response to a fearful event, but the older animals didn't upregulate the process. A broad-based search using microarrays showed that a wide range of genes were regulated by the young mice when learning to avoid a fear stimulus, but were not altered to nearly the same degree in the older ones. And as it turns out, the H4K12 acetylation looks to be one of the common factors in the regulation of these genes.
The authors went so far as to use Vorinostat (SAHA), a marketed histone deacetylase inhibitor, to test this hypothesis. Administering that to the older mice (directly into the brain; it doesn't really cross on its own) led to both H4K12 effects and to beneficial effects on learning.
This is a long way from being a therapy, but it's a very interesting lead towards one. The effects of messing around with histone acylation states could be profound (both in the sense of "profoundly good" as well as "profoundly bad"), so it's going to be quite a while before the dust settles enough for us to know what to do. But I'm encouraged to see things like this coming up. Given that I'm 48, we're going to have to keep moving right along in order to have something ready by the time I'm going to need it!
+ TrackBacks (0) | Category: Aging and Lifespan | Alzheimer's Disease | The Central Nervous System
April 28, 2010
I wrote here some time ago about human cells actually making their own morphine - real morphine, the kind that everyone thought was only produced in poppy plants. Now there's a paper in PNAS where various deuterium-labeled precursors of morphine were dosed in rats, and in each case they converted it to the next step in the known biosynthesis. The yields were small, since each compound was metabolically degraded as well, but it appears that rats are capable of all steps of a morphine synthesis from at least the isoquinoline compound tetrahydropapaveroline (THP).
And that's pretty interesting, because it's also been established that rats have small THP in their brains and other tissues - as do humans. And humans, it appears, almost always have trace amounts of morphine in the urine - which leads one to think that our bodies may well, in fact, be making it themselves.
Why that's happening is quite another question, and where the THP comes from is another one. Working under the assumption that all this machinery is not just there for the heck of it, you also wonder if this system could be the source of one or more drug targets (I spoke about that possibility here). What you probably don't want to assume is that these targets would necessarily have to do with pain. We still don't know if there's room to work in here. But it's worth thinking about, if (for no other reason) to remind ourselves that there are plenty of things going on inside the human body that we don't understand at all.
+ TrackBacks (0) | Category: Biological News | The Central Nervous System
April 16, 2010
You know, let's just declare this "Sketchy Biotech Day" around here. A reader sends along this intriguing news item from Maryland regarding Rexahn Pharmaceuticals. They recently reported clinical data on their lead compound, Serdaxin,:
On Tuesday, the Rockville company reported the drug performed well in a phase 2a clinical trial for treating patients with one such ailment: major depressive disorder. But the announcement also said "the overall study did not achieve statistical significance," worrying investors and sending Rexahn's stock price tumbling from $3.53 to $1.76 that day.
Wednesday morning, executives felt compelled to issue a follow-up statement, offering "additional commentary, clarifications and insights" to allay investors' concerns. That apparently did the trick — at least somewhat. By the end of trading on Wednesday, the price had rebounded to $2.15. By Thursday morning, shares had climbed to $2.51; they were trading at $2.47 Thursday afternoon.
In its initial statement, Rexahn said that results from the trial, which enrolled 77 patients at several sites in the U.S., "are compelling and warrant further study in a larger phase 2 trial."
Well, to me, "compelling" clinical trial numbers are a hard thing to sell without the statistics to back them up. But that's not slowing these folks down. Here I offer you what is perhaps the most breathtaking rationalization I have yet heard about drug development - and mind you, that is saying a lot. Says Rexahn's CEO:
"Based on the feedback and reaction from our shareholders, stakeholders and other market participants, it is clear that neither the purpose of the Serdaxin trial or its results were well understood.
"The purpose of the Serdaxin Phase IIa trial was to establish, as a proof of concept, that Serdaxin can work as an antidepressant drug for patients suffering from Major Depressive Disorder," Ahn said. "I am happy to say that this is exactly what the study accomplished. The trial results unambiguously reach the conclusion that patients, especially those suffering from severe depression, respond positively to Serdaxin.
"Some market participants have asked us why our overall trial results were not statistically significant," he said. "The answer is simply that the Serdaxin study was never designed to achieve statistical significance as a primary objective, but rather to establish a positive signal among treated patients. This is exactly what the trial succeeded in accomplishing."
So here you have it: a clinical trial that was, apparently, not designed to show statistical significance. And it didn't! Champagne for everyone! Think of how many other drugs have had results just this compelling, but we've all just been too stupid to realize what we had. Throw open the pharma mausoleums and let the dead compounds come forth!
Perhaps some day we'll all look back on this event as the Day the Drug Industry Changed Forever. Or perhaps it's time to ask just what Serdaxin is. . .well, you'll never guess. It's clavulanic acid. (See, I told you that you wouldn't get it). Yep, the beta-lactamase inhibitor that's given as part of Augmentin, to overcome resistant strains of bacteria. Weirdly, it does seem to penetrate the blood-brain barrier, which is not something I would have guessed. And the Rexahn people have done some animal studies that suggest it has anxiolytic effects (as well as effects on sexual arousal, which they're not ignoring: that, friends, is the drug development candidate Zoraxel on their web site. Still clavulanic acid, though, but a rose by any other name. . .).
But none of that means a thing unless you achieve results in humans. And though I hate to contradict such a visionary mind as Dr. Ahn's, I'm afraid I'm going to have to hold out for statistical significance. And wonder, in the meantime, if any of the zillions of people who've taken clavulanate before ever noticed any elevation in their mood. Never happened to me, that's for sure. . .
+ TrackBacks (0) | Category: Clinical Trials | Drug Development | Infectious Diseases | The Central Nervous System
April 15, 2010
Protip: making slides that refer to your company's drug as "snake oil" and illustrate its use with a cartoon of witches standing around a cauldron is perhaps unwise. Particularly when you're in Marketing. Particularly when you also include unapproved uses for your drug on the slides. Worth noting, Pfizer.
+ TrackBacks (0) | Category: Business and Markets | The Central Nervous System | Why Everyone Loves Us
March 4, 2010
Robert Langreth, an editor at Forbes, points to a possible way that Dimebon could get approval for Alzheimer's: for its behavioral effects, not anything to do with amyloid or memory.
I'm not buying it, I have to say. Even Langreth's source admits that behavioral numbers didn't reach statistical significance. I don't see how this will be enough to rescue this one, even if one of the ongoing trials does use a behavioral score as an endpoint.
Update: Langreth has an earlier piece on how Dimebon appears to have been overhyped from the beginning, a viewpoint I concur with. The same thing happens with any drug for Alzheimer's, and is a constant problem in cancer and obesity, too.
+ TrackBacks (0) | Category: Alzheimer's Disease | Clinical Trials | The Central Nervous System
February 3, 2010
Looking through the latest papers to show up in the Journal of Medicinal Chemistry, this one on BACE-1 inhibitor compounds caught my eye. Perhaps I'm about to be unfair to it. At any rate, I'm going to ask of it something it doesn't provide: data in something that's alive. Doesn't have to be a person, a dog, or even a rat. A cell would do: something with a membrane to cross, with metabolic processes, and with the ability to accept or reject someone's new compound. Enzymes just have to sit there and take whatever you throw at them; living systems fight back.
I sometimes think that we'd be better served if each of the medicinal chemistry journals were split. In J. Med. Chem.'s case, we would then have the Journal of In Vitro Medicinal Chemistry and the Journal of In Vivo Medicinal Chemistry. The criteria for publishing in the two journals would be exactly the same, except to get into the latter one, you would have at least had to have tried your compounds out on something besides an in vitro assay. Doesn't mean that they have to have worked - you just have to have looked.
Although the case of compounds with molecular weights of 900 that have four amides and a sulfonamide in them, and are directed against a target in the central nervous system, might still be a bit of a stretch. I supposed what irritates me about this paper is that it starts off talking about Alzheimer's disease. And that's natural enough in a study dedicated to finding inhibitors of BACE-1, but the problem is, Alzheimer's disease occurs in human beings. And these compounds do not look to have much chance of doing anything inside any human's body. The best I can say for them is that they might give someone else an insight into something that they might be able to do to make something that might have a better chance of working.
Cranky folks like me would probably refer to the latter of my two new journals as just "J. Med. Chem.", and would refer to the former one by a variety of other easy-to-remember names. I offer this suggestion for free to the scientific publishing community, who will, I'm sure, reciprocate with things of equal value.
+ TrackBacks (0) | Category: Alzheimer's Disease | The Central Nervous System | The Scientific Literature
Dimebon (dimebolin) is a perfect example of the black-box nature of drug research for the central nervous system. Any medicinal chemist who looks at its structure would immediately say "CNS", but shrug when asked what specific receptors it might hit. I'd have guessed histamine (correctly), since loratidine used to pay my salary, and I also would have guessed a clutch of 5-HT stuff as well. But it also has activity at AMPA and NMDA glutamate receptors, L-type calcium channels, and more. If you can tell me what it's really doing up there, you shouldn't bother: hang up on me and start calling people with money, because you're ready to take over the CNS therapeutic area for sure.
This blunderbuss is getting a lot of attention these days, since the data for a Phase III trial against Alzheimer's should be available sometime in the spring. The road to that was a strange one. Dimebolin was used for years as an antihistamine in Russia, although I'm not aware if it had any particular reputation for cognitive enhancement in its time as a Soviet allergy pill. It was picked up in screening done during the 1990s at a research institute in the (once secret) military/industrial research city of
Chemogolovka Chernogolovka, about two hours from Moscow. It showed effects on learning in rodent models, and gradually advanced to human trials for Alzheimer's. Impressive data came out in 2008, and Medivation, who own the rights to it here, partnered with Pfizer for development.
Update: the city mentioned above is surely Chernogolovka, but it's interesting that it's appeared many times as Chemogolovka in the English press and literature. I chalk that up to the "rn" looking very much like an "m", and to the mistaken name being semi-plausible in a Stalinist-industrial way, as witness Magnitogorsk. Chernogolovka's much older, though.)
That Bloomberg report I linked to above has a lot of people excited, since there hasn't been a new therapy for Alzheimer's in quite a while (or, arguably, a decent one ever). I don't know what to think, myself. It's absolutely possible that the drug could turn out to have beneficial effects, but it's just as possible that it could miss meeting the high expectations that many investors seem to have for it. (Medivation's stock is up 80% over the last year, for example). A lot of eye-catching numbers from small Phase II trials tend to flatten out in the wider world of Phase III, and if forced, that's the way I'd bet here. (I am most definitely not giving investment advice, though - Alzheimer's drug development is a total crap shoot, and should only be approached with money you can afford to see incinerated).
I hope that Dimebon actually works, though - the world could use something that does. Just don't let anyone convince you that they know how it works, if it makes it through. Unraveling that will take quite a while. . .
+ TrackBacks (0) | Category: Alzheimer's Disease | Clinical Trials | The Central Nervous System
January 28, 2010
I had not been following the progress of Acorda's recently approved drug Ampyra for MS. (Well, more specifically, it's to improve gait and walking speed in MS patients). Opinion seems to be rather divided about how successful it'll be. On the one hand, new therapies for multiple sclerosis are certainly needed, but there's also room to argue about just how efficacious Ampyra really is.
I'm not going to fight that one out here, because we'll have the judgment of the market pretty soon. What I find interesting is the structure of this new drug: it's 4-aminopyridine. If there's a more simple, lower molecular weight structure approved within the next few years as an oral drug for anything, I'll be quite surprised.
This brings up several interesting topics relating to drug development and intellectual property. For one thing, this compound has been known for many years as a ligand for neuronal voltage-gated potassium channels, which is the mechanism by which it seems to work for MS patients. Some of these patients have experimented with it themselves over the years; the idea of using it for multiple sclerosis is certainly not new. (Here's a good history, taking things back a good 30 years through many players, with Elan a prominent one).
Secondly, it's not like the compound's chemical structure can be patented as such, either, since it's nowhere near novel. I have no idea of when 4-aminopyridine first makes its appearance in the chemical literature, but it's surely back into the 19th century. Nor is it anything like a rare chemical. For many years it was used as a bird-control poison. (High doses are fatal, but lower ones cause bird seizures that cause the rest of the flock to leave in consternation). We've got some on the shelf in our stockroom; I see in my Aldrich catalog that they're selling the 99% grade for $18/gram. And Aldrich is not exactly the world's low-cost chemical supplier. A railroad car full of the stuff could surely be arranged through someone, although it wouldn't exactly be pharmaceutical grade.
So. . .how then, some might wonder, does Acorda Therapeutics (partnered with Biogen Idec) get to charge several thousand dollars a year for Ampyra? (I don't think the actual price is known yet, but that's the best guess I've seen). One key factor is the bird-repellant aspect. Messing with ion channels in nerves is a tricky business, and 4-aminopyridine can and will cause trouble in humans if it's not dosed carefully. It's also (I believe) cleared pretty quickly, as you'd expect from something with that structure. Ampyra is a time-release formulation, an attempt to get enough of the compound into circulation over a long enough period, but without crossing over the line to too high a concentration, which could set off seizures and worse. Taking 4-aminopyridine from that railroad car and using that instead would be very much not recommended, considering what's waiting out there at inappropriate doses.
And that's Acorda's intellectual property. Plenty of work was done to find a good formulation for the drug, and Acorda spent the time and money to test one for safety and efficacy. They get to reap the fruits of their labors, if fruits there are. And that's what the market will decide for them. . .
+ TrackBacks (0) | Category: Patents and IP | The Central Nervous System
January 22, 2010
This one's also from the Department of Placebo Effects - read on. An interesting paper out in Nature details a study where volunteers took small doses of testosterone or placebo, and then participated in a standard behavioral test, the "Ultimatum Game". That's the one where two people participate, with one of them given a sum of money (say, $10), that's to be divided between the two of them. The player with the money makes an offer to divide the pot, which the other player can only take or leave (no counteroffers). A number of interesting questions about altruism and competition have been examined through this game and its variants - basically, the first thing to ask is how much the "dictator" player will feel like offering at all. (If you like, here's the Freakonomics guys talking about the game, which features in a chapter of their latest, SuperFreakonomics).
What's been found in many studies is that the second players often reject offers that they feel are insultingly low, giving up a sure gain for the sake of pride and sending a message to the first player. I think of this as the "Let me tell you what you can do with your buck-fifty" option. So what does exposure to testosterone do for this behavior? As the authors of the new paper talk about, there are two (not necessarily exclusive) theories about some of the hormone's effects. Increases in aggression and competitiveness are widely thought to be one of these, but there's also a good amount of literature to suggest that status-seeking behavior is perhaps more important. But if someone is going to be aggressive about the ultimatum game, they're going to make a lowball offer and damn the consequences, whereas if they're looking for status, they may well choose a course that avoids having their offer thrown back in their face.
Using known double-blind conditions for testosterone dosing in female subjects (sublingual dosing four hours before the test), the second behavior was observed. Update: keep in mind, women have endogenous testosterone, too. The subjects who got testosterone made more generous offers (from about $3.50 to closer to $4.00). The error bars on that measurement just miss overlapping, p = 0.031. But here's the part I found even more interesting: the subjects who believed that they got testosterone made significantly less fair/generous offers than the ones who believed that they got the placebo (P = 0.006). Because, after all, testosterone makes you all tough and nasty, as everyone knows. As the authors sum it up:
"The profound impact of testosterone on bargaining behaviour supports the view that biological factors have an important role in human social interaction. This does, of course, not mean that psychological factors are not important. In fact, our finding that subjects’ beliefs about testosterone are negatively associated with the fairness of bargaining offers points towards the importance of psychological and social factors. Whereas other animals may be predominantly under the influence of biological factors such as hormones, biology seems to exert less control over human behaviour. Our findings also teach an important methodological lesson for future studies: it is crucial to control for subjects’ beliefs because the pure substance effect may be otherwise under- or overestimated. . ."
+ TrackBacks (0) | Category: Biological News | General Scientific News | The Central Nervous System
January 18, 2010
Anyone looking over large data sets from human studies needs to be constantly on guard. Sinkholes are everywhere, many of them looking (at first glance) like perfectly solid ground on which to build some conclusions. This, to be honest, is one of the real problems with full release of clinical trial data sets: if you're not really up on your statistics, you can convince yourself of some pretty strange stuff.
Even people who are supposed to know what they're doing can bungle things. For instance, you may well have noticed a lot of papers coming out in the last few years correlating neuroimaging studies (such as fMRI) with human behaviors and personality traits. Neuroimaging is a wonderfully wide-open, complex, and important field, and I don't blame people for a minute for pushing it as far as it can go. But just how far is that?
A recent paper (PDF) suggests that the conclusions have run well ahead of the numbers. Recent papers have been reporting impressive correlations between the activation of particular brain regions and associated behaviors and traits. But when you look at the reproducibility of the behavioral measurements themselves, the correlation is 0.8 at best. And the reproducibility of the blood-oxygen fMRI measurements is about 0.7. The highest possible correlation you could expect from those two is the square root of their product, or 0.74. Problem is. . .a number of papers, including ones that get the big press, show correlations much higher than that. Which is impossible.
The Neurocritic blog has more details on this. What seems to have happened is that many researchers found signals in their patients that correlated with the behavior that they were studying, and then used that same set of data to compute the correlations between the subjects. I find, by watching people go by the in the street, that I can pick out a set of people who wear bright red jackets and have ugly haircuts. Herding them together and rating them on the redness of their attire and the heinousness of their hair, I find a notably strong correlation! Clearly, there is an underlying fashion deficiency that leads to both behaviors. Or people had their hair in their eyes when they bought their clothes. Further studies are indicated.
No, you can't do it like that. A selection error of that sort could let you relate anything to anything. The authors of the paper (Edward Vul and Nancy Kanwisher of MIT) have done the field a great favor by pointing this out. You can read how the field is taking the advice here.
+ TrackBacks (0) | Category: Biological News | Clinical Trials | The Central Nervous System
December 23, 2009
Another interesting approach to Alzheimer's therapy has just taken a severe jolt in the clinic. Elan and Transition Therapeutics were investigating ELEND005, also known as AZD-103, which was targeted at breaking down amyloid fibrils and allowing the protein to be cleared from the brain.
Unfortunately, the two highest-dose patient groups experienced a much greater number of severe events - including nine deaths, which is about as severe as things get - and those doses have been dropped from the study. I'm actually rather surprised that the trial is going on at all, but the safety data for the lowest dose (250mg twice daily) appear to justify continuing. The higher doses were 1g and 2g b.i.d., and the fact that they were going up that high makes me think that the chances of success at the lowest dose may not be very good.
So what is this drug? Oddly enough, it's one of the inositols, the scyllo isomer. Several animal studies had shown improvements with this compound, and there were promising results for Parkinson's as well. At the same time, scyllo-inositol has been implicated as a marker of CNS pathology when it's found naturally, so it's clearly hard to say just what's going on. As it always is with the brain. . .
+ TrackBacks (0) | Category: Alzheimer's Disease | Clinical Trials | The Central Nervous System | Toxicology
November 12, 2009
There's a disturbing article out at the New England Journal of Medicine on studies conducted on Neurontin (gabapentin) for various unapproved indications. Parke-Davis (and later Pfizer) looked at a wide range of possible indications for the drug - migraine, neuropathic pain, bipolar disorder, and more. That in itself isn't unusual, since CNS drugs often have rather broad and poorly defined mechanisms, and it's not like we understand any of them all that well.
What is unusual is the pattern found when comparing the internal reports with the published versions that showed up in the literature. The authors found that:
"More than half the clinical trials that we included in our analysis (11 of 20) were not published as full-length research articles. For 7 of the 9 trials that were published as full-length research articles, a statistically significant primary outcome was reported, and for more than half these trials, the outcome specified in the published report differed from the outcome originally described in the protocol. Three of the four trials with an unchanged primary outcome had statistically significant results for the protocol-specified primary outcome. Secondary outcomes also frequently differed between the protocol and the published report. Thus, trials with findings that were not statistically significant (P≥0.05) for the protocol-defined primary outcome, according to the internal documents, either were not published in full or were published with a changed primary outcome. . .all the changes that took place between what was specified in the protocol, what was known before publication (as presented in the internal company research reports), and what was reported to the public led to a more favorable presentation in the medical literature. . ."
The authors go on to point out that changing a primary outcome after you see the data is, in fact, a statistical sin (although that's not quite the phrase they use!) You really can't go around doing that, because you can end up chasing after random chance (and avoiding that is the whole point of running well-controlled trials). This does not cover Pfizer and Parke-Davis with glory, but it's worth noting that there's plenty of blame to go around when it comes to this practice:
"Our study is based on a relatively small number of trials undertaken to test a single drug manufactured by a single company and its successors. Furthermore, if a major purpose of the studies we examined was to promote off-label uses of gabapentin, the selective reporting we observed could be more extreme than that observed for studies conducted for other reasons. Previous studies in different settings have shown evidence of these same biases, however. Indeed, selective outcome reporting does not appear to be limited to studies funded by drug companies. Chan and colleagues examined published trials funded by the Canadian Institutes of Health Research and found that 40% of stated primary outcomes differed between the protocol and the published report. In addition, we cannot be certain that selective reporting was a decision made by employees of Pfizer and Parke-Davis, since the authors of the published reports included nonemployees. We did not systematically assess the methodologic quality of the included trials as described in the publications we examined. Previous research has indicated that quality scores are higher for trials conducted by the pharmaceutical industry than for trials conducted by not-for-profit entities, although reports from industry-sponsored trials have potentially distorted the scientific record because of other, less easily measured study factors."
That doesn't get the folks who conducted these gabapentin studies off the hook, although I should note that Pfizer disputes the conclusions of this article (as you'd certainly think that they would). And it's also worth noting that some of its authors have done work for the plaintiffs in suits against Pfizer over gabapentin (thus all the familiarity with the internal company documents, which came to light during discovery proceedings). But again, I don't see how that negates the paper's conclusions, and if Pfizer has any hard data that would do so, I think they should produce it with all speed.
And no, it's just a coincidence that this post involve Pfizer, after I've been going on about their merger business all week. Unfortunately, I think that they're probably not the only company that could be pointed at. But we in the industry shouldn't have things like this for others to uncover in the first place. Should we?
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System | The Dark Side | The Scientific Literature
October 13, 2009
Chronic fatigue syndrome has long been controversial and mysterious. Is the mystery clearing up, or getting deeper? There have been diagnoses of something like CFS for a long time, under a lot of different names. The common sign is persistent fatigue with no obvious physical cause, often accompanied by joint pain, disrupted sleep, and other symptoms. It's more common in women than in men - but then, so are a lot of autoimmune disorders, which has made some sort of immune syndrome a popular explanation. All sorts of contradictory data have been generated around that idea, but nothing convincing has emerged.
There's a preprint in Science from teams at the National Cancer Institute, the Cleveland Clinic, and Whittemore Peterson Institute that's attracting a lot of interest. It presents evidence for a viral infection which is far more common in patients diagnosed with CFS. What's even more intriguing is that the virus (XMRV, a mouse retrovirus) is already one that's suspected of involvement in some cases of prostate cancer, as shown by analysis of biopsy samples. (Commentary on that work here). About two-thirds of the CFS patients were found to be positive for the virus, as opposed to about three per cent of the control group. The WPI people are now saying that since the manuscript went in that further work has shown 98% of a 300-CFS-patient sample as positive for XMRV. More on that below.
In the case of the prostate patients, there seems to be a link with a deficiency in the RNAse L pathway, which is part of the interferon-induced antiviral response. It may be that patients with this immune system vulnerability are more susceptible to infection by XMRV, which then goes on to cause (or exacerbate) prostate cancer. There may be a link between RNAse L function and a diagnosis of CFS as well. It makes a neat story, and I hope that it's true.
But we're not quite there yet. No one's seen the data yet on that 300-patient cohort mentioned above, and it's not clear if a different diagnostic method was used on them compared to the group in the Science paper. And that paper itself doesn't have enough details on the patients to satisfy some readers - a specialist at the CDC complained about this to the New York Times, and said that his team would try to reproduce the results, but that he wasn't hopeful. (Working on chronic fatigue has not been the sort of thing that breeds a hopeful outlook, to be sure). Other researchers in the field have voiced their doubts to Science (who, to be sure, did accept the original paper).
One of the problems in this area has been defining who's a patient and who isn't. It's a bit of a catch-all diagnosis, or can be, so there's always the suspicion that even if there's a solid underlying cause that the data are hard to dig out of a heterogeneous patient sample. And there's the whole psychological-or-physical question, too, which is a sure route to raised voices and waving fists. My thinking is that there are very likely a number of people with other issues (which I will leave undefined) piled into this area, and that the necessary attempts to draw boundaries will be sure to leave someone upset.
As for this retrovirus angle, there are a number of other steps that need to be taken. Looking over historical blood and tissue samples will be very interesting - could you find that a person showed no sign of the virus when younger, then went positive before showing signs of the disease? Or does it stay latent for a longer period before finally breaking through? Are there animals that are susceptible to infection, and do they show similar symptoms to humans?
Can we at least demonstrate infection of cultured cells in vitro? (Update: I see that they've shown that, which is a very good step). Do any of the existing antiretroviral drugs have any effect on either of those processes, and if so, what happens when you give them to patients with CFS? What about the 3% or so of the population that seems to be positive for XMRV but shows no sign of either prostate cancer or CFS - what's different about them, if anything? And so on.
The Whittemore Peterson Institute people are way out in front on these questions, for better or worse. You may have said, as I did, "Who they?", but it turns out that they've only been around since 2004. The institute was set up by the parents of a CFS patient to do research in the field, and they've apparently been quite busy. Their web site gives the impression that the question of CFS as a retroviral infection is basically settled, but I'm not there yet. I have a lot of sympathy for the unidentified-infectious-agent line of thinking, and I believe that there are probably several things out there that will eventually fit into this category, but it can be a hard thing to prove. Let's hope this one is solid, so we can get to work.
+ TrackBacks (0) | Category: Infectious Diseases | The Central Nervous System
October 2, 2009
There's been a lot of valuable research into the placebo effect in recent years. That has interest in and of itself, and it also has a practical side. Understanding how people feel better on their own could tell us more about how to make our actual drugs work better, and it could also help us design clinical trials more efficiently. It would be a great help to know accurately how much of a positive effect is due to an investigational drug, without having to run thousands of people to separate that out statistically from a robust (but highly variable) placebo effect.
A new paper in the journal Pain (which has always gotten my vote for "Most To-the-Point Journal Title Possible") sheds some light on this issue, and on the mirror image "nocebo effect". The authors have looked over trials of several migraine drugs. In each case, there was a study arm and a placebo arm, and (since no one knew which group they were in), every patient got the lecture about possible side effects if you were in the treatment group.
The key point is that the migraine trials were investigating three different classes of drugs (anti-inflammatories, triptans, and anticonvulsants), and these three, not surprisingly, have different sets of possible side effects. The patients taking the drugs certainly manifested some of these, but what about the placebo groups?
Well, the placebo groups in the anti-inflammatory trials reported more dry mouth, nausea and vomiting than the placebo arms of the triptan studies. The placebo patients in the anticonvulsant trials, though, had a higher incidence of fatigue, sleepiness, and dizziness than the anti-inflammatory placebo groups reported. In short:
We found specific side effects in the placebo arms of anti-migraine trials when analyzing the three groups of drugs. We observed that the side effects that are expected for the active drug against which the placebo is compared, are also more frequent in the placebo group. In particular, anticonvulsant-placebos appear to have a higher rate of AEs (adverse events) than the other two classes of anti-migraine drugs. . .
. . .Moreover, it is also important to note that a larger number of patients in the anticonvulsant-placebo group discontinued the study (withdrawals due to AEs) than those in the triptan-placebo and NSAID-placebo groups. Both patients’ and experimenters’ expectations may have affected the AEs occurrence in the placebo groups. . .
This sort of thing has been observed before, but this is a particularly neat example. As a researcher (or a patient), it's important to remember that we tend to get what we think we're going to get. And we need to be aware of that, and be ready to correct for it if we have to.
+ TrackBacks (0) | Category: Cardiovascular Disease | Clinical Trials | The Central Nervous System
September 10, 2009
I was looking through my RSS feed of journal articles this morning, and came across this new one in J. Med. Chem.. Now, there's nothing particularly unusual about this work. The authors are exploring a particular subtype of serotonin receptor (5-HT6), using some chemotypes that have been looked at in serotinergic ligands before. They switch the indole to an indene, put in a sulfonamide, change the aminoethyl side chain to a guanidine, and. . .wait a minute.
Guanidine? I thought that the whole point of making a 5-HT6 ligand was to get it into the brain, and guanidines don't have the best reputation for allowing you to do that. (They're not the easiest thing in the world to even get decent oral absorption from, either, come to think of it). So I looked through the paper to see if there were any in vivo numbers, and as far as I can see, there aren't.
Now, that's not necessarily the fault of the paper's authors. They're from an academic med-chem lab in Barcelona, and animal dosing (and animal PK measurements) aren't necessarily easy to get unless you have a dedicated team that does such things. But, still. The industrial medicinal chemist in me looks at these structures, finds them unlikely to ever reach their intended site of action, can find no evidence in the paper's references that anyone else has ever gotten such a guanidine hydrazone into the brain, either, and starts to have if-a-tree-falls-in-the-forest thoughts.
Now, it's true that we learn some more about the receptor itself by finding new ligands for it, and such compounds can be used for in vitro experiments. But it's not like there aren't other 5-HT6 antagonists out there, in several different chemical classes, and that's just from the first page of a PubMed search. Many of these compounds do, in fact, penetrate the brain, because they were developed by industrial groups for whom in vitro experiments are most definitely not an end in themselves.
I don't mean to single out the Barcelona group here. Their work isn't bad, and it looks perfectly reasonable to me. It's just that my years in industry have made me always ask what a particular paper tells me that I didn't know, and what use might some day be made of the results. Readers here will know that I have a weakness for out-there ideas and technologies, so it's not like I have to see an immediate practical application for everything. But I would like to see the hope of one. And for this work, and for a lot of medicinal chemistry that comes out of academic labs, I just don't see it.
Update: it's been pointed out in the comments that there's a value in academic work that doesn't have to be addressed in industry, that is, training the students who do it. That's absolutely right. But at the same time, couldn't people be trained just as well by working on systems that are a bit less dead on arrival?
And no, I'm not trying to make that case that academic labs should make drugs. If they want to try, then come on down. If they don't, that's fine, too - there's a lot of important research to be done in the world that has no immediate practical application. But this sort of paper that I've written about today seems to miss both of these boats simultaneously: it isn't likely to produce a drug, and it doesn't seem to be addressing any other pressing needs that I can see, either.
And yes, I could say the same about my own PhD work. "The world doesn't need another synthesis of a macrolide antibiotic", I told people at the time. "But I do". Does it have to be like that?
+ TrackBacks (0) | Category: Academia (vs. Industry) | Drug Assays | Drug Development | The Central Nervous System | The Scientific Literature
September 2, 2009
Forest Labs has done very, very well with Lexapro (escitalopram) over the years. They're a comparatively small company, and their collaboration with Lundbeck (also a comparatively small company) in the antidepressant field has been the biggest event in their history.
Lexapro is the pure enantiomer of the earlier Lundbeck drug Celexa (citalopram), and it's been a very successful follow-on. (For a nasty spat over generic production of citalopram, see here). I'm generally not too keen on the follow-up-with-the-single-enantiomer strategy, I have to say. In general, I think it's slowly disappearing from the world as regulatory agencies look down on racemic mixtures. (I've never worked on a program myself where we seriously considered taking a racemate to the clinic - we always assumed that we'd end up developing a single enantiomer).
The New York Times has an article out detailing some of Forest's marketing plans, as revealed in documents before a Senate committee. Some of what the article has to say I agree with, and some of it I have to raise an eyebrow at, and we'll get to both of those. First off, in an area as large and competitive as antidepressants, I don't think that anyone should be surprised at what was in Forest's plan: lots and lots of lunches for physicians' offices, plenty of continuing medical education lectures (with plenty of food), and so on. One line shows that the company budgeted $34.7 million dollars to pay 2,000 physicians to deliver about 15,000 talks on the drug to their colleagues.
The Senate seems to be shocked at all this - well, pretending to be shocked, because no national politician can ever really be surprised at any way that money is used to influence anyone's decisions. But I'm not shocked, either. Leaving aside (just for a moment) the question of whether drugs should be promoted this way, the fact is that they are promoted this way, and have been for a very long time. And breaking down that lecture figure, that means a bit over $2,000 per lecture, and we don't know if that figure is supposed to cover just the honoraria for the speakers, or the whole cost of the lectures. Even if we assume the former, that comes to nearly eight lectures per physician per year, giving each of them about $17,000, pre-tax. Compared to the cost of advertising in the medical journals, general-interest magazines, or especially on television, that probably represents an excellent return for the money.
And Forest has been spending plenty of it. The article mentions that Vermont, for example, found that Forest (despite their size) was outspent in that state only by Lilly, Pfizer, Novartis, and Merck. Considering that those companies have many more drugs to sell than Forest does, that's an impressive figure. Of course, the only reason you spend money on marketing is to make even more of it back in sales, and they've certainly been doing that, too.
There are several questions here, and perhaps it's best to take them one by one. First off, is Lexapro worth what people (and insurance companies) are paying for it? The snappy economic answer is that of course it is, since that's the price that's willingly being paid, but let's talk utility instead. It does seem to be a good drug, arguably better than many of the others. It's been run head-to-head with Cymbalta (duloxetine), which is no poor performer itself, and shown to be superior And earlier this year, a Lancet article analyzed 117 controlled trials and found that there were clear clinical differences between the various antidepressants, and that Lexapro and Zoloft (sertraline) stood out as better than the rest.
The article recommended starting with the latter in new patients, I should note, and sertraline's now generic. I think that Forest's battle in the market is both against their similarly expensive competitors (where I think that they can claim to have an edge) and against cheap sertraline, where they may well not. (Update: and against their own (now generic) racemate - I'm digging into that comparison, and it'll be the subject of a follow-up post.) That said, depression is a famously heterogeneous field, and patients often have to try several drugs before somethings works, for reasons that are unclear. So yes, overall, I think that Lexapro is a useful drug, and that patients are getting benefit for their money.
The New York Times article is rather disingenuous on this point, by the way - you'd never know from it that there were differences between antidepressants, since they treat Lexapro and Prozac as interchangable, and you'd never know that there was evidence that Forest's drug might well be near the top of the list.
Next question: is Lexapro worth what Forest is spending to promote it? That question also splits into two, economically, depending on what we mean by "worth". As in the price question, from a strictly accounting perspective, we have to presume that Forest is seeing a financial benefit from their marketing activities; marketing does not run at a loss, not for long, it doesn't. And from a utility/societal benefit perspective, if Lexapro really is superior to most of their competitors, then I think the company is justified in making that case as loudly as they can.
Now we get to the tough one: are Forest's marketing activities appropriate or ethical? The arguing can now commence, because this is where we try to figure out what "as loudly as they can" actually means. I think the industry would be better off if there were less of an arms race in the marketing area. (Update: just to pick one benefit, it would make us look, in general, less sleazy, which is not to be underestimated). Even though marketing doesn't run at a loss, the return from it could be still higher if it were less expensive to do. Huge sales forces are expensive, and one of the reasons the sales forces are so big is that the competition's sales forces are so big, and so on. It's hard for any one company to climb down from its position, just from a game-theory point of view, so the most likely way for this to happen is through across-the-board restrictions on marketing, as enforced by the FDA, the FTC, or by physicians themselves. (I should mention, though, that there has been a voluntary retreat in the area of brand-covered swag). We're already seeing this pendulum swing back in the last few years, and it's fine with me if the process continues for a while longer. Doctors are perfectly free to close their doors in the faces of drug reps, and if I were in their position, I'd be tempted to do just that in many cases.
So if we come back around to that Times headine, it reads "Document Details Plan to Promote Costly Drug". And to that, I can say yes, it's a costly drug, set as high as the company thinks that people will pay for it, and to a level that they think they can make the most money with before its patent expires. And yes, Forest has a plan to maximize those profits, and if I were a shareholder (I'm not), I'd be righteously steamed if they didn't. And they did indeed write that plan down, so there are plenty of documents. I'd rather, myself, that the plan looked different than it does, and that's the way the world seems to be heading. But no matter what regulations come into force, there will always be plans to promote things that cost money.
+ TrackBacks (0) | Category: Business and Markets | Drug Prices | Press Coverage | The Central Nervous System | Why Everyone Loves Us
July 20, 2009
Here's an interesting look at the current state of the Alzheimer's field from Bloomberg. The current big hope is Wyeth (and Elan)'s bapineuzumab, which I last wrote about here. That was after the companies reported what had to be considered less-than-hoped-for efficacy in the clinic. The current trial is the one sorted out by APOE4 status of the patients. After the earlier trial data, it seems unlikely that there's going to be a robust effect across the board - the people with the APOE4 mutation are probably the best hope for seeing real efficacy.
And if bapineuzumab doesn't turn out to work even for them? Well:
“Everyone is waiting with bated breath on bapineuzumab,” said Michael Gold, London-based Glaxo’s vice president of neurosciences, in an interview. “If that one fails, then everyone will say we have to rethink the amyloid hypothesis.”
Now that will be a painful process, but it's one that may well already have begun. beta-Amyloid has been the front-runner for. . .well, for decades now, to be honest. And it's been a target for drug companies since around the late 1980s/early 1990s, as it became clear that it was produced by proteolytic cleavage from a larger precursor protein. A vast amount of time, effort, and money have gone into trying to find something that will interrupt that process, and it's going to be rather hard to take if we find out that we've been chasing a symptom of Alzheimer's rather than a cause.
But there's really no other way to find such things out. Human beings are the only animals that really seem to get Alzheimer's, and that's made it a ferocious therapeutic area to work in. The amyloid hypothesis will die hard if die it does.
+ TrackBacks (0) | Category: Alzheimer's Disease | Clinical Trials | Drug Industry History | The Central Nervous System
July 1, 2009
I wrote last summer about Vanda Pharmaceuticals and their difficulty getting a new antipsychotic Fanapt (iloperidone) through the FDA. At the time, they'd received one of those wonderful requests for more information from the agency, of the kind that spread cheer whenever they appear. I couldn't see how the company could clear this up without (probably) having to spend a lot of money that it didn't have, and I was very pessimistic about their survival.
And I was wrong. Big-time. Vanda received approval for iloperidone, in what is a major surprise not just for me, but for the company's hardy shareholders and for the few analysts left covering them. After congratulating the company, I feel like asking them "So, how did you do that, anyway?" To the best of my knowledge, the company didn't go back into the clinic - and it's hard to see how they even could have. Less than a year just isn't feasible from a standing start in an antipsychotic trial just on logistic grounds, let alone the fact that Vanda doesn't seem to have had the funds to even try.
So was this all just a regrettable misunderstanding? And if so, on whose part? Did the FDA misinterpret something, only to be argued back by the company? Or did Vanda mess something up in the original regulatory package? We may never know.
The question now that the dog has caught the mail truck is what to do with it. No deal has been announced yet to market the compound, and Vanda still doesn't seem to have the funds to sell it by itself. (Moreover, they don't seem to be recruiting a sales force). Some observers think that the company may have had time selling itself off, and that the run in the stock was overdone just for that reason.
In the meantime, though, the company should enjoy its good fortune (as should anyone who was holding its stock when the news hit). And readers of this blog should make a note that, in case there was any doubt, I can be completely, totally wrong about the field I work in. . .
+ TrackBacks (0) | Category: Business and Markets | Regulatory Affairs | The Central Nervous System
June 12, 2009
Well, this doesn't look good for Lilly. A huge pile of court documents has been unsealed in the ongoing lawsuits about Zyprexa's off-label promotion. The company has already paid some serious fines, and is now fighting it out with insurance companies and other plaintiffs who are seeking to recover their costs. Several states are suing them as well; those cases are still on their way.
Bloomberg News was given a lengthy list of internal company statements that will surely be difficult to explain in court. These were provided by one of the plaintiff's attorneys, Hagens Berman Sobol Shapiro LLP, so it's hardly a neutral selection (as Lilly is saying in response). But it's going to be interesting to see what sorts of explanations the company has for these. On the one hand, you have this:
In 1998, Lilly went back to the FDA seeking approval to market Zyprexa to those battling Alzheimer’s, the most common form of dementia, the company said in its 2003 request for a meeting on a proposed label change. Lilly withdrew its bid to promote Zyprexa for Alzheimer’s cases in 1999, according to the document.
In a November 2000 memo to Lilly salespeople, company executives said the dementia marketing initiative was abandoned because the FDA questioned Zyprexa’s effectiveness in treating the ailment.
“It was withdrawn due to vagueness on the FDA’s part regarding a definition of efficacy,” Lilly officials said in the document.
In a 2003 memo to FDA regulators citing the clinical studies, Lilly researchers acknowledged the death rates among older dementia patients on Zyprexa in the reviews were two times higher than their counterparts taking placebos.
Deaths among the patients taking Zyprexa in the studies were “significantly greater than placebo-treated patients (3.5 percent v. 1.5 percent, respectively),” Lilly officials said, according to the unsealed documents.
The studies didn’t find Zyprexa was effective in treating dementia, the company acknowledged in this document.
Lilly recognized this earlier, according to a 2002 document entitled “Zyprexa in serious mental illness (65 plus years) -- A Strategy Review.”
“The treatment of serious mental illness for people over the age of 65 has been identified as a growing opportunity for Zyprexa,” the authors wrote. “Unfortunately, attempts to gain the data to support an application for an indication in the treatment of dementia have to date been unsuccessful.”
But on the other hand, we have:
Lilly’s long-term care unit also saw Zyprexa sales rise 2.9 percent in the second quarter of 2002 as sales of Risperdal, Johnson & Johnson’s rival antipsychotic, fell, according to the 2002 marketing plan.
At that time, long-term care sales made up about 20 percent of Zyprexa prescriptions, according to the summary. Of that number, 65 percent were written for nursing-home patients.
Overall, prescriptions for older patients were the “2nd biggest money-producing segment” for Zyprexa in the U.S., according to a Feb. 15, 2002, e-mail from Lilly researcher Peter Feldman to Denice Torres, the company’s global marketing director.
In that e-mail, Feldman said company officials were saying in internal memos that they were going to stop studying Zyprexa’s potential health benefits for elderly consumers.
That would risk “killing the goose that lays the golden eggs to save on poultry feed costs,” Feldman said in the unsealed messages.
Torres assured him older consumers would continue to be a prime target for Zyprexa sales, according to the e-mail.
“Elderly remains an important aspect of target PT and affiliate focus,” she said in the message.
Increased Zyprexa sales to elderly patients also won Lilly’s long-term care unit praise in a 2003 newsletter unsealed as part of the documents.
“For two consecutive years, you have been on top and have turned in above-plan performance,” Grady Grant, Lilly’s national sales director, wrote in the newsletter. “I look forward to working with you as we set our sights on overtaking Risperdal as the number one antipsychotic in the marketplace!”
Lilly says these are cherry-picked quotes taken out of context. I'll await seeing what context they can be put in that will make them look less like. . .what they look like now.
+ TrackBacks (0) | Category: Regulatory Affairs | The Central Nervous System | The Dark Side
March 30, 2009
Over the years of this blog, I’ve occasionally made comments about how no one really knows much about how drugs for the major central nervous system diseases work. Well, actually, I’ve stated things more forcefully than that, but you get the idea. And although many people who work in the area have written in to say that they agree, I’ve had questions from people completely outside it (journalists and others) about whether I’m serious when I say these things.
Oh, I am. For the latest piece of evidence, see what’s just happened to LY2140023, Eli Lilly’s new drug candidate for schizophrenia. The company was running a three-armed Phase II trial: placebo vs. their existing drug Zyprexa vs. the new one, which is a metabotropic glutamate ligand. And what happens? The placebo group performs about twice as well as the usual average in such trials, for some reason. And that not only swamped the investigational drug, but Zyprexa as well, which has been on the market for years.
Now, there's been a lot of argument about whether the current generation of antipsychotic drugs is really better than the older ones. But I believe that they're all supposed to come in better than a placebo. As Lilly points out, though, "inconclusive trials are common in neuroscience", and they're going to run another one and hope that the patients don't all start improving again on powdered sucrose or whatever the placebo was. But this is especially surprising (and disappointing) because an earlier Phase II trial, run in a very similar design to the latest one, showed the compound working very well indeed. How do you go from such impressive results to no better than placebo in the same sort of trial design? Easy - just make sure that you're developing a drug for schizophrenia. Or depression. Or chronic pain, or Alzheimer's. Stick with the central nervous system, and your drug discovery career will never be boring.
Oh, and one last note: after all the recent stories about buried clinical results, I'm glad to see a company fall completely flat with one of its most promising drugs - and then get up at a large scientific meeting and tell everyone about it in detail. It's not that it's so unusual, but it's good to show people that it happens, and how it's handled when it does.
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
March 23, 2009
Last week's discussions around here about the merits (and demerits) of pharma-industry research seem to be coming at what's either a really good or a really bad time. Take a look at this Washington Post article on the handling of clinical data at AstraZeneca.
These details have come up during a large array of lawsuits over Seroquel (quetiapine). And if they're as represented in this article, it doesn't make AZ's marketing folks look very good, and (by extension) the rest of the industry's. We shouldn't be doing this sort of thing, on general principle. But if that's not enough, and it probably isn't, here's a more practical concern: does it take much imagination or vision to think that, with all kinds of health care reform ideas in the air, this sort of behavior might just make Congress want to reform our industry really good and hard?
+ TrackBacks (0) | Category: Clinical Trials | Press Coverage | Regulatory Affairs | The Central Nervous System | Why Everyone Loves Us
December 8, 2008
Depending on what news sources you follow, you may have heard a lot about it already: taking cognition-enhancing drugs to improve normal brain function. An editorial in Nature has just come out in favor of it, so although I wrote about this back in April, it’s time to talk over the issue again.
Let's define what we're talking about first. We really don’t have anything to selectively affect memory or general intelligence per se, but we do know something about how to affect attention span and wakefulness. So right now, cognition enhancement is mostly going to be found via the stimulants used for attention-deficit disorders, along with Cephalon’s Provigil (modafinil) for narcolepsy. These are the drugs of issue.
Nature started off this latest debate on this a few months ago, when they took an informal survey to see how many scientists used these. The results came in as “more than you might think”, although still a decided minority. One got the impression that these were reached for during grant-writing time in academia, for the most part, which would make their usage pattern similar to what you’d find among the student population. My guess is that the number of people using these in industrial research would be far smaller, for several reasons. For one thing, our work moves in different rhythms. As opposed to academia, we rarely have situations where a Big Creative Work has to be produced (or a huge pile of facts memorized) under time pressure. We do have big reports and presentations that come due, of course, but by the time the big ones are due there have been a lot of smaller ones, and the slides and material are largely summaries of those. It’s not to say that many of us couldn’t benefit from some extra attention to our work, it’s just that the opportunities for such aid aren’t as clear-cut.
Any discussion of this topic has to start with the question of how much good such drugs do. I’m willing to stipulate that for situations like the ones I’ve been describing – a need for long, sustained periods of focus and attention to detail – that these compounds do indeed help. They may be more beneficial for some people than for others, but yes, I think that their effect is real. (If anyone has evidence to the contrary, I’d be glad to hear it – I should also mention that I have no personal experience to draw on).
And that brings up another question, the second big one that always comes up in such a discussion: is it right to do this sort of thing? Now that’s a tangle, because a value judgment has come into the room. And anyone who wants to take a hard line has to deal with the fact that we already have a legal, well-known, widely used drug for cognitive enhancement: caffeine. If that doesn’t increase wakefulness, I’d like to know what does.
The comparison with steroid use in sports will also come up, although I regard that one as partially a red herring. The whole point of athletic competition is different from the point of achievement in the arts and sciences. All sports are essentially artificial constructs that we agree on rules for, and doping makes people worried and/or furious that these rules are being bent. Science, on the other hand, is the real world. If Barry Bonds did indeed break home run records with chemical aid – personally, I think he did – then a lot of people (including me) have a problem with that. But if someone comes up with, say, a proof of the Riemann Hypothesis with the use of modafinil and methylphenidate, well. . .a proof is a proof.
But there is a competitive aspect that the sports analogy does bear on: several junior faculty may all be vying for tenure at the same time, for example. If they’re all roughly equal in ability, does the appointment end up going to the one who uses pharmacological help most effectively? That’s where the same uneasy feeling starts to set in. It’s when you look at head-to-head, human-to-human cases that the arguing really gets going.
We’re going to have more and more of this to deal with in the future. I don’t expect it any time soon, but we’ll eventually be able to do more for memory – and, for all I know, for higher cognition. There are too many therapeutic reasons to investigate such things, and too many reasons for any useful drugs not to quickly escape to the population that doesn’t necessarily have anything wrong with it.
All of these issues are addressed by the authors of the latest Nature commentary, naturally. For example:
"Consider an examination that only a certain percentage can pass. It would seem unfair to allow some, but not all, students to use cognitive enhancements, akin to allowing some students taking a maths test to use a calculator while others must go without. (Mitigating such unfairness may raise issues of indirect coercion, as discussed above.) Of course, in some ways, this kind of unfairness already exists. Differences in education, including private tutoring, preparatory courses and other enriching experiences give some students an advantage over others.
Whether the cognitive enhancement is substantially unfair may depend on its availability, and on the nature of its effects. Does it actually improve learning or does it just temporarily boost exam performance? In the latter case it would prevent a valid measure of the competency of the examinee and would therefore be unfair. But if it were to enhance long-term learning, we may be more willing to accept enhancement. After all, unlike athletic competitions, in many cases cognitive enhancements are not zero-sum games. Cognitive enhancement, unlike enhancement for sports competitions, could lead to substantive improvements in the world."
The editorial comes down to several main points: that we need more solid data on the benefits and risks of such drugs for normal individuals, that competent adults should have to option to use them, and that policies should be worked out to deal with issues of fairness, coercion, and the like.
My own thoughts on this are deeply confused and divided. That’s partly because I’m a weirdo: I don’t drink alcohol, and in fact, I don’t even drink coffee. That goes back to what I’d have to classify as a deep reluctance to mess with the way my brain works through chemical means, a trait that was already well in place by the time I was a teenager, but which was only reinforced as I learned more and more biochemistry. So on one level, I have to think that we really don’t know enough about how the existing cognitive enhancing drugs work, let alone what we’ll know about future ones, and that alone would keep me away from them.
But I can come up with plenty of thought experiments that shake me up: imagine that the risks are better known, and that they're as much as, say, caffeine (but with more benefits). What then? What if such things turn out, many years in the future, to be necessary to work at any reasonably high level in science, since everyone else will be taking them, too? Is part of my problem with drugs that alter brain function a streak of Puritanism - would I feel better about using such things if I knew that they were guaranteed not to be enjoyable? And so on. . .I have to confess, I found such issues a lot easier to deal with inside the confines of old science fiction stories.
+ TrackBacks (0) | Category: General Scientific News | The Central Nervous System
November 17, 2008
There was a legal ruling last week in California that we’re going to hear a lot more of in this business. Conte v. Wyeth. This case involved metaclopramide, which was sold by Wyeth as Reglan before going off-patent in 1982. The plaintiff had been prescribed the generic version of the drug, was affected by a rare and serious neurological side effect (tardive dyskinesia, familiar to people who’ve worked with CNS drugs) and sued.
But as you can see from the name of the case, this wasn’t a suit against her physician, or against the generic manufacturer. It was a suit against Wyeth, the original producer of the drug, and that’s where things have gotten innovative. As Beck and Herrmann put it at the Drug and Device Law Blog:
The prescribing doctor denied reading any of the generic manufacturer's warnings but was wishy-washy about whether he might have read the pioneer manufacturer's labeling at some point in the more distant past.
Well, since the dawn of product liability, we thought we knew the answer to that question. You can only sue the manufacturer of the product that injured you. Only the manufacturer made a profit from selling the product, and only the manufacturer controls the safety of the product it makes, so only the manufacturer can be liable.
Not any more, it seems. The First District Court of Appeals in San Francisco ruled that Wyeth (and other drug companies) are also liable for harm caused by the generic versions of their drugs. At first glance, you might think “Well, sure – it’s the same drug, and if it causes harm, it causes harm, and the people who put it on the market should bear responsibility”. But these are generic drugs we’re talking about here – they’ve already been on the market for years. Their behavior, their benefits, and their risks are pretty well worked out by the time the patents expire, so we’re not talking about something new or unexpected popping up. (And in this case, we're talking about a drug that has been generic for twenty-six years).
The prescribing information and labeling has been settled for a long time, too, you’d think. At any rate, that’s worked out between the generic manufacturers and the FDA. How Wyeth can be held liable for the use of a product that it did not manufacture, did not label, and did not sell is a mystery to me.
Over at Law and More, a parallel is drawn between this ruling and the history of public nuisance law during the controversy over lead paint; the implication is that this ruling will stand up and be with us for a good long while. But at Cal Biz Lit, the betting is that “this all goes away at the California Supreme Court”. We’ll see, because that’s exactly where it’s headed and maybe beyond that, eventually.
And if this holds up? Well, Beck and Herrmann lay it out in their extensive follow-up post on the issue, which I recommend to those with a legal interest:
Conte-style liability can only drive up the cost of new drugs – all of them. Generic drugs are cheaper precisely because their manufacturers did not incur the cost of drug development – costs which run into the hundreds of millions of dollars for each successful FDA approval. Because they are cheap, generics typically drive the pioneer manufacturer’s drug off the market (or into a very small market share) within a few years, if not sooner. Generic drugs will stay cheap under Conte. But imposing liability in perpetuity upon pioneer manufacturers for products they no longer sell or get any profit from means that the pioneer manufacturers (being for-profit entities) have to recoup that liability expense somewhere. There’s only one place it can come from. That’s as an add-on to the costs of new drugs that still enjoy patent protection.
Exactly right. This decision establishes a fishing license for people to go after the deepest-pocketed defendents. Let’s hope it’s reversed.
+ TrackBacks (0) | Category: Regulatory Affairs | The Central Nervous System | Toxicology
October 31, 2008
Let’s talk sugar, and how you know if you’ve eaten enough of it. Just in time for Halloween! This is a field I’ve done drug discovery for in the past, and it’s a tricky business. But some of the signals are being worked out.
Blood glucose, as the usual circulating energy source in the body, is a good measure of whether you’ve eaten recently. If you skip a meal (or two), your body will start mobilizing fatty acids from your stored supplies, and circulate them for food. But there’s one organ that runs almost entirely on sugar, no matter what the conditions: the brain. Even if you’re fasting, your liver will make sugar from scratch for your brain to use.
And as you’d expect, brain glucose levels are one mechanism the body uses to decide whether to keep eating or not. A cascade of enzyme signals has been worked out over the years, and the current consensus seems to be that high glucose in the brain inactivates AMP kinase (AMPK). (That’s a key enzyme for monitoring the energy balance in the brain – it senses differences in concentration between ATP, the energy currency inside every cell, and its product and precursor, AMP). Losing that AMPK enzyme activity then removes the brakes on the activity of another enzyme, acetyl CoA-carboxylase (ACC). (That one’s a key regulator of fatty acid synthesis – all this stuff is hooked together wonderfully). ACC produces malonyl-CoA, and that seems to be a signal to the hypothalamus of the brain that you’re full (several signaling proteins are released at that point to spread the news).
You can observe this sort of thing in lab rats – if you infuse extra glucose into their brains, they stop eating, even under conditions when they otherwise would keep going. A few years ago, an odd result was found when this experiment was tried with fructose: instead of lowering food intake, infusing fructose into the central nervous system made the animals actually eat more. That’s not what you’d expect, since in the end, fructose ends up metabolized to the same thing as glucose does (pyruvate), and used to make ATP. So why the difference in feeding signals?
A paper in PNAS (open access PDF) from a team at Johns Hopkins and Ibaraki University in Japan now has a possible explanation. Glucose metabolism is very tightly regulated, as you’d expect for the main fuel source of virtually every living cell. But fructose is a different matter. It bypasses the rate-limiting step of the glucose pathway, and is metabolized much more quickly than glucose is. It appears that this fast (and comparatively unregulated) process actually uses up ATP in the hypothalamus – you’re basically revving up the enzyme machinery early in the pathway (ketohexokinase in particular) so much that you’re burning off the local ATP supply to run it.
Glucose, on the other hand, causes ATP levels in the brain to rise – which turns down AMPK, which turns up ACC, which allows malonyl-CoA to rise, and turns off appetite. But when ATP levels fall, AMPK is getting the message that energy supplies are low: eat, eat! Both the glucose and fructose effects on brain ATP can be seen at the ten-minute mark and are quite pronounced at twenty minutes. The paper went on to look at the activities of AMPK and ACC, the resulting levels of malonyl CoA, and everything was reversed for fructose (as opposed to glucose) right down the line. Even expression of the signaling peptides at the end of the process looks different.
The implications for human metabolism are clear: many have suspected that fructose could in fact be doing us some harm. (This New York Times piece from 2006 is a good look at the field: it's important to remember that this is very much an open question). But metabolic signaling could be altered by using fructose as an energy source over glucose. The large amount of high-fructose corn syrup produced and used in the US and other industrialized countries makes this an issue with very large political, economic, and public health implications.
This paper is compelling story – so, what are its weak points? Well, for one thing, you’d want to make sure that those fructose-metabolizing enzymes are indeed present in the key cells in the hypothalamus. And an even more important point is that fructose has to get into the brain. These studies were dropping it in directly through the skull, but that’s not how most people drink sodas. For this whole appetite-signaling hypothesis to work in the real world, fructose taken in orally would have to find its way to the hypothalamus. There’s some evidence that this is the case, but that fructose would have to find its way past the liver first.
On the other hand, it could be that this ATP-lowering effect could also be taking place in liver cells, and causing some sort of metabolic disruption there. AMPK and ACC are tremendously important enzymes, with a wide range of effects on metabolism, so there's a lot of room for things to happen. I should note, though, that activation of AMPK out in the peripheral tissues is thought to be beneficial for diabetics and others - this may be one route by which Glucophage (metformin) works. (Now some people are saying that there may be more than one ACC isoform out there, bypassing the AMPK signaling entirely, so this clearly is a tangled question).
I’m sure that a great deal of effort is now going into working out these things, so stay tuned. It's going to take a while to make sure, but if things continue along this path, there could be reasons for a large change in the industrialized human diet. There are a lot of downstream issues - how much fructose people actually consume, for one, and the problem of portion size and total caloric intake, no matter what form it's in, for another. So I'm not prepared to offer odds on a big change, but the implications are large enough to warrant a thorough check.
Update: so far, no one has been able to demonstrate endocrine or satiety differences in humans consuming high-fructose corn syrup vs. the equivalent amount of sucrose. See here, here, and here.
+ TrackBacks (0) | Category: Biological News | Diabetes and Obesity | The Central Nervous System
October 15, 2008
A recent correspondence on the topic of “Why aren’t there more drugs for the big CNS disorders” got me thinking about the topic. My take, having worked in the field, is that there is still so much unmet need in that area because we just don’t understand what's going on. It’s hard to come up with disease-altering therapies when you don’t really understand a single disease in the whole field.
Does amyloid cause Alzheimer’s, or does Alzheimer’s give you amyloid, or is amyloid just a sideshow? What sets off the chain of events that ends up killing off cells in the substantia nigra in Parkinson’s? What are the detailed molecular mechanisms of depression, or schizophrenia? Why don’t neurons remyelinate in multiple sclerosis? We don’t know. We know a lot more than we used to; we know more every year. But we don't know enough to cure anyone yet. Even in the areas where we know more than average, we still don’t know enough to step in with therapies that can do what people really want them to do.
By that, I mean do for these diseases what insulin does to Type I diabetes, or what antibiotics do to infections. To any working CNS researcher, such results in their field would be hard to distinguish from magic. We can’t even touch the surrogate endpoints, and do what statins do for LDL levels, or the various antihypertensives do for blood pressure. We understand those areas a lot better than we understand the brain. Even so, we still get surprised, as witness the controversy over Vytorin, and the various ongoing attempts to find something that will raise HDL – you push a bit beyond the mechanisms that you’ve worked out, and all sorts of things start to happen.
The best way I can illustrate how difficult it is to find a disease-stopping therapy for something like Alzheimer’s is to point out the incentives for one. Any drug company that came out with such a therapy would immediately have one of the most profitable drugs on the market, and they would go on to reap more and more money every year. Think of the sensation that a treatment that stopped – just plain stopped – schizophrenia. As I said, indistinguishable from magic. But the success that such a thing would have would be immense. The incentives are there; it’s just that the barriers are very, very high.
Of course, it may not be possible to do some of these things. I’d be very careful to rule anything out, at our current stage of ignorance, but schizophrenia may well be one of these things where a dozen (or a hundred) different pathways lead to the same roughly similar disease state. (Cancer, as I’ve said here before, is the best example of something like this). And even if it’s not quite that bad, it may be that the tangle of the disease just doesn’t lend itself to a single agent – that, I’d say, is quite likely. I strongly doubt if just stepping in and adjusting the D-whatever dopamine receptor a bit will turn out to do the trick. This doesn’t mean that it’ll be impossible to treat, it just means that it’ll be very complex.
And so it is, and so are most of the other big CNS conditions. I find it hard to explain to people outside the field just how complex these things are, and why progress has been so painfully slow for the patients who need these things now. It’s not that there’s no explanation. It’s that actually finding a drug that works for anything is ridiculously hard and expensive, a very difficult task by anyone’s standards. And CNS drugs are fiendishly difficult even by the standards of drug discovery.
+ TrackBacks (0) | Category: Alzheimer's Disease | Drug Development | Drug Industry History | The Central Nervous System
October 2, 2008
Merck has taken a step that many people have been expecting, and announced that they are no longer developing taranabant, their cannabinoid antagonist (or is it an inverse agonist?)
I'd expressed grave doubts about the drug earlier this year, which turned out to be well-founded. That latter post included the line "I don't see how they can get this compound through the FDA", and now Merck seems to have come to the same conclusion. Further clinical data seem to have shown far too many psychiatric side effects (anxiety, depression, and so on), which increased along with the dose of the drug.
The cannabinoid antagonist field has already experienced a crisis of confidence after Sanofi-Aventis's rimonabant failed to gain approval in the US. This latest news should ensure that no company tries to develop one of these drugs until we've learned a great deal more about their pharmacology. Given how little we know about the mechanisms of these mental processes, though, that could take a long, long time. We can pull the curtain over this area, I think.
+ TrackBacks (0) | Category: Diabetes and Obesity | Drug Development | The Central Nervous System | Toxicology
September 9, 2008
As I’ve noted here, and many others have elsewhere, we have very little idea how many important central nervous system drugs actually work. Antidepressants, antipsychotics, antiseizure medications for epilepsy – the real workings of these drugs are quite obscure. The standard explanation for this state of things is that the human brain is extremely complicated and difficult to study, and that’s absolutely right.
But there’s an interesting paper on antipsychotics that’s just come out from a group at Duke, suggesting that there’s an important common mechanism that has been missed up until now. One thing that everyone can agree on is that dopamine receptors are important in this area. Which ones, and how they should be affected (agonist, antagonist, inverse partial what-have-you) – now that’s a subject for argument, but I don’t think you’ll find anyone who says that the dopaminergic system isn’t a big factor. Helping to keep the argument going is the fact that the existing drugs have a rather wide spectrum of activity against the main dopamine receptors.
But for some years now, the D2 subtype has been considered first among equals in this area. Binding affinity to D2 correlates as well as anything does to clinical efficacy, but when you look closer, the various drugs have different profiles as inverse agonists and antagonists of the receptor. What this latest study shows, though, is that a completely different signaling pathway – other than the classic GPCR signaling one – might well be involved. A protein called beta-arrestin has long been known to be important in receptor trafficking – movement of the receptor protein to and from the cell surface. A few years ago, it was shown that beta-arrestin isn’t just some sort of cellular tugboat in these systems, but can participate in another signaling pathway entirely.
Dopamine receptors were already complicated when I worked on them, but they’ve gotten a lot hairier since then. The beta-arrestin work makes things even trickier: who would have thought that these GPCRs, with all of their well-established and subtle signaling modes, also participated in a totally different signaling network at the same time? It’s like finding out that all your hammers can also drive screws, using some gizmo hidden in their handles that you didn’t even know was there.
When this latest team looked at the various clinical antipsychotics, what they found was that no matter what their profile in the traditional D2 signaling assays, they all are very good at disrupting the D2/beta-arrestin pathway. Since some of the downstream targets in that pathway (a protein called Akt and a kinase, GSK-3) have already been associated with schizophrenia, this may well be a big factor behind antipsychotic efficacy, and one that no one in the drug discovery business has paid much attention to. As soon as someone gets this formatted for a high-throughput assay, though, that will change – and it could lead to entirely new compound classes in this area.
Of course, there’s still a lot that we don’t know. What, for example, does beta-arrestin signaling actually do in schizophrenia? Akt and GSK-3 are powerful signaling players, involved in all sorts of pathways. Untangling their roles, or the roles of other yet-unknown beta-arrestin driven processes, will keep the biologists busy for a good long while. And the existing antipsychotics hit quite a few other receptors as well – what’s the role of the beta-arrestin system in those interactions? The brain will keep us busy for a good long while, and so will the signaling receptors.
+ TrackBacks (0) | Category: Biological News | The Central Nervous System
July 29, 2008
I've talked about a lot of difficult therapeutic areas, but here's another boulevard of broken dreams: schizophrenia drugs. I was working on follow-ups to a promising clincial candidate, which has since been promising a number of times without ever delivering. It certainly missed its endpoints in schizophrenia by a mile in Phase II. That was actually my introduction to the drug industry back in 1989 - I followed that up with several years working on Alzheimer's, another notorious graveyard of good ideas, which makes me wonder why I didn't just quit at some point and open that chain of all-you-can-eat catfish restaurants that the Northeast so desperately needs.
Of course, once in a while a drug for dementia actually works a bit, and since there's a huge underserved market out there, it's a prize worth seeking (ask Lilly or J&J). But clinical success rates are absolutely horrific in the whole CNS area, and the latest company to demonstrate this is Vanda Pharmaceuticals in Maryland (I've always wondered if they're named after a spectacular, and spectacularly finicky, genus of orchid).
Vanda's drug iloperidone has been kicking around for years now. Hoechst Marion Roussel (now Aventis) seems to have discovered it in the early 1990s, and they, Novartis, and Titan have all handed it off to someone else over the years. Vanda was the last in line, but they got the dreaded "Not Approvable" letter from the FDA yesterday, and the company's stock was blitzed, down 73 per cent at the close. And the thing is, this drug got a lot closer than anything I used to work on. Vanda did hit their endpoints against placebo and against haloperidol, but the problem is, these are not necessarily the standard of care in schizophrenia:
" The FDA stated that Vanda had demonstrated the effectiveness of iloperidone at 24 mg/day in the 3101 study for which the company reported results in December, 2006, and that the efficacy was similar to the active comparator, ziprasidone (Geodon(R), Pfizer Inc.). In addition, the FDA also stated that iloperidone was superior to placebo in patients with schizophrenia at doses of 12-16 mg/day and 20-24 mg/day in a prior study. However, the FDA expressed concern about the efficacy of iloperidone in patients with schizophrenia relative to the active comparator, risperidone (Risperdal(R), Johnson & Johnson), used in prior studies. The FDA indicated that it would require an additional trial comparing iloperidone to placebo and including an active comparator such as olanzapine (Zyprexa(R), Eli Lilly & Company) or risperidone in patients with schizophrenia to demonstrate the compound's efficacy further. The FDA also stated that it would require Vanda to obtain additional safety data for patients at a dose range of 20 to 24 mg/day."
So iloperidone works, but quite possibly not well enough compared to what's already on the market. That alone won't quite sink your drug - you can always hunt for a patient cohort that benefits from a new compound, and you'll quite likely be able to find one if you have the resources. But as that last line mentions, there are additional safety concerns.
Reading between the lines, it would appear that iloperidone had the best chance of distinguishing itself in efficacy at the higher doses, but that the FDA wanted to make sure that side effects didn't start kicking in up there. This paper makes you wonder if one problem is the (dreaded) QT interval prolongation. Many other factors have looked relatively clean in some of the reported trials.
I greatly doubt if we'll see iloperidone surface again. Vanda wouldn't seem to have the resources, and too many other organizations have passed on it. At this point, it's hard to see why more money would be put into the compound. . .
+ TrackBacks (0) | Category: Business and Markets | Clinical Trials | The Central Nervous System
April 3, 2008
I was having a discussion the other day about which therapeutic areas have the best predictive assays. That is, what diseases can you be reasonably sure of treating before your drug candidate gets into (costly) human trials? As we went on, things settled out roughly like this:
Cardiovascular (circulatory): not so bad. We’ve got a reasonably good handle on the mechanisms of high blood pressure, and the assays for it are pretty predictive, compared to a lot of other fields. (Of course, that’s also now one of the most well-served therapeutic areas in all of medicine). There are some harder problems, like primary pulmonary hypertension, but you could still go into humans with a bit more confidence than usual if you had something that looked good in animals.
Cardiovascular (lipids): deceptive. There aren’t any animals that handle lipids quite the way that humans do, but we’ve learned a lot about how to interpolate animal results. That plus the various transgenic models gives you a reasonable read. The problem is, we don’t really understand human lipidology and its relation to disease as well as we should (or as well as a lot of people think we do), so there are larger long-term problems hanging over everything. But yeah, you can get a new drug with a new mechanism to market. Like Vytorin.
CNS: appalling. That goes for the whole lot – anxiety, depression, Alzheimer’s, schizophrenia, you name it. The animal models are largely voodoo, and the mechanisms for the underlying diseases are usually opaque. The peripheral nervous system isn’t much better, as anyone who’s worked in pain medication will tell you ruefully. And all this is particularly disturbing, because the clinical trials here are so awful that you’d really appreciate some good preclinical pharmacology: patient variability is extreme, the placebo effect can eat you alive, and both the diseases and their treatments tend to progress very, very slowly. Oh, it’s just a nonstop festival of fun over in this slot. Correspondingly, the opportunities are huge.
Anti-infectives: good, by comparison. It’s not like you can’t have clinical failures in this area, but for the most part, if you can stop viruses or kill bugs in a dish, you can do it in an animal, or in a person. The questions are always whether you can do it to the right extent, and just how long it’ll be before you start seeing resistance. With antibacterials that can be, say, "before the end of your clinical trials". There aren’t as many targets here as everyone would like, and none of them is going to be a gigantic blockbuster, but if you find one you can attack it with more confidence than usual.
Diabetes: pretty good, up to a point. There are a number of well-studied animal models here, and if your drug’s mechanism fits their quirks and limitations, then you should be in fairly good shape. Not by coincidence, this is also a pretty well-served area, by current standards. If you’re trying something off the beaten path, though, a route that STZ or db/db rats won’t pick up well, then things get harder. Look out, though, because this disease area starts to intersect with lipids, which (it bears saying again) We Don't Understand Too Well.
Obesity: deceptive in the extreme. There are an endless number of ways to get rats to lose weight. Hardly any of them, though, turn out to be relevant to humans or relevant to something humans would consider paying for. (Relentless vertigo would work to throw the animals off their feed, for example, but would probably be a loser in the marketplace. Although come to think of it, there is Alli, so you never know). And the problem here is always that there are so many overlapping backup redundant pathways for feeding behavior, so the chances for any one compound doing something dramatic are, well, slim. The expectations that a lot of people have for a weight-loss therapy are so high (thanks partly to years of heavily advertised herbal scams and bizarre devices), but the reality is so constrained.
Oncology: horrible, just horrible. No one trusts the main animal models in this area (rat xenografts of tumor lines) as anything more than rough, crude filters on the way to clinical trials. And no one should. Always remember: Iressa, the erstwhile AstraZeneca wonder drug from a few years back, continues to kick over all kinds of xenograft models. It looks great! It doesn’t work in humans! And it's not alone, either. So people take all kinds of stuff into the clinic against cancer, because what else can you do? That leads to a terrifying overall failure rate, and has also led to, if you can believe it, a real shortage of cancer patients for trials in many indications.
OK, those are some that I know about from personal experience. I’d be glad to hear from folks in other areas, like allergy/inflammation, about how their stuff rates. And there are a lot of smaller indications I haven’t mentioned, many of them under the broad heading of immunology (lupus, MS, etc.) whose disease models range from “difficult to run and/or interpret” on the high side all the way down to “furry little random number generators”.
+ TrackBacks (0) | Category: Animal Testing | Cancer | Cardiovascular Disease | Diabetes and Obesity | Drug Assays | Drug Development | Infectious Diseases | The Central Nervous System
March 25, 2008
There’s an interesting article in Angewandte Chemie by Richard Silverman of Northwestern, on the discovery of Lyrica (pregabalin). It’s a rare example of a compound that came right out of academia to become a drug, but the rest of its story is both unusual and (in an odd way) typical.
The drug is a very close analog of the neurotransmitter GABA. Silverman’s lab made a series of compounds in the 1980s to try to inhibit the aminotransferase enzyme (GABA-AT) that breaks GABA down in the brain, as a means of increasing its levels to prevent epileptic seizures. They gradually realized, though, that their compounds were also hitting another enzyme, glutamic acid decarboxylase (GAD), which actually synthesizes GABA. Shutting down the neurotransmitter’s breakdown was a good idea, but shutting down its production at the same time clearly wasn’t going to work out.
So in 1988 a visiting Polish post-doc (Ryszard Andruszkiewicz) made a series of 3-alkyl GABA and glutamate analogs as another crack at a selective compound. None of them were particularly good inhibitors – in fact, most of them were substrates for GABA-AT, although not very good ones. But (most weirdly) they actually turned out to activate GAD, which would also work just fine to raise GABA levels. Northwestern shopped the compounds around because of this profile, and Parke-Davis took them up on it. One enantiomer of the 3-isobutyl GABA analog turned out to be a star performer in the company’s rodent assay for seizure prevention, and attempts to find an even better compound were fruitless. The next few years were spent on toxicity testing and optimizing the synthetic route.
The IND paperwork to go into humans was filed in 1995, and clinical trials continued until 2003. The FDA approved the drug in 2004, and no, that’s not an unusual timeline for drug development, especially for a CNS compound. And there you’d think the story ends – basic science from the university is translated into a big-selling drug, with the unusual feature of an actual compound from the academic labs going all the way. Since I’ve spent a good amount of time here claiming that Big Pharma doesn’t just rip off NIH-funded research, you’d think that this would be a good counterexample.
But, as Silverman makes clear, there’s a lot more to the story. As it turned out, the drug’s efficacy had nothing to do with its GABA-AT substrate behavior. But further investigation showed that it’s not even correlated with its activation of the other enzyme, GAD. None of the reasons behind the compound’s sale to Parke-Davis held up, except the biggest one: it worked well in the company’s animal models.
The biologists at P-D eventually figured out what was going on, up to a point. The compound also binds to a particular site on voltage-gated calcium channels. That turns out to block the release of glutamate, whose actions would be opposed to those of GABA. So they ended up in the same place (potentiation of GABA effects) but through a mechanism that no one suspected until after the compound had been recommended for human trials! There were more lucky surprises: Lyrica has excellent blood levels and penetration into the brain, while none of the other analogs came close. As it happened, and as the Parke-Davis folks figured out, the compound was taken up by active transport into the brain (via the System L transporter), which also helps account for its activity.
And Silverman goes on to show that while the compound was originally designed as a GABA analog, it doesn’t even perform that function. It has no binding to any GABA receptor, and doesn’t affect GABA levels in any way. As far as I can see, a really thorough, careful pharmacological analysis before going into animals would probably have killed the compound before it was even tested, which goes to show how easy it is to overthink a black-box area like CNS.
So on one level, this is indeed an academic compound that went to industry and became a drug. But looked at from another perspective, it was an extremely lucky shot indeed, for several unrelated reasons, and the underlying biology was only worked out once the compound went into industrial development. And from any angle, it’s an object lesson in how little we know, and how many surprises are waiting for us. (Silverman himself, among other things, is still in there pitching, looking for a good inhibitor of GABA aminotransferase. One such drug, a compound going back to 1977 called vigabatrin, has made it to market for epilepsy in a few countries, but has never been approved in the US because of retinal toxicity).
+ TrackBacks (0) | Category: Academia (vs. Industry) | Drug Development | Pharmacokinetics | The Central Nervous System
March 19, 2008
One of the less appealing ways that companies have tried to fill their drug portfolios over the years has been to look through their current drugs in search of one with a main active metabolite. That altered structure then becomes a clinical candidate for the next generation. I’ve said bad things before about Clarinex (desloratadine), son of Claritin (loratadine), the most famous example of this practice. That “des” prefix tells you that the newer drug is just the older one minus some part of its structure, in this case, minus a carbamate group that the liver clips off anyway. Even non-chemists can see the change, looking at the top parts of the structures in those Wikipedia articles.
Now comes Pristiq (desvenlafaxine), spawn of Effexor (you guessed it, venlafaxine). This one's also a simple metabolic change, OH from O-methyl. Wyeth has done very well with Effexor over the last few years, and they’re not ready to give up on that market share once it goes off patent this year. The timing of this new drug is, as they say, no coincidence. The Carlat Psychiatry Blog, not a place to go to find lots of warm feelings for the drug industry, has its “Top Five Reasons to Forget About Pristiq”. From the way things look, I have to agree with them; at the moment it’s hard to see much need for the stuff.
But there’s a good point made there by an investigator on the clinical trials, Dr. Michael Liebowitz of Columbia. He, quite reasonably, is waiting for the market to settle whether the drug is of any use or not: “If it is useful, then it will make money for the company, and if it is not, it won’t.” Update: there's more from Liebowitz on this topic, and on follow-on CNS drugs in general.
Exactly. I’m very much in favor of letting drugs stand or fall on their merits, if any. My first guess is that Pristiq is not much of an addition to the pharmacopeia – and if it isn’t, Wyeth deserves to lose the money they’ve put into it, since that, frankly, would have been the presumption from very early in the drug’s development. They took this drug forward at their own risk, and should profit or lose by it accordingly.
One thing I’ll say for the company, though: they actually seem to be running a head-to-head study between the two drugs. That’s good to see, and it’ll be quite interesting to see what case Wyeth can make, if any, after the data come in. At least they’re not just banging on tin cans and shouting “Now with the great taste of fish!” or something. Interestingly, as a comment on the Carlat blog points out, the company has already published data on one unimpressive trial with Pristiq, and I have to thank them for doing that, too. If there was ever a head-to-head efficacy study run between Claritin and Clarinex, I definitely missed it – I’m willing to be corrected, of course, but I’m pretty sure that there never was one).
So one-and-a-half cheers for Wyeth. I wish, in most cases, that companies would avoid the metabolite-drug idea. Alternatively, I wish that everyone’s drug pipeline was well stocked enough that such follow-ups didn’t look financially appealing. But if you’re going to have them, taking an honest look at their benefits is the only way to go.
+ TrackBacks (0) | Category: "Me Too" Drugs | Drug Development | The Central Nervous System | Why Everyone Loves Us
March 17, 2008
I'm a bit under the weather today, so this one will be short. Since we were talking about CNS drugs and clinical trials the other day, I thought I'd mention this article from Neuropsychopharmacology.
The authors compare reported trials of first- and second-generation antipsychotics, looking to see if potentially biasing factors have skewed the results. One (perhaps surprising) result is that the authors couldn't confirm that the newer drugs necessarily work better through showing fewer extrapyramidal side effects (those are the muscle and coordination problems seen with many drugs in this class). While they may well show fewer EPS problems, that doesn't seem to be related to their efficacy.
Something of a relief is that the efficacy of the various drugs didn't seem to be related to whether or not the drug industry sponsored the trials involved. Given the publication bias of submitting favorable results (and given the obvious commercial interests involved), that's perhaps surprising. But it's welcome data to bring up the next time someone e-mails me about the eeevil Pharma companies and their bought-and-paid-for studies. I don't get a steady stream of that stuff, fortunately, but it still shows up often enough.
I still keep an occasional eye on the antipsychotic drugs, since that was the first therapeutic area I ever worked in when I joined the industry. The project came to a bad end, which was probably a good thing for my professional development. We took the drug into Phase I, gave substantial doses to normal volunteers, and rejoiced when it did nothing to them whatsoever. Then the compound went into Phase II and into real schizophrenics, and it did nothing whatsoever to them either, sad to say. And so it goes in CNS drug development. I don't think that study was ever published; if it had been it would have presumably made the correlation between industry sponsorship and efficacy even less likely. . .
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
March 12, 2008
Well, I wish I hadn’t been right about this one. Last month I spent some time expressing doubts about Merck’s new obesity drug candidate taranabant, a cannabinoid-1 ligand similar to Sanofi-Aventis’s failed Acomplia (rimonabant). S-A ran into a number of central nervous system side effects in the clinic, and although they’ve gotten the drug approved in a few markets, it’s not selling well. US approval, now long delayed, looks extremely unlikely.
I couldn’t see why Merck wouldn’t run into the same sort of trouble. If a report from a Wall St. analyst (Aileen Salares of Leerink Swann) is correct, they have. Merck’s presenting on the compound at the next American College of Cardiology meeting (at the end of this month in Chicago), and information from the talk has apparently leaked out in violation of the ACC's embargo. There appears to be some difficulty both on the efficacy and side effect fronts – bad news all around.
The company was aiming for a 5% weight loss, but only reached that at the highest dose (4 mg). The report is that CNS side effects were prominent at this level, twice the rate of the placebo group. The next lower dose, 2 mg, missed the efficacy endpoint and still seems to have shown CNS effects. According to Salares, nearly twice the number of patients in the drug treatment group dropped out of the trial as compared to placebo, citing neurological effects which included thoughts of suicide.
While there’s no confirmation from Merck on these figures, they’re disturbingly plausible, because that’s just the profile that got rimonabant into trouble. If this holds up, I think we can say that CB-1 ligands as a CNS therapeutic class are dead, at least until we understand a lot more about their role in the brain. Two drugs with different structures and different pharmacological profiles have now run into the same suite of unacceptable side effects, and the main thing they have in common is CB-1 receptor occupancy. There’s always the possibility that a CB-1 antagonist (or inverse agonist) might have a use out in the periphery – they could have immunomodulatory effects – but anyone who tries this out would be well advised to do it with a compound that doesn’t cross the blood-brain barrier.
And as for taranabant, if the data are as reported I don’t see how Merck can get this compound through the FDA. Even if they did, by some weird accident, I don’t see why they’d pull the pin on such a potential liability grenade. Can you imagine what the labeling would have to look like in order to try (in vain, most likely) to insulate the company from lawsuits? That makes a person wonder how on earth the company could have been talking about submitting it for approval later this year, which is what they were doing just recently. They must have had these numbers when they made that statement – wouldn’t you think? And they must have immediately realized that this would be trouble – you’d think. If that Leerink Swan report is correct, the company’s recent statements are just bizarre.
+ TrackBacks (0) | Category: Clinical Trials | Diabetes and Obesity | The Central Nervous System | Toxicology
February 27, 2008
There’s an interesting analysis in the latest PLoS Medicine on the clinical effectiveness of four modern antidepressant drugs: Prozac (fluoxetine), Effexor (venlafaxine), the partially discontinued Serzone (nefazodone), and Paxil (paroxetine). The authors compared all the published placebo-controlled studies on these drugs, and further included all the regulatory filing data. (Update: not so! See below). The result made headlines all over the place yesterday, because one of the things they found was that these drugs hardly seem, compared to placebo, to do anything at all.
Here’s the odd part: that shouldn’t have been such a big surprise. It wasn’t surprising to the authors of the paper – in fact, they started with the belief that this would be the case, because that analysis has been done before. Their interest was in seeing if there was some difference between different populations of depressed patients – is there some group for which the drugs really show efficacy or not?
As it turns out, there is, but perhaps not for the reasons you’d think. The most severely depressed cohort do seem to show a statistically meaningful response, but that seems largely because the placebo group’s response goes down. That’s been the difficulty with antidepressant clinical trials forever: there is a huge placebo response. This isn’t news; people have been studying this effect and trying to figure out what it means (or figure out a way around it) for years.
So, what does this do to the whole popular culture around the SSRI drugs – you know, “Listening to Prozac”, “Prozac Nation”, all that sort of thing? In this case, popular culture probably has it wrong. These drugs are not magical happy pills, but “Placebo Nation” just doesn’t have the same ring to it. The whole subject is too tangled to make for a catchy title.
It makes sense, though, that this is the area of drug discovery where the biggest placebo effect would turn up – you’d have to think that for depressed patients, a big step would have to be the thought that something can actually affect their condition. It’s bound to help for them to believe (correctly) that their moods aren’t necessarily part of the drab fabric of the universe, but depend instead on the (changeable) chemical weather inside their brains. Knowing those things, and the act of taking a medication that is supposed to work, is enough to help between a quarter and a half of depressed patients right there.
The actual mechanism of the placebo effect is a field of great interest and potentially great importance. (See here, here, here, and here). News like this makes a person wonder, though: if large parts of the public become convinced that antidepressant drugs don’t work, will they? And the question remains: do the SSRI drugs do anything at all through their supposed chemical mechanisms? (It's not like we know). One way to find out would be to run a placebo versus placebo trial. You could blind things at the start, even though everyone was getting the same sugar pills, and you’d presumably see the same response in each group. Then you unblind and cross everyone over, telling people that they’d been in one group and were now headed to the other. Careful work would give you four study arms: (1) people who responded to placebo, and who were then told they’d been taking sugar but were now getting the real drug, (2) people who responded and were told that they were taking a real drug but were now being switched off of it, (3) people who didn’t respond, but were told that this was because they’d been taking sugar, but help was now on the way, and (4) people who didn’t respond, and were told that they’d been getting (apparently ineffective) drug, but were now coming off even that. Fascinating stuff, but we’re going to have to wait for the North Koreans to set it up for us, because no other regulatory agency would let it through.
But from this latest analysis, we can conclude something interesting. The fact that the placebo effect diminishes in the most severely depressed patients, but that the drugs continue to show the same level of efficacy, suggests that they do have some effects of their own. To me, that’s the real news from this study. It reminds me of G. K. Chesterton’s line about journalism being the business of saying “Lord Jones Is Dead” to people who never knew he was alive. In this case, the headlines have been “Antidepressants Don’t Work”, but that should have been the headline years ago. This one should have come in as “Antidepressants Might Actually Do Something”.
Update: A closer look, as suggested in the comments section, shows that the trials included in the meta-analysis were mostly quite short (six weeks or less), when a good deal of evidence would suggest that these drugs take longer to become truly worthwhile. And there is only one study on moderate depressed patients, making it hard to draw conclusions about that group. See the comments page on the article here for more criticisms. So, do antidepressants work or not? You can find an answer that fits, no matter what you need it to be. . .
+ TrackBacks (0) | Category: Clinical Trials | The Central Nervous System
February 11, 2008
One of the first projects I ever worked on when I started in industry was targeting Alzheimer's disease. Things could have easily worked out to find me still targeting Alzheimer's disease, nearly twenty years later, because the standard of care really hasn't advanced all that much in the intervening years.
It's a hard, hard area to work in. CNS programs are always difficult, since we understand less about the brain's workings than those of any other organ, and since the brain's own blood supply is another barrier to getting a drug through to do anything. And Alzheimer's has tough features on top of that, since (for one thing) we're the only animal that gets the disease, and (for another) the clinical trials needed to show efficacy can be hideously long, large, and expensive. And the underlying biochemistry has been a tangle, too: I've said for years that if you'd told me back in 1990 that people would still be arguing in 1999 (or 2002, or 2007. . .) about whether amyloid caused Alzheimer's or not, that I probably would have buried my head in my hands.
Well, it's 2008, and the arguments may finally get settled. There's a report in Nature from a group at Harvard who did an experiment that's simultaneously brute-force and elegant. The elegant part was the monitoring live brain cells in mutant mice as amyloid protein deposited among them - and the brute force part was that this monitoring involved surgically implanting a small window into their skulls to do it.
What they found was that the characteristic amyloid plaques of Alzheimer's can form startlingly quickly - on a time scale of hours. This is beyond what anyone had suspected, for sure. And the further pathologies (microglia, etc.) that form around the plaques definitely come later, settling a long-standing dispute. There's always the worry that the mouse model (which was engineered to develop amyloid within the brain) might not reflect the human disease, but this is pretty compelling (and alarming) stuff.
If this is even close to what's going on in humans, a therapy that tries to prevent amyloid formation or deposition is going to have some real work to do. We'll be finding that out, though, and good luck to everyone involved. . .
+ TrackBacks (0) | Category: Alzheimer's Disease | The Central Nervous System
January 8, 2008
I came across a neat article in Nature from a group working on a new technique in neuroscience imaging. They expressed an array of four differently colored fluorescent proteins in developing neurons in vivo, and placed them so that recombination events would scramble the relative expression of the multiple transgenes as the cell population expands. That leads to what they’re calling a “brainbow”: a striking array of about a hundred different shades of fluorescent neurons, tangled into what looks like a close-up of a Seurat painting.
The good part is that the entire neuron fluoresces, not just a particular structure inside it. Being able to see all those axons opens up the possibility of tracking how the cells interact in the developing brain – where synapses form and when. That should keep everyone in this research group occupied for a good long while.
What I particularly enjoyed, though, was the attitude of the lab head, Jeff Lichtman of Harvard. He states that he doesn’t really know exactly what they’re looking for, but that this technique will allow them to just sit back and see what there is to see. That’s a scientific mode with a long history, basically good old Francis-Bacon style induction, but we don’t actually get a chance to do it as much as you’d think.
That varies by the area being under investigation. In general, the more complex and poorly understood the object of study, the more appropriate it is to sit back and take notes, rather than go in trying to prove some particular hypothesis. (Neuroscience, then, is a natural!) In a chemistry setting, though, I wouldn’t recommend setting up five thousand sulfonamide formations just to see what happens, because we already have a pretty good idea of what’ll happen. But if you’re working on new metal-catalyzed reactions, a big screen of every variety of metal complex you can find might not be such a bad idea, if you’ve got the time and material. There’s a lot that we don’t know about those things, and you could come across an interesting lead.
Some people get uncomfortable with “fishing expedition” work like this, though. In the med-chem labs, I’ve seen some fishy glances directed at people who just made a bunch of compounds in a series because no one else had made them and they just wanted to see what would happen. While I agree that you don’t want to run a whole project like that, I think that the suspicion is often misplaced, considering how many projects start from high-throughput screening. We don’t, a priori, usually have any good idea of what molecules should bind to a new drug target. Going in with an advanced hypothesis-driven approach often isn’t as productive as just saying “OK, let’s run everything we’ve got past the thing, see what sticks, and take it from there”.
But the feeling seems to be that a drug project (and its team members) should somehow outgrow the random approach as more knowledge comes in. Ideally, that would be the case. I’m not convinced, though, that enough med-chem projects generate enough detailed knowledge about what will work and what won’t to be able to do that. (There’s no percentage in beating against structural trends that you have evidence for, but trying out things that no one’s tried yet is another story). It’s true that a project has to narrow down in order to deliver a lead compound to the clinic, but getting to the narrowing-down stage doesn’t have to be (and usually isn’t) a very orderly process.
+ TrackBacks (0) | Category: Biological News | Drug Development | The Central Nervous System | Who Discovers and Why
September 27, 2007
Yet another study has shown no link between the former vaccine additive thimerosal and neurological problems in children. This one evaluated over a thousand seven-to-ten year olds for a long list of outcomes, and came up negative. No strong correlations were found, and the weak ones seemed to spread out evenly among positive and negative consequences.
This is just the kind of data that researchers are used to seeing. Most experiments don't work, and most attempts to find correlations come up empty. The leftovers are a pile of weak, unconvincing traces, all pointing in different directions while not reaching statistical significance. For a study like this one, though, this is a good answer. The question is "Does thimerosal exposure show any connection to any of these forty-two neurological symptoms?", and the answer is "No. Not as far as we can see, and we looked very hard indeed."
And this isn't the first study to find the same sorts of results. The fact that reports of autism do not appear to decrease after thimerosal is removed from circulation should be enough on the face of it, but there's the problem. To the committed believers, those data are flawed. And these latest data are flawed. All the data that do not confirm that thimerosal is a cause of autism are flawed. Now, if this latest study had shown the ghost of statistical significance, well, that would no doubt be different. But it didn't, and that means that there's something wrong with it.
The director of SafeMinds, a group of true thimerosal believers if ever there was, actually was on the consulting board of this latest study. But she withdrew her name from the final document. The CDC is conducting a large thimerosal-and-autism study whose results should come out next year. Here's a prediction for you: if that one fails to show a connection, and I have every expectation that it'll fail to show one, SafeMinds will not accept the results. Anyone care to bet against that?
As a scientist, I've had to take a lot of good, compelling ideas of mine and toss them into the trash when the data failed to support them. Not everything works, and not everything that looks as if it makes sense really does. It's getting to the point with the autism/thimerosal hypothesis- has, in fact, gotten to the point quite some time ago - that the data have failed to support it. If you disagree, and I know from my e-mail that some readers will, then ask yourself what data would suffice to make you abandon your belief? If you can't think of any, you have moved beyond medicine and beyond science, and I'll not follow you.
+ TrackBacks (1) | Category: Autism | The Central Nervous System | Toxicology
June 15, 2007
Everyone will have heard the news about Wednesday's FDA Advisory Commitee vote on Accomplia / Zimulti (rimonabant). If you'd tried to convince folks a few years ago that this drug wouldn't make it to a vote until summer of 2007, and would be unanimously rejected when it did, you'd have been looked at with pity and concern. No, this drug was going to conquer the world, and now people are talking merger-of-desperation.
Hey, you don't even have to go back a few years. Here's an article from 2006:
"A new anti-obesity pill that market observers say could become the world's biggest-selling drug is close to getting approval from the European Commission. . .
Gbola Amusa, an analyst with research firm Sanford C Bernstein, said that Acomplia could achieve $4.1bn in annual sales by 2010, in part because it has been shown in clinical trials not only to trim fat but to increase levels of good cholesterol and control diabetes.
"In the blue sky scenario, this could become the world's best- selling drug as the indication is so broad," he said. "It has a path to revenues that we rarely ever see from a pharma product."
Oh, the blue sky scenario. I'm no stranger to it myself - I love the blue sky scenario. But how often does it ever descend to earth? It's not going to do it this time. Sanofi-Aventis was reduced to making the suggestion that every potential patient be first screened for depression, which doesn't sound like the sort of iron wrecking ball that usually gets welded to the world's best-selling drugs.
In the wake of this development disaster, here are a few points that may not get the attention they deserve: first, consider the money that S-A has spent on this drug. We're never going to be shown an accurate accounting; no one outside the upper reaches of the company will ever see that. But I seriously doubt if they've ever spent more on any program. There's an excellent chance that most of it will never be recovered, not by rimonabant - it'll have to be recovered by whatever drugs the company can come up with in the future. They'll be priced accordingly.
Second, think about the position of their competitors. All sorts of companies have pursued this wonder blockbuster opportunity. If you run CB-1 antagonists through the databases, all kinds of stuff comes hosing out. Merck and Pfizer are the companies that were most advanced - you don't get much more advanced than Phase III clinical trials - but plenty of others spent time and money on the chase. All of those prospects have taken grievous damage. Odds are that rimonbant's problems are mechanism-related, and proving otherwise will be an expensive job. This is something to consider when you next hear about all those easy, cheap me-too drugs.
And finally, it's worth thinking about what this says about our abilities to prosecute drug development in general. Just as in the case of Pfizer's torcetrapib, we have here a huge, expensive, widely anticipated drug that comes down out of the sky because of something we didn't know about. It's going to happen again, too. Never think it won't. This is a risky, white-knuckle business, and it's going to be that way for a long time to come.
+ TrackBacks (0) | Category: Clinical Trials | Diabetes and Obesity | The Central Nervous System | Toxicology
June 11, 2007
The FDA briefing documents for Wednesday's discussion of Accomplia / Zimulti (rimonabant) have been posted, and they're an interesting read indeed. As everyone in the industry knows, this drug was once looked on as the next potential record-breaker, and writing the first part of this sentence in that verb form tells you a lot about what's happened since. It's the first antagonist targeting the cannabinoid CB-1 receptor, and at one point it looked like it was going to make people lose their excess weight, shed their addictions, and for all I know refinance their mortgages.
But then the delays hit in the US - long, long ones, delays which made fools of everyone who tried to predict when they would be over. And the drug meanwhile made it to market in Europe, where it has very quietly done not very much.
Now we may be seeing some of the reasons for the FDA'a "approvable" letter over a year ago. It's not efficacy - the FDA's briefing summary states that:
"Rimonabant 20 mg daily vs. placebo was associated with statistically and clinically
significant weight loss. Rimonabant 5 mg daily vs. placebo was associated with
statistically significant but clinically insignificant weight loss. . .rimonabant 20 mg daily vs. placebo was associated with a statistically significant 8% increase in HDL-C and a statistically significant 12% decrease in TG levels. There were no significant improvements in levels of total or LDL-C in the rimonabant 20 mg daily vs. placebo group. . .rimonabant 20 mg compared with placebo was associated with a statistically significant 0.7% reduction in HbA1c in overweight and obese subjects with type 2 diabetes taking either metformin or a sulfonylurea."
Not bad - just the sort of thing you'd want to go after the whole obesity/diabetes/cardiovascular area, you'd think. But the problem is in the side effects, and one in particular:
"The incidence of suicidality – specifically suicidal ideation – was higher for 20 mg
rimonabant compared to placebo. Similarly, the incidence of psychiatric adverse events,
neurological adverse events and seizures were consistently higher for 20 mg rimonabant compared to placebo. . ."
They're also concerned about other neurological side effects, and seizures as well. The seizure data don't look nearly as worrisome, except in the obese diabetic patients, for whom everything seems to be amplified. And all of this happens at the 20-mg dose, not at the 5 (which doesn't do much for weight, either, as noted above). And for those who are wondering, yes, on my first pass through the data, I find these statistics much more convincing than I did the ones on the Avandia (rosiglitazone) association with cardiac events.
I had my worries about rimonabant a long time ago, but not for any specific reason. It's just that I used to work on central nervous system drugs, and you have to be ready for anything. Any new CNS mechanism, I figured, might well set off some things that no one was expecting, given how little we understand about that area.
But isn't it good to finally hear what the arguing is about? Sanofi-Aventis has been relentlessly tight-lipped about everything to do with the drug. I can see why, after looking at the FDA documents, but this isn't a problem that's going to go away by not talking about it. The advisory committee meeting is Wednesday. Expect fireworks.
+ TrackBacks (0) | Category: Cardiovascular Disease | Clinical Trials | Diabetes and Obesity | The Central Nervous System | Toxicology
April 2, 2007
Here's something that you don't see discussed very often, but it's worth some thought: what kind of personality do you need to have to do drug discovery research? Clearly, any conclusions are going to carry over well to other fields, but drug work has some peculiarities that can't be ignored.
The most obvious one is that the huge, horrible, overwhelming majority of projects never lead to a marketed drug. Many readers will have seen the sobering statistics of 85 to 95% failure rates in the clinic, but (bad as that is) it doesn't get across the number of times that projects get nowhere near the clinic at all. Take it from the top: the majority of targets that are screened for chemical matter don't turn up anything useful (it's not even close). The majority of the ones that do still die on their way to clinical trials. And then a solid 90% of those don't make it to market.
So, if you define yourself as a success by whether or not you've put something on a pharmacy shelf, you've set a very high bar, one that many people in basic research don't reach. It's different for people further down the line, where the field has already narrowed. But if you're working on early med-chem, for example, you're likely to go years between realistic shots at a drug you can claim part of the credit for.
That'll vary by your company's culture, too. Some companies bang out projects like a sawmill spitting out boards - or try to, anyway - while others carefully take their time for years and years. There's no certain advantage to either method, as far as I can see (else the companies doing the best one would have taken over by now and driven other modes out of existence). But you'll certainly have more shots on goal at the first type of company, which might keep your spirits up. Of course, the fact that you're largely going to be getting more chances to fail in the clinic might just depress them again, so you have to take that into account.
It'll also vary by therapeutic area. Central nervous system projects are going to run slower than oncology ones, by and large. In cancer, the clinical goals are comparatively clear, and where the disease is often (and most terribly) progressing at such a pace to give you solid numbers in a reasonably short period. Contrast that to Alzheimer's disease, for example, whose ruinous clinical trials could take years to tell you anything useful. Cancer will also give you more shots per compound, since a drug that does zilch for pancreatic cancer (and most do just that) might be useful in the lung or liver. While what we call cancer is several hundred diseases, what we call Alzheimer's might only be one. Depression and schizophrenia are clearly more complicated and split up, but (as opposed to cancer), there's no easy way to tell how many types there are or what particular one a patient might be presenting with, so the clinical work is correspondingly more difficult.
So, this is the pharmaceutical world you're going to have to live in. If you take each drug project personally, as an indicator of your own worth, you're probably not going to make it. You'll be beaten down by the numbers. As an antidote, a bit of realistic fatalism is helpful, although too much of it will shade into ah-that'll-never-work cynicism, which is the ditch on the other side of the road from prideful optimism. I'd recommend learning to enjoy the upside surprises, and to not be surprised by the failures (while still looking them over to see if there's something you can avoid next time around). You really have to draw a line between the things you can affect through your own talent and hard work, and the things you can't. Most of the crucial stuff is in the second category. A sense of humor about your own abilities and limitations will serve you well. But that goes for a lot of other jobs besides the drug business, doesn't it?
+ TrackBacks (0) | Category: Alzheimer's Disease | Cancer | Drug Development | The Central Nervous System | Who Discovers and Why
March 14, 2007
Schering-Plough woke everyone up with a large surprise bid for Organon, the long-suffering pharmaceutical arm of Akzo Nobel. Many people are spinning this as a good deal for everyone involved, and that may be. But then again, people always seem to say that about mergers and buyouts, and they're not always right, are they?
Organon has strengths in endocrinology and CNS, two areas where Schering-Plough has never had much of a presence (despite a number of shots on goal in the latter one). The problem is, even the companies that have had success in CNS have had to take a lot of shots, because it's that kind of field. No one really understands antipsychotic and antidepressant drugs, for example, and thinking that you do has been a recipe for trouble. The biggest prospect in Organon's portfolio is asenapine, an antipsychotic, which Schering-Plough seems to have their eye on. But that's a drug that Pfizer walked away from last year, citing "a commercial analysis of the compound". It was my impression that that commercial analysis took place after Pfizer got a look at some of the clinical data, though, and I see that I'm not alone in thinking that way (nor alone in my worries about betting big money on drugs in this area).
There's also the question of how much Schering-Plough is paying. When Bayer bought up German Schering (no relation!), they paid around eight times earnings (and that was already more than they wanted to spend, thanks to Merck-Darmstadt). Schering-Plough is paying around 14 times earnings for Organon. As pointed out here, Akzo Nobel was hoping to raise 9 billion by spinning Organon off, and estimates were that an outside buyer might be willing to go as high as 10. Schering-Plough offered 14.5, which news seems to have been greeting by incredulous delight over in Holland, as well it might. Words like "phenomenal" have been used.
There's no word yet (that I've seen) on what will happen to various sites and divisions of the two companies after the buyout goes through. You'd have to assume that there will be some real cuts - that's the only way to make that price work out - and I'd guess that it'll be more on the Organon side. Most of the press coverage has been about how Schering-Plough is picking up all these late-stage drugs, with nothing about the earlier research at all. (Of course, my assumptions about where a drug company will make cuts in research has already been shown to be imperfect, so keep that in mind. . .)
Well, Fred Hassan is a dealmaker, no doubt about it. And it's true that you have to take risks to make it in the drug industry. As (disclosure!) someone who still holds a reasonable amount of Schering-Plough stock, I hope this one works out for him. It'll be interesting to watch.
+ TrackBacks (0) | Category: Business and Markets | The Central Nervous System
February 21, 2007
The last panel of the day (I missed a good part of one in between, unfortunately) is on the FDA's Critical Path initiative and personalized medicine in general. It's moderated by Greg Simon of FasterCures, and features Michelle Hoffman of Drug Discovery and Development, Robert McBurney of BG Medicine, Gualberto Ruaño of Genomas, John Swen of Pfizer, and Janet Woodcock of the FDA.
Hoffman makes the point that some of the hyper-sceptical reporting of drug and medical issues is a reaction to the genomics hype of a few years ago. (I know, some of you out there who've seen stories that were ripped right from an idiotic press release are wondering where this sceptical reporting is, but I think she's talking about, say, the New York Times.
McBurney spoke about his academic background, saying that he cares even more about data now than he did back then, since millions of dollars are riding on the results. He also mentions the genomic craze, using a good analogy - that a caterpillar and the corresponding butterfly have exactly the same genetic sequence. "I have the same genome I did when I was born," he said, "but some things have changed along the way". His company has recently signed a deal with the FDA to look at preclinical liver toxicity, wirh funding from several large drug companies.
Ruaño is speaking about reverse genomics, "bedside to bench" work for figuring out drug and tox mechanisms. He's summarizing a recent paper in Mol. Psych. on the metabolic effects of antipsychotic drugs - the weight gain and prediabetic symptoms seen in a subset of patients. He and his company did a large parallel search for DNA markers between the patient populations on the two ends of the weight-gain distribution. As it turned out, in olanzapine-treated patients, an ApoE marker was higher in the heavy group, and and ApoE4 one was higher in the lean. For risperidone-treated patients, the leptin receptor and the NPY5 receptor fit the same pattern. They're starting to use their markers prospectively to predict how new patients will respond.
That leads into John Swen's view from Pfizer. He makes the point right at first that he doesn't blame the media for the overhyping of new technologies, as opposed to the people promoting them. (He's got a point, although I'd share the blame out a bit more - compare Michelle Hoffman's view at the beginning of this post). His view of the Critical Path initiatives is that it's going to be long slog to get biomarkers and transitional medicine to work out - worth it, certainly, but not something that's going to start delivering in a short time frame. (No argument here!) He also thinks that we could be doing a lot better than we are in things like new clinical trial designs (which is interesting coming from a company that's run the first large published Bayesian clinical trial).
And finally, Woodcock of the FDA is being asked about how the whole Critical Path initiative is going to fare at its current level of funding. She also feels that the media are very cynical about the sorts of technologies that are being promoted, which corroborates the over-reaction theme. She also says that the parts of the scientific community that are "more vested in the reductionist model" are also pushing back a bit. (My take is that the minute something useful comes out of the whole personalized medicine field, most of the critics will shut up with great alacrity. Success has a thousand fathers, for sure, and nowhere more than in a drug company). She largely dodges the funding question, saying that's it not really the agency's job to lobby for funds, but says that the biggest obstacle she faces right now is getting enough reviewer time to evaluate proposals properly. She thinks that the single best use of the money, though, is personalized medicine (which I find a bit arguable at this point, but eventually she may well be right).
+ TrackBacks (0) | Category: Current Events | Press Coverage | The Central Nervous System
The third conference is on the CATIE and ALLHAT trials, the large comparative studies of antipsychotic and hypertensive medications. These studies are taking a real beating, I have to say. Herbert Meltzer of Vanderbilt took on the CATIE work, saying that its design was too complex and tried to do too many things at once. He pointed out that the study's results - that older and newer antipsychotics were essentially equivalent - is very much at odds with evidence-based medicine. He says that its conclusions haven't had that much effect with clinicians, because it's so at variance with their experience.
Michael Weber of SUNY-Downstate has a lot of bad things to say about the ALLHAT study, too. He points out that the HAT part stood for "Heart Attack Treatment", and that although the diuretic treatment group showed somewhat better blood pressure data, the heart attack outcomes were no different. His other surprising claim was that a large number of African-American trial subjects ended up in groups that did not meet the best standard of care for that population, and asked what would have happened if a drug company ran a similar trial. He was clearly frustrated with the initial coverage of the results in places like the New York Times, which he said were the result of a very well-planned press offensive by the study's authors.
Ralph Snyderman of Duke spoke about the problem of working on complex diseases that aren't driven by a single molecular defect (which, more and more, is what we're left to work on). These things are terribly heterogeneous, on more than one level - for instance, referring to his specialty, he said that as far as he's concerned rheumatoid arthritis is at least three diseases, and perhaps as many as six or seven.
Susan Horn of the Institute for Clinical Outcomes Research made the case for "practice-based medicine", trying to work out the real-world effects of compounds after they've been launched. Meltzer wasn't so sure about how well these sorts of studies replicate, though.
In other news, Matt Herper of Forbes has reluctantly admitted that he doesn't find medical journals to be the most exciting reading in the world - his challenge is turning these results into things that people will read voluntarily. He had a great quote about the difficulty of turning ambiguity into a story, mimicing an editor: "What you you mean these experts don't know? Call them back and get them to tell you!"
Post updated in sections - I've been recharging my laptop batteries - DBL
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October 26, 2006
The late-stage clinical failure of a small company/big company drug partnership story gets told over and over, and today it was the turn of Renovis and AstraZeneca. Renovis had come up with a candidate (NXY-059) for post-stroke therapy that targeted free-radical oxidative damage. Initial clinical trials were fairly positive, but this latest one, a larger and more rigorous effort, totally failed to demonstrate any benefits for the drug.
They've got plenty of company. I've lost count of the number of neuroprotective drug candidate failures I've heard about during my time in industry. It's humbling, like much of drug discovery is when you look at it closely. I mean, if you get your information from the newspapers or (God help you) television news segments, you'd think that we know just how tissues are damaged after an event like a stroke, which means we know just how to block the process, so all it takes it just sending in some drug to keep it from happening. The folks in the lab coats should be whipping one right out any day now.
Nope. Hasn't worked out. Excitatory glutamate toxicity for example, was all the rage about ten years ago, but a number of Phase II and III wipeouts showed that even if these drugs could work (a big if), they would have to be given very, very quickly, which isn't clinically realistic. Since that run of failures, a new set of standards were developed to try to improve the quality of clinical candidates and trials in the field. The Renovis drug is one of the first to come in under those criteria, but little good did they do in this case. Neuroprotection is hard.
+ TrackBacks (0) | Category: Cardiovascular Disease | Clinical Trials | The Central Nervous System
September 24, 2006
I see that Dylan found an old bottle of L-DOPA in his stockroom - I'd handle that one with gloves, but that's the medicinal chemist in me talking. He segues into a discussion of the MPTP story, which I talked about here a while back. Every med-chemist who's done work on central nervous system drugs knows the story, in my experience.
But that knowledge doesn't seem to be universal. I once, some years ago, had a lab associate from another group mention to me casually that he'd just made a batch of an intermediate, which when he drew it out on the hood sash, turned out to be the para-bromo analog of MPTP. I couldn't believe my eyes, and I stared at him in horror, wondering if this was some sort of joke. "You what?" It was then his turn to stare at me, wondering what was wrong. He had never heard of MPTP, of the irreversible Parkinson's syndrome that it causes, had no idea that there was a problem, and so on.
We established that he'd made a good-sized load of the stuff, but that he hadn't been handling it to any great degree (and had been wearing gloves when he worked up the reaction). I put the fear into him, warning him under no circumstances to touch the stuff or mess with any glassware involved, and contacted the toxic waste disposal folks. They charge quite a bit to haul things like that away, I think.
In the meantime, I read up on the structure-activity relationships that had been worked out for these compounds. A key paper by Mabic and Castagnoli in J. Med. Chem. (39, 3694) showed that the 4-bromo compound was, unfortunately, an "excellent substrate" for MAO-B, the enzyme that turns these structures into the neurotoxic species, so odds were excellent that the compound was trouble.
But not once it was taken away and destroyed, anyway. The person who made it developed no symptoms over the next couple of years that I was able to observe him, as far as I could see. (And I believe that you need a pretty good internal dose to get into trouble - light skin contact probably won't do it). Memos went out to everyone reminding them of these structures and why they shouldn't be messed with. But I still wonder how many people might stumble across these compounds and whip up a batch of something that shouldn't be made. That's another argument for electronic lab notebooks. You could set the things to start honking and flashing if you entered such a target structure into them, to alert the clueless. . .
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June 25, 2006
It's been an awful time to hold the stock of a small company called Neurocrine. They've been developing an insomnia therapy (Indiplon), and things seemed to be going along reasonably well. It's a crowded field. The compound is in the same GABA mechanistic class as the existing drug Ambien (which makes it in the same class as Lunesta, naturally, since that's one of those "Sepracor special" follow-on compounds). But Neurocrine signed up with Pfizer, who weren't getting any of the insomnia market and were willing to give several formulations of the compound their well-known marketing push, including a long-acting one that might have provided an advantage over the competition.
Then a few weeks ago, they got the dread "approvable" letter for the lower doses, and a flat-out "not approvable" for the long-acting formulation. Neurocrine's shares really took a beating as investors wondered if this was an approvable letter of the "new clinical trials needed" variety, and since then, it's become clear that that's exactly what it was. Late last week, Pfizer announced that it had had enough and pulled out of the deal. Neurocrine's stock has, in the space of a bit more than a month, gone from the mid-50s to single digits.
Neurocrine's putting a brave face up, saying that they're going to go ahead and develop Inidiplon themselves (and presumably look for another partner as they do so). It's going to be tough, but they may feel as if they have no choice but to try to get the drug through to the market. They have a few things in Phase II, but Inidiplon was going to be what paid the bills. Another partner will be essential, because they're going to have to come up with a lot of cash to get the drug through to a point where it could be approved, and to then try to market the drug themselves might be suicidal. By that time, they'd be up against generic Ambien, among other things. I don't see them doing that on their own.
No, I think that their choice is this: either ditch Inidiplon completely, contract back to a smaller development company with some stuff in the clinic, and hope for the best - or - cut back on all those other projects and put all the money on Inidiplon, trying to clean it up enough to attract another partner. The problem is, the ideal partner would be someone with a big pile of cash, a need for something to fill their pipeline, and a powerful marketing arm to deal with the competition. Someone, in other words, like Pfizer. Who's just told them that they want no part of it.
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February 26, 2006
Some readers will have already come across reports suggesting that some drugs for Parkinson's disease can lead to odd behavioral problems, including compulsive gambling. Given their effects on dopaminergic pathways, which seem to be involved in stimulus/reward behavior, it's a believable effect. (Actually, as I mentioned the other day, just about anything is a believable side effect with CNS drugs, especially at low rates of incidence).
Now (via Overlawyered) comes a case from Texas. A (once)-wealthy retiree named Max Wells is suing GlaxoSmithKline over their Requip drug (ropinirole), claiming that he wasn't warned that the drug could cause compulsive behavior. His particular compulsive behavior took place in Las Vegas, a city well equipped for it, and involved the loss of some 14 million dollars.
As the Austin newspaper story has it, Wells had started on another Parkinson's drug, Mirapex, in 2004 and lost several thousand dollars gambling, both online and in Vegas. (As it turns out, Boehringer Ingleheim is being sued over that drug, too, for similar reasons). He told his doctor about the problem, and was switched to Requip, which is when things apparently really started to roll.
Wells is also suing at least seven casinos, claiming that they knew that he was taking Parkinson's medication and should have been aware that he had a problem. I think these suits have even less of a chance, because casinos have been sued many times on similar "they should have stopped me" grounds. I recall a Philadelphia businessman in the early 1990s who took an Atlantic City casino to court because of his losses at his favorite game, which was high-stakes blackjack played with the aid of a bottle of bourbon. The casino, he contended, knew that he was impaired and should never have allowed him to continue. This argument didn't make much headway, as you'd probably guess.
This Parkinsonian case is a bit different, but I don't think it's going to get very far. It might bring up interesting questions about free will and human behavior, but no court is going to want to wade into that philosophical swamp. If the facts are as stated, the case will surely be decided on more practical grounds: why Wells didn't go back to his doctor when he started compulsively gambling again on the new medication instead of spending the next several months ripping through millions of dollars, and how casinos are not required to evaluate the motives of their customers.
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September 22, 2005
One of the other incorrect lessons that people might take away from the press accounts of the antipsychotic trial is that drug companies have been comparing their medications to placebo too often. And why would you do that unless you were scared that you wouldn't be better than the competition? What's with these people, anyway?
Well, there are fields where placebo-controlled trials take place, and fields where they don't. It depends on the disease and options available to treat it. Cancer trials, for example, are very rarely run against placebo, unless there's just nothing left to do. (You'll see this with drugs that are meant for late-stage patients or those who have failed existing therapies.)
Antipsychotics are generally compared to an existing standard of care, because it's unethical to leave someone untreated when they've already been diagnosed as schizophrenic. The problem that the CATIE trial uncovered, though, is that many trials are run against haloperidol (known as Haldol). That's a typical older drug, and companies have been showing that they have better efficacy and fewer side effects than it does. (It's known to have significant problems with tardive dyskinesia, among other things).
But now we know that perphenazine is a better standard among the older drugs, mostly because of fewer side effects. I don't think that anyone is going to be able to run a haloperidol-controlled trial for a new antipsychotic. Now you're going to have to beat perphenazine, which will be a higher standard. The newer drugs have been able to get rid of the so-called extrapyramidal side effects, like tardive dyskinesia, but they haven't been able to increase their efficacy that much. That's not going to be enough any more - the ante has gone up in the field of schizophrenia therapy.
Now, if you think that your new drug is really going to cream the competition, running a trial against them is a smart move. There's no better way to persuade people to prescribe your drug than to show that it's clearly better than what's out there now. Another time you see head-to-head trials is when a company is making a run at the leader in a given category. The various attempts to out-do Lipitor are good examples, not that any of them have succeeded. But there really wasn't a clear leader in the antipsychotic area, and thus no real target to try to knock down. I'd bet that the companies involved strongly suspected that their own drugs weren't head and shoulders above everything else, either. This is the perfect situation for an outside agency like the NIH to do a comparison study, because if you're waiting for the companies involved to do it, you're going to have a pretty long wait.
+ TrackBacks (0) | Category: "Me Too" Drugs | Clinical Trials | The Central Nervous System
September 21, 2005
You've probably seen the headlines about the recent NIH-sponsored "CATIE" study comparing five anti-psychotic medications. The result, which is what made the whole thing newsworthy to the popular press, was that it was hard to distinguish among them, with the oldest generic working as well as (or better than) the newer drugs.
But I think that people outside of the medical world are going to learn the wrong lessons from all this. Does this study mean that everyone taking anti-schizophrenia medication should switch to the old generic? Not at all, although if they need to try a different medication, they should definitely consider it. Does it mean that all these newer drugs are unnecessary? No, again. There's an awful lot of patient-to-patient variation in central nervous system drugs. Says the study's principal investigator, Dr. Jeffrey Lieberman of Columbia:
"There is considerable variation in the therapeutic and side effects of antipsychotic medications. Doctors and patients must carefully evaluate the tradeoffs between efficacy and side effects in choosing an appropriate medication. What works for one person may not work for another."
But I think that this study does make clear that the newer antipsychotics aren't as good as they should be. The field is a tough one, as I know from personal experience, having played a small role in helping a company spend I've-no-idea-how-many millions of dollars to find out that a potential schizophrenia medication didn't do squat. There's a lot of room for improvement, and we haven't been able to improve things very much.
It's important to emphasize that this was a surprising result. No one expected the side effect profiles of the four "second-generation" drugs to be so similar to the older one (perphenazine), and so similar to each other. That's one reason that a study like this is so valuable - huge clinical trials that tell you something that you already knew aren't too wonderful. I think that this is an excellent thing for the NIH to be doing. Tomorrow: what this says about head-to-head trials in general.
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August 25, 2005
I had a question from a reader about Substance P, a peptide that's been known since the 1930s as something that was involved in pain and neurotransmission. Its biological target is the neurokinin receptor subtype NK1, and there's been a huge amount of research on this system over the years, studying its role in the peripheral nerves, the spinal cord, and the brain.
And most of this work pointed to the idea that something that blocked this pathway would be an excellent analgesic. Stimulation of SP-responsive neurons produces sensations of burning pain, for one thing, and injection of the peptide is very unpleasant.) Weirdly, naked mole rats don't use the SP pain pathway, and are impervious to normally painful things like treatment with pure capsaicin. (Capsaicin, the hot pepper active ingredient, causes quick release of SP and the accompanying pain sensations, but ends up depleting it from presynaptic neurons, eventually raising the pain threshold.)
Pain relief is one of those things that some people think has been solved, but it really hasn't been. It's hard to knock down severe pain without knocking out the patient or using something with a high addictive potential. There are plenty of conditions - burn injuries, diabetic neuropathy and cancer come to mind - where a powerful analgesic with fewer side effects would be welcomed with rejoicing.
Several groups took a shot at making antagonists, but there were a lot of wrong turns along the way. For one thing, the NK1 receptors in mice are rather different from the ones in humans, something that was only worked out after many people had been led astray by mouse models of pain. (The good ol' guinea pig, which in spite of its reputation isn't really used much in drug research, turned out to have closer homology to the human receptor.)
And when good compounds were finally developed at Merck and other companies, and were taken into clinical trials for pain relief, an interesting thing happened: they didn't work. Not at all. The title of a review article from a group at Merck (Handbook of Experimental Pharmacology, p. 441, 2004) shows the frustration: "Substance P (NK1) receptor antagonists - analgesics or not?" They go on to say:
"Despite the identification of high affinity and selective substance P (NK1) receptor antagonists and a plethora of preclinical data supporting an analgesic profile of these agents, the outcome from clinical trials has been extremely disappointing with no clear analgesic efficacy being observed in a variety of pain states. This has led the pain community to seriously question the predictability and utility of preclinical pain assays, especially for novel targets."
Indeed it has, and the situation is far from being sorted out, from what I know of it. But Substance P had more life in it. As its distribution (and that of the NK1 receptor) in the brain began to be worked out, people noticed that it was often co-localized with the serotonin system, and these lines of evidence suggested a role in depression. Merck's MK-869 was the first compound to go into the clinic for this purpose.
And it died there, too. Initial results looked promising - check out this glowing report from 1998. But the next year, it was dropped, after failing to work better than placebo under controlled conditions. (That link is well worth reading for those interested in the topic of placebo controls, BTW.) After much searching around, NK1 antagonism was found to be imporatant enough in nausea and emesis for MK-869 to make it as an adjunct to cancer therapy. It's on the market as Emend (aprepitant), selling (as I put it in 2003, about one-fiftieth of what Merck had originally hoped. You have to wonder how long it'll take them to get their money back.
Many other companies have reported development of NK1 ligands, but I don't think that any have reached the market yet - and I don't know what they'll do if they get there. The whole area is an excellent lesson in the crazy complexity of drug target validation and drug discovery, and an interesting thing to consider when you wonder why drugs cost what they do. But we won't have to worry about Merck spending the time and money to learn such things if we sue them until they're crippled, now will we?
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June 21, 2005
So, I do a post where I wonder if the reductionist target-driven approach to drug discovery is running out of gas, then I do one on the possibility of some interesting new drug targets in the brain. Am I deliberately talking out of both sides of my mouth, or do I just not remember what I've written the day before?
Actually, I can hold both of those views simultaneously. Order now and I'll send you my exciting at-home kit which will allow you to do the same! Here's how it's done: the morphine-synthesizing enzymes in brain cells that I spoke about yesterday are, indeed, possible drug targets. But I'm defining "target" pretty loosely here, as "theoretical possibility for therapeutic intervention." The step beyond that is "validated target", and we're a long way from that.
The problem is, no one has the faintest idea what brain cells are up to when they make morphine. I should start out by saying that we don't know which brain cells, of the insane number of different types, actually make it in vivo, what parts of the brain they're located in, or what factors cause them to increase or decrease its production. And once it's made, we don't know what it does or why. Presumably it's binding to the known opioid receptors, whose biology was complicated enough already, thanks. (See this recent paper, pointed out in a comment to the last post.) But there are already families of endogenous peptides that do that, so you have to wonder why morphine is in there, too. Under physiological conditions, perhaps there are other signaling roles for it (intracellular ones, maybe?) of which we are entirely ignorant.
But it's fair to assume that it's in there for a reason, and it's also fair to assume that disrupting its production would have an effect, even if we don't know that that might be. That makes endogenous morphine production a potential target, and an interesting one. But if we wait until these questions are well worked out, we could be in for a long wait. That's been the problem with many molecular-level targets, and Monday's post spoke about some of the difficulties with them.
How do you get more information? One way to approach the problem would be to disrupt one of the key enzymes used in endogenous morphine synthesis, once we know what they are, and see what happens. You could do that with RNA interference in cell cultures, but it can be hard to see what the effects are unless you touch on something vital. That's especially true with CNS targets, because cells in a dish are an extremely poor surrogate for the complex properties of the intact brain. A better route would be to go into whole animals: you could knock out the enzyme in mice and see how they develop, but the big question with knockout animals is how they compensate during development for that induced loss of function. Sometimes the changes you bring on end up being too subtle to catch, and you get what looks just like a normal mouse.
You'd probably be better off with a small-molecule enzyme inhibitor which could be dosed in a normal adult animal. If it's selective and nontoxic enough, you'd have a chance to see what the loss of endogenous morphine does under real-world conditions - assuming that it's something that can be noticed at all in an animal model, and assuming that you're sharp-eyed enough to catch it. Does it affect motor control, memory, emotional state, sensory input, or what? If you give it to a rat and he goes off and flops down, is that because he's dizzy, because his legs don't feel right, because he feels sick to his stomach, because he's suddenly sleepy, or because he's overcome with waves of rodent ennui? You can untangle some of those, but it isn't easy. You'd know, though, that it certainly does something, even if you're not quite sure what it is.
So, your choices are: go with the molecular approach, but be prepared to wait years for answers. (Be prepared to wait decades if the answer ends up requiring a molecular-level understanding of something like long-term memory or emotional state.) Or, go with the whole-animal approach once you've got some idea of the target, but be prepared to see no changes, or changes that you're unable to interpret or extrapolate to humans.
What I'd do, were I in charge of such an effort, is give the molecular approach some time at the beginning to see if they could narrow things down a bit. Is morphine made only in the brain, or also in the peripheral nervous system or also in other tissues entirely? What regions of the brain look most important? What enzyme should we be targeting to best affect the whole system? These could take a while, but not as long as working out the whole story would. Once we had some idea about the enzyme, I'd turn around and screen against it, looking for some chemical matter to try animal studies with. Getting something suitable might be a matter of months, or it might be a matter of years. How much time and money were you thinking about spending? This would be a major effort, clearly, and one unlikely to take place inside one research organization, no matter how dedicated and well-funded.
But here's the problem: this target, compared to some of the things that came spilling out during the genomics craze, is actually pretty well-grounded. Think about it - we have receptors that we know will bind morphine, and a lot is known about their biology (even if we don't understand what morphine is doing in there with them in vivo.) We're pretty sure that this will be a CNS target, rather than, say, cancer or diabetes (although I'd never say never until I saw more data.) We even know what kind of enzymes to search for in the morphine biosynthesis pathway, based on what we know from plants.
No, although I've just spent all this time talking about how hard it would be, this project would have a real head start compared to many of the things out there. And if you find that a bit unnerving, then you can see why the strict molecular from-the-bottom-up approach is running into problems.
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June 20, 2005
All sorts of odd things have turned out to be neurotransmitters, that's for sure. I wrote about this over a year ago, in a post about hydrogen sulfide, of all things, and its role in the brain.
Well, there's another odd one that's been uncovered. And like hydrogen sulfide (or carbon monoxide, also a neurotransmitter, if you can believe it), it's a molecule that we already know about. Heck, we already know that it does all sorts of things to the brain. We just didn't know that the brain could make its own. Are you ready?
It's morphine. Who would have thought? The brain certainly has plenty of opioid receptors, but it was thought that some classes of short peptides (enkephalins and endorphins) were the endogenous ligands that bound to them. Morphine and the other alkaloids of its family were supposed to be the interlopers from the plant kingdom that could mimic our peptides, but it appears that story is going to need revisions.
A group at Halle (Germany) has done the detective work here. There were reports over the years of small amounts of morphine in mammalian cells, but no one was sure what to make it them. With modern analytical techniques, everything is contaminated: you can find little bits of almost anything you're looking for. Morphine had shown in up things like lettuce, milk, and rat chow before, in trace amounts, so who could say?
The connection seems solid now. The Halle group took human neuroblastoma cells in culture and gave them isotopically labeled dopamine as a starter. That's the (distant) precursor for morphine in poppies, and the cells used it to spit out small amounts of isotopically labled morphine. The same went for a number of other known morphine intermediates (but not quite all of them.) It appears that human cells use a very similar set of reactions to make morphine, but differ from the plant route at one key step.
The authors note, dryly, that "The function of endogenous morphine is still a matter of discussion." I'll bet it is. Why on earth do we make morphine when we have the enkephalins and endorphins? But it's at least a 19-step synthesis for the cells, and you can be sure that they're not going through that for nothing. The paper points out that identifying the various enzymes involved in the synthesis could provide some interesting targets for CNS drug discovery, and I'll bet that they're right about that, too.
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March 9, 2005
Just how do antidepressant drugs work? The answer you get (and the confidence with which it's delivered) will vary according to the experience of the person giving it: the more experienced and knowledgeable they are, the more tentative and uncertain the answer. I worked on central nervous system drugs for eight years, and I can confidently state that we know just slightly more than jack.
Well, the more, um, standard answer is that antidepressants act by changing the concentrations of key neurotransmitters like serotonin or noradrenaline. That's certainly what they're designed to do, by shutting off metabolic and clearance pathways and allowing serotonin, say, to build up. Underlying all this is a larger hypothesis, one so large that we usually don't even think about it: that depressio is indeed a disorder of those neurotransmitters, a chemical imbalance that could in theory be righted if we just studied the relevant pathways hard enough.
There's been a feeling, though, that we've been a bit too reductionist about this. This view is well stated in a new article in Nature Reviews Neuroscience (6, 241) by Eero Castren. It's a proposal that will appeal to software engineers in particular:
"This new hypothesis, the network hypothesis, proposes that problems in activity-dependent neuronal communication might underlie depression, and that antidepressants might work by improving information processing in the affected neural networks. A key aspect of the network view is the recognition that the principal role of the nervous system is not to handle chemicals but to store and process information. . .Although chemical neurotransmitters are crucial for the transfer of information between neurons, information in the brain is not stored in a chemical form but is thought to be processed by the complex interactions of neurons in neural networks. These networks develop through interactions with the environment, and the neuronal structure of, and neurotransmission in these networks are constantly being refined. . ."
That makes the difference between the two approaches sound bigger than it really is, as Castren goes on to point out:
"It should be noted that the chemical and network hypotheses are not mutually exclusive, but are complementary. As the synthesis and release of several important signaling molecules are regulated by neuronal activity, changes in the activity of neural networks produce changes in the concentration of these signaling molecules. Therefore, although the initial effects of antidepressants are obviously chemical. . .the ensuing adaptive changes in the concentrations of those signaling molecules are tightly linked to the structure of the neural network, and might be a consequence of the altered information processing rather than its cause. According to this view, antidepressants initiate a 'self-repair' process, whereby plasticity in neural networks and chemical neurotransmission indivisibly cooperate and gradually bring about mood elevation."
Rodent studies have shown that antidepressants stimulate the growth of new neurons, and that this correlates with their mood-elevating effects. Brain-derived neurotrophic factor (BDNF), which has long been known as a key signal for neuronal sprouting, might be the player here, as several lines of evidence have begun to implicate it in changes in mood. All this, if true, points to a combination of drug and behavior therapy as the best combination to take advantage of the brain network remodeling, and I think that this is considered the best clinical practice as well.
The author is honest about some of the evidence against the hypothesis, such as the several factors that can bring on rapid (albeit temporary) mood changes in depressed patients. Rewiring a neural network isn't going to be rapid. But these observations don't have to invalidate the hypothesis (although they could), and there are others that support it. For example, antidepressant drugs have a very slow onset of action, an effect that's been noted for decades, and many people have suspected that there must be some sort of slow reorganization going on.
So where does that leave drug discovery folks like me? We're used to going after defined targets, and "Loosening up the synapses" doesn't sound like one. Here's Castren again, and I hope that he's right:
"The hypothesis that mood represents a functional state of neural networks might sound incompatible with the efforts of rational drug development. However, the data reviewed above indicate that the antidepressant drugs that have been used successfully for several decades might function by initiating such plastic processes, apparently indirectly, by influencing monoamine metabolism. It is possible that a similar process could also be initiated through other pharmacological mechanisms, which might become the targets of new antidepressants. . ."
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December 4, 2002
One reason that I have doubts about thimerosal as a cause of autism goes back to mechanism of action. Are there any specific compounds that are know to cause specific neurological problems? (There are plenty that cause more diffuse symptoms, often motor-related, such as tardive dyskinesia.)
Well, there's one prominent example: MPTP, known to the trade as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. It's a reasonably simple organic molecule, and to a medicinal chemist it certainly looks like a central nervous system agent (if I had a dollar for every CNS-active piperidine or piperazine that's been reported in the patent literature, I could retire.) But no one could have predicted what it actually does.
The compound gets oxidized by monoamine oxidase B, which is a common fate for molecules of its type. That produces a pyridinium compound which is the real problem. As fate would have it, it's a fine substrate for the dopamine transporter protein, which imports dopamine into cells that require it. And in a further stroke of bad luck, the same compound is also an inhibitor of a key enzyme in mitochondria - and you don't want to do anything to your mitochondria. Cell death follows in short order if you shut them down too hard.
So everything's set up for a disastrous cascade: MPTP's turned into something dangerous, which is taken up selectively into cells that import a lot of dopamine, which process then kills them. Unfortunately, the cells that import the most dopamine are those in the substantia nigra, up in the forebrain. Which is why in the late 1970s and early 1980s, a number of young drug users started showing up in emergency rooms on the west coast with what appeared to be some sort of catatonia. They didn't move; they weren't responsive - everyone waited for whatever it was to wear off so they could start to recover.
It didn't, and they didn't. At first, no one recognized what was going on, mainly because no one had ever seen a twenty-year-old with advanced Parkinson's disease before. These patients had taken batches of some sort of home-brewed meperidine (better known as Demerol) or a derivative, and the synthetic route had produced some MPTP as a contaminant. Quality control isn't a big feature of the basement drug industry.
The affected users improved slightly when given L-Dopa, as you'd expect from a Parkinson's patient. But not much, and not for long. The damage is permanent - they skipped years of the normally slow progression of the disease and went straight to its worst phase in one night. Is this what's happening with thimerosal and autism?
I strongly doubt it. Here's why: Parkinson's is caused by a lesion in a specific area of the brain, in a specific (and unusual) cell type. MPTP is toxic to some specific and unusual cell types, and it's just a terrible stroke of misfortune that they happen to overlap. But despite a tremendous search, no one has been able to tie autism to primary lesions in a specific region of the brain, much less down to certain cells. I'm not saying that it's impossible - just that it's been looked for strenuously, and thus far in vain. Studies of brain activity in autistic patients show a variety of differences, but nothing that can be pinned down as a cause.
The other half of the story is the reactivity of thimerosal itself. There's nothing known about the compound that would suggest that it has a particular affinity (or particular toxicity) to any one type of cell over another. Organomercury compounds are (in high doses) pretty bad news in general, causing all sorts of neurological problems. They just don't seem to be specifically toxic.
So there's no evidence, mechanistically, on either side of the hypothesis. That doesn't disprove it, of course - it's not impossible that there would be some sort of subtle effect that we've missed so far. It's just that I believe that the odds are very much against it. We'd have to string together too many (big) assumptions in a row, and the evidence isn't nearly compelling enough to make us do that.
If thimerosal is cleared as a possible agent for autism, that'll be good news and bad news. The good news is, of course, that we haven't been damaging children without realizing what we're doing. The bad news will be that we still won't know why some children become autistic and others don't, a lack of knowledge that's hard to bear.
The only other good news I can think of - and a hard, sour piece of good news it is - would be that parents of autistic children who have feared that they were the cause of their children's condition - just by having them vaccinated - could at least put that part of their burden down. It's not enough, but it's something. Believe me, I have two small kids myself, and the thought of either of them showing signs of neurological trouble makes me start to double over. I can't even imagine what it must be like. But to those in that situation, all I can say is that I really don't think that some doctor did it to your child. Or that some drug company did it to your child. Or that you did, either. For what it's worth.
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October 31, 2002
Talking about the urge to quantify things - even the stubbornly unquantifiable - leads me back to what I spoke of earlier ("Faces in the Clouds", Oct. 20) about finding patterns even in random noise. I think these are two aspects of the same phenomenon.
We seem to have this information-processing machinery in our brains, constantly grinding away trying to integrate the flood of sensory input. Back in the visual cortex, for example, there are layers of neurons that specialize in things like horizontal contrast lines and sideways-moving objects. Further up in the processing, we're especially tuned in to important things like human faces and facial expressions, to the point that people see them in rock formations and half-cooked tortillas. (If anyone thinks I made that last one up, I'd be happy to cite chapter and verse.) Other senses seem to be broken down in the same way, with local processing picking out specialized patterns in the raw sensory stream.
We're looking for ordered data, because random noise doesn't give our brains any traction, and they can't stand it. Noise is the enemy of sensory processing - consider, say, blank-channel TV static. "What do you mean," says the brain, "random flashes of light all over the visual spectrum? That's not how the world works. Things stay pretty much the same color on that time scale, and stuff doesn't just pop in and out that way without leaving a trail of motion. Something's wrong. I'll figure it out, just give me a minute. . ."
If we use our brains to think about non-sensory abstractions, we tend to map them to sensory data so we can get a handle on them. "Employee performance" is a tough concept to picture, but how about a ranking from 1 to 10? That's something we can grasp (whether we should, in the first place, is a topic for another day.)
So we look for lines and curves on our graphs, and clumps of points on our scatterplots. The same systems that served us to warn about crouching sabretooth tigers now try to tip us off to epidemiology. And it wouldn't surprise me a bit if we uncover higher-order structures (or neuronal patterns, at least) that work in a similar way. Higher cortical functions might have taken sensory processing as their model, and set themselves up to do unconscious curve-fitting and shape-filling in the world of logic and causality. Being able to infer cause-and-effect must have been quite a survival advantage, too.
Steve Postrel at SMU wrote me after my earlier post on this subject. He pointed that it's true that the general public gets basic statistical patterns wrong pretty regularly, but scientists don't do much better once things get past that. He's got a point: one of his examples was the handling of global warming data. There's so much information out there that you can argue just about any direction you want to on the subject. I am not going to get that debate right now (neither was he!) but whichever side of the argument you take is a statistical minefield. There are so many things that can influence the presentation of the data, and the conclusions drawn from it (starting and ending dates for sampling, location of same, error bars of the measurements - when you can even state them, hidden variables or assumptions in the models - it's a mess.)
No doubt about it, whatever the human brain is optimized for, statistics and probability isn't it. (Quantum mechanics sure isn't it, either, come to think of it - and depending on your take, that has a generous dose of probability in it, too.) I suppose we shouldn't be wondering why we don't do it better, and be impressed that we can do it at all. . .
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February 25, 2002
The mention of schizophrenia last week brought up something I've thought about since I worked in the field: the limited forms of mental illness. When you first read about insanity (or deal with them firsthand,) it's easy to think that everyone who's insane is sui generis.The varieties of symptoms seem limitless.
But the more I've thought about it, the more I think the opposite. There are only a set number of ways in which humans go insane. Think of any given case of dementia, and you can come up with plenty of similar ones: you have paranoids convinced that their thoughts are being read - by their TV, by aliens, by invisible beams - or that the people they see on the street are all agents. There are the people who let piles of paper and garbage crowd them out of their houses. And the obsessives convinced that they are good friends with, are going to marry, are already married to some celebrity. You'll certainly find differences among these and among the many other types. But they're variations on the same master templates, differences of degree rather than kind.
Contrast the familiar dementias with superficially similar ones that don't seem to exist, like an inverse paranoid: someone who's convinced that people are sneaking around behind his back, helping him out and doing him favors.
Now, the nuts-and-bolts biochemistry of the brain is overwhelmingly complex. That's one of the big reasons that drug development in the field is such a slog. But at a systems level, it may be that there are several broad pathological states that the neuronal net can fall into. These could be based on an uncorrectable excess (or deficiency) of signaling in some part of the network, or some defect of timing in the handoff of processing from one region to another.
It might be analogous to similar low-energy states of a chemical or physical system, local minima on a surface. There could be any number of genetic and/or environmental factors that push the brain into one of these conditions, just the same way that you can tumble into a hole by coming from any direction on the surface. But you end up in one of a set number of places, one defined hole or another.
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February 22, 2002
As I mentioned previously, I've been reading the letters of both Kingsley Amis and Philip Larkin. One thing you notice in any Collected Letters book (try Evelyn Waugh's) is old age creeping up on the writers. It's less noticable in Larkin's case; his personality famously made him sound about 70 years old for decades. But with Amis, it's clear that you're reading the thoughts of a young, a middle-aged, and then an old man. This process is chronicled from just outside in his son Martin's book Experience
Don't get me wrong - Amis's letters are wonderful, even the late ones. But a sort of hardening of the personality takes place, kin to atherosclerosis, and it's a common thing to see. What I wonder is how much is due to just plain experience and weariness with the world (seeing the same mistakes being made the same ways, again and again,) and how much has a neurologic base.
Circulatory problems, Alzheimer's (we won't get into the debate about what causes it,) any number of other biological causes affect the number and activity of the neurons. And that, in turn affects higher functions of thought and personality. But that statement broad-jumps over a huge pit of unknown detail. These questions are going to keep everyone in the biomedical sciences busy for a long time, and won't the world be an odd place when answers start to show up?
More on this later. There are many things coming much sooner from modern neuroscience, and we'll have our hands full with those just the same.
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