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About this Author
DBL%20Hendrix%20small.png College chemistry, 1983

Derek Lowe The 2002 Model

Dbl%20new%20portrait%20B%26W.png 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: derekb.lowe@gmail.com Twitter: Dereklowe

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August 21, 2014

Why Not Bromine?

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Posted by Derek

So here's a question for the medicinal chemists: how come we don't like bromoaromatics so much? I know I don't, but I have trouble putting my finger on just why. I know that there's a ligand efficiency argument to be made against them - all that weight, for one atom - but there are times when a bromine seems to be just the thing. There certainly are such structures in marketed drugs. Some of the bad feelings around them might linger from the sense that it's sort of unnatural element, as opposed to chlorine, which in the form of chloride is everywhere in living systems.

But bromide? Well, for what it's worth, there's a report that bromine may in fact be an essential element after all. That's not enough to win any arguments about putting it into your molecules - selenium's essential, too, and you don't see people cranking out the organoselenides. But here's a thought experiment: suppose you have two drug candidate structures, one with a chlorine on an aryl ring and the other with a bromine on the same position. If they have basically identical PK, selectivity, preliminary tox, and so on, which one do you choose to go on with? And why?

If you chose the chloro derivative (and I think that most medicinal chemists instinctively would, for just the same hard-to-articulate reasons we're talking about), then what split in favor of the bromo compound would be enough to make you favor it? How much more activity, PK coverage, etc. do you need to make you willing to take a chance on it instead?

Comments (14) + TrackBacks (0) | Category: Drug Development | Odd Elements in Drugs | Pharmacokinetics | Toxicology

August 20, 2014

Did Pfizer Cut Back Some of Its Best Compounds?

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Posted by Derek

John LaMattina has a look at Pfizer's oncology portfolio, and what their relentless budget-cutting has been doing to it. The company is taking some criticism for having outlicensed two compounds (tremelimumab to AstraZeneca and neratinib to Puma) which seem to be performing very well after Pfizer ditched them. Here's LaMattina (a former Pfizer R&D head, for those who don't know):

Unfortunately, over 15 years of mergers and severe budget cuts, Pfizer has not been able to prosecute all of the compounds in its portfolio. Instead, it has had to make choices on which experimental medicines to keep and which to set aside. However, as I have stated before, these choices are filled with uncertainties as oftentimes the data in hand are far from complete. But in oncology, Pfizer seems to be especially snake-bit in the decisions it has made.

That goes for their internal compounds, too. As LaMattina goes one to say, palbociclib is supposed to be one of their better compounds, but it was shelved for several years due to more budget-cutting and the belief that the effort would be better spent elsewhere. It would be easy for an outside observer to whack away at the company and wonder how incompetent they could be to walk away from all these winners, but that really isn't fair. It's very hard in oncology to tell what's going to work out and what isn't - impossible, in fact, after compounds have progressed to a certain stage. The only way to be sure is to take these things on into the clinic and see, unfortunately (and there you have one of the reasons things are so expensive around here).

Pfizer brought up more interesting compounds than it later was able to develop. It's a good question to wonder what they could have done with these if they hadn't been pursuing their well-known merger strategy over these years, but we'll never know the answer to that one. The company got too big and spent too much money, and then tried to cure that by getting even bigger. Every one of those mergers was a big disruption, and you sometimes wonder how anyone kept their focus on developing anything. Some of its drug-development choices were disastrous and completely their fault (the Exubera inhaled-insulin fiasco, for example), but their decisions in their oncology portfolio, while retrospectively awful, were probably quite defensible at the time. But if they hadn't been occupied with all those upheavals over the last ten to fifteen years, they might have had a better chance on focusing on at least a few more of their own compounds.

Their last big merger was with Wyeth. If you take Pfizer's R&D budget and Wyeth's and add them, you don't get Pfizer's R&D post-merger. Not even close. Pfizer's R&D is smaller now than their budget was alone before the deal. Pyrrhus would have recognized the problem.

Comments (18) + TrackBacks (0) | Category: Business and Markets | Cancer | Drug Development | Drug Industry History

August 19, 2014

Don't Optimize Your Plasma Protein Binding

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Posted by Derek

Here's a very good review article in J. Med. Chem. on the topic of protein binding. For those outside the field, that's the phenomenon of drug compounds getting into the bloodstream and then sticking to one or more blood proteins. Human serum albumin (HSA) is a big player here - it's a very abundant blood protein that's practically honeycombed with binding sites - but there are several others. The authors (from Genentech) take on the disagreements about whether low plasma protein binding is a good property for drug development (and conversely, whether high protein binding is a warning flag). The short answer, according to the paper: neither one.

To further examine the trend of PPB for recently approved drugs, we compiled the available PPB data for drugs approved by the U.S. FDA from 2003 to 2013. Although the distribution pattern of PPB is similar to those of the previously marketed drugs, the recently approved drugs generally show even higher PPB than the previously marketed drugs (Figure 1). The PPB of 45% newly approved drugs is >95%, and the PPB of 24% is >99%. These data demonstrate that compounds with PPB > 99% can still be valuable drugs. Retrospectively, if we had posed an arbitrary cutoff value for the PPB in the drug discovery stage, we could have missed many valuable medicines in the past decade. We suggest that PPB is neither a good nor a bad property for a drug and should not be optimized in drug design.

That topic has come up around here a few times, as could be expected - it's a standard med-chem argument. And this isn't even the first time that a paper has come out warning people that trying to optimize on "free fraction" is a bad idea: see this 2010 one from Nature Reviews Drug Discovery.

But it's clearly worth repeating - there are a lot of people who get quite worked about about this number - in some cases, because they have funny-looking PK and are trying to explain it, or in some cases, just because it's a number and numbers are good, right?

Comments (13) + TrackBacks (0) | Category: Drug Assays | Drug Development | Pharmacokinetics

July 25, 2014

The Antibiotic Gap: It's All of the Above

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Posted by Derek

Here's a business-section column at the New York Times on the problem of antibiotic drug discovery. To those of us following the industry, the problems of antibiotic drug discovery are big pieces of furniture that we've lived with all our lives; we hardly even notice if we bump into them again. You'd think that readers of the Times or other such outlets would have come across the topic a few times before, too, but there must always be a group for which it's new, no matter how many books and newspaper articles and magazine covers and TV segments are done on it. It's certainly important enough - there's no doubt that we really are going to be in big trouble if we don't keep up the arms race against the bacteria.

This piece takes the tack of "If drug discovery is actually doing OK, where are the new antibiotics?" Here's a key section:

Antibiotics face a daunting proposition. They are not only becoming more difficult to develop, but they are also not obviously profitable. Unlike, say, cancer drugs, which can be spectacularly expensive and may need to be taken for life, antibiotics do not command top dollar from hospitals. What’s more, they tend to be prescribed for only short periods of time.

Importantly, any new breakthrough antibiotic is likely to be jealously guarded by doctors and health officials for as long as possible, and used only as a drug of last resort to prevent bacteria from developing resistance. By the time it became a mass-market drug, companies fear, it could be already off patent and subject to competition from generics that would drive its price down.

Antibiotics are not the only drugs getting the cold shoulder, however. Research on treatments to combat H.I.V./AIDS is also drying up, according to the research at Yale, mostly because the cost and time required for development are increasing. Research into new cardiovascular therapies has mostly stuck to less risky “me too” drugs.

This mixes several different issues, unfortunately, and if a reader doesn't follow the drug industry (or medical research in general), then they may well not realize this. (And that's the most likely sort of reader for this article - people who do follow such things have heard all of this before). The reason that cardiovascular drug research seems to have waned is that we already have a pretty good arsenal of drugs for the most common cardiovascular conditions. There are a huge number of options for managing high blood pressure, for example, and they're mostly generic drugs by now. The same goes for lowering LDL: it's going to be hard to beat the statins, especially generic Lipitor. But there is a new class coming along targeting PCSK9 that is going to try to do just that. This is a very hot area of drug development (as the author of the Times column could have found without much effort), although the only reason it's so big is that PCSK9 is the only pathway known that could actually be more effective at lowering LDL than the statins. (How well it does that in the long term, and what the accompanying safety profile might be, are the subject of ongoing billion-dollar efforts). The point is, the barriers to entry in cardiovascular are, by now, rather high: a lot of good drugs are known that address a lot of the common problems. If you want to go after a new drug in the space, you need a new mechanism, like PCSK9 (and those are thin on the ground), or you need to find something that works against some of the unmet needs that people have already tried to fix and failed (such as stroke, a notorious swamp of drug development which has swallowed many large expeditions without a trace).

To be honest, HIV is a smaller-scale version of the same thing. The existing suite of therapies is large and diverse, and keeps the disease in check in huge numbers of patients. All sorts of other mechanisms have been tried as well, and found wanting in the development stage. If you want to find a new drug for HIV, you have a very high entry barrier again, because pretty most of the reasonable ways to attack the problem have already been tried. The focus now is on trying to "flush out" latent HIV from cells, which might actually lead to a cure. But no one knows yet if that's feasible, how well it will work when it's tried, or what the best way to do it might be. There were headlines on this just the other day.

The barriers to entry in the antibiotic field area similarly high, and that's what this article seems to have missed completely. All the known reasonable routes of antibiotic action have been thoroughly worked over by now. As mentioned here the other day, if you just start screening your million-compound libraries against bacteria to see what kills them, you will find a vast pile of stuff that will kill your own cells, too, which is not what you want, and once you've cleared those out, you will find a still-pretty-vast pile of compounds that work through mechanisms that we already have antibiotics targeting. Needles in haystacks have nothing on this.

In fact, a lot of not-so-reasonable routes have been worked over, too. I keep sending people to this article, which is now seven years old and talks about research efforts even older than that. It's the story of GlaxoSmithKline's exhaustive antibiotics research efforts, and it also tells you how many drugs they got out of it all in the end: zip. Not a thing. From what I can see, the folks who worked on this over the last fifteen or twenty years at AstraZeneca could easily write the same sort of article - they've published all kinds of things against a wide variety of bacterial targets, and I don't think any of it has led to an actual drug.

This brings up another thing mentioned in the Times column. Here's the quote:

This is particularly striking at a time when the pharmaceutical industry is unusually optimistic about the future of medical innovation. Dr. Mikael Dolsten, who oversees worldwide research and development at Pfizer, points out that if progress in the 15 years until 2010 or so looked sluggish, it was just because it takes time to figure out how to turn breakthroughs like the map of the human genome into new drugs.

Ah, but bacterial genomes were sequenced before the human one was (and they're more simple, at that). Keep in mind also that proof-of-concept for new targets can be easier to obtain in bacteria (if you manage to find any chemical matter, that is). I well recall talking with a bunch of people in 1997 who were poring over the sequence data for a human pathogen, fresh off the presses, and their optimism about all the targets that they were going to find in there, and the great new approaches they were going to be able to take. They tried it. None of it worked. Over and over, none of it worked. People had a head start in this area, genomically speaking, with an easier development path than many other therapeutic areas, and still nothing worked.

So while many large drug companies have exited antibiotic research over the years, not all of them did. But the ones that stayed have poured effort and money, over and over, down a large drain. Nothing has come out of the work. There are a number of smaller companies in the space as well, for whom even a small success would mean a lot, but they haven't been having an easy time of it, either.

Now, one thing the Times article gets right is that the financial incentives for new antibiotics are a different thing entirely than the rest of the drug discovery world. Getting one of these new approaches in LDL or HIV to work would at least be highly profitable - the PCSK9 competitors certainly are working on that basis. Alzheimer's is another good example of an area that has yielded no useful drugs whatsoever despite ferocious amounts of effort, but people keep at it because the first company to find a real Alzheimer's drug will be very well rewarded indeed. (The Times article says that this hasn't been researched enough, either, which makes me wonder what areas have been). But any great new antibiotic would be shelved for emergencies, and rightly so.

But that by itself is not enough to explain the shortage of those great new antibiotics. It's everything at once: the traditional approaches are played out and the genomic-revolution stuff has been tried, so the unpromising economics makes the search for yet another approach that much harder.

Note: be sure to see the comments for perspectives from others who've also done antibiotic research, including some who disagree. I don't think we'll find anyone who says it's easy, though, but you never know.

Comments (56) + TrackBacks (0) | Category: Business and Markets | Drug Development | Drug Industry History | Infectious Diseases

July 24, 2014

Phenotypic Assays in Cancer Drug Discovery

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Posted by Derek

The topic of phenotypic screening has come up around here many times, as indeed it comes up very often in drug discovery. Give your compounds to cells or to animals and look for the effect you want: what could be simpler? Well, a lot of things could, as anyone who's actually done this sort of screening will be glad to tell you, but done right, it's a very powerful technique.

It's also true that a huge amount of industrial effort is going into cancer drug discovery, so you'd think that there would be a natural overlap between these: see if your compounds kill or slow cancer cells, or tumors in an animal, and you're on track, right? But there's a huge disconnect here, and that's the subject of a new paper in Nature Reviews Drug Discovery. (Full disclosure: one of the authors is a former colleague, and I had a chance to look over the manuscript while it was being prepared). Here's the hard part:

Among the factors contributing to the growing interest in phenotypic screening in drug discovery in general is the perception that, by avoiding oversimplified reductionist assumptions regarding molecular targets and instead focusing on functional effects, compounds that are discovered in phenotypic assays may be more likely to show clinical efficacy. However, cancer presents a challenge to this perception as the cell-based models that are typically used in cancer drug discovery are poor surrogates of the actual disease. The definitive test of both target hypotheses and phenotypic models can only be carried out in the clinic. The challenge of cancer drug discovery is to maximize the probability that drugs discovered by either biochemical or phenotypic methods will translate into clinical efficacy and improved disease control.

Good models in living systems, which are vital to any phenotypic drug discovery effort, are very much lacking in oncology. It's not that you can't get plenty of cancer cells to grow in a dish - they'll take over your other cell cultures if they get a chance. But those aren't the cells that you're going to be dealing with in vivo, not any more. Cancer cells tend to be genetically unstable, constantly throwing off mutations, and the in vitro lines are adapted to living in cull culture. That's true even if you implant them back into immune-compromised mice (the xenograft models). The number of drugs that look great in xenograft models and failed out in the real world is too large to count.

So doing pure phenotypic drug discovery against cancer is very difficult - you go down a lot of blind alleys, which is what phenotypic screening is supposed to prevent. The explosion of knowledge about cellular pathways in tumor cells has led to uncountable numbers of target-driven approaches instead, but (as everyone has had a chance to find out), it's rare to find a real-world cancer patient who can be helped by a single-target drug. Gleevec is the example that everyone thinks of, but the cruel truth is that it's the exceptional exception. All those newspaper articles ten years ago that heralded a wonderful era of targeted wonder drugs for cancer? They were wrong.

So what to do? This paper suggests that the answer is a hybrid approach:

For the purpose of this article, we consider ‘pure’ phenotypic screening to be a discovery process that identifies chemical entities that have desirable biological (phenotypic) effects on cells or organisms without having prior knowledge of their biochemical activity or mode of action against a specific molecular target or targets. However, in practice, many phenotypically driven discovery projects are not target-agnostic; conversely, effective target-based discovery relies heavily on phenotypic assays. Determining the causal relationships between target inhibition and phenotypic effects may well open up new and unexpected avenues of cancer biology.

In light of these considerations, we propose that in practice a considerable proportion of cancer drug discovery falls between pure PDD and TDD, in a category that we term ‘mechanism-informed phenotypic drug discovery’ (MIPDD). This category includes inhibitors of known or hypothesized molecular targets that are identified and/or optimized by assessing their effects on a therapeutically relevant phenotype, as well as drug candidates that are identified by their effect on a mechanistically defined phenotype or phenotypic marker and subsequently optimized for a specific target-engagement MOA.

I've heard these referred to as "directed phenotypic screens", and while challenging, it can be a very fruitful way to go. Balancing the two ways of working is the tricky part: you don't want to slack up on the model just so it'll give you results, if those results aren't going to be meaningful. And you don't want to be so dogmatic about your target ideas that you walk away from something that could be useful, but doesn't fit your scheme. If you can keep all these factors in line, you're a real drug discovery scientist, and no mistake.

How hard this is can be seen from the paper's Table 1, where they look over the oncology approvals since 1999, and classify them by what approaches were used for lead discovery and lead optimization. There's a pile of 21 kinase inhibitors (and eight other compounds) over in the box where both phases were driven by inhibition of a known target. And there are ten compounds whose origins were in straight phenotypic screening, with various paths forward after that. But the "mechanism-informed phenotypic screen" category is the shortest list of the three lead discovery approaches: seven compounds, optimized in various ways. (The authors are upfront about the difficulties of assembling this sort of overview - it can be hard to say just what really happened during discovery and development, and we don't have the data on the failures).

Of those 29 pure-target-based drugs, 18 were follow-ons to mechanisms that had already been developed. At this point, you'd expect to hear that the phenotypic assays, by contrast, delivered a lot more new mechanisms. But this isn't the case: 14 follow-ons versus five first-in-class. This really isn't what phenotypic screening is supposed to deliver (and has delivered in the past), and I agree with the paper that this shows how difficult it has been to do real phenotypic discovery in this field. The few assays that translate to the clinic tend to keep discovering the same sorts of things. (And once again, the analogy to antibacterials comes to mind, because that's exactly what happens if you do a straight phenotypic screen for antibacterials. You find the same old stuff. That field, too, has been moving toward hybrid target/phenotypic approaches).

The situation might be changing a bit. If you look at the drugs in the clinic (Phase II and Phase III), as opposed to the older ones that have made it all the way through, there are still a vast pile of target-driven ones (mostly kinase inhibitors). But you can find more examples of phenotypic candidates, and among them an unusually high proportion of outright no-mechanism-known compounds. Those are tricky to develop in this field:

In cases where the efficacy arises from the engagement of a cryptic target (or mechanism) other than the nominally identified one, there is potential for substan- tial downside. One of the driving rationales of targeted discovery in cancer is that patients can be selected by pre- dictive biomarkers. Therefore, if the nominal target is not responsible for the actions of the drug, an incorrect diagnostic hypothesis may result in the selection of patients who will — at best — not derive benefit. For example, multiple clinical trials of the nominal RAF inhibitor sorafenib in melanoma showed no benefit, regardless of the BRAF mutation status. This is consistent with the evidence that the primary target and pharmacodynamic driver of efficacy for sorafenib is actually VEGFR2. The more recent clinical success of the bona fide BRAF inhibitor vemurafenib in melanoma demonstrates that the target hypothesis of BRAF for melanoma was valid.

So, if you're going to do this mechanism-informed phenotypic screening, just how do you go about it? High-content screening techniques are one approach: get as much data as possible about the effects of your compounds, both at the molecular and cellular level (the latter by imaging). Using better cell assays is crucial: make them as realistic as you can (three-dimensional culture, co-culture with other cell types, etc.), and go for cells that are as close to primary tissue as possible. None of this is easy, or cheap, but the engineer's triangle is always in effect ("Fast, Cheap, Good: Pick Any Two").

Comments (22) + TrackBacks (0) | Category: Cancer | Drug Assays | Drug Development

July 15, 2014

K. C. Nicolaou on Drug Discovery

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Posted by Derek

K. C. Nicolaou has an article in the latest Angewandte Chemie on the future of drug discovery, which may seem a bit surprising, considering that he's usually thought of as Mister Total Synthesis, rather than Mister Drug Development Project. But I can report that it's relentlessly sensible. Maybe too sensible. It's such a dose of the common wisdom that I don't think it's going to be of much use or interest to people who are actually doing drug discovery - you've already had all these thoughts yourself, and more than once.

But for someone catching up from outside the field, it's not a bad survey at all. It gets across how much we don't know, and how much work there is to be done. And one thing that writing this blog has taught me is that most people outside of drug discovery don't have an appreciation of either of those things. Nicolaou's article isn't aimed at a lay audience, of course, which makes it a little more problematic, since many of the people who can appreciate everything he's saying will already know what he's going to say. But it does round pretty much everything up into one place.

Comments (58) + TrackBacks (0) | Category: Drug Development | Drug Industry History

July 14, 2014

How to Run a Drug Project: Are There Any Rules at All?

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Posted by Derek

Here's an article from David Shayvitz at Forbes whose title says it all: "Should a Drug Discovery Team Ever Throw in the Towel?" The easy answer to that is "Sure". The hard part, naturally, is figuring out when.

You don’t have to be an expensive management consultant to realize that it would be helpful for the industry to kill doomed projects sooner (though all have said it).

There’s just the prickly little problem of figuring out how to do this. While it’s easy to point to expensive failures and criticize organizations for not pulling the plug sooner, it’s also true that just about every successful drug faced some legitimate existential crisis along the way — at some point during its development , there was a plausible reason to kill the program, and someone had to fight like hell to keep it going.

The question at the heart of the industry’s productivity struggles is the extent to which it’s even possible to pick the winners (or the losers), and figuring out better ways of managing this risk.

He goes on to contrast two approaches to this: one where you have a small company, focused on one thing, with the idea being that the experienced people involved will (A) be very motivated to find ways to get things to work, and (B) motivated to do something else if the writing ever does show up on the wall. The people doing the work should make the call. The other approach is to divide that up: you set things up with a project team whose mandate is to keep going, one way or another, dealing with all obstacles as best they can. Above them is a management team whose job it is to stay a bit distant from the trenches, and be ready to make the call of whether the project is still viable or not.

As Shayvitz goes on to say, quite correctly, both of these approaches can work, and both of them can run off the rails. In my view, the context of each drug discovery effort is so variable that it's probably impossible to say if one of these is truly better than the other. The people involved are a big part of that variability, too, and that makes generalizing very risky.

The big risk (in my experience) with having execution and decision-making in the same hands is that projects will run on for too long. You can always come up with more analogs to try, more experiments to run, more last-ditch efforts to take a crack it. Coming up with those things is, I think, better than not coming up with them, because (as Shayvitz mentions) it's hard to think of a successful drug that hasn't come close to dying at least once during its development. Give up too easily, and nothing will ever work at all.

But it's a painful fact that not every project can work, no matter how gritty and determined the team. We're heading out into the unknown with these drug candidates, and we find out things that we didn't know were there to be found out. Sometimes there really is no way to get the selectivity you need with the compound series you've chosen - heck, sometimes there's no way to get it with any compound series you could possibly choose, although that takes a long time to become obvious. Sometimes the whole idea behind the project is flawed from the start: blocking Kinase X will not, in fact, alter the course of Disease Y. It just won't. The hypothesis was wrong. An execute-at-all-costs team will shrug off these fatal problems, or attempt to shrug them off, for as long as you give them money.

But there's another danger waiting when you split off the executive decision-makers. If those folks get too removed from the project (or projects) then their ability to make good decisions is impaired. Just as you can have a warped perspective when you're right on top of the problems, you can have one when you're far away from them, too. It's tempting to thing that Distance = Clarity, but that's not a linear function, by any means. A little distance can certainly give you a lot of perspective, but if you keep moving out, things can start fuzzing back up again without anyone realizing what's going on.

That's true even if the managers are getting reasonably accurate reports, and we all know that that's not always the case in the real world. In many large organizations, there's a Big Monthly Meeting of some sort (or at some other regular time point) where projects are supposed to be reviewed by just those decision makers. These meetings are subject to terrible infections of Dog-And-Pony-itis. People get up to the front of the room and they tell everyone how great things are going. They minimize the flaws and paper over the mistakes. It's human nature. Anyone inclined to give a more accurate picture has a chance to see how that's going to look, when all the other projects are going Just Fine and everyone's Meeting Their Goals like it says on the form. Over time (and it may not take much time at all), the meeting floats away into its own bubble of altered reality. Managers who realize this can try to counteract it by going directly to the person running the project team in the labs, closing the office door, and asking for a verbal update on how things are really going, but sometimes people are so out of it that they mistake how things are going at the Big Monthly Meeting for what's really happening.

So yes indeed, you can (as is so often the case) screw things up in both directions. That's what makes it so hard to law down the law about how to run a drug discovery project: there are several ways to succeed, and the ways to mess them up are beyond counting. My own bias? I prefer the small-company back-to-the-wall approach, of being ready to swerve hard and try anything to make a project work. But I'd only recommend applying that to projects with a big potential payoff - it seems silly to do that sort of thing for anything less. And I'd recommend having a few people watching the process, but from as close as they can get without being quite of the project team themselves. Just enough to have some objectivity. Simple, eh? Getting this all balanced out is the hard part. Well, actually, the science is the hard part, but this is the hard part that we can actually do something about.

Comments (14) + TrackBacks (0) | Category: Drug Development | Drug Industry History | Life in the Drug Labs

July 10, 2014

A Drug Candidate from NCATS

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Posted by Derek

I've written several times about the NIH's NCATS program, their foray into "translational medicine". Now comes this press release that the first compound from this effort has been picked up for development by a biopharma company.

The company is AesRx (recently acquired by Baxter), and the compound is AES-103. This came from the rare-disease part of the initiative, and the compound is targeting sickle cell anemia - from what I've seen, it appears to have come out of a phenotypic screening effort to identify anti-sickling agents. It appears to work by stabilizing the mutant hemoglobin into a form where it can't polymerize, which is the molecular-level problem underlying the sickle-cell phenotype. For those who don't know the history behind it, Linus Pauling and co-workers were among the first to establish that a mutation in the hemoglobin protein was the key factor. Pauling coined the term "molecular disease" to describe it, and should be considered one of the founding fathers of molecular biology for that accomplishment, among others.

So what's AES-103? Well, you'll probably be surprised: it's hydroxymethyl furfural, which I would not have put high on my list of things to screen. That page says that the NIH screened "over 700 compounds" for this effort, which I hope is a typo, because that's an insanely small number. I would have thought that detecting the inhibition of sickling would be something that could be automated. If you were only screening 700 compounds, would this be one of them?

For those outside the business, I base that opinion on several things. Furans in general do not have a happy history in drug development. They're too electron-rich to play well in vivo, for the most part. This one does have an electron-withdrawing aldehyde on it, but aldehydes have their own problems. They're fairly reactive, and they tend to have poor pharmacokinetics. Aldehydes are, for example, well-known as protease inhibitors in vitro, but most attempts to develop them as drugs have ended in failure. And the only thing that's left on the molecule, that hydroxymethyl, is problematic, too. Having a group like that next to an aromatic ring has also traditionally been an invitation to trouble - they tend to get oxidized pretty quickly. So overall, no, I wouldn't have bet on this compound. There must be a story about why it was tested, and I'd certainly like to know what it is.

But for all I know, those very properties are what are making it work. It may well be reacting with some residue on hemoglobin and stabilizing its structure in that way. The compound went into Phase I in 2011, and into Phase II last year, so it does have real clinical data backing it up at this point, and real clinical data can shut me right up. The main worry I'd have at this point is idiosyncratic tox in Phase III, which is always a worry, and more so, I'd think, with a compound that looks like this. We'll see how it goes.

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June 26, 2014

Alzheimer's Bonds

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Posted by Derek

I wrote a couple of years ago about Andrew Lo of MIT, and his idea for securitization of drug discovery. For those of you who aren't financial engineers, that means raising funds by issuing securities (bonds and the like), and that's something that (as far as I know) has never been used to fund any specific drug development project.

Now Pharmalot has an update in an interview with Lo (who's recently published a paper on the idea in Science Translational Medicine). In particular, he's talking about issuing "Alzheimer's bonds", to pick a disease with no real therapies, a huge need for something, and gigantic cost barriers to finding something. Lo's concerned that the risks are too high for any one company to take on (and Eli Lilly might agree with him eventually), and wants to have some sort of public/private partnership floating the bonds.

We would create a fund that issues bonds. But if the private sector isn’t incentivized on its own, maybe the public sector can be incentivized to participate along with some members of the private sector. I will explain. But let’s look at the costs for a moment. The direct cost of treating the disease – never mind home care and lost wages – to Medicare and Medicaid for 2014 is estimated at $150 billion. We did a calculation and asked ourselves what kind of rate of return can we expect? We came up with $38.4 billion over 13 years. . .

. . .Originally, I thought it could come from the private sector. We’d create a fund – a mega fund of private investors, such as hedge funds, pension,