A reader has sent along the question: "Have any repurposed drugs actually been approved for their new indication?" And initially, I thought, confidently but rather blankly, "Well, certainly, there's. . . and. . .hmm", but then the biggest example hit me: thalidomide. It was, infamously, a sedative and remedy for morning sickness in its original tragic incarnation, but came back into use first for leprosy and then for multiple myeloma. The discovery of its efficacy in leprosy, specifically erythema nodosum laprosum, was a complete and total accident, it should be noted - the story is told in the book Dark Remedy. A physician gave a suffering leprosy patient the only sedative in the hospital's pharmacy that hadn't been tried, and it had a dramatic and unexpected effect on their condition.
That's an example of a total repurposing - a drug that had actually been approved and abandoned (and how) coming back to treat something else. At the other end of the spectrum, you have the normal sort of market expansion that many drugs undergo: kinase inhibitor Insolunib is approved for Cancer X, then later on for Cancer Y, then for Cancer Z. (As a side note, I would almost feel like working for free for a company that would actually propose "insolunib" as a generic name. My mortgage banker might not see things the same way, though). At any rate, that sort of thing doesn't really count as repurposing, in my book - you're using the same effect that the compound was developed for and finding closely related uses for it. When most people think of repurposing, they're thinking about cases where the drug's mechanism is the same, but turns out to be useful for something that no one realized, or those times where the drug has another mechanism that no one appreciated during its first approval.
Eflornithine, an ornithine decarboxylase inhibitor, is a good example - it was originally developed as a possible anticancer agent, but never came close to being submitted for approval. It turned out to be very effective for trypanosomiasis (sleeping sickness). Later, it was approved for slowing the growth of unwanted facial hair. This led, by the way, to an unfortunate and embarrassing period where the compound was available as a cream to improve appearance in several first-world countries, but not as a tablet to save lives in Africa. Aventis, as they were at the time, partnered with the WHO to produce the compound again and donated it to the agency and to Doctors Without Borders. (I should note that with a molecular weight of 182, that eflornithine just barely missed my no-larger-than-aspirin cutoff for the smallest drugs on the market).
Drugs that affect the immune system (cyclosporine, the interferons, anti-TNF antibodies etc.) are in their own category for repurposing, I'd say, They've had particularly broad therapeutic profiles, since that's such a nexus for infectious disease, cancer, inflammation and wound healing, and (naturally) autoimmune diseases of all sorts. Orencia (abatacept) is an example of this. It's approved for rheumatoid arthritis, but has been studied in several other conditions, and there's a report that it's extremely effective against a common kidney condition, focal segmental glomerulosclerosis. Drugs that affect the central or peripheral nervous system also have Swiss-army-knife aspects, since that's another powerful fuse box in a living system. The number of indications that a beta-blocker like propanolol has seen is enough evidence on its own!
C&E News did a drug repurposing story a couple of years ago, and included a table of examples. Some others can be found in this Nature Reviews Drug Discovery paper from 2004. I'm not aware of any new repurposing/repositioning approvals since then, but there's an awful lot of preclinical and clinical activity going on.
August 15, 2014
There's a post by Peter Bach, of the Center for Health Policy and Outcomes, that's been getting a lot of attention the last few days. It's called "Unpronounceable Drugs, Incomprehensible Prices", and you know what it says.
No, really, you do, even if you haven't seen it. Too high, unconscionable, market can't support, what they can get away with, every year, too high. Before I get to the uncomfortable parts of my own take on this, let me stipulate a couple of things up front: (1) I do think that the industry is inviting trouble for itself by the way it it raising prices. It is in drug companies' short term interest to do so, but long term I worry that it's going to bring on some sort of price-control regimen. (2) Some drug prices probabl