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July 17, 2009
Drug Approvals, Natural And Unnatural
I seem to have been putting a lot of graphics up this week, so here's another one. This is borrowed from a recent Science paper on the future of natural-products based drug discovery. It's interesting both from that viewpoint, and because of the general approval numbers:
And there you have it. Outside of anomalies like 2005, we can say, I think, that the 1980s were a comparative Golden Age of Drug Approvals, that the 1990s held their own but did not reach the earlier heights, and that since 2000 the trend has been dire. If you want some numbers to confirm your intuitions, you can just refer back to this.
As far as natural products go, from what I can see, the percentage of drugs derived from them has remained roughly constant: about half. Looking at the current clinical trial environment, though, the authors see this as likely to decline, and wonder if this is justified or not. They blame two broad factors, one of them being the prevailing drug discovery culture:
The double-digit yearly sales growth that drug companies typically enjoyed until about 10 years ago has led to unrealistically high expectations by their shareholders and great pressure to produce "blockbuster drugs" with more than $1 billion in annual sales (3). In the blockbuster model, a few drugs make the bulk of the profit. For example, eight products accounted for 58% of Pfizer’s annual worldwide sales of $44 billion in 2007.
As an aside, I understand the problems with swinging for the fences all the time, but I don't see the Pfizer situation above as anything anomalous. That's a power-law distribution, and sales figures are exactly where you'd expect to see such a thing. A large drug company with its revenues evenly divided out among a group of compounds would be the exception, wouldn't it?
The other factor that they say has been holding things back is the difficulty of screening and working with many natural products, especially now that we've found many of the obvious candidates. A lot of hits from cultures and extracts are due to compounds that you already know about. The authors suggest that new screening approaches could get around this problem, as well as extending the hunt to organisms that don't respond well to traditional culture techniques.
None of these sound like they're going to fix things in the near term, but I don't think that the industry as a whole has any near-term fixes. But since the same techniques used to isolate and work with tricky natural product structures will be able to help out in other areas, too, I wish the people working on them luck.
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