Wednesday, January 24, 2007

New contraceptives languishing

Yesterday's NYT Science section featured an interview with Dr. David E. Clapham, a research scientist at Harvard Medical School whose work on ion channels (pores in the cell membrane that regulate chemical uptake and output) has revealed a promising new approach to birth control. Clapham's lab has identified a gene called CatSper that encodes for a set of proteins that make up a specific type of ion channel necessary for sperm to fertilize an egg. Clapham explains:
As you know, a human sperm needs to swim through the female reproductive tract for something like 15 minutes to get to the egg. They have a kind of built-in motor that permits them to do that. When sperm get to the egg, they need to crash through the ovum’s membrane to deposit their DNA there.

The way that happens is that at the end of its run, this ion channel brings the sperm calcium, which changes the shape of its tail and turns it into a kind of whip. The sperm is then propelled into hyper drive — pushing it into the egg with 20 times the force of normal swimming. Now, if this ion channel is blocked, there can be no fertilization.
Finding a compound capable of blocking this ion channel could lead to a new, nonhormonal contraceptive that could be taken by women and men. If you're thinking that this would be great news to women and men for whom current contraceptives aren't cutting it, you'd be right. Unfortunately, if you're thinking that there must be drug companies beating down Clapham's lab door, you'd be wrong. Clapham says:
There’s a general feeling throughout the industry that reproduction is just too risky in terms of potential liability and in terms of controversy. They feel that the estrogen-based birth control pill works fine. As far as they are concerned, the problem is solved.
If there's one thing I trust drug companies to do, it's accurately assess the moneymaking prospects of a drug. Drug companies are businesses with a responsibility to their bottom line, but they're not the only game in town. Federal funding of contraceptive research can help in the pursuit if new and better contraceptive methods. Given the Bush administration's abysmal record on contraception, we could to be waiting a while before we see a CatSper-blocking contraceptive on the market, but with new and familiar allies of choice representing us in the 2007 Democratic-majority congress, there may be potential for progress.

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