Can medicines treat obesity? When, in 1994, loss of a single gene encoding a protein hormone called leptin was shown to cause mice to balloon to five times their normal size, optimism was high.
Human beings have leptin, too. Released into the blood after feeding, it tells the brain to stop feeling hungry. But giving leptin to most hungry people does little to curb their appetite.
It does not control all cravings, and where it does, a diminished response to the protein, rather than reduced production, lessens its effect. Recent
results from the Weizmann Institute in Israel show how lack of one control-cascade protein, a phosphatase called PTPe, decreases appetite in female mice. Most drug firms are pursuing phosphatase inhibitors (which control many processes in the body); as such, hopes of hunger-regulating drugs have received a boost.
The dietary products market runs into many billions of dollars, so PTPe-inhibitor investment may be significant. However, as inhibitors of one phosphatase often inhibit others, the chances of finding one that quells appetite without any side effects are slim.
A new drug to fight a neglected tropical disease, such as the deadly African sleeping sickness, caused by parasites replete with specific protein targets, would be easier to develop. Are many pharmaceutical companies doing that? Fat chance.