A Heavyweight Contender

This breakthrough may be the key to a fat pill

Last July, Amgen Inc. looked like it had a lock on one of the drug industry's most heated races: the search for a "fat drug." In a much-heralded study whose announcement boosted Amgen's stock by $900 million, researchers disclosed that a protein called leptin, produced by the newly discovered OB gene, stripped away body fat when injected into obese mice.

Barely five months later, an Amgen rival may have taken the lead: On Dec. 28, Millennium Pharmaceuticals Inc. in Cambridge, Mass., was to announce that it had found the "receptor" for leptin--the structure on cell walls that is a crucial part of regulating leptin's function. Receptors don't make anyone skinny, but many drugs target receptors to inhibit or stimulate a bodily function. While Amgen is testing an injectable drug, Millennium says its receptor may be the key to an antiobesity pill, which would be far more lucrative.

MIND-SET. Researchers had hoped a shortage of leptin--the protein that signals the brain to stop eating--was a big factor in obesity. But studies now show that obese people often have high leptin levels. Millennium believes the receptor it found will lead it to another obesity gene, called DB, that determines whether the brain can recognize leptin's stop-eating signal. "The receptor may lead to drugs for potentially the most prevalent form of human obesity--one resulting from the brain's resistance to leptin rather than the lack of leptin," says Millennium CEO Mark Levin.

Weight-watchers shouldn't rethink New Year's resolutions yet: Researchers say a wonder drug is years away.

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