Anti-obesity drug bites the dust

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The search for anti-obesity drugs got a setback with Merck’s announcement Thursday that the company has ended obesity research on its experimental drug taranabant. According to a statement from the company, though phase three results showed it did help people lose weight, it also had too many side effects. Here’s the company’s Oct. 2 statement.

Taranabant is a chemical that blocks a receptor in the brain that is activated by THC, the main psychoactive ingredient in marijuana. (Readers may be aware that partaking of marijuana stimulates the appetite; conversely, blocking the brain receptor through which this effect occurs might be expected to have an anti-munchie effect.) But the receptor blocked by taranabant is widely distributed in the brain and presumably involved in a variety of brain processes. Plus it’s also found in certain other tissues of the body, including fat cells and the adrenal, thyroid and pituitary glands. So it’s not surprising the drug would have other effects unrelated to appetite.

According to an article in the Wall Street Journal, ‘The company said Thursday that both effectiveness and side effects are dependent on dose levels, with higher doses producing greater effectiveness but more adverse events. Essentially, Merck wasn’t able to find a dose level that adequately minimizes risk while helping people lose weight to a significant degree.’

This isn’t the first anti-obesity drug developed that acts on cannabinoid receptors. Another, Sanofi-Aventis’ rimonabant (Accomplia), is available in some countries in Europe but hasn’t received FDA approval in the U.S.; in 2007 an FDA advisory committee recommended against approval because of side effect concerns.


-- Rosie Mestel