Sanofi's Prospects Get Leaner

Subsequently, it was revealed that the FDA was worried about clinical trial results showing that 26% of Zimulti users experienced some psychiatric side effects vs. 14% of patients receiving a placebo. Increased suicidal thinking was a key side effect.

Sanofi-Aventis told the FDA advisers that it would institute a program to make sure Zimulti wasn't prescribed for people with a risk of depression, suicidal thinking and other psychiatric problems.

The panel's vote against Zimulti offers an unsettling signal for several other drugmakers working on antiobesity medications using the same strategy as Zimulti. The Sanofi-Aventis drug targets the brain, seeking to block signals that help regulate how the body monitors food intake and how it uses and stores fats and sugars. Zimulti focuses on a part of the brain called a cannabinoid receptor 1.

Companies working on similarly acting drugs include Merck (MRK), Pfizer (PFE) and Bristol-Myers Squibb. The Merck and Pfizer compounds are in late-stage clinical testing. The Bristol-Myers Squibb drug and two other Sanofi-Aventis products are in midstage testing.

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