June 13, 2007 -- A new weight loss drug designed for obese adults failed to win approval from an FDA advisory panel Wednesday, mainly because of fears that it can lead to depression and suicidal thoughts in some patients.
Outside experts unanimously rejected the bid of Sanofi-Aventis to market Zimulti (rimonabant) in the U.S. despite its approval in dozens of other countries. The drug was previously known as Acomplia.
"My level of concern ... is very high," says Sid Gilman, MD, a member of the panel and a professor of neurology at the University of Michigan.
"I think this is a drug that needs further understanding with respect to what it does to people's psyche," he says.
The panel's conclusion, in a 14-0 vote, throws up a major hurdle in a longtime effort by its manufacturer to market the drug in the U.S. The decision makes it unlikely that regulators will approve the drug for U.S. sales because the FDA usually follows the recommendations of its advisory panels.
Studies conducted by its manufacturer, Sanofi-Aventis, show that many obese patients can lose up to 10% of their body weight after one year on the drug. It also appears to improve blood sugar control in obese diabetes patients.
In early 2006, the FDA was close to approving the drug, which at the time carried the brand name Acomplia.
But the agency asked the company first to study reports that the drug seemed to cause depression and suicidal thoughts and behaviors in some patients. It also asked Sanofi-Aventis to abandon the name Acomplia because regulators considered it potentially misleading to consumers.
The company responded by offering to minimize the risk by urging doctors not to use the drug in patients with a history of depression or other mental illnesses. In the process, the name Acomplia was changed to Zimulti.
Company officials clashed with regulators over the size of the psychiatric risk, saying that thousand of patients who took the drug had suicide rates essentially identical to the general population. Sanofi-Aventis said they'd found a 30% increase in the risk of suicidal thoughts with the drug but that in studies those thoughts almost never led to suicide attempts.
"The safety profile can only be interpreted in light of the demonstrated benefits," Paul Chew, MD, Sanofi-Aventis' vice president for international clinical development, told the committee.
Amy Egan, MD, an FDA safety official, says the agency had become worried because the company excluded patients being treated for depression from its analysis.
But Sanofi-Aventis took a novel approach to weight loss with Zimulti. The drug works by blocking the brain's cannabinoid receptors, the same receptors stimulated by marijuana. That seems to account for the drug's weight loss effect: blocking the same receptors that underlie the appetite- stimulating effect of marijuana.
Experts praised Sanofi-Aventis for what they said was an original approach to helping control obesity. "I think we all look forward to new data. I think this is an exciting area," says Clifford J. Rosen, MD, a senior scientist at the Maine Center for Osteoporosis and the panel's chairman.
- At what point do you say "no" to medication for weight loss? If taking it puts any of your organs at risk, is it worth it? Give us your take on WebMD's Dieting Clubs: 100+ Lbs. message board.