U.S. panel rejects Sanofi obesity drug

SILVER SPRING, Maryland (Reuters) - U.S. regulators should reject a proposed weight-loss pill called Zimulti because of concerns it may increase suicidal thinking and depression, an advisory panel unanimously said on Wednesday.

French drugmaker Sanofi-Aventis SA (SASY.PA)(SNY.N) sells the medicine in 18 countries under the name Acomplia. Advisers to the Food and Drug Administration said there were too many questions about potential side effects to support U.S. approval.

"I think this is a drug that needs further understanding with respect to what it does to people's psyche," said Dr. Sid Gilman, a panel member and a University of Michigan neurologist.

The FDA usually follows panel recommendations. A final decision is expected by July 26.

Sanofi said in a statement it would work with the FDA to address the committee's decision.

In the past, the company has forecast peak annual sales of $3 billion or more for the drug, but the negative ruling makes it unlikely the company will be able to sell it in the world's largest pharmaceutical market.

Known generically as rimonabant, Zimulti is a new type of drug that helps people shed pounds by blocking food craving signals in the brain. Sanofi developed it to target receptors that trigger intense hunger after marijuana use.

In company studies, Zimulti plus a reduced-calorie diet helped patients lose about 5 percent more than diet alone over one year. Patients who took the drug lost an average of 14.2 pounds, while others who got a placebo dropped about 3.5 pounds.

Zimulti also reduced waist size and improved levels of "good" cholesterol, blood sugar and blood fats called triglycerides, Sanofi said.

"I believe rimonabant can offer a positive balance between likely benefits and potential risks," said Dr. Louis Aronne, a Sanofi consultant and professor of medicine at Weill Cornell Medical College.

But FDA reviewers said data showed Zimulti patients were twice as likely to have suicidal thoughts or mental problems such as depression and anxiety. Twenty-six percent of patients reported a psychiatric symptom, compared with 14 percent of placebo patients.

"The potential market for this drug and our continued uncertainty about its risks, both known and unknown, lead to our concern" about use in the general population, said FDA medical officer Amy Egan.

Sanofi said the risks were manageable, mainly by warning against use by people with past or current depression or on antidepressant treatment.

Company officials also said suicidal thinking and behavior was rare. In studies, 0.63 percent of Zimulti patients reported thoughts of suicide, compared with 0.38 percent of placebo patients.

Sanofi said there was no evidence Zimulti caused suicidal thoughts or actions, but the FDA's Egan disagreed.

"We strongly believe it is causal," she said.

Zimulti has been touted as an important drug for Sanofi, which faces potential generic competition for its key products.

"The drug was controversial before the meeting, but we were pretty confident it would be approved because its benefits would be deemed to outweigh its risks," said Mehta Partners analyst Shaojing Tong.

Tong had expected the drug to garner worldwide peak annual sales of $2.5 billion, including about $1.5 billion in the United States.

"But now its chances in the U.S. are close to zero and the rejection here could end up hurting its sales overseas," Tong said. "In the next 3 to 4 years, I don't expect its sales to be meaningful."

Sales for the first quarter of 2007 were about $20 million.

The panel decision came after U.S. markets closed. New York-listed shares of Paris-based Sanofi fell 1.3 percent in electronic trading to $42.50 after closing earlier at $43.07, down 3 percent on the New York Stock Exchange.

(Additional reporting by Ransdell Pierson in New York)