FDA shoots down another weight loss drug [Updated]
The FDA has told the makers of the proposed weight-loss drug Lorcaserin that it will not at this time approve the marketing of  the medication, citing concerns about its marginal effectiveness and about cancers that occurred at higher-than-usual rates in animal studies. [Updated Oct. 25, 10:35 a.m. An earlier version of this article said cancers occurred at higher-than-usual-rates during clinical trials.]

The FDA's decision comes just two weeks after the makers of the prescription diet-pill Meridia pulled it from the U.S. and Canadian markets at the request of the FDA. It is the first signal of how the U.S. drug agency will deliberate on a trio of new weight-loss drugs proposed for the U.S. market, where about one in three adults are obese.

Arena Pharmaceuticals, the San Diego drug company that has developed Lorcaserin in partnership with Eisai Co., released the contents of an FDA letter Saturday in which the agency outlined its concerns. Among those concerns were weight-loss results that failed to rise to the FDA's standards for approval, and a worrisome increase in cancerous breast and brain tumors in rats that were given a dose of the drug that is higher than that proposed for humans. A clinical trial of Lorcaserin published in the New England Journal of Medicine found that two-thirds of patients lost at least 5% of their body weight, while a third lost at least 10% of body weight, with an average loss of 17 to 18 pounds.

With the results of a new clinical trial on Lorcaserin for obese patients with Type-2 diabetes due to be unveiled in the coming weeks, Arena Pharmaceuticals officials said they will meet with FDA officials soon to address the concerns. The company held out hope for a change of heart on the part of the FDA after those results become available.

"This is an important step for us toward the FDA's approval of Lorcaserin," said Jack Lief, Arena's president and chief executive.

The FDA's preliminary disapproval of Lorcaseri, which works on the brain to alter metabolism and appetite, comes as the agency also considers two other weight-loss drug candidates: Qnexa, a diet drug that combines an anti-seizure drug with a component of the banned diet drug Phen-Fen, and Contrave, a drug that combines the antidepressant Wellbutrin with the addiction drug naltrexone. Qnexa got a thumbs-down recommendation in June from an FDA advisory panel, and the agency is expected to issue a decision on the drug this week. Contrave is to be considered by an FDA advisory panel for the first time in December. 

The FDA's approach in recent months to regulating weight-loss drugs has come in for criticism from physicians and other experts, who argue that the agency is too risk-averse in its deliberations. Responding to Saturday's report of the FDA's preliminary decision on Lorcaserin, Morgan Downey, editor and publisher of the Downey Obesity Report, said, "the action of the FDA is consistent with the pattern that no drug for obesity can be approved. They are searching for an unrealistic 'magic bullet.' ... It is about the FDA fear of some future embarrassment." 

--Melissa Healy / Los Angeles Times