The Food and Drug Administration has rejected three prescription diet pills in the last three years, raising questions of whether any weight loss drug can win approval in the U.S. The agency has not approved a new prescription weight loss drug in 13 years. Historically, medications that attempt to burn fat or suppress appetite have been plagued by safety issues.
Despite the latest rejections, all three drugmakers are resubmitting their products for a second review. Here's a look at the contenders and where they are in the review process:
— Qnexa is a combination of two older drugs: the amphetamine phentermine, which is approved for short-term weight loss, and topiramate, an anti-convulsant drug sold by Johnson & Johnson as Topamax. Phentermine helps suppress appetite, while topiramate is believed to make patients feel more satiated
Many experts view the combination pill as the most promising of the new weight loss drugs, due to studies showing most patients lost nearly 10 percent of their weight — the highest reduction reported with any recent diet pill. But the FDA rejected the drug in October 2010, raising a number of safety concerns, including higher heart rate and birth defects in women who become pregnant.
This week a panel of advisers to the FDA overwhelmingly recommended approval for Qnexa, on the condition Vivus Inc. conduct a follow-up study to make sure the drug doesn't cause heart problems. The FDA is expected to make its second ruling on the drug by April 17.
— Orexigen Therapeutics Inc.'s Contrave is another combination pill aimed at curbing appetite, mixing the antidepressant ingredient in Wellbutrin with the anti-smoking drug bupropion. The company's results have been lackluster, with about 40 percent of patients taking Contrave losing 5 percent of their body weight. Those figures narrowly achieved FDA's minimum requirements for an effective weight loss pill. But Contrave has also been plagued by the heart safety concerns associated with past diet pills. The FDA is requiring the company to conduct a 10,000-patient study of cardiovascular health. That study is slated for completion by 2014.
— Arena Pharmaceutical Inc.'s lorcaserin is the only first-of-a-kind diet drug currently before the FDA. It uses a new type of ingredient to stimulate serotonin receptors in the brain linked with feelings of satiety. But lorcaserin has faced the most severe safety questions from FDA, which rejected the drug in 2010 after raising concerns about cancerous tumors seen in rats who received the drug.
Early this year Arena submitted new information evaluating the link between its drug and cancer. The FDA is scheduled to make a new ruling on the drug by June 27.