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FDA panel backs obesity pill Qnexa: What happens next?

Qnexa CBS News

(CBS/AP) Qnexa, the anti-obesity pill, might be one step closer to hitting the market and American waistlines, now that a panel of advisors to the Food and Drug Administration has overwhelmingly endorsed the pill.

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Vivus Inc.'s Qnexa was previously rejected by the FDA in 2010 over safety concerns, one of three weight loss drugs rejected by the FDA in the past two years. That raised questions of whether any pharmaceutical treatment for obesity would ever be considered safe.

At a public meeting Wednesday, the panel of outside physicians voted 20-2 in favor of Qnexa, setting the stage for a potential comeback for a drug that could help some of the estimated 75 million obese Americans.

Nearly all the panelists backed the drug due to its impressive results, with most patients losing nearly 10 percent of their overall weight after a year on the drug. But the group stressed that the drugmaker must be required to conduct a large, follow-up study of the pill's effects on the heart. Studies of Qnexa show it raises heart rate and causes heart palpitations, a longtime concern with diet pills over the years. The expert panel said it is still unclear if those side effects will lead to serious heart problems.

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"The potential benefits of this medication seem to trump the side effects, but in truth, only time will tell," said Dr. Kenneth Burman of the Washington Hospital Center.

What happens next? The FDA will make a final decision by mid-April, and though it is not required to follow the advice of its panels, it often does.

"There is an urgent need for better pharmacologic options for individual patients with obesity," said Dr. Elaine Morrato, of the University of Colorado. "I believe Qnexa demonstrated a meaningful efficacy benefit and that there are consequences to not treating obesity."

The FDA rejected Qnexa in October 2010, citing numerous side effects including elevated heart rate, psychiatric problems and birth defects. Vivus has resubmitted the drug with additional follow-up information on safety, hoping for a more favorable ruling.

Currently there is just one prescription drug on the market for long-term weight loss: Roche's Xenical, which is sold over the counter as alli by GlaxoSmithKline. The drug is not widely used because of modest weight loss results and unpleasant side effects, including gas and diarrhea.

Vivus President Peter Tam said the overwhelming panel vote Wednesday indicates doctors recognize the urgent need for effective weight loss drugs. "Right now there aren't any good treatments out there besides dieting and bariatric surgery - clearly there's a huge gap," Tam said.

More than one-third of all adult Americans are obese, according to the CDC. Obesity raises the risk for chronic conditions including heart disease, stroke, type 2 diabetes and certain types of cancer. And even a modestly effective drug could have blockbuster potential, experts say.

What's in Qnexa? It's a combination of two older drugs: the amphetamine phentermine, which is approved for short-term weight loss, and topiramate, an anti-seizure and anti-migraine drug sold by Johnson & Johnson as Topamax. Phentermine helps suppress appetite, while topiramate is supposed to make patients feel fuller.

Along with heart safety, panelists raised concerns about potential birth defects in women who become pregnant while taking Qnexa: topiramate is known to more than double the risk of birth defects. There were 34 pregnancies among 3,386 women enrolled in Vivus' studies of Qnexa, despite precautions to make sure women used contraception. An FDA expert on birth defects estimated there would be five babies born with a cleft lip defect for every 1,000 women who became pregnant while taking Qnexa. If approved, FDA scientists said they would require Vivus to train prescribers to educate patients on the pregnancy risks of Qnexa.

Qnexa's other ingredient, phentermine, was one half of the dangerous fen-phen combination, a weight loss treatment pushed by doctors that was never approved by the FDA. The regimen was linked to heart-valve damage and lung problems in the late 1990s, and the FDA forced drugmaker Wyeth to withdraw two versions of its drug fenfluramine.

Patient advocates who spoke at the FDA's meeting are hopeful the drug will get approved to provide more options to obese Americans. Joe Nadglowski, president and CEO of the patient advocacy group, Obesity Action Coalition, told WebMD there's "a significant treatment gap from Weight Watchers to (bariatric) surgery."

The CDC has more on the U.S. obesity epidemic.