FDA panel recommends new diet drug Qnexa

Posted: February 23, 2012

For 10 years, Louis Aronne has been giving patients a combination of phentermine, a 50-year-old stimulant widely used to control appetite, and topiramate, a newer antiseizure drug, to help them lose weight.

The combination works, he said, and with fewer side effects than when the drugs are given alone.

"If it's used in appropriate patients and monitored judiciously, I think that a medicine like this can play an important role," said Aronne, who directs the weight-loss program at New York Presbyterian Weill Cornell Medical Center. "One of the biggest problems . . . is we don't have many options."

An FDA advisory panel agreed Wednesday.

The drugs Aronne is already using, in a slightly different formula, are the components of Qnexa, a new and controversial diet drug that won the recommendation of the panel of experts by a 20-2 vote. The group also said the drug's safety should be monitored in a large study after its approval.

Most of the time, the FDA accepts such recommendations. It is expected to rule on the drug in April. In its recent decision on another diet medication, it required that the larger safety study be done before final approval.

If approved, Qnexa would be the first new diet drug in 13 years. In trials, it helped patients lose about 10 percent of their body weight. Even though that's not enough to make most overweight people thin, it's a strong showing for a diet medication. Losing even small amounts decreases the health risks associated with obesity.

The FDA had said it had concerns about potential side effects of the drug: heart problems and birth defects in the babies of women who take Qnexa while pregnant.

The federal agency rejected the drug in October 2010 but its maker, Vivus Inc. of Mountain View, Calif., asked for a chance to present new information.

The only drug now on the market for long-term weight loss is orlistat (brand names Xenical and Alli), which prevents the body from using 30 percent of fat consumed. That reduces the number of calories the body uses but produces some really unpleasant gastrointestinal problems if users keep eating fatty foods. Experts say it hasn't been popular.

Critics of Qnexa worry that America's obesity epidemic - a third of adults are obese - will create huge demand, potentially exposing millions to the side effects.

Doctors such as Aronne, who specialize in helping obese patients lose weight, said the FDA has often seemed to set the bar higher for weight-loss drugs than it does for medications to treat other serious conditions such as high blood pressure or heart disease. They argue that the health risks of obesity are significant, as are the health benefits of losing weight.

"Obviously, no drug is without side effects or risks. . . . Sometimes the consequences of obesity aren't taken seriously enough," said Gary Foster, director of Temple University's Center for Obesity Research.

Aronne doesn't use the drug combination in women who are thinking about becoming pregnant or in people at high risk of heart problems. He asks patients to sign a consent form that tells them the drugs are being used off label. "This is not a mill," he said. "We are very, very serious about what we do here."

Thomas Wadden, director of the Center for Weight and Eating Disorders at the University of Pennsylvania School of Medicine, has been involved in studies of Qnexa and Contrave, another drug in the pipeline that combines the antidepressant buproprion and the anti-addiction drug Naltrexone. The FDA earlier this year declined to approve Contrave until its maker proves it doesn't increase heart risks.

Wadden hasn't used the combo outside of a study. And he doesn't use phentermine alone because he thinks its safety has not been well enough studied. Plus, it's only supposed to be used for six to 12 weeks.

It can be as effective alone as Qnexa, but it also can raise heart rate and blood pressure, he said. For most people, the biggest problem of topiramate is mental fogginess. When put together, in much smaller doses, in Qnexa, the side effects tend to cancel each other out, he said.

"If this drug were approved, we would certainly use it in some of our trials and combine with lifestyle modification," Wadden said.

He said that phentermine seems to reduce the desire to eat. It was half of the discredited diet treatment fen-phen, but Wadden said it was the fen part of the pair - fenfluramine - that caused heart-valve problems. Topiramate is not as well studied, but it is thought to increase satiation.

Some critics have said people regain the weight after they stop taking Qnexa. But obesity experts countered that people's blood pressure also goes back up when they stop taking their blood-pressure medicines.

Aronne said he also gives some patients the drugs used in Contrave. The interesting thing, he said, is that some people respond to one combination and not the other, just as they would to different blood-pressure or depression drugs. "I see this as part of the spectrum of treatment that should evolve," he said.

Obesity specialists expect high demand for Qnexa.

"There's always going to be a demand for a drug that's going to help people lose weight," said Matthew Pinto, who runs the Center for Medical Weight Loss of South Jersey. He currently uses phentermine, combined with meal replacements and counseling on lifestyle changes. "People are always going to be looking for a pill."


Contact staff writer Stacey Burling at 215-854-4944 or sburling@phillynews.com.

The Associated Press contributed to this article.

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