Qnexa Yields Up to Nearly a 10% Weight Loss: Study

April 10, 2011 -- The experimental weight loss drug  Qnexa produces a loss of up to nearly 10% of excess weight, according to a study just published in the Lancet.

''The weight loss is impressive," researcher Kishore M. Gadde, MD, director of the obesity clinical trials program at Duke University, tells WebMD.

The report published in The Lancet includes all the data that was already presented to the FDA last July by Vivus, the company developing the drug combination, Gadde says. However, he says, "this is the first time the data are presented in a peer-reviewed journal."

In July, an FDA expert advisory panel recommended against approval of Qnexa.

Qnexa includes phentermine, a drug already approved for obesity, and topiramate, a drug already approved for epilepsy and to prevent migraine headaches.

Since the rejection by the FDA advisory panel, the company has been addressing the concerns, says Peter Tam, the president of Vivus, which funded the study.

One concern is the use of topiramate, linked with birth defects such as  cleft lip and cleft palate, by women who may become pregnant. Vivus is in discussion with the FDA now about how to address those concerns, Tam says.

"Our goal is to resubmit the new drug applications by the end of 2011," he says.

Qnexa: Study Details

For the study, researchers enrolled 2,487 participants, assigning them randomly to take either placebo pills or two different doses of the drug combination during the 56-week study.

In all, 2,448 patients were evaluated. This included 979 on placebo, 488 on the lower-dose regimen, and 981 on the higher dose. The lower dose included 7.5 milligrams of phentermine and 46 milligrams of topiramate. The higher dose was 15 milligrams of phentermine and 92 milligrams of topiramate.

To be eligible, patients had to have a body mass index of 27 to 45. No lower limit of BMI was in place for participants with diabetes. They also had to have two or more obesity-related conditions, such as high blood pressure or type 2 diabetes managed with lifestyle changes and/or the drug metformin.

Qnexa: Study Results

The average weight loss for those who completed the study was 28 pounds on the high dose, 22 on the low dose, and 4 pounds for those taking the placebo. The results meet criteria suggested by the FDA for weight loss products, Gadde tells WebMD.

Besides weight loss, Gadde tells WebMD, "this treatment led to significant improvement in excess weight-related diseases such as diabetes and high blood pressure and risk factors such as high cholesterol."

Those on the drug had a greater reduction blood pressure and improvement in so-called good cholesterol, HDL cholesterol, than those on placebo. Those who had diabetes at the study start and took the drug were less likely to need an increase in diabetes drugs than those on placebo.