WebMD Newsroom

by Daniel J. DeNoon

Patients and doctors eagerly awaiting FDA approval of the new weight-loss drug Qnexa will have to wait at least another three months.

Expected to approve the drug on April 17, the FDA now says it will take another three months to evaluate the risk-reduction plan offered by Vivus in return for approval.

And that’s not the only stumbling block to Qnexa approval.  Vivus also has to conduct a clinical trial designed to show that the slightly increased heart rate seen in people taking Qnexa will not cause heart problems over time. But an FDA advisory panel last February voted 20-2 to recommend Qnexa approval before the study is completed, or even under way.

The FDA doesn’t appear to be worried about the drug’s effectiveness. While people taking the drug don’t get thin, they do lose some 6% to 10% of their body weight (some more, some less) if they also eat less and exercise more. That weight loss occurs over the first year of Qnexa use. A bit tends to get gained back in the second year, but people who stayed on the drug for a second year tended to maintain most of their weight loss.

And the FDA may not be particularly worried about Qnexa safety, given the advisory panel’s strong opinion that the drug’s weight-loss benefit appears to outweigh its known risks.

Part of Vivus’s risk reduction plan is a strategy to keep women from getting pregnant while taking the drug. One of Qnexa’s ingredients is topiramate, a seizure/migraine drug known to cause birth defects, particularly cleft palate. This was one of the main concerns expressed by advisory panel members who voted for Qnexa’s approval.

Qnexa has a second ingredient: a low dose of phentermine, an amphetamine. Amphetamines (“speed”) are controlled substances with serious abuse potential.

Even when Qnexa is approved, it may be a while before Vivus is able get all its ducks in a row to satisfy all of the FDA’s requirements.

Meanwhile, the FDA panel is planning to vote next month on  lorcaserin, another weight-loss drug.