Drug maker Vivus Inc., is hoping to win Food and Drug Administration (FDA) approval for its diet drug Qnexa this week after a rejection in 2010 due to serious health concerns. Experts say the chances of the weight loss drug being cleared are 50-50.
Qnexa is a combination of two FDA-approved drugs. One is phentermine, the “safer” part of the fen-phen diet drug that was banned due to heart problems. The other active ingredient is topiramate, a drug used to treat seizures and migraines. Topiramate has side effects that include suicidal thoughts and birth defects.
The FDA rejected Qnexa its first go-round, requesting that the pharmaceutical company quantify what the risk of birth defects might be. The agency also raised questions about whether the slight increase in heart rate linked the drug increases risk of cardiovascular events such as heart attack or stroke.
On the upside, Qnexa does exceed the FDA’s minimum effectiveness requirement. On average, people taking the dose of Qnexa proposed for approval lost 6.6 percent of their body weight. The FDA requires that a drug result in an average loss of at least 5 percent of body weight in order to gain approval. One study also found that 62 percent of obese and overweight people taking Qnexa lost at least 5 percent of their body weight – about three times as many as the placebo group. The FDA requires that 35 percent of people must lose 5 percent of body weight in order to gain clearance for marketing.
However, questions about the drug’s safety persist. The FDA says that only a long-term study can identify whether Qnexa increases the risk of heart disease in obese people already at high risk for heart problems. Also, a large number of women in the clinical study became pregnant while on Qnexa despite agreeing to be on birth control. While no birth defects were seen during the clinical trial, the FDA worries that with 36 percent of women in the U.S. obese, a lot of them may become pregnant while on the medication.
A 22-member panel is expected to vote on the fate of Qnexa this week. The FDA isn’t required to follow the advice of its advisory panels, but it usually does.