MOUNTAIN VIEW, Calif. (AP) -- Drug developer Vivus Inc. reported clinical data on Wednesday that linked one of the ingredients of its experimental weight loss drug Qnexa to an increased risk of birth defects.
Vivus said women who took topiramate, one of the two main ingredients of Qnexa, during the first trimester of pregnancy were about twice as likely to give birth to a child with cleft lip or cleft palate as women who had taken Qnexa in the past but did not take the drug while they were pregnant. The rate of cleft lip and cleft palate in women who took topiramate during pregnancy was 0.36 percent, compared with 0.16 percent for the former users of topiramate.
The data is based on an analysis of more than 15,000 past medical claims and was not taken from a clinical trial of Qnexa. Vivus agreed to conduct the analysis after the Food and Drug Administration refused to approve Qnexa last year. Vivus said it is working to confirm the medical claims and expects to complete that process during the third quarter of 2012.
Shares of Vivus rose 10 cents to $10.40 in Wednesday trading, but lost 74 cents, or 7.1 percent, to $9.66 after-hours. The stock has traded between $6 and $11.48 over the last year.
The women in the study were taking topiramate as a treatment for epilepsy. Johnson & Johnson markets the drug under the name Topamax, and generic versions are also available. Topiramate is also approved as a treatment for migraines.
Qnexa combines topiramate with phentermine, an amphetamine. Vivus says that topiramate makes patients feel more satiated and phentermine helps suppress appetite.
The Food and Drug Administration refused to approve Qnexa in October 2010 because of concerns about birth defects including cleft lip and palate. The company said it has shared the data with the FDA and is preparing to meet with an FDA advisory committee during the first quarter of 2012.
The FDA changed the classification of topiramate in March to reflect the fact that there is evidence the drug can harm a human fetus.