MOUNTAIN VIEW, Calif.
Shares of the drug company Vivus Inc. slumped 15 percent before the market opened Friday on concerns over the potential side effects of its obesity drug candidate.
The Food and Drug Administration wants it to study the rate of side effects associated with one of the ingredients of Qnexa.
The FDA did not ask for any new clinical trials, which could take a long time and lead to significant new expenses for Vivus. Still, it raised fears about Qnexa's chances of winning marketing approval. Shares of Vivus fell $1.52 to $8.91 in premarket trading.
Vivus said it met with the FDA on Wednesday. The company said the agency asked it to find out if it is feasible to analyze existing health care databases to determine how often women who use the drug topiramate as a migraine drug give birth to children who have cleft palates. Johnson & Johnson sells topiramate under the name Topamax, and it is one of the ingredients in Qnexa.
The Topamax website says birth defects and low birth weight may be linked to the use of Topamax during pregnancy. Topiramate is also used to treat epileptic seizures.
Vivus said 15 pregnant women used Qnexa during its clinical trials and there were no reports of birth defects. The company said it will evaluate the feasibility of the study as part of its plan to make a new request for approval of Qnexa. The FDA declined to approve the drug in October. Qnexa was associated with significant weight loss, but was also linked to birth defects, potential heart problems, suicidal thoughts, and memory lapses in some patients.