Vivus Inc. said Friday the Food and Drug Administration has asked the drug developer to assess the feasibility of a study on whether an ingredient in the weight-loss drug Qnexa causes birth defects.

The request represents another setback for the drug intended to treat obesity. Vivus and rival Arena Pharmaceuticals Inc. had their diet drugs rejected by the agency in October, as competitor Orexigen Therapeutics Inc.’s weight-loss drug Contrave continued to move through the approval process.
Vivus said it will determine the date of the next new drug application for Qnexa after it finishes its feasibility assessment.

The newly requested investigation of health-care records would determine the incidence of oral clefts in children born to women treated with topiramate, an ingredient in Qnexa.

Vivus said it believes the new request stems from reports of defects in two children born in the U.K. and four in North America.

The company said there were no reports of any fetal malformations in the 15 births from women exposed to Qnexa or topiramate in the initial Qnexa studies.

The FDA in October asked the company for a comprehensive assessment of Qnexa’s potential to cause birth defects and evidence that the product doesn’t increase the risk for major adverse cardiovascular events.

Shares were inactive premarket and closed Thursday at $10.43. The stock is up 76 percent the last three months.