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. Get the full story »