U.S. regulators are requiring Sarepta Therapeutics to conduct additional studies to confirm the safety of Elevidys, the FDA-approved gene therapy for Duchenne muscular dystrophy, following reports of patient deaths and elevated liver function markers. Sarepta initially resisted but eventually paused shipments in the U.S. The FDA’s call for new analyses aims to refine dosing or manufacturing to establish safer profiles without conducting a new clinical trial. This regulatory tension underscores challenges in evaluating accelerated approval drugs for rare diseases.