Capricor Therapeutics has received a complete response letter from the U.S. FDA rejecting its biologics license application for deramiocel, an allogeneic cardiosphere-derived cell therapy intended to treat cardiomyopathy in Duchenne muscular dystrophy (DMD). The FDA cited insufficient evidence of effectiveness and outstanding chemistry, manufacturing, and controls issues. This decision breaks from recent FDA flexibility in cell and gene therapy reviews, surprising the company. The ongoing Phase III trial is expected to generate additional data that may address the regulator's concerns. Capricor's shares fell significantly following the announcement.