Shares of Regenxbio sank sharply despite positive pivotal Phase III data for its Duchenne muscular dystrophy gene therapy candidate RGX-202. Reporting highlighted investor concerns after the company disclosed that the FDA recommended a randomized controlled trial to evaluate the therapy during discussions. The episode underscores how regulatory design requirements can dominate market reactions even when efficacy signals are favorable. It also points to uncertainty around the timing of potential accelerated approval and commercialization sequencing in the competitive DMD gene therapy landscape.