Regenxbio’s RGX-202 generated positive pivotal phase 3 data for Duchenne muscular dystrophy, but investors reacted negatively after the FDA recommended the company run a randomized controlled trial (RCT) during discussions with regulators. The stock dropped sharply over two days amid uncertainty over timing and what evidence standards will ultimately be required. The report highlighted prior FDA guidance suggesting externally controlled trials may be adequate when treatment effects are sufficiently large, but the prospect of an RCT has put market entry timelines in flux. Regenxbio said it plans to discuss the dataset and alternative proposals with the FDA. For the DMD gene-therapy landscape, the situation underscores how much late-stage regulatory flexibility can vary and how RCT demands can reshape competitive pacing and launch planning.