The FDA said it would reconsider Regenxbio’s Hunter syndrome gene therapy (RGX-121) after rejecting the application earlier this year. Regenxbio said the agency acknowledged existing clinical data as sufficient for an accelerated pathway, and that the company would not need to run additional trials or add enrollees. Regenxbio reported that it has alignment with regulators on next steps, including a planned Type A meeting to review longer-term biomarker and clinical data. The approach reflects a broader shift in how the FDA is handling rare-disease submissions, including earlier refusals and subsequent reversals as leadership changed. For the rare neurodegeneration space, the decision is a concrete example of regulatory turnaround impacting timelines and trial design requirements, with implications for other gene therapy applicants facing comparable issues around control arms and endpoints.