The FDA cleared Ultragenyx’s one-time AAV8 gene therapy Genglycos (pariglasgene brecaparvovec; DTX-401) for glycogen storage disease type Ia (GSDIa), marking the company’s first approved gene therapy and its first marketed product for an ultra-rare metabolic disorder. The accelerated approval is for patients aged 8 and older, targeting the underlying enzyme deficiency that drives potentially life-threatening blood-sugar crashes. Separately, the FDA approved Regeneron’s Pasatru (garetosmab) for fibrodysplasia ossificans progressiva (FOP), introducing a new Activin A blockade option and setting up commercial competition with Ipsen’s Sohonos. Regeneron’s Phase 3 Optima program linked Pasatru to large reductions in new abnormal bone formation over 56 weeks and fewer flare-ups in adults. Together, the two FDA actions underscore regulators’ continuing willingness to advance therapies for small, underserved populations, particularly where mechanism-based trial endpoints align with clear clinical risks.