The FDA cleared Ultragenyx’s one-time AAV gene therapy Genglycos (pariglasgene brecaparvovec; DTX-401) for glycogen storage disease type Ia (GSDIa), giving the company its first approved gene therapy and its first treatment marketed for an ultra-rare indication. The approval is accelerated and targets the underlying enzymatic deficiency that drives life-threatening metabolic destabilization between meals. Regulators cleared the therapy for patients age 8 and older, placing it into a narrow patient population with historically limited disease-modifying options. With the decision, Ultragenyx moves to five approved products overall, and analysts expect a structured rollout through specialized treatment centers. The approval also sustains the company’s monetization pathway around priority review vouchers, which can support development funding and timing for follow-on gene therapy programs in its pipeline.