Ultragenyx released long‑term clinical data for UX‑111 (rebisufligene etisparvovec), its AAV9 gene therapy for Sanfilippo syndrome type A, pairing biomarker improvements with measurable functional benefits across ages and disease severities. The company resubmitted a BLA after addressing earlier CMC concerns and now expects a PDUFA date in the third quarter of 2026. Ultragenyx said UX‑111 remains well tolerated with sustained effects in treated patients. The new dataset is intended to support the resubmission and bolster FDA confidence ahead of regulatory action; rare‑disease stakeholders will watch safety, durability and manufacturing resolution closely.