UX111 - (ABO-102)

April 2, 2026: Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) said the FDA accepted for review its resubmitted Biologics License Application (BLA) seeking accelerated approval of UX111 (rebisufligene etisparvovec), an AAV9 gene therapy, to treat Sanfilippo syndrome Type A (MPS IIIA). The FDA set a PDUFA action date of September 19, 2026. The company noted the BLA previously received Priority Review in February 2025. Ultragenyx said the updated long-term clinical data included in the BLA—presented at WORLD Symposium 2026—provide up to 8 years of follow-up and show clinical improvement versus natural history decline, durable effects across clinical evaluations and multiple biomarkers, and an acceptable safety profile. If approved, UX111 would be the first approved therapy for MPS IIIA and would be manufactured in the U.S. at Andelyn Biosciences (Columbus, Ohio) and Ultragenyx’s Bedford, Massachusetts facility.