Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) announced that the U.S. Food and Drug Administration granted standard full approval of FAYUVI (rebisufligene etisparvovec-hopf) for the treatment of pediatric patients with mucopolysaccharidosis type IIIA, also known as Sanfilippo syndrome Type A.

According to the company's press release, FAYUVI is the first FDA-approved treatment for Sanfilippo syndrome Type A, a progressive neurodegenerative disease estimated to affect approximately 3,000 to 5,000 patients in commercially accessible geographies, with a median life expectancy of 15 years. The disease is caused by a deficiency of the sulfamidase enzyme, resulting in the accumulation of heparan sulfate in cells and progressive damage to the central nervous system.

FAYUVI is a single-dose intravenous AAV9 gene therapy designed to deliver a functional copy of the deficient enzyme gene. Approval was supported by data from the pivotal Transpher A trial, in which treated patients demonstrated a 23.5-point higher cognitive score compared to a natural history cohort (p<0.0001). Clinical follow-up data now extend to nearly eight years.

Ultragenyx received a Priority Review Voucher upon the approval. The therapy represents the company's second gene therapy approval and sixth FDA approval overall.

The therapy was originally developed at Ohio State University and Nationwide Children's Hospital, licensed to Abeona Therapeutics, and subsequently out-licensed to Ultragenyx. FAYUVI is manufactured at Ultragenyx's facility in Bedford, Massachusetts, and at Andelyn Biosciences in Columbus, Ohio.

Ultragenyx said commercial product is expected to be available for shipment to Qualified Treatment Centers within 30 to 60 days. The company's UltraCare program will provide patient and caregiver support for insurance coverage and treatment access.

Reported adverse reactions occurring in 5% or more of patients include elevated liver enzymes (85%), vomiting (67%), abnormal behavior (56%), diarrhea (48%), and pyrexia (41%), among others. Warnings include hepatotoxicity, thrombocytopenia, thrombotic microangiopathy, hypersensitivity reactions, and risk of malignancy.