Sep 17, 2026 —
The U.S. Food and Drug Administration (FDA) has approved Fayuvi (rebisufligene etisparvovec), an adeno-associated virus (AAV) gene therapy from Ultragenyx, for children with Sanfilippo syndrome type A (mucopolysaccharidosis type IIIA, or MPS IIIA). It is the first approved treatment for the disease, which until now could only be managed for its symptoms.
Sanfilippo type A is a rare, progressive neurodegenerative disorder caused by mutations in the SGSH gene. The missing enzyme lets heparan sulfate build up in the brain, driving severe cognitive decline in early childhood. Fayuvi is a one-time intravenous infusion of an AAV9 vector carrying a working copy of the gene, given at a dose of 3×10¹³ vector genomes per kilogram.
The accelerated approval rested on reduction of heparan sulfate in cerebrospinal fluid. In the 27-patient efficacy population, the median CSF heparan sulfate reduction was about 64% from baseline, and younger treated children showed a 23.2-point advantage in Bayley-III cognitive raw score compared with natural-history controls. Ultragenyx has set a list price of $3.95 million; Fayuvi is the company’s second gene therapy to reach the market since August.
