FDA Approves First Gene Therapy for Children with Sanfilippo Syndrome Type A

In a landmark moment for rare-disease medicine, the U.S. Food and Drug Administration (FDA) approved Fayuvi™ (rebisufligene etisparvovec-hopf), developed by Ultragenyx Pharmaceutical, Inc. (NASDAQ: RARE). The therapy is the first approved treatment for Sanfilippo syndrome type A (MPS IIIA), a devastating, fatal neurodegenerative disease in children.

The approval was granted in September 2026 and is receiving widespread coverage as families share their emotional journeys.

Sanfilippo syndrome type A is caused by mutations in the SGSH gene, which prevent the body from breaking down heparan sulfate—a molecule critical to normal cell function. As heparan sulfate accumulates, children can progressively lose the ability to speak and walk, and may develop seizures. Most do not survive past their teenage years.

Fayuvi is a one-time intravenous gene therapy that uses a modified, non-infectious AAV9 virus to deliver a working copy of the SGSH gene into a patient’s cells. The therapy emerged from more than a decade of research that began at Nationwide Children’s Hospital in Columbus, Ohio. Ultragenyx acquired the therapy rights in 2022 and led its development through regulatory approval. Its U.S. list price is $3.95 million.

The research also received significant support from the Cure Sanfilippo Foundation. The O’Neill family founded the organization after their daughter Eliza was diagnosed with the disease and raised millions of dollars to fund early research.

Source: NPR — How One Family Gave a Critical Boost to Gene Therapy Research