What is Fayuvi, the first FDA-approved treatment for Sanfilippo syndrome type A?

We have folded our coverage of this story into one complete guide: Is there really a first FDA-approved treatment for Sanfilippo syndrome?

The short version: Fayuvi is a one-time IV gene therapy approved for eligible pediatric patients with Sanfilippo syndrome type A — the first treatment ever approved for this disease. For the full picture — how the therapy works, what FDA approval actually means, what families usually do next, and what to watch from here — read the complete guide.

Why gene therapy changes the conversation

Sanfilippo syndrome is a missing-enzyme disease: without one working enzyme, the body cannot break down a complex sugar, and it slowly builds up — most cruelly in the brain. Enzyme treatments struggle to reach the brain at all. A gene therapy takes a different route, delivering working instructions so the body makes its own enzyme continuously.

What to do, step by step

1. Ask whether eligibility depends on subtype and age. Gene therapies for Sanfilippo target specific types (A, B) and often work best early.
2. Confirm diagnosis with genetic testing if it was only ever clinical — the subtype letter decides which treatments apply.
3. Connect with the Cure Sanfilippo Foundation and MPS Society, which track trial sites and treatment centers faster than general news does.