Ultragenyx’s Fayuvi becomes first FDA-approved treatment for Sanfilippo syndrome
The FDA has approved Fayuvi, a one-time gene therapy from Ultragenyx, as the first treatment for Sanfilippo syndrome type A. The therapy, priced at $3.95 million, addresses the underlying genetic cause of the neurodegenerative disorder, offering hope to families previously left with only symptom management.
Key points
- The FDA granted full approval to Fayuvi (formerly UX111) on September 17, 2026, for Sanfilippo syndrome type A (MPS IIIA).
- Fayuvi uses an adeno-associated viral vector to deliver a functional copy of the SGSH gene, correcting the enzyme deficiency that causes brain damage.
- Ultragenyx set the wholesale acquisition cost at $3.95 million per dose, though final patient costs may vary based on discounts and reimbursement policies.
- Clinical data showed a 23.2-point cognitive improvement in young children compared to natural history, with some patients reaching 36-month developmental milestones.
- This approval follows a previous FDA rejection due to manufacturing issues and comes after Ultragenyx’s recent phase 3 failure for an Angelman syndrome candidate.
Background
Sanfilippo syndrome type A is an ultra-rare neurodegenerative disorder affecting an estimated 3,000 to 5,000 patients in the developed world. It is caused by a mutation in the SGSH gene, leading to the buildup of heparan sulfate in cells, which damages the brain and causes progressive loss of cognitive and language abilities. Prior to this approval, treatment focused solely on managing symptoms. The approval follows a period of heightened FDA scrutiny on rare disease therapies, including recent holds on other gene therapies for related mucopolysaccharidosis disorders.
How outlets are covering it
STAT emphasized the emotional impact on families, quoting the Cure Sanfilippo Foundation on the shift from despair to hope. Fierce Pharma highlighted the regulatory hurdles, noting the prior FDA rejection due to manufacturing issues and the recent phase 3 failure of Ultragenyx’s Angelman syndrome candidate, which led to stock lows and cost-cutting. Yahoo Finance framed the approval as a financial win for Ultragenyx, citing Cantor’s view of a $400 million market opportunity. Endpoints News focused on the high price point of $3.95 million. All sources agree on the historic nature of the approval as the first disease-altering treatment for MPS IIIA.
Why it matters
This approval marks a significant milestone in gene therapy for rare neurodegenerative diseases, providing the first disease-modifying treatment for Sanfilippo syndrome type A. It demonstrates the potential of gene therapy to address underlying genetic causes rather than just symptoms, potentially improving outcomes for ultra-rare conditions. The high cost and regulatory challenges highlight the complexities of bringing such therapies to market.
What to watch
Ultragenyx is focusing on supporting timely access in the U.S. through treatment centers and payers. The company is also managing cost reductions following the phase 3 failure of its Angelman syndrome candidate. The FDA may continue to scrutinize other gene therapy applications, as seen with recent holds on MPS II therapies.
- FDA approves a new gene therapy for Sanfilippo syndrome, an ultra-rare disease STAT
- FDA approves Ultragenyx’s gene therapy Fayuvi for rare neurodegenerative disorder Fierce Pharma
- Ultragenyx Gets A ‘Much-Needed Win,’ Says Cantor – Sees $400M Opportunity After FDA Approves Neurodegenerative Disease Therapy Yahoo Finance
- Ultragenyx sets $3.95 million price for rare disease gene therapy Reuters
- Updated: Ultragenyx’s new gene therapy will cost $3.95 million Endpoints News
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