Family-funded research leads to first FDA-approved gene therapy for Sanfilippo syndrome
The FDA approved Fayuvi, a one-time gene therapy for Sanfilippo syndrome, in September 2026. Developed by researcher Haiyan Fu, the treatment was sustained by funding from patient families before being acquired by Ultragenyx. Priced at nearly $4 million, it offers the first disease-modifying option for a condition that previously had no cure.
Key points
- Fayuvi, a one-time infusion, received FDA approval in September 2026 as the first treatment for Sanfilippo syndrome type A.
- The therapy uses a modified virus to deliver a functional copy of the broken gene, addressing the inability to break down heparin sulfate.
- Ultragenyx acquired the rights to the therapy in 2022 after initial research by Haiyan Fu at Nationwide Children's Hospital.
- The treatment is priced at approximately $4 million, making it the second most expensive gene therapy ever, according to drug price research firm 46brooklyn.
- Early intervention is critical; Ultragenyx CEO Emil Kakkis noted that treating children under age two yields better results than treating older children who have already lost motor and speech skills.
Background
Our archive from September 2026 confirmed the FDA approval of Fayuvi, highlighting its role as the first treatment for this neurodegenerative disorder. Recent developments in gene therapy, such as epigenetic therapies for hepatitis B and vision restoration trials, underscore the broader momentum in genetic medicine, though Sanfilippo remains a distinct challenge due to its rapid progression in early childhood.
Why it matters
This approval marks a shift from symptom management to addressing the root genetic cause of Sanfilippo syndrome. For families of affected children, it offers a potential cure if administered early, though the high cost and narrow window for efficacy present significant logistical and financial challenges.
What to watch
Ultragenyx is committed to ensuring patient access regardless of location or state regulations. The company will likely focus on identifying and treating younger patients to maximize therapeutic outcomes, while monitoring long-term efficacy data for those treated at older ages.
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