–FAYUVI is a highly anticipated, first-ever treatment option with the potential to stop or slow the devastating, irreversible neurologic progression and loss of function associated with Sanfilippo syndrome Type A
–Ultragenyx’s UltraCare® program will support access, and commercial product is expected to be available to ship to Qualified Treatment Centers within 30-60 days
–FAYUVI marks the second gene therapy approval, and sixth FDA approval overall, for Ultragenyx
–The Company received a Priority Review Voucher upon FAYUVI approval–Ultragenyx
On September 17, 2026, Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) announced that the U.S. Food and Drug Administration (FDA) granted standard full approval of FAYUVI™ (rebisufligene etisparvovec-hopf), also known as UX111, for the treatment of pediatric patients with mucopolysaccharidosis type IIIA (MPS IIIA, Sanfilippo syndrome Type A). FAYUVI is the first-ever FDA-approved treatment for Sanfilippo syndrome Type A, a progressive and fatal neurodegenerative disease, and the second gene therapy approval for Ultragenyx. The Company received a Priority Review Voucher upon this approval. “The approval of FAYUVI reflects years of research from scientists and developers, as well as unwavering support from so many families and patient organizations in the face of a devastating, universally fatal disease with no treatment options. This is a historic milestone for a community that has waited far too long, but has never given up hope,” said Emil D. Kakkis, MD, PhD, Chief Executive Officer and President of Ultragenyx. “We recognize the profound urgency of making this therapy available to families, and our focus now is on supporting timely access in the U.S. as we work closely with treatment centers and payers to support families on the gene therapy treatment journey. FDA approval is an important first step toward our long-term goal to bring this treatment option to families of children with Sanfilippo syndrome Type A around the world.”
“The U.S. FDA approval of FAYUVI is a milestone that the Sanfilippo syndrome Type A community spent decades fighting to achieve: the first-ever treatment for a disease that relentlessly steals a child’s abilities, independence, and future,” said Glenn O’Neill, President and Co-Founder of the Cure Sanfilippo Foundation, and Terri Klein, CNPM, MPA, President and Chief Executive Officer of the National MPS Society.
“This remarkable scientific achievement is the culmination of decades of advocacy, fundraising, collaboration, and perseverance across the Sanfilippo community along with researchers, clinicians, and industry partners who never lost faith that progress was possible. We celebrate by honoring every family who contributed and remembering the children we lost while waiting for this day. Together, we look ahead with renewed hope knowing that this treatment is now approved for children and families affected by this heartbreaking disease.”
About Sanfilippo Syndrome Type A and FAYUVI
Sanfilippo syndrome Type A is an ultra-rare, fatal lysosomal storage disease that primarily affects the brain and is marked by rapid, progressive neurodegeneration beginning in early childhood. Children with Sanfilippo syndrome Type A typically experience progressive global developmental delay, followed by the loss of cognitive, language, and motor function, ultimately leading to early death. Sanfilippo syndrome Type A is estimated to affect approximately 3,000 to 5,000 patients in commercially accessible geographies, with a median life expectancy of 15 years. The disease is caused by a deficiency of the sulfamidase (SGSH) enzyme, which results in the accumulation of heparan sulfate substrate in cells and progressive damage to the central nervous system. FAYUVI is a single-dose intravenous AAV9 gene therapy designed to deliver a functional copy of the deficient enzyme gene that can express and replace the SGSH enzyme.
“This gene therapy addresses a pressing unmet clinical need and offers families a promising therapeutic option,” said Kevin M. Flanigan, MD, Director of the Center for Gene Therapy at Nationwide Children’s Hospital and principal investigator on the study that led to its approval. “It is additionally gratifying in that this vector was first developed at Nationwide Children’s more than a decade ago, and its approval highlights our commitment to developing therapies that meaningfully impact children’s health.”
The final delivery of this therapy did not come without tremendous difficulties during its development, and the Company hopes this approval will revitalize the investment in other ultra-rare gene therapies. The therapy was developed by Haiyan Fu, PhD, and Doug McCarty, PhD, during their tenures at Ohio State University/Nationwide Children’s Hospital and was licensed to Abeona. When funding constraints arose despite positive clinical data, Abeona made the pivotal decision to out-license the asset to Ultragenyx, ensuring this vital treatment reached the finish line for patients. Ultragenyx thanks the researchers, the development and leadership team at Abeona, and so many families, patient advocacy groups, and investigators who worked tirelessly through so many obstacles over the many years to lead the Company to this moment of shared success.
Clinical Program Supporting FAYUVI
The approval of FAYUVI is supported by data from the pivotal Transpher A trial and long-term follow-up studies, which demonstrated clinical benefit relative to the decline observed in natural history, along with durable treatment effect across clinical assessments and multiple biomarkers while maintaining an acceptable safety profile. Clinical data now extend to up to nearly 8 years of follow-up.
Biochemical efficacy in replacing the missing enzyme was demonstrated by a reduction in accumulated cerebral spinal fluid (CSF) heparan sulfate (HS) levels throughout the study and across all age groups. Clinical efficacy was assessed based on patients’ mean change in Bayley-III Cognitive raw score from 24 to 60 months of age. FAYUVI-treated patients from the modified intention-to-treat (mITT) population (N=17) were compared to untreated patients with Sanfilippo syndrome Type A from an external, comparable natural history cohort (N=27). FAYUVI-treated patients (mITT) demonstrated a 23.5 point higher (p<0.0001) cognitive score over natural history during the period of study, providing the efficacy basis for standard full approval.
Enabling Access for Eligible Patients
Ultragenyx will provide support to help enrolled patients and caregivers navigate access to treatment through its UltraCare® program, which now includes specially trained UltraCare® Gene Therapy Guides to help understand insurance coverage, assist in obtaining treatment support, and answer questions about the treatment process. Dedicated in-house UltraCare Gene Therapy Guides are available Monday through Friday from 9 a.m. to 8 p.m. Eastern Time at 888-756-8657. More information is available at www.ultracaresupport.com.
FAYUVI will be available through a network of Qualified Treatment Centers (QTCs), which are U.S.-based healthcare institutions with specialized expertise and training to administer gene therapy. Ultragenyx expects commercial product will be available for shipment to QTCs within 30-60 days.
FAYUVI is manufactured entirely within the U.S., at Ultragenyx’s Gene Therapy Manufacturing Facility in Bedford, Massachusetts, and Andelyn Biosciences in Columbus, Ohio.
Additional details, including information on the QTC network, will be available on fayuvi.com, which is expected to be live within the coming days.
Investor Conference Call
Ultragenyx hosted a conference call September 17 to discuss the FAYUVI approval. The replayed webcast of the call will be available through the company’s website at https://ir.ultragenyx.com/events-presentations.
INDICATION
FAYUVI™ (rebisufligene etisparvovec-hopf) is an adeno-associated virus (AAV) vector-based gene therapy indicated for the treatment of neurologic manifestations of mucopolysaccharidosis type IIIA (MPS IIIA, Sanfilippo syndrome type A) in pediatric patients with preserved neurodevelopmental function.