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ultragenyx Ultragenyx Announces Approval of FAYUVI ™ Gene Therapy , the First - Ever FDA - Approved Treatment for Sanfilippo Syndrome Type A ( MPS IIIA ) September 17 , 2026 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 to Host Conference Call on September 17 , 2026 at 5:30 p.m. Eastern Time NOVATO , Calif . , Sept. 17 , 2026 ( GLOBE NEWSWIRE ) -- Ultragenyx Pharmaceutical Inc. ( NASDAQ : RARE ) today announced that the U.S. Food and Drug Administration ( FDA ) granted standard full approval of FAYUVITM ( 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 , M.D. , Ph.D. , 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 , M.D. , 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