Ultragenyx Reports Positive Long-Term Data for UX111 Gene Therapy in Sanfilippo Syndrome Type A
Ultragenyx Pharmaceutical announced positive long-term clinical data for UX111 gene therapy for Sanfilippo syndrome Type A, with up to 8.5 years of follow-up showing sustained biomarker reductions and functional improvements. The company resubmitted its BLA to the FDA in January 2026.
On February 3, Ultragenyx Pharmaceutical announced positive long-term data for UX111, which is an investigational AAV9 gene therapy for Sanfilippo syndrome Type A (MPS IIIA). This demonstrates sustained reductions in cerebrospinal fluid heparan sulfate (CSF-HS) and significant improvements in clinical function.
With up to 8.5 years of follow-up, the study showed that treated children achieved a median 63.98% reduction in CSF-HS and exhibited unprecedented separation from natural history data, specifically regarding cognitive, communication, and motor skills.
Younger patients and those with earlier-stage disease showed the most robust treatment effects, while older children retained critical functional abilities, such as verbal communication and independent ambulation, far beyond the typical age of decline seen in untreated peers. The safety profile of UX111 remains favorable and well-tolerated.
Following these encouraging results, Ultragenyx Pharmaceutical Inc. (NASDAQ:RARE) resubmitted its BLA to the US FDA in January 2026, seeking accelerated approval for UX111. The submission includes the latest long-term functional and biomarker data to support the clinical benefit of the gene therapy across various patient ages and disease severities. The company anticipates a review period of up to six months per FDA guidelines, with a PDUFA action date expected in Q3 2026.
Ultragenyx Pharmaceutical Inc. (NASDAQ:RARE) is a biopharmaceutical company that identifies, acquires, develops, and commercializes novel products for the treatment of rare and ultra-rare genetic diseases in North America, Latin America, Europe, the Middle East, Africa, and the Asia-Pacific.