Ultragenyx Seeks FDA Approval After 63.98% CSF-HS Reduction Over 8.5 Years
Ultragenyx’s UX111 gene therapy achieved a median 63.98% reduction in cerebrospinal fluid heparan sulfate over 8.5 years, with treated children showing significant cognitive, communication and motor improvements compared to natural history controls. The company resubmitted its BLA in January 2026 for accelerated FDA approval, targeting a Q3 2026 PDUFA date.
1. Sustained Biomarker Reductions
UX111 demonstrated a median 63.98% reduction in cerebrospinal fluid heparan sulfate at up to 8.5 years post-treatment, marking unprecedented separation from natural history data in Sanfilippo syndrome Type A patients.
2. Functional Improvements in Treated Children
Treated children exhibited significant improvements in cognitive, communication and motor skills, with the most robust effects observed in younger and earlier-stage patients.
3. Favorable Safety and Subgroup Outcomes
The treatment’s safety profile remained favorable, with no new adverse signals reported and older children maintaining verbal communication and independent ambulation beyond typical decline ages.
4. Regulatory Resubmission and Next Steps
Ultragenyx resubmitted its biologics license application in January 2026 seeking accelerated FDA approval, with a PDUFA action date expected in the third quarter of 2026.