Ultragenyx's Angelman syndrome therapy misses goal in Phase 3 study

Ultragenyx announced that its experimental treatment for Angelman syndrome did not show a statistically significant benefit compared with a sham procedure in a Phase 3 trial. The company said the therapy failed to meet its primary endpoint.

Ultragenyx’s candidate for Angelman syndrome, a rare neurogenetic disorder, failed to outperform a sham control on the trial’s primary efficacy measure. The Phase 3 result marks a setback for the company’s pipeline, as the therapy had been considered a potential first disease-modifying treatment for the condition. No secondary outcomes or safety details were disclosed in the announcement. The study’s failure underscores the difficulty of translating preclinical promise into clinical benefit for complex developmental disorders, where endpoints often rely on caregiver-reported changes. Investors and patient communities will now await further data to assess whether any subgroups showed meaningful response.