Ultragenyx Reports Positive Phase 1/2 Results for GTX-102 in Angelman Syndrome

Ultragenyx Pharmaceutical Inc. has reported promising results from their Phase 1/2 study supporting the Phase 3 Aspire study for GTX-102, an investigational antisense oligonucleotide aimed at treating Angelman syndrome. The Phase 1/2 data revealed improvements across all domains, confirming that the Phase 3 Aspire study is well-positioned to demonstrate the efficacy of GTX-102.

By the September data cut-off, patients in the Dose Expansion Cohorts showed continued improvement at Week 48 (Day 338). A total of 40 patients in these cohorts exhibited a mean change in the Bayley-4 Cognition Growth Scale Value (GSV) score from baseline of +6.7, surpassing the minimally important difference of +5. The primary endpoint of the Phase 3 study, the Bayley-4 Cognition Raw score, showed a mean change from baseline of +10.9. These results suggest the Phase 3 study has over 95% power to detect a treatment effect, even if the response in the sham arm is significantly higher than changes seen in available natural history data.

Data from 28 patients in Expansion Cohorts A & B were assessed for the Phase 3 key secondary endpoint of MDRI, revealing a total net response of +2.0. Approximately 80% of these patients (22 of 28) achieved clinically meaningful net improvement in at least one domain.

The safety profile of GTX-102 was consistent and acceptable as of the data cutoff, supporting the continuation of the Phase 3 Aspire study.