Ultragenyx's Angelman drug apazunersen fails Phase 3 Aspire trial on primary and key secondary endpoints

Ultragenyx

The Phase 3 Aspire study of apazunersen (GTX-102) in Angelman syndrome missed both its cognition endpoint and a combined multi-domain responder index. Earlier open-label results had been strong enough to win breakthrough designation. Ultragenyx said it would weigh the program's future, including its ongoing Phase 2 Aurora study.

• About 129 children aged 4-17 with full maternal UBE3A deletion enrolled.
• Missed primary endpoint (Bayley-4 cognition) and key secondary (MDRI).
• Safety matched the earlier Phase 1/2 study.
• FDA had granted breakthrough designation in June 2025 on open-label Phase 1/2 data.