GTX-102 - (Aspire)

Sept. 2, 2026: Ultragenyx Pharmaceutical (NASDAQ: RARE) reported that the Phase 3 Aspire study of apazunersen (GTX-102) in Angelman syndrome failed to meet both the primary endpoint and key secondary endpoint. The trial did not show a treatment benefit versus control on change from baseline in Bayley-4 cognitive raw score, and it also missed the key secondary endpoint of net response in the Multidomain Responder Index (MDRI). The company said there were no differences between treated and control groups in Bayley cognition scores, MDRI net response, or mean changes across the five individual MDRI endpoints.

Ultragenyx said the safety profile in Aspire was consistent with Phase 1/2. Following the result, the company will evaluate the future of the apazunersen program and decide on its disposition. It also plans to assess operations and implement significant expense reductions.

The release also mentioned other catalysts outside apazunersen: recent approval of GENGLYCOS for glycogen storage disease type Ia, and potential approval of UX111 for Sanfilippo syndrome. Apazunersen is an investigational intrathecal antisense oligonucleotide targeting UBE3A-AS and has received FDA Breakthrough Therapy, Orphan Drug, Rare Pediatric Disease, and Fast Track designations, plus EMA Orphan and PRIME designations.