Ultragenyx Pharmaceutical has announced results from the phase 3 Aspire study for apazunersen (GTX-102) in Angelman syndrome. The study did not achieve the primary endpoint of change from Baseline in Bayley-4 cognitive raw score nor the key secondary endpoint of net response in Multidomain Responder Index (MDRI). The safety profile observed in Aspire was consistent with phase 1/2.

Emil Kakkis, MD, PhD, Chief Executive Officer (CEO) and President, Ultragenyx, said, “Based on everything we observed in the robust phase 1/2 clinical development program and long-term extension study, we are disappointed by the Aspire result. Even more, we are disappointed for the global patient community who has invested so much in early-stage research, working to bring a first-ever treatment to their children.”

In Aspire, the randomised groups were comparable at baseline and consistent with the patients studied in phase 2. There were no differences between the treated and control groups that could support efficacy in the Bayley Cognition raw scores nor in the MDRI when looking at net response or mean changes of the individual 5 endpoints included in the MDRI.

The company will evaluate the apazunersen program in light of this outcome and make a decision on its disposition. The company will also assess its planned operations to define and implement significant expense reductions, while supporting its growing commercial business.

Dr. Kakkis continued, “We will maintain focus on our growing commercial business, which continues to create meaningful value, including new sources of revenue from the recent approval of GENGLYCOS for glycogen storage disease type Ia, the potential approval of UX111 for Sanfillipo syndrome, and the expansion of existing products to new territories. This strong commercial foundation will support our pipeline, while continuing toward profitability in 2027.”