Ultragenyx Wilson Disease Gene Therapy Trial Update for WDA

As requested, we are providing an update on Stage 1 of our Cyprus2+ study, assessing safety and efficacy of UX701, an investigational gene therapy for the treatment of Wilson disease.
The status update below is based on the first dosing group of 5 patients as of October 8, 2023:

• Four out of 5 patients have had reductions in urinary copper and are tapering off of chelators and/or zinc therapy, including 2 of 3 earlier treated patients in the group that are now completely off standard therapy
• Duration of time on the study for this group ranged from 16 to 82 weeks
• Tapering of chelators and/or zinc therapy began at 12 weeks following a single intravenous infusion of UX701
• While none of the patients have experienced treatment-related adverse events, we do not have sufficient data to reach any conclusions regarding the safety of UX701 or whether adverse events will occur as the study continues.

Additional information:

• The study is expected to complete dosing of all 15 patients in Stage 1 at the end of 2023
• Additional information on safety and efficacy is expected to be shared in the first half of 2024
• Ultragenyx is sponsoring this global study of UX701, an investigational gene therapy for which safety and effectiveness has not been established. This type of research takes time, so it will be a while before we know whether and when UX701 will receive regulatory approval.

Ultragenyx would like to express our gratitude to those individuals who are participating in our study. These experiences and insights help advance our understanding of Wilson disease and have the potential to move research forward for future generations. As requested, we will continue to share updates as new information becomes available. For questions, please email PatientAdvocacy@ultragenyx.com.