Ultragenyx Announces Completion of Dosing Across Stage 1 Cohorts in Pivotal Phase 1/2/3 Cyprus2+ Study Evaluating UX701 Gene Therapy for the Treatment of Wilson Disease

Safety and initial efficacy data from Stage 1 expected in the first half of 2024

Dose selection and initiation of Stage 2 to follow in the second half of 2024

NOVATO, Calif., Jan. 25, 2024 (GLOBE NEWSWIRE) -- Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) today announced that all patients have been dosed with UX701 across the three dose-escalation cohorts in Stage 1 of its pivotal Phase 1/2/3 Cyprus²⁺ study. The company's investigational AAV9 gene therapy is designed to deliver stable expression of the ATP7B copper transporter following a single intravenous infusion, with the goal of normalizing copper metabolism in patients with Wilson disease.

“With the support of patients, physicians and the Wilson disease community, we’ve completed Stage 1 enrollment in the Cyprus²⁺ program, which moves us one step closer to beginning Stage 2, the pivotal, randomized placebo-controlled stage of the study,” said Eric Crombez, M.D., chief medical officer at Ultragenyx. “Beyond the seamless nature of this study, another important differentiator of this program is that it leverages our Pinnacle PCL platform, which enabled a single run to support Stage 1, demonstrating that the productivity improvements generated by our platform are able to support larger-scale clinical programs.”

Data presented in October 2023 at a Company Analyst Day demonstrated that UX701 has been well tolerated in the first dose cohort, with no unexpected related treatment emergent adverse events observed as of the data cut-off date. Four of five patients enrolled in Cohort 1 had started tapering standard-of-care treatment, including two that came completely off of chelators and/or zinc therapy. Additional interim data from all three Stage 1 dose cohorts are expected in the first half of 2024, which will be followed by dose selection and initiation of Stage 2 in the second half of 2024.

U.S. residents can learn more by visiting www.ultraclinicaltrials.com.

Phase 1/2/3 Cyprus²⁺ study design
This study evaluating UX701 for the potential treatment of Wilson disease is designed with three stages. During the first stage, the safety and efficacy of up to three dose levels of UX701 will be evaluated over the course of 52 weeks and a dose will be selected for further evaluation in Stage 2. In this first stage, 15 patients were enrolled into three sequential dosing cohorts to evaluate doses of 5.0 x 10^12 GC/kg, 1.0 x 10^13 GC/kg, and 2.0 x 10^13 GC/kg.