Ultragenyx Pharmaceutical Inc. 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. 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. In Stage 2, a new cohort of patients will be randomized 2:1 to receive the selected dose of UX701 or placebo. The primary safety and efficacy analyses will be conducted at Week 52 of Stage 2. The primary efficacy endpoints are change in 24-hour urinary copper concentration and percent reduction in standard-of-care medication by Week 52.

After the initial 52-week study period, all patients will have long-term follow up in Stage 3.