Ultragenyx Pharmaceutical Inc. announced that the U.S. Food and Drug Administration (FDA) has cleared the Investigational New Drug (IND) application for UX701, an investigational AAV9 gene therapy being evaluated for the treatment of Wilson Disease. Enrollment in a seamless single-protocol Phase 1/2/3 study is expected to begin in the first half of 2021. This will be the company’s third in-house clinical gene therapy program and the second program in the clinic with the HeLa producer cell line manufacturing system. UX701 will be studied in a seamless, single-protocol Phase 1/2/3 clinical trial. Manufacture and testing of GMP-grade drug product to supply the clinical study are complete using the company’s proprietary HeLa 2.0 producer cell line (PCL) process at the 2,000 liter scale. In the first stage of the study, the safety and efficacy of three dose levels of UX701 will be evaluated in 27 patients (nine per cohort), randomized 2-to-1 (gene therapy versus placebo). The dose cohorts will be enrolled sequentially using ascending doses. The patients will be followed for 52 weeks before transitioning to long-term follow-up and selecting a pivotal dose. The dose will be determined based on the safety profile, changes in biomarkers of copper metabolism, copper chelator and/or zinc. The second and pivotal stage will use the dose selected from Stage 1 and enroll an additional 63 patients, randomized 2-to-1 (gene therapy versus placebo). The co-primary endpoints in Stage 2 will evaluate the effect of UX701 on copper regulation based on 24-hour urinary copper concentration and % reduction in SOC at Week 52. Key secondary endpoints in Stage 2 include the effect of UX701 on additional biomarkers of copper metabolism and patient- and clinician-reported outcomes from a modified Wilson Disease Functional Rating Scale. All patients in Stage 1 and Stage 2 who are randomized to receive placebo may be eligible to receive UX701 at the Stage 2 dose. Patients receiving UX701 will be continued to be monitored for long term safety and durability of response. UX701 is an investigational AAV type 9 gene therapy designed to deliver stable expression of a truncated version of the ATP7B copper transporter following a single intravenous infusion. It has been shown in preclinical studies to improve copper distribution and excretion from the body and reverse pathological findings of Wilson liver disease. UX701 was granted Orphan Drug Designation in the United States and European Union.