NOVATO, Calif. — Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) has announced promising results from the ongoing Phase 1/2/3 Cyprus2+ study evaluating UX701 gene therapy for Wilson disease. Early-stage data from Stage 1 of the trial revealed significant clinical activity, including improvements in copper metabolism and responses across all three dose cohorts. Several patients have successfully transitioned off standard treatments, such as chelators and zinc therapy, further showcasing the potential of UX701.

In Stage 1, 15 patients received varying doses of UX701, and six have completely stopped their standard treatment, with copper levels normalizing in these patients. A seventh patient is currently in the process of tapering off. UX701 was well-tolerated with no unexpected safety concerns or major immunological events. Ultragenyx is now planning to introduce an additional cohort in Stage 1 with a moderately higher dose and optimized immunomodulation to boost the therapy’s efficiency.
Dr. Eric Crombez, Chief Medical Officer at Ultragenyx, expressed optimism, saying, “The clinical activity we’re observing, alongside a number of patients transitioning off standard treatments, gives us confidence that UX701 could represent a novel treatment for people with Wilson disease. Enhancing the dose and immunomodulation could potentially allow more patients to discontinue current treatments.”
Study Design
The Cyprus2+ study is divided into three stages. Stage 1 focuses on evaluating the safety and efficacy of multiple UX701 dose levels to determine the optimal dose for further stages. To date, 15 patients have been enrolled across three dose cohorts. In the upcoming Stage 2, a randomized trial will evaluate the selected dose against a placebo. Patients will continue to be monitored in Stage 3 for long-term effects.
About Wilson Disease
Wilson disease is a rare genetic disorder caused by mutations in the ATP7B gene, leading to abnormal copper accumulation in the liver and other organs. Patients experience hepatic, neurological, and psychiatric symptoms that can worsen over time, resulting in severe liver disease or even death. Current treatments, including lifelong chelation therapy, aim to reduce copper buildup but are not without limitations. Wilson disease affects over 50,000 individuals globally.
About UX701
UX701 is an investigational gene therapy using an AAV9 vector to deliver the ATP7B copper transporter. Preclinical studies have shown its potential to restore copper trafficking and balance within the body. UX701 has been granted Orphan Drug Designation in the U.S. and EU, and Fast Track Designation in the U.S.
For more information, visit Ultragenyx’s website or Ultragenyx clinical trials page.
This update highlights the promising future of UX701 as a potential treatment option for Wilson disease, addressing unmet needs and offering hope to patients affected by this rare disorder.

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