UX701
An investigational treatment for Wilson Disease.
The same compound appears under different names depending on the context. Here is how to identify UX701 wherever you encounter it, plus the key facts at a glance.
- Generic name
- UX701
- Development code
- UX701
- Drug class
- AAV gene therapy (ATP7B)
- Manufacturer
- UltraGenyx Pharmaceutical
An investigational AAV9-based gene therapy for Wilson disease in the pivotal Phase 1/2/3 Cyprus2+ trial run by UltraGenyx. Several patients in earlier dose cohorts have tapered off standard-of-care chelation or zinc. Ultragenyx expects Stage 1 dose-finding data in the fourth quarter of 2026. Those data will inform dose selection for the randomized Stage 2.
Where UX701 fits
Investigational, not currently approved. The most clinically advanced Wilson disease gene therapy program based on dose-finding completion. If pivotal data support efficacy, UX701 could move to BLA submission within the next several years.
How UX701 works
Investigational AAV-based gene therapy that delivers a functional ATP7B gene to liver cells using an AAV9 capsid, with the goal of restoring the body's ability to excrete copper and reducing or eliminating the need for chelation or zinc therapy
Side effects and safety
Across the first three dose groups of the Cyprus2+ trial, UX701 was well tolerated, with no unexpected treatment-related side effects and no significant immune-related safety events reported[1]. As with other gene therapies delivered by an AAV vector, the main thing doctors watch for is the body's immune reaction to the virus shell that carries the gene, which can inflame the liver and blunt the therapy's effect. The highest-dose group adds two immune-calming medicines, rituximab and tacrolimus, to prevent that reaction, and those medicines carry their own risks, including a higher chance of infection while on them. A fuller safety picture will come with the Stage 1 results UltraGenyx has yet to report.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Clinical trial results
The pivotal Cyprus2+ trial (Phase 1/2/3) is evaluating UX701 in adults with Wilson disease. The trial uses a Stage 1 dose-finding portion followed by a Stage 2 randomized, placebo-controlled portion. Stage 1 has enrolled four cohorts at escalating doses. The fourth cohort, evaluating the highest dose (4.0e13 GC/kg) with rituximab and tacrolimus immunomodulation, completed enrollment in September 2025. In August 2026, Ultragenyx said it expects Stage 1 data in the fourth quarter of 2026. Earlier cohorts demonstrated no significant immunologic safety events, no unexpected treatment-related adverse events, and multiple responders who completely tapered off chelation or zinc.
Development history
UltraGenyx initiated UX701 development to address Wilson disease as one of several gene therapy programs in its rare disease pipeline. The Cyprus2+ trial began in 2022 and has progressed through dose finding into the higher-dose, immunomodulated cohort.
Explore Wilson Disease trials
Other Wilson Disease treatments
Common questions about UX701
▸What is UX701?
An investigational AAV9-based gene therapy for Wilson disease in the pivotal Phase 1/2/3 Cyprus2+ trial run by UltraGenyx. Several patients in earlier dose cohorts have tapered off standard-of-care chelation or zinc. Ultragenyx expects Stage 1 dose-finding data in the fourth quarter of 2026. Those data will inform dose selection for the randomized Stage 2.
▸What is the mechanism of action of UX701?
Investigational AAV-based gene therapy that delivers a functional ATP7B gene to liver cells using an AAV9 capsid, with the goal of restoring the body's ability to excrete copper and reducing or eliminating the need for chelation or zinc therapy
▸What are the side effects of UX701?
Across the first three dose groups of the Cyprus2+ trial, UX701 was well tolerated, with no unexpected treatment-related side effects and no significant immune-related safety events reported[1]. As with other gene therapies delivered by an AAV vector, the main thing doctors watch for is the body's immune reaction to the virus shell that carries the gene, which can inflame the liver and blunt the therapy's effect. The highest-dose group adds two immune-calming medicines, rituximab and tacrolimus, to prevent that reaction, and those medicines carry their own risks, including a higher chance of infection while on them. A fuller safety picture will come with the Stage 1 results UltraGenyx has yet to report.
▸Is UX701 FDA approved?
UX701 is currently in phase 3 clinical trials for Wilson Disease. It has not yet received FDA approval.
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- UltraGenyx Pharmaceutical. Ultragenyx Announces Completion of Dosing Across Stage 1 Cohorts in Pivotal Phase 1/2/3 Cyprus2+ Study Evaluating UX701 Gene Therapy for Wilson Disease. https://ir.ultragenyx.com/news-releases/news-release-details/ultragenyx-announces-completion-dosing-across-stage-1-cohorts
- UltraGenyx Pharmaceutical · February 12, 2026. Ultragenyx Reports Fourth Quarter and Full Year 2025 Financial Results and Corporate Update. https://ir.ultragenyx.com/news-releases/news-release-details/ultragenyx-reports-fourth-quarter-and-full-year-2025-financial
- Ultragenyx Pharmaceutical · 2026-08-04. Ultragenyx Reports Second Quarter 2026 Financial Results and Corporate Update. https://ir.ultragenyx.com/news-releases/news-release-details/ultragenyx-reports-second-quarter-2026-financial-results-and