UX701

Ultragenyx said on November 3, 2026 that it is ending UX701 because the dose-finding stage of the Cyprus2+ trial did not meet its goals^[1]. UX701 was an investigational AAV9-based gene therapy for Wilson disease tested in the Phase 1/2/3 Cyprus2+ trial. In an October 2024 update covering data through August 2024, Ultragenyx reported that 6 of the 15 patients in the first 3 dose cohorts had fully tapered off standard-of-care chelation or zinc.

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

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^[2]. 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 uses an adjusted immune-calming plan to prevent that reaction, and immune-calming medicines can raise the chance of infection while on them. When it ended the program, Ultragenyx said UX701 had a favorable safety profile across all dosed groups and that it plans to present the completed study at a medical meeting^[1].

Given once as an infusion into a vein. Outside of the Cyprus2+ trial, UX701 is not available.

UX701 is currently in discontinued clinical trials for Wilson Disease. It has not yet received FDA approval.

UX701 is an investigational AAV9-based gene therapy for Wilson disease developed by Ultragenyx and studied in adults in the pivotal Phase 1/2/3 Cyprus2+ trial, which began in September 2021. In an October 2024 update covering data through August 2024, Ultragenyx reported that 6 of the 15 patients in the first 3 dose cohorts had completely tapered off standard-of-care chelation or zinc. ^[2]

No, UX701 is not FDA-approved. It is in the Phase 1/2/3 Cyprus2+ trial, and Ultragenyx has said Stage 1 dose-finding data are expected in the fourth quarter of 2026, and it has not given a date for filing with the FDA. ^[5]

Stage 1 of Cyprus2+ enrolled 4 cohorts of UX701 at escalating doses, and enrollment is complete for the fourth cohort, which tests a moderately higher dose with an adjusted immune-suppressing regimen. ^[5] In the first 3 cohorts there were no significant immunologic safety events and no unexpected treatment-related adverse events, and in data through August 2024, reported in October 2024, 6 of 15 patients had completely tapered off chelation or zinc. Stage 1 results will inform dose selection for the randomized, open-label Stage 2, which compares UX701 with standard treatment. ^[2][5]

Across the first 3 dose groups of Cyprus2+, UX701 was well tolerated, with no unexpected treatment-related side effects and no significant immune-related safety events reported. As with other AAV gene therapies, doctors watch for an immune reaction to the virus shell, which can inflame the liver and blunt the therapy's effect; the highest-dose group uses an adjusted immune-calming plan to prevent that reaction, and immune-calming medicines raise the chance of infection. A fuller safety picture will come with the Stage 1 results. ^[2]