Study of UX701 Gene Transfer for the Treatment of Wilson Disease

Key Inclusion Criteria:

• Confirmed diagnosis of Wilson disease

• Stable Wilson disease as evidenced by ongoing copper chelator (ie, penicillamine,trientine) and/or zinc therapy for at least 6 months at screening, with nomedication or dose changes for at least 6 months at screening.

• Ongoing restriction of high copper containing foods for at least 6 months atScreening, continued through study participation.

• Willing and able to comply with all study procedures and requirements, includingfrequent blood collection, total urine collection over a 24-hour period,patient-reported outcome assessments, and long-term follow-up

Key Exclusion Criteria:

• Detectable pre-existing antibodies to the AAV9 capsid.

• Stage 1 only: History of copper chelator or zinc therapy noncompliance, in theInvestigator's judgment, within 6 months prior to Screening.

• History of liver transplant.

• Decompensated hepatic cirrhosis or presence of advanced liver disease as evidencedby portal hypertension, ascites, splenomegaly, esophageal varices, hepaticencephalopathy.

• Significant hepatic inflammation as evidenced by laboratory abnormalities.

• Model for End-Stage Liver Disease (MELD) score > 13.

• Hemoglobin < 9 g/dL

• Presence of Stage 3 or higher chronic kidney disease based on estimated glomerularfiltration rate < 60 mL/min/1.73 m2.

• Marked neurological deficit or compromise that, in the Investigator's opinion, wouldinterfere with the subject's safety or ability to participate in the study.

• Moderate to severe depression, recent or active suicidal ideation with intent orsuicidal behavior, psychosis, or unstable psychiatric illness.

• Participation in another gene transfer study or use of another gene transfer productbefore or during study participation.

• Subjects with known hypersensitivity to amide-containing local anesthetics areexcluded from participating in the optional liver biopsy substudy.

Note: Other protocol defined Inclusion/ Exclusion criteria may apply