The primary objective of this study is to investigate the effect of gene therapy (UX704) on copper distribution and excretion in Wilson disease patients. The effect is investigated using 64Cu positron emission tomography scans combined with a CT scan.

Patients entering this study are included from the ongoing clinical study "A Phase 1/ 2/ 3 Study of UX701 Gene Therapy in Adults With Wilson Disease" (NCT04884815). The patients will have received gene therapy as part of the clinical study. This study is an extension study that aims to specifically monitor the effect of gene therapy on copper distribution and excretion using 64Cu PET/CT.

Patients will receive 40-80 MBq 64CuCl2 intravenously and will undergo three PET/CT scans during the next 20 hours.

Inclusion Criteria:

• Patients with Wilson disease who have received gene therapy (UX701) as part of NCT04884815
• Age above 18 years
• Women of childbearing potential must accept to use safe contraception at the time of the PET scans: Spiral or hormonal contraception (oral pills, implants, transdermal patches, vaginal rings, or depot injections)
• At the day of the first PET scan, a negative urine pregnancy test is required for women of childbearing potential
• Before the first PET scan, a signed informed consent must be completed

Exclusion Criteria:

• Known hypersensitivity to Cu-64, copper in general, or other components of the radiotracer formulation
• Claustrophobia
• Pregnancy, breastfeeding, or plans to become pregnant

Patients with Wilson disease who have received gene therapy (UX701) as part of NCT04884815 are referred by the primary investigator of NCT04884815 to participate in this study. If they fulfil other eligibility criteria, they are invited to participate in the study.

Individual patient data will not be shared in order to safeguard patient privacy. Group data will be available upon reasonable request after publication of the results.