A Study to Investigate the Safety and Effectiveness of a Coagulation Factor IX Gene Insertion Therapy (REGV131-LNP1265) in Pediatric, Adolescent and Adult Participants With Hemophilia B

Exclusion Criteria

• •1. History of FIX inhibitor (clinical or laboratory-based assessment) on 2 or more occasions
• •2. Bethesda inhibitor titer greater than the Upper Limit of Normal (ULN) at screening
• •3. Detectable pre-existing antibodies to the AAV8 capsid; as measured by Enzyme-Linked ImmunoSorbent Assay (ELISA) at prescreening (or final lead-in visit, if applicable)
• •4. Any significant underlying liver disease such as: cholestatic liver disease, liver cirrhosis, portal hypertension, splenomegaly, hepatic encephalopathy
• •5. Evidence of advanced liver fibrosis or significant fatty liver, as defined in the protocol
• •6. Evidence of cirrhosis and/or portal hypertension as assessed by abdominal ultrasound at screening or measured within 6 months prior to the screening visit
• •7. History of arterial or venous thrombo-embolic events, as defined in the protocol
• •8. History of hypersensitivity to corticosteroids or known medical condition that requires chronic administration of corticosteroids
• •9. Previously received any AAV gene-based therapy or intends to receive approved or investigational AAV-based gene therapy other than REGV131-LNP1265 during the study period
• •NOTE: Other Inclusion/Exclusion Protocol Defined Criteria Apply