Inclusion Criteria: * Male or female ≥ 18 years of age. * Untreated and/or treated LDL-C levels and clinical presentation consistent with the diagnosis of homozygous FH (Familial hypercholesterolemia) * Molecularly defined LDLR mutations at both LDLR alleles. * A baseline serum AAV8 NAb (Neutralizing antibody) titer ≤ 1:10. Exclusion Criteria * Unwilling to wash out of the following lipid lowering therapies for the pre-specified time period: 1. niacin \> 250 mg/day: within 6 weeks of baseline 2. fibrates: within 4 weeks of baseline 3. lomitapide: within 8 weeks of baseline 4. mipomersen: within 24 weeks of baseline * History of cirrhosis or chronic liver disease based on documented histological evaluation or non-invasive imaging or testing. * Abnormal liver function tests (LFTs) at screening (AST (Aspartate aminotransferase) or ALT (Alanine aminotransferase) \> 2 × upper limit of normal (ULN) and/or Total Bilirubin of \> 1.5 × ULN