Children's National

• Male or female participants, 2 to <12 years of age at screening - HoFH diagnosed by genetic confirmation - Note: Participants with known null (negative) mutations in both LDLR alleles are not eligible (see also

) - Fasting LDL-C >130 mg/dL (3.4 mmol/L) at screening - On an optimal dose of statin (investigator's discretion), unless statin intolerant, with or without other lipid-lowering therapy (e.g. ezetimibe) - Participants on lipid-lowering therapies (such as e.g. statins, ezetimibe) must be on a stable dose for ≥30 days before screening with no planned medication or dose changes during study participation - Participants on a documented regimen of LDL-apheresis for ≥ 3 months before screening will be allowed to continue the apheresis during the study, if needed. The apheresis schedule/settings/duration must be stable prior to screening, are not allowed to change during the double-blind period of the trial and must permit that an apheresis coincides with each study visit. Exclusion Criteria: - Documented evidence of a null (negative) mutation in both LDLR alleles - Previous treatment (within 90 days of screening) with monoclonal antibodies directed towards PCSK9 - History of poor response to therapy with any monoclonal antibody directed towards PCSK9 (e.g. <15% reduction in LDL-C) - Treatment with mipomersen or lomitapide (within 5 months of screening) - Secondary hypercholesterolemia, e.g. hypothyroidism or nephrotic syndrome - Heterozygous familial hypercholesterolemia (HeFH) - Body weight (at the screening and/or randomization (Day 1) visit) <16 kg for participants 6 to <12 years (at screening) or <11 kg for participants 2 to <6 years (at screening) - Active liver disease defined as any known current infectious, neoplastic, or metabolic pathology of the liver or unexplained alanine aminotransferase (ALT), aspartate aminotransferase (AST) elevation >3x ULN, or total bilirubin elevation >2x ULN (except patients with Gilbert's syndrome) - Pregnant or nursing females - Recent and/or planned use of other investigational medicinal products or devices