Inclusion Criteria:

• Genotype-confirmed heterozygous familial hypercholesterolemia with written documentation of the genetic diagnosis at the time of screening and LDL-C >=210 mg/dL (5.43 mmol/L), or clinical diagnosis of heterozygous familial hypercholesterolemia, defined as LDL-C >=210 mg/dL (5.43 mmol/L) and at least one of the following:

  • tendinous xanthoma
  • child <18 years of age with hypercholesterolemia (LDL-C >159 mg/dL (4.11 mmol/L)
  • has a sibling with hypercholesterolemia (LDL-C >190 mg/dL [4.91 mmol/L]) and tendinous xanthoma
  • family history with an LDL-C value distribution pattern compatible with dominant autosomal transmission and at least one relative presenting fasting total cholesterol values >348 mg/dL (9.0 mmol/L) after exclusion of secondary causes of dyslipidemia
• LDL-C >=210 mg/dL (5.43 mmol/L) 1 week before randomization
• plasma triglyceride level <=400 mg/dL (4.52 mmol/L)

Exclusion Criteria:

• pregnancy or any other situation, condition, or illness that, in the opinion of the investigator, may interfere with optimal participation in the study
• presence of an apolipoprotein B gene mutation with confirmed absence of an LDL receptor mutation in either allele
• undergoing LDL-apheresis or plasma apheresis
• unsuitable plaque or artery morphology
• use of certain drugs, foods, or other agents known to alter cholesterol levels or to cause pharmacokinetic interactions with either ezetimibe or simvastatin