A Study of the Safety and Efficacy of Two Different Regimens of Mipomersen in Patients With Familial Hypercholesterolemia and Inadequately Controlled Low-Density Lipoprotein Cholesterol

Primary objective: Determine whether mipomersen (ISIS 301012) significantly reduces atherogenic lipid levels in patients with severe heterozygous familial hypercholesterolemia (severe HeFH), defined as low-density lipoprotein cholesterol (LDL-C) levels ≥200 mg/dL plus the presence of coronary heart disease (CHD)/risk equivalents or LDL-C levels ≥300 mg/dL regardless of the presence of CHD/risk equivalents (referred to as Cohort 1) compared to placebo. Two different mipomersen dosing regimens will be studied: subcutaneous (SC) mipomersen 200 mg once weekly versus placebo, and SC mipomersen 70 mg thrice weekly versus placebo. Secondary Objectives: * Determine whether there are qualitative differences between the safety profiles of the 2 dosing regimens and placebo in Cohort 1, patients with HeFH with LDL-C levels ≥160 mg/dL and \<200 mg/dL plus the presence of CHD/risk equivalents (referred to as Cohort 2), and the overall study population * Determine whether there are qualitative differences between the tolerability of the 2 dosing regimens and placebo in Cohort 1, Cohort 2, and the overall study population * Further characterize the pharmacokinetics (PK) of the 2 dosing regimens in Cohort 1, Cohort 2, and the overall study population * Determine whether the 2 mipomersen dosing regimens significantly reduce atherogenic lipid levels in Cohort 2 compared to placebo * Obtain additional data regarding ongoing safety and efficacy of mipomersen in patients with FH and inadequately controlled LDL-C who complete the primary efficacy assessment visit (PET) in the Blinded Treatment Period and continue treatment in Open-Label Continuation Period