Abstract 52: Efficacy and Safety of Mipomersen in Patients with Familial Hypercholesterolemia and Inadequately Controlled LDL-C Levels
Aim: Mipomersen is an antisense oligonucleotide inhibitor of apolipoprotein B-100 synthesis, FDA-approved to treat homozygous familial hypercholesterolemia. The primary objective of this study was to determine whether mipomersen significantly reduced atherogenic lipid levels in patients with severe heterozygous familial hypercholesterolemia (HeFH). Methods: This was a randomized, double-blind, placebo-controlled, parallel-group study comprised of two cohorts (NCT01475825). Cohort 1 had severe HeFH (LDL-C ≥200 mg/dL + coronary heart disease, or LDL-C ≥300 mg/dL) and Cohort 2 had milder HeFH (LDL-C ≥160 and <200 mg/dL). For each cohort, patients were randomized 1:1 to 200 mg SC once weekly or 70 mg SC thrice weekly, then 2:1 to receive mipomersen or placebo for 60 weeks. The primary outcome was percent change from baseline in LDL-C in Cohort 1. The % change from baseline in LDL-C at Week 61 for mipomersen treated patients was compared to placebo using a mixed model for repeated measures (MMRM), as well as by ANCOVA on the value closest to 7 days post last treatment (LOCF). Results: Mean baseline LDL-C levels were 265 mg/dL in Cohort 1 (N=200) and 176 mg/dL in Cohort 2 (N=109). In Cohort 1, mipomersen 200 mg weekly reduced LDL-C levels by -29.7% (vs -7.9% placebo, P <.001) in the mixed model, and by -36.3% (vs -7.6% placebo, P <.001) using the LOCF. Analysis of LDL-C over time (Figure) showed a mean absolute reduction of 138 mg/dL in mipomersen patients who completed the blinded treatment period (n=32), achieving a mean level of 147 mg/dL from a mean 285 mg/dL baseline level. Tolerability to treatment and adverse events were similar between dose regimens. Adverse events were consistent with the drug’s known safety and tolerability profile. Conclusions: The primary analysis showed a significant reduction in LDL-C levels in patients with severe HeFH who received mipomersen 200 mg once weekly versus placebo. A highly relevant absolute reduction in LDL-C was achieved over time.