Targeting PCSK9 With Antibodies and Gene Silencing to Reduce LDL Cholesterol

Abstract

The discovery of PCSK9 and its role in regulating the low-density lipoprotein (LDL) receptor, and the effect of loss-of-function mutations of its gene, identified it as a therapeutic target in 2006. Fully humanized monoclonal antibodies to PCSK9 (alirocumab and evolocumab) proved effective for lowering LDL cholesterol and subsequently for reducing atherosclerotic events in large outcome trials. Suppressing PCSK9 synthesis via gene silencing using inclisiran, a small interfering RNA, is another approach that effectively reduces LDL cholesterol, and a cardiovascular outcome trial is in progress. These treatments are given subcutaneously on a background of maximally tolerated statin treatment and are long-lasting: dosing is once or twice a month, self-administered, for alirocumab and evolocumab, and every 6 months for inclisiran, in the clinic, with an extra dose at 3 months in the initial year of therapy. These 3 agents produce mean LDL reductions of about 55% with no important adverse effects detectable to date. They are indicated in patients with atherosclerotic vascular disease or familial hypercholesterolemia who cannot achieve LDL cholesterol targets with maximally tolerated statin treatment. Such therapy can produce very low plasma LDL cholesterol and PCSK9, but there is no evidence this is harmful. Introduction into clinical practice has been impeded by economic considerations. The barrier to their use has not been scientific or medical, but rather the impact on healthcare resources. Prices have been reduced, but whether they are now cost-effective varies from country to country.

Keywords: LDL cholesterol; PCSK9; monoclonal antibody; small interfering RNA.