Harnessing RNA Interference for Cholesterol Lowering: The Bench-to-Bedside Story of Inclisiran

Abstract

Lowering low-density lipoprotein cholesterol (LDL-C) is a cornerstone of reducing risk for atherosclerotic cardiovascular disease. Despite the approval of nonstatin therapies for LDL-C lowering over the past 2 decades, these medications are underused, and most patients are still not at guideline-recommended LDL-C goals. Barriers include poor adherence, clinical inertia, concern for side effects, cost, and complex prior authorization processes. With atherosclerotic cardiovascular disease-related mortality increasing globally, there remains a need for additional therapeutic options for lowering LDL-C as part of an atherosclerotic cardiovascular disease prevention strategy. Following the identification of PCSK9 (proprotein convertase subtilisin/kexin type 9) as a promising therapeutic target, inclisiran was developed using the natural process of RNA interference for robust, sustained prevention of hepatic PCSK9 synthesis. Twice-yearly maintenance subcutaneous inclisiran (following initial loading doses at Day 1 and Day 90) reduces circulating LDL-C levels by ≈50% versus placebo when added to maximally tolerated statins. Long-term safety and tolerability of inclisiran have been assessed, with studies underway to evaluate the effects of inclisiran on cardiovascular outcomes and to provide additional safety and effectiveness data. In 2021, <20 years after the discovery of PCSK9, inclisiran became the first RNA interference therapeutic approved in the United States for LDL-C lowering in patients with established atherosclerotic cardiovascular disease or familial hypercholesterolemia and has since been approved for use in patients with primary hyperlipidemia. This article reviews the journey of inclisiran from bench to bedside, including early development, the clinical trial program, key characteristics of inclisiran, and practical points for its use in the clinic.

Keywords: atherosclerotic cardiovascular disease; inclisiran; low‐density lipoprotein cholesterol; proprotein convertase subtilisin/kexin type 9; small interfering RNA.

Figure 1. Timeline of inclisiran development., , , , , , , , , , , , , , , , , , , , , , , , ,

The start and estimated completion dates are correct as of the article submission date. EU indicates European Union; GalNAc, triantennary N‐acetylgalactosamine; LNP, lipid nanoparticle; PCSK9, proprotein convertase subtilisin/kexin type 9; RNAi, ribonucleic acid interference; siRNA, small interfering RNA; US, United States; and V, VICTORION.

Figure 2. Inclisiran mechanism and key characteristics.,

(1) Inclisiran is conjugated with a triantennary GalNAc moiety at the 3′ end of the passenger strand. GalNAc is specifically recognized by ASGPR, which is widely expressed on hepatocytes; 1 2′‐deoxy, 12 2′‐fluoro, and 31 2’‐O‐methyl ribose‐modified nucleotides confer stability; 5′‐phosphorothioate modifications facilitate RISC loading. (2) The inclisiran‐ASGPR interaction modifies the hepatocyte membrane, forming clathrin‐coated vesicles and promoting the formation of endosomes in which the inclisiran‐ASGPR complex enters the cell; ASGPR is recycled to the hepatocyte membrane, while the GalNAc moiety is degraded within the lysosome. (3) Inclisiran gradually exits the endosome, which may act as an intracellular store of inclisiran, increasing the duration of action from a single dose. (4) Active inclisiran is then loaded into the RISC. (5) The sense strand is degraded while the antisense strand remains within the complex; RISC protects the antisense strand from nucleases. (6) The antisense strand hybridizes with PCSK9 mRNA within the RISC, triggering its catalytic cleavage, thereby preventing translation and PCSK9 production; once loaded, one complex can prevent the translation of multiple copies of PCSK9 mRNA. (7) Decreased PCSK9 protein production results in increased LDLR recycling, leading to increased hepatic LDL‐C clearance. ASGPR indicates asialoglycoprotein receptor; GalNAc, triantennary N‐acetylgalactosamine; LDL, low‐density lipoprotein; LDL‐C, LDL cholesterol; LDLR, LDL receptor; PCSK9, proprotein convertase subtilisin/kexin type 9; and RISC, RNA‐induced silencing complex. Reproduced from Soffer et al 2022, available under creative commons license CC BY‐NC‐ND 4.0.

Figure 3. A pathway for managing patients with FH or ASCVD, or at risk of ASCVD, adapted from the UK NHS pathway and ACC ECDP.,

*ACS, history of MI, stable/unstable angina, coronary or other arterial revascularization, stroke, TIA, or PAD; ^†History of multiple major cardiovascular events (ACS [past 12 months], history of MI, ischemic stroke, symptomatic PAD), or a major cardiovascular event plus high‐risk conditions (≥65 years of age, heterozygous FH, history of coronary artery bypass, diabetes, hypertension, chronic kidney disease, smoking, LDL‐C ≥100 mg/dL despite maximally tolerated LLT, history of congestive heart failure); ^‡Intolerant of ≥2 statins with 1 attempt at lowest recommended dose; ^§Increase to 150 mg Q2W if required; ^‖At 12 weeks increase to 420 mg Q2W, if required. ACC indicates American College of Cardiology; ACS, acute coronary syndrome; ASCVD, atherosclerotic cardiovascular disease; ECDP, Expert Consensus Decision Pathway; FH, familial hypercholesterolemia; LDL‐C, low‐density lipoprotein cholesterol; LLT, lipid‐lowering therapy; MI, myocardial infarction; NHS, National Health Service; PAD, peripheral arterial disease; PCSK9, proprotein convertase subtilisin/kexin type 9; Q2W, every 2 weeks; Q4W, every 4 weeks; SASE, statin‐associated side effect; SC, subcutaneously; TIA, transient ischemic attack; and UK, United Kingdom.