Definition and therapeutic rationale
Inclisiran is a liver-directed small interfering RNA (siRNA) designed to reduce production of proprotein convertase subtilisin/kexin type 9 (PCSK9). It acts through degradation of the messenger RNA encoding PCSK9 within hepatocytes. Reduced hepatic PCSK9 synthesis decreases circulating PCSK9, increases the availability of hepatic low-density lipoprotein cholesterol (LDL-C) receptors at the cell surface, and thereby enhances removal of LDL-C from the circulation.
This mechanism differs from that of the monoclonal antibodies alirocumab and evolocumab, which bind circulating PCSK9. The prolonged intracellular effect of inclisiran permits subcutaneous administration only twice yearly, an important practical distinction from therapies requiring monthly or biweekly injections. Inclisiran is used as an adjunct to dietary measures and maximally tolerated statin therapy, with or without other LDL-C-lowering drugs, when additional LDL-C reduction is required, including in patients with atherosclerotic cardiovascular disease (ASCVD) or heterozygous familial hypercholesterolaemia.
The broader therapeutic principle is that LDL-C reduction is associated with cardiovascular benefit regardless of the pharmacological route used. In patients with acute coronary syndromes (ACS), the early post-event period is particularly vulnerable, and delayed intensification of lipid-lowering therapy may leave patients exposed to avoidable risk. Contemporary guidance therefore supports an early, intensive approach: treatment should begin immediately, with combination therapy added when necessary to achieve the recommended LDL-C target.
Inclisiran: pharmacology and lipid effects
Inclisiran produces a dose-dependent reduction in PCSK9 and LDL-C. Across clinical studies, LDL-C reductions have generally been approximately 50%, with reported reductions of up to 50–55% in guideline summaries. It also lowers non-HDL-C by up to approximately 50% and apolipoprotein B by approximately 20–40%. Effects on triglycerides and lipoprotein(a) are variable or modest.
In phase III studies involving patients with ASCVD or at least one ASCVD risk equivalent who were receiving statins, inclisiran produced a further reduction in LDL-C of approximately 50%. The effect was consistent in patients with and without diabetes. A pooled analysis of studies involving patients with heterozygous familial hypercholesterolaemia or ASCVD found an LDL-C reduction of approximately 50.5% when inclisiran was added to maximally tolerated statin therapy, with or without other lipid-lowering treatment.
The durability of the response is central to its clinical use. After the initial treatment phase, administration is required only twice annually. This may reduce the adherence barriers associated with more frequent injectable therapy, although the clinical importance of improved adherence remains dependent on sustained follow-up and administration.
Clinical indications and place in therapy
Inclisiran has been approved in several European countries as an adjunct to diet and maximally tolerated statin therapy in patients with heterozygous familial hypercholesterolaemia or ASCVD who require further LDL-C lowering.
It should be considered within a stepwise, target-based lipid-lowering strategy:
Dietary and lifestyle interventions form the foundation of treatment.
Statins are the preferred first-line pharmacological therapy for patients at increased ASCVD risk.
Ezetimibe is appropriate when the LDL-C goal is not achieved with statin therapy or when statins cannot be prescribed.
PCSK9-directed treatment, including monoclonal antibodies or inclisiran, provides additional LDL-C lowering when further reduction is required.
Combination therapy should be selected according to the magnitude of additional LDL-C lowering needed and the patient’s prior treatment.
Inclisiran is particularly attractive when a durable treatment effect and infrequent dosing are clinically desirable. Its effect on cardiovascular outcomes, however, remains under evaluation in a dedicated outcomes trial.
Evidence from clinical studies
In a phase II study of patients at high risk for ASCVD, a single dose of inclisiran produced LDL-C reductions at day 180 ranging from approximately 28% to 42%, depending on dose. After two doses, reductions ranged from approximately 36% to 53%, with all comparisons against placebo statistically significant.
The phase III ORION-10 and ORION-11 studies evaluated patients with elevated LDL-C and ASCVD or at least one ASCVD risk factor who were receiving statins. Inclisiran produced an additional LDL-C reduction of approximately 50%, including among patients with diabetes.
A pooled analysis of patient-level data from ORION-9, ORION-10 and ORION-11 included approximately 3,600 patients with heterozygous familial hypercholesterolaemia or ASCVD. Inclisiran reduced LDL-C by approximately 50.5% when added to maximally tolerated statin therapy, with or without other lipid-lowering agents, and was generally well tolerated. In an exploratory analysis, composite major adverse cardiac events were reduced; however, these findings require confirmation in a dedicated cardiovascular outcomes trial.
The ORION-4 outcomes trial is evaluating whether inclisiran reduces major cardiovascular events in patients with established cardiovascular disease. Consequently, the biochemical efficacy of inclisiran is established more firmly than its definitive effect on cardiovascular morbidity and mortality.
Administration and practical considerations
Inclisiran is administered subcutaneously twice yearly after the initial treatment schedule. The twice-yearly maintenance regimen is the defining practical feature of the drug and may address adherence difficulties associated with monthly or biweekly monoclonal antibody injections.
Injection-site reactions occur more frequently with inclisiran than with placebo. Apart from this finding, long-term extension data describe the drug as generally well tolerated. The available source material does not provide a specific loading schedule, injection volume, dose in milligrams, or detailed renal or hepatic dosing instructions.
Because the magnitude of LDL-C response varies among individuals, biochemical monitoring remains necessary. LDL-C should be assessed approximately 4–6 weeks after initiation or any treatment change. Continued monitoring is also required to ensure that treatment goals remain achieved and that additional therapy is not needed.
Other PCSK9-directed approaches
Monoclonal antibodies
Alirocumab and evolocumab are monoclonal antibodies directed against circulating PCSK9. They reduce LDL-C by up to approximately 60%, either as monotherapy or in combination with maximally tolerated statin therapy and/or ezetimibe. When added to high-intensity or maximally tolerated statins, they have produced LDL-C reductions of approximately 46–73% more than placebo and approximately 30% more than ezetimibe.
Their effects appear largely independent of background therapy. They also lower triglycerides and lipoprotein(a), and increase high-density lipoprotein cholesterol and apolipoprotein A-I, although the contribution of these changes to clinical benefit is uncertain.
The principal practical limitation highlighted in the source material is dosing frequency, with monthly or biweekly injections potentially impairing adherence. Cost, long-term safety, cost-effectiveness, and the role of these agents in primary prevention remain important considerations.
Investigational oral and protein-based PCSK9 inhibitors
An orally bioavailable cyclic peptide PCSK9 inhibitor has produced an LDL-C reduction of approximately 60% from baseline in a phase IIb study. Lerodalcibep, a small binding protein directed against PCSK9, has also significantly lowered LDL-C in a recent phase III study. These agents remain part of the evolving therapeutic landscape described in the source material.
A base-editing strategy intended to permanently inhibit PCSK9 gene expression is being evaluated in human clinical trials. This approach differs fundamentally from both antibody-mediated inhibition and transient RNA interference because it seeks a durable genetic alteration.
Conventional lipid-lowering therapy
Diet and lifestyle
Dietary patterns associated with lower cardiovascular event incidence include greater consumption of fruit, non-starchy vegetables, nuts, legumes, fish, vegetable oils, yoghurt and wholegrains, together with lower intake of red and processed meat, refined carbohydrates and salt. Replacing animal fats, including dairy fat, with vegetable fats and polyunsaturated fatty acids may further reduce ASCVD risk.
Lifestyle intervention affects cardiovascular risk both directly and through effects on plasma lipids, blood pressure and glucose levels. It remains necessary even when pharmacological treatment is prescribed.
Statins
Statins inhibit 3-hydroxy-3-methylglutaryl-coenzyme A reductase and reduce LDL-C, ASCVD morbidity and mortality, and the need for coronary intervention. They also lower triglycerides and may reduce the risk of pancreatitis. For these reasons, they remain the preferred first-line pharmacological treatment in patients at increased ASCVD risk.
Myopathy is the most frequently discussed adverse effect, although severe muscle disease is uncommon and rhabdomyolysis is extremely rare. Myalgia is reported by approximately 5–10% of patients, but in most cases the symptoms are not attributable to the statin. Mild increases in blood glucose and glycated haemoglobin may occur, with a dose-dependent increase in the risk of type 2 diabetes. Liver enzyme elevations can also occur and are usually reversible; routine liver enzyme monitoring is not indicated.
Management of myalgia without a major creatine kinase increase commonly involves changing to another statin or using a very low dose on several days per week, followed by gradual escalation in frequency or dose. Drug interactions should be reviewed continuously because statins are frequently used alongside therapy for other chronic conditions.
Ezetimibe
Ezetimibe inhibits intestinal cholesterol absorption. It is considered second-line therapy, either added to a statin when the LDL-C goal is not reached or used when statin therapy cannot be prescribed. The additional benefit of combining ezetimibe with a statin is consistent with the principle that LDL-C reduction confers benefit independently of the specific treatment modality.
Bempedoic acid
Bempedoic acid is an oral inhibitor of cholesterol synthesis. Its use is mainly described in combination with ezetimibe for patients with statin intolerance. At the time represented in the source material, cardiovascular outcomes data were not yet expected until after the end of 2022.
Acute coronary syndromes: early combination therapy
Patients with ACS are at particularly high risk of recurrent events, especially during the first year after hospital discharge. Observational data cited in the source material describe a cumulative incidence of recurrent myocardial infarction, stroke or cardiovascular death of approximately 10% within the first 100 days after myocardial infarction and approximately 33% at 5 years.
A conventional stepwise approach may require up to 12 weeks to achieve optimal LDL-C-lowering therapy. This delay is clinically important because the period immediately after ACS corresponds to a phase of heightened vulnerability. Prescription inertia, inadequate treatment intensity, adverse effects, reluctance to use statins and loss to follow-up may all contribute to failure to reach LDL-C goals.
The preferred strategy is therefore to initiate intensive LDL-C lowering early:
Start statin therapy immediately during the ACS episode.
Add one or more non-statin agents with demonstrated cardiovascular benefit when the expected LDL-C reduction from statin therapy alone is insufficient.
Select combination therapy according to the additional reduction required and the patient’s previous lipid-lowering regimen.
Reassess LDL-C 4–6 weeks after treatment initiation or intensification.
Continue lifelong LDL-C-lowering treatment to the recommended target.
The addition of ezetimibe to statin therapy within the early post-ACS period has been associated with incremental LDL-C lowering and a modest but significant reduction in adverse cardiovascular events. Very intensive LDL-C lowering initiated during the acute phase has been described as feasible and safe in small studies, and acute treatment with PCSK9 monoclonal antibodies has been associated with improvements in coronary plaque size and composition in the cited trials.
The source material supports the principle of “sooner, lower and better” after ACS, but it does not provide specific LDL-C target values or a complete drug-by-drug acute ACS dosing protocol.
Triglyceride-lowering strategies
Triglycerides are associated with coronary risk, although their relationship is described as less potent than that of LDL-C. Genetic activation of lipoprotein lipase reduces serum triglycerides and is associated with a lower incidence of coronary artery disease. However, pharmacological reduction of moderately elevated triglycerides with pemafibrate did not reduce cardiovascular events in a large clinical trial.
By contrast, icosapent ethyl was associated with a 25% reduction in adverse ischaemic events, including cardiovascular death, in patients with moderate hypertriglyceridaemia. It remains uncertain whether the benefit was mediated by triglyceride reduction itself.
Other emerging strategies include inhibition of angiopoietin-like protein 3 (ANGPTL3). In a small phase II trial involving patients with severe hypertriglyceridaemia, the response to evinacumab varied substantially according to genotype, ranging from no reduction to an 83% reduction. An antibody directed against the ANGPTL3/8 complex is also being evaluated in early studies for its potential to lower both triglycerides and LDL-C.
Several medications may worsen lipid profiles. Thiazide diuretics can increase triglycerides; non-selective beta blockers may increase triglycerides and lower high-density lipoprotein cholesterol; retinoic acid, oestrogens, corticosteroids and immunosuppressive drugs may increase triglycerides. Anabolic steroids may produce hypertriglyceridaemia and very low high-density lipoprotein cholesterol. Atypical antipsychotics, some antidepressants and highly active antiretroviral therapy may cause lipoprotein abnormalities and metabolic disturbances.
Lipoprotein(a)-targeted therapies
Elevated lipoprotein(a) is associated with several mechanisms that may increase cardiovascular risk, including accelerated atherogenesis, enhanced vascular inflammation, worsening calcific aortic stenosis and promotion of a prothrombotic state.
In the absence of established specific lipoprotein(a)-lowering agents, management consists of intensive control of other cardiovascular risk factors, tailored to overall cardiovascular risk and the lipoprotein(a) concentration. Lipoprotein apheresis may be considered in patients with very high lipoprotein(a) and progressive cardiovascular disease.
Most LDL-C-lowering drugs have little or no effect on lipoprotein(a), although PCSK9-directed therapies and obicetrapib may produce modest reductions. Hepatocyte-targeted antisense oligonucleotides and siRNA therapies have produced striking biochemical reductions and are being evaluated for cardiovascular outcomes.
Pelacarsen
Pelacarsen is an antisense oligonucleotide directed against the LPA gene. In a dose-ranging study of patients with established cardiovascular disease and lipoprotein(a) concentrations of at least 60 mg/dL, it reduced lipoprotein(a) in a dose-dependent manner by up to 80%, independent of isoform size or genetic variant. Injection-site reactions were the most common adverse events. A phase III outcomes trial is assessing its effect on cardiovascular events.
Olpasiran and related agents
Olpasiran is an siRNA that suppresses hepatic lipoprotein(a) synthesis. In patients with established ASCVD and lipoprotein(a) concentrations above 150 nmol/L, it reduced lipoprotein(a) in a dose-dependent manner by up to 100%; injection-site reactions were the most common adverse events.
Other siRNA therapies, including zerlasiran and lepodisiran, are in clinical development. Muvalaplin is an oral small molecule that inhibits lipoprotein(a) formation by blocking the interaction between apolipoprotein(a) and apolipoprotein B100; it can lower lipoprotein(a) by up to approximately 65%.
Whether these biochemical effects translate into fewer cardiovascular events remains under investigation.
Anti-inflammatory therapy as an adjunct to lipid lowering
Inflammation is a modifiable contributor to atherothrombosis. Statins and glucagon-like peptide-1 receptor agonists may exert anti-inflammatory effects in addition to their principal metabolic actions, while other treatments target inflammation directly.
Canakinumab, an interleukin-1β monoclonal antibody, lowered high-sensitivity C-reactive protein and interleukin-6 without changing lipid levels and modestly reduced a composite of cardiovascular death, myocardial infarction and stroke in patients with previous myocardial infarction and high-sensitivity C-reactive protein ≥2 mg/L. It did not reduce all-cause mortality and was associated with an excess of fatal infections. It will therefore not proceed for clinical development for this indication.
Low-dose methotrexate did not reduce cardiovascular events, and it also failed to affect inflammatory biomarkers at the dose studied.
Colchicine is the most promising currently available anti-inflammatory option described in the source material. It interferes with inflammatory-cell chemotaxis and phagocytosis, reduces adhesion molecule expression and modifies cytokine production. In patients treated within 30 days of myocardial infarction, colchicine 0.5 mg orally once daily reduced the primary ischaemic endpoint over approximately 2 years, although pneumonia was more frequent and all-cause mortality was not reduced. In patients with stable ischaemic heart disease, colchicine 0.5 mg once daily reduced the primary composite endpoint over approximately 3 years, but an excess of non-cardiovascular deaths was observed and cardiovascular mortality was not improved.
Low-dose colchicine may be considered as an adjunct to guideline-directed preventive treatment in patients with stable ischaemic heart disease who remain at high risk despite maximally tolerated therapy. Its narrow therapeutic window requires caution. The drug has a long half-life dependent on renal clearance, is metabolized by CYP3A4 and is a substrate for P-glycoprotein; these properties create clinically important interaction risks and require additional monitoring.
Other cardiovascular therapies relevant to lipid management
Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are widely used after myocardial infarction, in hypertension, chronic ischaemic heart disease and high-risk vascular disease such as diabetes. Their benefits are most evident in patients with increased risk, particularly those with diabetes or left ventricular dysfunction, and in those whose blood pressure and LDL-C remain inadequately controlled despite other therapy. Routine use in patients with normal left ventricular function who have already achieved blood pressure and LDL-C goals does not reduce events and is not cost-effective.
Sodium–glucose cotransporter-2 inhibitors have cardiovascular and renal protective effects in patients with and without diabetes who have reduced left ventricular ejection fraction. They promote weight loss, lower blood pressure and reduce plasma volume.
Non-steroidal anti-inflammatory drugs should generally be avoided in patients with ischaemic heart disease because they may be associated with a small but finite increase in myocardial infarction and mortality. If required, the lowest-risk agent should be used at the lowest effective dose for the shortest possible duration; coadministration of aspirin is advised in the source material.
Guideline-based monitoring and follow-up
The principal monitoring requirements are clinical assessment of tolerability, attention to adherence, review of drug interactions and serial measurement of LDL-C.
LDL-C should be checked 4–6 weeks after:
starting lipid-lowering therapy;
changing the dose or treatment combination;
intensifying therapy during or after ACS.
Because treatment response varies between individuals, biochemical confirmation is necessary rather than relying solely on the expected average reduction. After ACS, lipid-lowering therapy should be continued lifelong, with ongoing efforts to maintain the recommended LDL-C target.
Follow-up should also address statin-associated symptoms, possible liver enzyme abnormalities, glycaemic effects and drug interactions. In patients receiving colchicine, renal clearance, CYP3A4 metabolism and P-glycoprotein substrate properties necessitate particular attention to concomitant medication and toxicity surveillance.
Prognosis and unresolved questions
Intensive LDL-C lowering is associated with better outcomes after ACS, and the available evidence supports initiating treatment early and intensifying it promptly. Inclisiran offers a durable approximately 50% LDL-C reduction with twice-yearly administration and is generally well tolerated, although injection-site reactions are more frequent than with placebo.
The definitive effect of inclisiran on cardiovascular morbidity and mortality remains to be established by a dedicated outcomes trial. Similarly, the clinical outcome benefits of therapies directed primarily at lipoprotein(a), ANGPTL3 or newer PCSK9 pathways remain uncertain. Anti-inflammatory treatment has demonstrated that inflammation is therapeutically modifiable, but the absence of a consistent reduction in all-cause mortality and the presence of infectious or other non-cardiovascular safety signals limit current application.
The future direction of lipid management is likely to involve increasingly durable therapies, combination treatment tailored to the required LDL-C reduction, and agents directed at residual risks such as lipoprotein(a), triglyceride-rich lipoproteins and vascular inflammation. siRNA, antisense oligonucleotides, orally bioavailable inhibitors and gene-editing strategies are all being investigated, but their ultimate place in routine cardiovascular prevention depends on confirmation of long-term clinical benefit and safety.
