Lipid-lowering interventions targeting proprotein convertase subtilisin/kexin type 9 (PCSK9): an emerging chapter in lipid-lowering therapy

Far-infrared irradiation increases the uptake of LDL cholesterol by downregulating PCSK9 through the activation of TRPV4 calcium channels in HepG2 cells

This study investigated the effects of far-infrared (FIR) irradiation on low-density lipoprotein cholesterol (LDL-C) uptake by human hepatocellular carcinoma G2 (HepG2) cells via the regulation of proprotein convertase subtilisin/kexin type 9 (PCSK9). FIR irradiation for 30 min significantly decreased PCSK9 expression (p < 0.01) in HepG2 cells. FIR irradiation substantially increased the low-density lipoprotein receptor (p < 0.0001) and LDL-C uptake (p < 0.01). Activation of transient receptor potential vanilloid (TRPV) channels mimicked the effects of FIR irradiation, significantly decreasing the protein expression of PCSK9 (p < 0.05). Conversely, inhibition of TRP channels using ruthenium red reversed the reduction in PCSK9 protein expression following FIR irradiation (p < 0.01). The specific activation of TRPV4 using 4α-PDD mimicked the effect of FIR irradiation (p < 0.01), whereas PCSK9 reduction by FIR irradiation was significantly reversed by the inhibition of TRPV4 using RN1734 (p < 0.05). These findings implied that FIR irradiation emitted from a ceramic lamp specifically increased TRPV4 activity. These findings provide insights into a novel therapeutic approach using FIR irradiation for LDL-C regulation and its implications for cardiovascular health.

Inclisiran: the preclinical discovery and development of a novel therapy for the treatment of atherosclerosis

INTRODUCTION

Atherosclerotic cardiovascular disease (ASCVD) remains a leading cause of global morbidity and mortality. Lipid lowering therapy (LLT) constitutes the cornerstone of ASCVD prevention and treatment. However, several patients fail to achieve therapeutic goals due to low treatment adherence or limitations of standard-of-care (SoC) LLTs. Inclisiran represents a pivotal low-density lipoprotein cholesterol (LDL-C) lowering agent aiming to address current unmet needs in LLT. It is the first available small interfering RNA (siRNA) LLT, specifically targeting PCSK9 mRNA and leading to post-transcriptional gene silencing (PTGS) of the PCSK9 gene.

AREAS COVERED

Promising phase III trials revealed an ~ 50% reduction in LDL-C levels with subcutaneous inclisiran administration on days 1 and 90, followed by semiannual booster shots. Coupled with inclisiran's favorable safety profile, these findings led to its approval by both the EMA and FDA. Herein, the authors highlight the preclinical discovery and development of this agent and provide the reader with their expert perspectives.

EXPERT OPINION

The evolution of gene-silencing treatments offers new perspectives in therapeutics. Inclisiran appears to have the potential to revolutionize ASCVD prevention and treatment, benefiting millions of patients. Ensuring widespread availability of Inclisiran, as well as managing additional healthcare costs that may arise, should be of paramount importance.

The promising novel therapies for familial hypercholesterolemia

Background

The incidence of premature atherosclerotic cardiovascular disease in familial hypercholesterolemia (FH) is high. In recent years, novel therapeutic modalities have shown significant lipid‐lowering ability. In this paper, we summarize the recent developments in novel therapies for FH via the treatment of different targets and discuss the characteristics of each targeted therapy. Based on the process of protein synthesis, we attempt to summarize the direct‐effect targets including protein, RNA, and DNA.

Methods

For this systematic review, relevant studies are assessed by searching in several databases including PubMed, Web of Science, Scopus, and Google Scholar. The publications of original researches are considered for screening.

Results

Most drugs are protein‐targeted such as molecule‐based and monoclonal antibodies, including statins, ezetimibe, alirocumab, evolocumab, and evinacumab. Both antisense oligonucleotide (ASO) and small interfering RNA (siRNA) approaches, such as mipomersen, vupanorsen, inclisiran, and ARO‐ANG3, are designed to reduce the number of mRNA transcripts and then degrade proteins. DNA‐targeted therapies such as adeno‐associated virus or CRISPR–Cas9 modification could be used to deliver or edit genes to address a genetic deficiency and improve the related phenotype.

Conclusion

While the therapies based on different targets including protein, RNA, and DNA are on different stages of development, the mechanisms of these novel therapies may provide new ideas for precision medicine.

New and emerging lipid-modifying drugs to lower LDL cholesterol

Cardiovascular disease (CVD) represents the leading cause of death worldwide. The role of low-density lipoprotein-cholesterol (LDL-C) in the pathophysiology of atherosclerosis and CVD has been well recognized. Statins are the standard of care for the management of hypercholesterolaemia, and their effectiveness in lowering LDL-C and reducing CVD risk in both primary and secondary prevention has been well established. However, several patients fail to attain optimal LDL-C goals or are intolerant to statins, especially at high doses. PCSK9 inhibitors, bempedoic acid, inclisiran, ANGPTL3 inhibitors, PPARβ/δ agonists and LXR agonists are novel or upcoming LDL-C-lowering agents that have shown promising beneficial results. This review aims to present and discuss the current clinical and scientific data pertaining to the new and emerging lipid-modifying LDL-C-lowering drugs.

Current Evidence and Future Directions of PCSK9 Inhibition

Recent scientific and therapeutic advances in proprotein convertase subtilisin kexin type 9 (PCSK9) inhibition have opened a chapter in the management of hypercholesterolemia, especially in patients who are inadequately controlled on or intolerant to statins. The two PCSK9 monoclonal antibodies, evolocumab and alirocumab, reduce LDL cholesterol by 60% and improve cardiovascular outcomes when taken in addition to statin therapy. More recently, inclisiran, a silencing RNA (siRNA) that inhibits translation of PCSK9 mRNA, demonstrated LDL cholesterol reduction by 45–50% with the advantage of dramatically reduced dose frequency. Other modes of PCSK9 inhibition include small molecule antagonists, vaccines, CRISPR gene editing, and antagonism at various steps of translation, and post-translational processing.

Kanglexin, a new anthraquinone compound, attenuates lipid accumulation by activating the AMPK/SREBP-2/PCSK9/LDLR signalling pathway

Hyperlipidaemia is one of the major risk factors for atherosclerosis, coronary heart disease, stroke and diabetes. In the present study, we synthesized a new anthraquinone compound, 1,8-dihydroxy-3-succinic acid monoethyl ester-6-methylanthraquinone, and named it Kanglexin (KLX). The aim of this study was to evaluate whether KLX has a lipid-lowering effect and to explore the potential molecular mechanism. In this study, Sprague-Dawley rats were fed a high fat diet (HFD) for 5 weeks to establish a hyperlipidaemia model; then, the rats were orally administered KLX (20, 40, and 80 mg kg-1·d-1) or atorvastatin calcium (AT, 10 mg kg-1·d-1) once a day for 2 weeks. KLX had prominent effects on reducing blood lipids, hepatic lipid accumulation, body weight and the ratio of liver weight/body weight. Furthermore, KLXdramatically reduced the total cholesterol (TC) and triglyceride (TG) levels and lipid accumulation in a HepG2 cell model of dyslipidaemia induced by 1 mmol/L oleic acid (OA). KLX may decrease lipid levels by phosphorylating adenosine monophosphate-activated protein kinase (AMPK) and the downstream sterol regulatory element binding protein 2 (SREBP-2)/proprotein convertase subtilisin/kexin type 9 (PCSK9)/low-density lipoprotein receptor (LDLR) signalling pathway in the HFD rats and OA-treated HepG2 cells. The effects of KLX on the AMPK/SREBP-2/PCSK9/LDLR signalling pathway were abolished when AMPK was inhibited by compound C (a specific AMPK inhibitor) in HepG2 cells. In summary, KLX has an efficient lipid-lowering effect mediated by activation of the AMPK/SREBP-2/PCSK9/LDLR signalling pathway. Our findings may provide new insight into and evidence for the discovery of a new lipid-lowering drug for the prevention and treatment of hyperlipidaemia, fatty liver, and cardiovascular disease in the clinic.

Safety and Tolerability of PCSK9 Inhibitors: Current Insights

The current era of preventive cardiology continues to emphasize on low-density lipoprotein cholesterol (LDL-C) reduction to alleviate the burden of atherosclerotic cardiovascular disease (ASCVD). In this regard, the pharmacological inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) enzyme via monoclonal antibodies has emerged as a novel lipid-lowering therapy, leading to a marked reduction in circulating LDL-C levels and subsequent improvement of cardiovascular outcomes. As these agents are increasingly used in current clinical practice, mounting scientific and clinical evidence supports that PCSK9 inhibitors offer an excellent safety and tolerability profile with a low incidence of adverse events. Notably, the most frequently reported side effects are injection-site reactions. In contrast to statins, PCSK9 inhibitors do not appear to exert a detrimental effect on glycemic control or to increase the incidence of new-onset diabetes mellitus. Accumulating evidence also indicates that PCSK9 inhibitors are a safe, well-tolerated and effective therapeutic strategy for patients with statin intolerance. On the other hand, as PCSK9 inhibitors reduce LDL-C to unprecedented low levels, a large body of current research has examined the effects of their long-term administration on neurocognition and on levels of vitamin E and other fat-soluble vitamins, providing encouraging results. This review aims to present and discuss the current clinical and scientific evidence pertaining to the safety and tolerability of PCSK9 inhibitors.

Inclisiran for the Treatment of Cardiovascular Disease: A Short Review on the Emerging Data and Therapeutic Potential

Proprotein convertase subtilisin kexin 9 (PCSK-9)-targeting therapy has arisen as a new line for the treatment of hyperlipidemia. Inclisiran is a double-stranded small RNA molecule that works by blocking the transcription of PCSK-9, leading to a reduction of PCSK9 levels in the hepatocytes, resulting in an increased expression of low-density lipoprotein (LDL) receptors in the hepatocyte membrane and, as a consequence, it reduces the circulating levels of LDL cholesterol (LDL-C). Compared to the other LDL-C-lowering medications, such as statins, ezetimibe and PCSK-9 inhibitors, inclisiran proposes an infrequent dosing of twice a year, while simultaneously providing a significant reduction of LDL-C. Its prolonged effect offers an advantage against medication non-compliance, which is one of the main causes for not achieving LDL-C goals with standard therapy. Inclisiran has also proven to have a relatively safe profile with adverse effects occurring in similar frequency as with placebo. This review aims to present and discuss the current clinical and scientific data pertaining to the role of inclisiran in the management of hypercholesterolemia and treatment of cardiovascular disease (CVD).

Research progress on alternative non-classical mechanisms of PCSK9 in atherosclerosis in patients with and without diabetes

The proprotein convertase subtilisin/kexin type 9 (PCSK9) acts via a canonical pathway to regulate circulating low-density lipoprotein-cholesterol (LDL-C) via degradation of the LDL receptor (LDLR) on the liver cell surface. Published research has shown that PCSK9 is involved in atherosclerosis via a variety of non-classical mechanisms that involve lysosomal, inflammatory, apoptotic, mitochondrial, and immune pathways. In this review paper, we summarized these additional mechanisms and described how anti-PCSK9 therapy exerts effects through these mechanisms. These additional pathways further illustrate the regulatory role of PCSK9 in atherosclerosis and offer an in-depth interpretation of how the PCSK9 inhibitor exerts effects on the treatment of atherosclerosis.

Therapeutic management of hyperlipoproteinemia (a)

Cardiovascular disease (CVD) has consistently been the leading cause of death worldwide. Several clinical and epidemiological studies have demonstrated that an elevated plasma concentration of lipoprotein (a) [Lp(a)] is a causative and independent major risk factor for the development of CVD, as well as calcific aortic valve stenosis. Thus, the therapeutic management of hyperlipoproteinemia (a) has received much attention, as significant reductions in Lp(a) levels may, potentially, favorably affect cardiovascular risk. Aspirin, niacin, estrogens, and statins, which act on different molecular pathways, may be prescribed to patients with mild or modest elevations of Lp(a) levels. Other therapeutic interventions, such as proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, Lp(a) apheresis, and the novel antisense oligonucleotides APO(a)-Rx and APO(a)-LRx, which are being evaluated in ongoing clinical trials, have provided some promising results and can potentially be used in severe cases of hyperlipoproteinemia (a). This review aims to present and discuss the current clinical and scientific data pertaining to the therapeutic options for the management of hyperlipoproteinemia (a).

An update on pharmacotherapies in diabetic dyslipidemia

Hyperlipidemia plays a crucial role in the underlying pathogenesis of multiple cardiovascular diseases (CVD), including coronary artery disease, peripheral arterial disease, carotid stenosis, and heart failure. The risk of developing such diseases in the diabetic population is relatively high. Diabetes mellitus (DM) is an independent risk factor for premature atherosclerosis. The hallmark of DM dyslipidemia is a demonstrably high level of atherogenic triglyceride rich lipids including very low-density lipoprotein, chylomicrons, and small dense low-density lipoprotein (LDL). Moderate to high intensity statins, targeting LDL cholesterol reduction, remain the cornerstone in the management of this unique disorder. Many 'non-statin' drugs have recently been studied in the DM patients who were either on a 'maximally tolerated statin' or 'statin intolerant'. Ezetimibe and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are particularly important and were incorporated in the recent guidelines by the European Society of Cardiology, American College of Cardiology, American Heart Association, and American Diabetes Association. Icosapent Ethyl has garnered huge interest this year following publication of the REDUCE-IT trial. There are several newer hypolipidemic drugs, including Bempedoic acid, Inclisiran and RVX-208, that are in different phases of clinical trials. In this article, we review the underlying pathophysiology of DM dyslipidemia, existing guidelines related to its management, and the potential of newer hypolipidemic and anti-inflammatory drugs being incorporated in the management of DM.

Impact of lipid-lowering therapy on glycemic control and the risk for new-onset diabetes mellitus

Lipid-lowering therapy is used very commonly nowadays not only for the optimization of the lipid profile but also to reduce cardiovascular risk. However, some studies have linked the use of certain lipid-lowering agents with an increased risk for impaired glycemic control and new-onset diabetes mellitus, a condition well established as an important risk factor for cardiovascular disease. On the other hand, some other lipid-lowering agents have been shown to have a beneficial effect on glucose metabolism. Profound knowledge of these differences would enable the clinician to choose the right lipid-lowering medication for each individual patient, so that the benefits would outweigh the risk of side effects. This review aims to present and discuss the clinical and scientific data pertaining to the impact of lipid-lowering therapy on glycemic control and the risk for new-onset diabetes mellitus.

Inclisiran: A New Promising Agent in the Management of Hypercholesterolemia

The discovery of proprotein convertase subtilisin-kexin type 9 (PCSK9), a serine protease which binds to the low-density lipoprotein (LDL) receptors and targets the receptors for lysosomal degradation, offered an additional route through which plasma LDL-cholesterol (LDL-C) levels can be controlled. Initially, the therapeutic approaches to reduce circulating levels of PCSK9 were focused on the use of monoclonal antibodies. To that effect, evolocumab and alirocumab, two human monoclonal antibodies directed against PCSK9, given on a background of statin therapy, have been shown to markedly decrease LDL-C levels and significantly reduce cardiovascular risk. The small interfering RNA (siRNA) molecules have been used recently to target the hepatic production of PCSK9. siRNA interferes with the expression of specific genes with complementary nucleotide sequences by affecting the degradation of mRNA post-transcription, thus preventing translation. Inclisiran is a long-acting, synthetic siRNA directed against PCSK9 and it has been shown to significantly decrease hepatic production of PCSK9 and cause a marked reduction in LDL-C levels. This review aims to present and discuss the current clinical and scientific evidence pertaining to inclisiran, which is a new promising agent in the management of hypercholesterolemia.

Patient adherence, compliance, and perspectives on evolocumab for the management of resistant hypercholesterolemia

Evolocumab is a PCSK9 inhibitor which is administered subcutaneously, and when added to statin therapy it has been shown to cause a significant incremental LDL-C reduction, leading to a reduction of cardiovascular risk. Evolocumab has a favorable side effect profile, and its self-administration at home appears to be safe and effective with the appropriate training and instructions from a health care provider. Current studies are showing encouraging results regarding adherence to evolocumab in real-life settings, and adherence rates to evolocumab appear to be better than those to statins. However, further larger studies are needed for a more definitive assessment of the short- and long-term patient adherence rates to evolocumab. In addition, reductions in the price of evolocumab may also be necessary to improve cost-effectiveness of the drug.