Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Inhibitors, Reality or Dream in Managing Patients with Cardiovascular Disease

Atherosclerosis Residual Lipid Risk-Overview of Existing and Future Pharmacotherapies

Patients with atherosclerotic disease remain at increased risk of future events despite receiving optimal medical treatment. This residual risk is widely heterogeneous, but lipoprotein particles and their content play a major role in determining future cardiovascular events. Beyond low-density lipoprotein cholesterol (LDL-c), other lipoprotein particles have not demonstrated similar contribution to the progression of atherosclerosis. Statins, ezetimibe, and more recently, proprotein convertase subtilisin kexin 9 (PCSK9) inhibitors and bempedoic acid have confirmed the causal role of LDL-c in the development of atherosclerosis. Data on high-density lipoprotein cholesterol (HDL-c) suggested a possible causal role for atherosclerosis; nonetheless, HDL-c-raising treatments, including cholesteryl-ester transfer protein (CETP) inhibitors and niacin, failed to confirm this relationship. On the other hand, mendelian randomisation revealed that triglycerides are more implicated in the development of atherosclerosis. Although the use of highly purified eicosapentaenoic acid (EPA) was associated with a reduction in the risk of adverse cardiovascular events, this beneficial effect did not correlate with the reduction in triglycerides level and has not been consistent across large phase 3 trials. Moreover, other triglyceride-lowering treatments, such as fibrates, were not associated with a reduction in future cardiovascular risk. Studies assessing agents targeting angiopoietin-like 3 (lipoprotein lipase inhibitor) and apolipoprotein C3 antisense will add further insights into the role of triglycerides in atherosclerosis. Emerging lipid markers such as lipoprotein (a) and cholesterol efflux capacity may have a direct role in the progression of atherosclerosis. Targeting these biomarkers may provide incremental benefits in reducing cardiovascular risk when added to optimal medical treatment. This Review aims to assess available therapies for current lipid biomarkers and provide mechanistic insight into their potential role in reducing future cardiovascular risk.

Atherosclerosis and Toll-Like Receptor4 (TLR4), Lectin-Like Oxidized Low-Density Lipoprotein-1 (LOX-1), and Proprotein Convertase Subtilisin/Kexin Type9 (PCSK9)

Atherosclerosis is a leading cause of death in the world. A significant body of evidence suggests that inflammation and various players are implicated and have pivotal roles in the formation of atherosclerotic plaques. Toll-like receptor 4 (TLR4) is linked with different stages of atherosclerosis. This receptor is highly expressed in the endothelial cells (ECs) and atherosclerotic plaques. TLR4 activation can lead to the production of inflammatory cytokines and related responses. Lectin-like oxidized low-density lipoprotein-1 (LOX-1), an integral membrane glycoprotein with widespread expression on the ECs, is involved in atherosclerosis and has some common pathways with TLR4 in atherosclerotic lesions. In addition, proprotein convertase subtilisin/kexin type9 (PCSK9), which is a regulatory enzyme with different roles in cholesterol uptake, is implicated in atherosclerosis. At present, TLR4, PCSK9, and LOX-1 are increasingly acknowledged as key players in the pathogenesis of atherosclerotic cardiovascular diseases. Herein, we presented the current evidence on the structure, functions, and roles of TLR4, PCSK9, and LOX-1 in atherosclerosis.

Advances in Cardiovascular Pharmacology in Atherosclerotic-Related Therapeutic Areas: Addressing Patients' Clinical Needs

Over the last three decades, a significant improvement has been achieved in reducing cardiovascular morbidity and mortality [...].

Novel Applications for Invasive and Non-invasive Tools in the Era of Contemporary Percutaneous Coronary Revascularisation

Percutaneous coronary intervention (PCI) is an expanding treatment option for patients with coronary artery disease (CAD). It is considered the default strategy for the unstable presentation of CAD. PCI techniques have evolved over the last 4 decades with significant improvements in stent design, an increase in functional assessment of coronary lesions, and the use of intra-vascular imaging. Nonetheless, the morbidity and mortality related to CAD remain significant. Advances in technology have allowed a better understanding of the nature and progression of CAD. New tools are now available that reflect the pathophysiological changes at the level of the myocardium and coronary atherosclerotic plaque. Certain changes within the plaque would render it more prone to rupture leading to acute vascular events. These changes are potentially detected using novel tools invasively, such as near infra-red spectroscopy, or non-invasively using T2 mapping cardiovascular magnetic resonance imaging (CMR) and ¹⁸F-Sodium Fluoride positron emission tomography/ computed tomography. Similarly, changes at the level of the injured myocardium are feasibly assessed invasively using index microcirculatory resistance or non-invasively using T1 mapping CMR. Importantly, these changes could be detected immediately with the opportunity to tailor treatment to those considered at high risk. Concurrently, novel therapeutic options have demonstrated promising results in reducing future cardiovascular risks in patients with CAD. This Review article will discuss the role of these novel tools and their applicability in employing a mechanical and pharmacological treatment to mitigate cardiovascular risk in patients with CAD.

Intensive lipid-lowering therapy, time to think beyond low-density lipoprotein cholesterol

Statins have been shown to be effective in reducing cardiovascular events. Their magnitude of benefits has been proportionate to the reduction in low-density lipoprotein cholesterol (LDL-c). Intensive lipid-lowering therapies using ezetimibe and more recently proprotein convertase subtilisin kexin 9 inhibitors have further improved clinical outcomes. Unselective application of these treatments is undesirable and unaffordable and, therefore, has been guided by LDL-c level. Nonetheless, the residual risk in the post-statin era is markedly heterogeneous, including thrombosis and inflammation risks. Moreover, the lipo-protein related risk is increasingly recognised to be related to other non-LDL-c markers such as Lp(a). Emerging data show that intensive lipid-lowering therapy produce larger absolute risk reduction in patients with polyvascular disease, post coronary artery bypass graft and diabetes. Notably, these clinical entities share similar phenotype of large burden of atherosclerotic plaques. Novel plaque imaging may aid decision making by identifying patients with propensity to develop lipid rich plagues at multi-vascular sites. Those patients may be suitable candidates for intensive lipid lowering treatment.

Meta-Analysis of Intensive Lipid-Lowering Therapy in Patients With Polyvascular Disease

Background Polyvascular atherosclerotic disease is associated with an increased risk of future cardiovascular events. Intensive lipid-lowering therapy (ILT) may mitigate this risk. The aims of this study-level meta-analysis were to examine the effects of ILT in patients with polyvascular disease and whether baseline low-density lipoprotein cholesterol (LDL-C) may determine the level of benefit. Methods and Results Electronic databases were searched through January 2020 to identify randomized controlled trials of treatments targeting upregulation of LDL-C receptors (ie, statins, ezetimibe, and PCSK9 [proprotein convertase subtilisin-kexin type 9] inhibitors). The primary end point was major adverse vascular events as defined by the included studies. A total of 94 362 patients (14 821 [18.6%] with polyvascular disease) from 7 studies were included. In patients with monovascular disease, ILT was associated with a 13% reduction in the primary end point (rate ratio [RR] 0.87; 95% CI, 0.81-0.93 [P=0.0002]) (absolute RR, 1.8%) compared with less ILT, while patients with polyvascular disease had 15% relative RR (0.85; 95% CI, 0.80-0.90 [P<0.00001]) (absolute RR, 6.5%) (P=0.66 for interaction). When factoring LDL-C, unlike patients with monovascular disease, the relative benefits of ILT, compared with less ILT, in patients with polyvascular disease were comparable with LDL-C >100 mg/dL (RR, 0.85; 95% CI, 0.80-0.90 [P<0.00001]) and LDL-C <100 mg/dL (RR, 0.88; 95% CI, 0.81-0.96 [P=0.003]) (P=0.23 for interaction). Conclusions Patients with polyvascular disease experienced comparable benefits to those with monovascular disease in response to ILT. The benefits of ILT in patients with polyvascular disease were not dependent on baseline LDL-C, challenging the approach of using LDL-C as a prerequisite to commence ILT for this high-risk subgroup.

Butein Synergizes with Statin to Upregulate Low-Density Lipoprotein Receptor Through HNF1α-Mediated PCSK9 Inhibition in HepG2 Cells

Downregulation of the low-density lipoprotein (LDL) receptor (LDLR) can lead to hypercholesterolemia and related conditions, including cardiovascular diseases. Statins are a class of LDL cholesterol-lowering agents and are best-selling medications for patients at high risk of developing cardiovascular diseases. Indeed, statins upregulate LDLR and proprotein convertase subtilisin/kexin type 9a (PCSK9), leading to LDLR lysosomal degradation, which interferes with the attenuation of hypercholesterolemia. In the present study, butein was found to decrease extracellular PCSK9 levels by reducing its mRNA expression, which was attributable to butein-mediated downregulation of HNF1α in HepG2 cells. Butein-mediated PCSK9 inhibition further reversed LDLR protein synthesis inhibition, which possibly occurred through butein-mediated inhibition of LDLR degradation. When treated as a combination of butein and a statin, butein reduced statin-mediated enhancement of PCSK9 protein expression. This resulted in a synergistic enhancement of LDLR protein expression, whereas butein alone marginally increased LDLR protein expression. These findings suggest that butein, a novel PCSK9 inhibitor, may be a potential alternative or adjunct to statin treatment.

A promising tool to tackle the risk of cerebral vascular disease, the emergence of novel carotid wall imaging

Stroke is a heterogeneous vascular disease. Carotid artery atherosclerosis is associated with almost one-quarter of ischemic strokes. Moreover, a large percentage of preventable strokes are currently attributed to carotid atherosclerosis. Over the past three decades, the management of carotid artery disease has evolved. The benefits of carotid revascularization alongside medical therapy have early been recognized. Nonetheless, the debate regarding the optimal strategy is still ongoing, particularly in patients with asymptomatic carotid artery disease. One of the challenges is the use of luminal stenosis to quantify the severity of the carotid artery disease and to guide decision-making regarding invasive revascularization. Characterizing carotid atherosclerotic plaque is a promising tool to identify vulnerable plaque. Certain features such as large lipid core have already been linked to acute vascular events, not only at the plaque level but also to predict systemic cardiovascular events. Recently, a quantitative T2 mapping magnetic resonance imaging technique was developed and validated against histology. The ability to accurately quantify plaque lipid content using this technique opens several new opportunities. In this review articles, we will discuss the current challenges in the management of carotid artery disease and the future roles of T2 mapping to aid therapeutic options. These roles may include how to determine the mode of invasive carotid revascularization in symptomatic patients. Moreover, there may be a rational to use T2 mapping as a risk stratification tool in asymptomatic patients with carotid artery stenosis. It may also provide an opportunity to stage atherosclerosis and identify patients with coronary atherosclerosis who may benefit maximally from intensive lipid interventions.

Mechanistic Insights to Target Atherosclerosis Residual Risk

Current pharmacological and mechanical therapies have reduced future cardiovascular risk. Nonetheless, a significant proportion of patients remained at high risk of recurrent events despite achieving guideline-directed therapeutic targets. This residual risk poses challenges despite tackling 'traditional' risk factors. Targeting the residual risk has been the focus of numerous pharmacotherapies which were associated with variable success. Incomplete understanding of the mechanistic nature combined with the lack of tools to precisely quantify the residual risk contributed to the relatively high residual risk after 'optimal' medical therapy. The development of atherosclerotic plaque is derived from lipid retention within arterial intima that triggers an inflammatory cascade accelerating atherosclerosis progression and rendering plaque more prone to rupture. The exposed subendothelial space with activated platelets causes arterial occlusion leading to potential fatality. Therefore, a distinctive approach to characterize these features may offer the opportunity to tailor novel antiatherosclerotic to reduce the residual risk. The traditional approach of measuring risk factors is beneficial at population-level but maybe less informative upon quantifying risk at an individual-basis. This review will discuss lipid accumulation, thrombosis, and inflammation as therapeutic targets of atherosclerosis. Additionally, we will summarize previous challenges of antiatherosclerosis therapies and the future role to tackle the residual risk.