PCSK9 inhibition in the management of hyperlipidemia: focus on evolocumab

Amino Acid Conjugates of 2-Mercaptobenzimidazole Ameliorates High-Fat Diet-Induced Hyperlipidemia in Rats via Attenuation of HMGCR, APOB, and PCSK9

PURPOSE

This study was designed to explore the antihyperlipidemic effects of amino acid derivatives of 2-mercaptobenzimidazole (4J and 4K) in high-fat diet (HFD)-fed rats.

METHODS

Male Sprague-Dawley rats were divided into nine groups which received either standard diet or HFD for 28 days. Blood samples were taken on 27th day from HFD-fed rats to ensure hyperlipidemia. HFD-induced hyperlipidemic rats later received daily dosing of either vehicle or simvastatin (SIM; 20 mg/kg) or 4J/4K compounds (10, 20, and 30 mg/kg) for 12 consecutive days. On 40th day, animals were sacrificed, and blood samples were collected for the determination of serum lipid profile and liver function parameters. Liver samples were harvested for histopathological, antioxidant, and qPCR analyses. Molecular docking of tested compounds with HMGCR was also performed to assess the binding affinities.

RESULTS

4J and 4K dose dependently decreased serum total cholesterol, triglycerides, low-density lipoprotein, very low-density lipoproteins, alanine transaminase (ALT), and aspartate aminotransferase (AST) levels while significantly alleviated high-density lipoproteins. However, SIM failed to reduce AST and ALT levels. Moreover, tested compounds displayed antioxidant effects by inducing superoxide dismutase and glutathione levels. Histopathology data also displayed protective effects of 4J and 4K against HFD-induced fatty changes and hepatic damage. In addition, 4J and 4K downregulated transcript levels of HMGCR, APOB, PCSK9, and VCAM1, and molecular docking analysis also supported the experimental data.

CONCLUSION

It is conceivable from this study that 4J and 4K exert their antihyperlipidemic effects by modulating multiple targets regulating lipid levels.

Meta-analysis of the Placebo and Nocebo Effects Associated with Placebo Treatment in Randomized Trials of Lipid Lowering Therapy

BACKGROUND

Randomized controlled trials (RCTs) of lipid-lowering therapy (LLT) in which the control groups received placebo without background LLT offer unique insights into the placebo and nocebo effects of lipid-lowering RCTs.

METHODS

Embase and Medline were searched for hyperlipidemia RCTs with placebo-controlled arms. Placebo arms with background LLT were excluded. A single arm meta-analysis of proportions was used to estimate major adverse cardiovascular events (MACE) and adverse events (AE). A meta-analysis of means was used to estimate the pooled mean differences of total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoproteins (HDL) and triglycerides.

RESULTS

A total of 40 RCTs and 37 668 placebo-treated participants were included. The pooled mean changes for TC, LDL, HDL, and triglycerides were -0.019 mmol/L, -0.028 mmol/L, 0.013 mmol/L and 0.062 mmol/L respectively among placebo-treated participants, indicating a modest placebo effect. The pooled average nocebo effect among placebo-treated participants was 42.62% for all AEs and 3.38% for musculoskeletal-related AEs, 11.36% for gastrointestinal-related AEs and 6.62% for headaches. Placebo-treated participants in secondary prevention RCTs had a far higher incidence of these nocebo effects than primary prevention RCTs: any AEs (OR 6.76, 95%CI: 5.56-8.24, P < 0.001), and gastrointestinal-related AE (OR 1.23, 95%CI: 1.00-1.51, P = 0.049). No differences in nocebo effects were found between the placebo arms of statin and non-statin trials.

CONCLUSION

Our meta-analysis of placebo-treated participants in RCTs with no background LLT indicate a modest placebo effect but prominent nocebo effect of musculoskeletal, headache and gastrointestinal symptoms that was greatest among secondary prevention RCTs. These findings may inform the design of future LLT RCTs.

The Use of Monoclonal Antibody-Based Proprotein Convertase Subtilisin-Kexin Type 9 (PCSK9) Inhibitors in the Treatment of Hypercholesterolemia

In this review, we evaluated several studies in the literature to analyze the benefits and deleterious effects of the use of monoclonal antibodies (MABs)-based proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors in patients with hypercholesterolemia. Increased low-density lipoprotein cholesterol (LDL-C) levels lead to an increase in the risk of cardiovascular (CV) disease. Statins are the cornerstones of hypercholesterolemia treatment, but the patient response may often vary, and additional therapies may be needed to control the increased LDL-C levels. MABs bind to PCSK9 receptors, causing a reduction in LDL-C levels. MAB-based PCSK9 inhibitors such as alirocumab and evolocumab have been approved for use in hypercholesterolemia in combination with statins. Studies have suggested that both alirocumab and evolocumab are effective in lowering LDL-C levels, have favorable side effect profiles, and can be administered at convenient dosing intervals; however, further double-blind, randomized trials evaluating the long-term safety and efficacy of both the agents could assist with clinical decision-making.

PCSK9 Inhibitors and Cardiovascular Disease: Impact on Cardiovascular Outcomes

Cardiovascular Disease (CVD) remains the leading cause of morbidity and mortality in the western world. Hypolipidemic drugs have long been used for the primary and secondary prevention of heart disease. However, the high frequency of recurrent events in patients despite hypolipidemic therapy has increased the need for new more targeted therapeutic approaches. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are monoclonal antibodies to the PCSK9 gene and represent a new class of drugs that have been shown to further decrease LDL-C when administered as a monotherapy or in combination with statins. In addition to LDL reduction, PCSK9 inhibitors are shown to decrease apolipoprotein B and lipoprotein (a) levels without major adverse effects. Whether or not PCSK9 inhibitors can actually reduce the incidence of cardiovascular events and ameliorate CVD prognosis is yet to be clarified. This review summarizes recent literature on the safety and efficacy of PCSK9 inhibitors on CVD outcome and its potential role in the management of patients with high-risk cardiovascular disease.

Cholesterol in LDL receptor recycling and degradation

The SREBP2/LDLR pathway is sensitive to cholesterol content in the endoplasmic reticulum (ER), while membrane low-density lipoprotein receptor (LDLR) is influenced by sterol response element binding protein 2 (SREBP2), pro-protein convertase subtilisin/kexin type 9 (PCSK9) and inducible degrader of LDLR (IDOL). LDL-C, one of the risk factors in cardiovascular disease, is cleared through endocytosis recycling of LDLR. Therefore, we propose that a balance between LDLR endocytosis recycling and PCSK9-mediated and IDOL-mediated lysosomal LDLR degradation is responsible for cholesterol homeostasis in the ER. For statins that decrease serum LDL-C levels via cholesterol synthesis inhibition, the mechanism by which the statins increase the membrane LDLR may be regulated by cholesterol homeostasis in the ER.

PCSK9 inhibitors and cardiovascular outcomes

Introduction: Dyslipidemia, particularly elevated low-density lipoprotein cholesterol (LDL-C), is a key risk factor for atherosclerotic cardiovascular disease (ASCVD), and lipid-lowering drugs are beneficial for the primary and secondary prevention of cardiovascular (CV) disease. While statins are clear first-line drugs, new drug developments such as proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have been shown to improve cardiovascular outcomes when added to statins. Evolocumab reduced the risk of cardiovascular events in patients with ASCVD when added to maximally tolerated statin therapy (± ezetimibe), and recent data from the ODYSSEY OUTCOMES trial indicate that alirocumab added to maximally tolerated statin therapy (± other lipid-lowering drugs) reduces the risk of cardiovascular events in patients with a recent acute coronary syndrome. In this article the authors review the available data on the effect of PCSK9 inhibitors on cardiovascular outcomes.Areas covered: This article reviews the available data on the effect of PCSK9 inhibitors on CV outcomes. Relevant papers were identified from a search of PubMed/Medline and the Cochrane Central Register of Controlled Trials (CENTRAL).Expert opinion: The authors conclude that PCSK9 inhibitors provide substantial and durable reductions in LDL-C levels and improve cardiovascular outcomes.

Pharmacological Options in Atherosclerosis: A Review of the Existing Evidence

Coronary heart disease (CHD) is the leading cause of mortality worldwide and high low-density lipoprotein (LDL) cholesterol levels have been shown to be key in the pathogenesis of this condition. Lipid control has therefore been the subject of decades of research and has led to many large and robust randomized controlled trials, as well as the highest grossing drug of all time—Lipitor (atorvastatin). Statin therapy has long been indicated for secondary and more recently primary prevention. However, despite the large-scale use of statins, CHD prevalence remains high, and some patients do not respond to statin therapy. There has been a large push to find and test alternative lipid-lowering agents, these include fibrates, cholesterol absorption inhibitors, and proprotein convertase subtilisin/kexin type 9 (PCSK-9) inhibitors. It is the aim of this review to assess the literature surrounding each of these groups of drugs.

The effects of single- and multiple-dose administration of bococizumab (RN316/PF-04950615), a humanized IgG2Δa monoclonal antibody binding proprotein convertase subtilisin/kexin type 9, in hypercholesterolemic subjects treated with and without atorvastatin: Results from four phase I studies

AIMS

Three single-dose and one multiple-dose phase I studies were conducted in subjects with primary hypercholesterolemia to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of bococizumab, a proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor.

METHODS

The dosing schedules for hypercholesterolemic subjects randomized in the four phase I studies were (1) ascending, single, intravenous (IV) bococizumab (0.3, 1, 3, 6, 12, or 18 mg/kg), or placebo (N = 48; baseline low-density lipoprotein cholesterol [LDL-C] ≥130 mg/dL); (2) single, IV bococizumab (0.5 or 4 mg/kg; no placebo) added to ongoing atorvastatin 40 mg/day (N = 24); (3) single, fixed, subcutaneous (SC) bococizumab (100 or 200 mg), or IV bococizumab (200 mg; no placebo; N = 49; baseline LDL-C ≥130 mg/dL); and (4) weekly IV bococizumab (0.25, 0.5, 1, or 1.5 mg/kg) or placebo for 4 weeks (N = 67; baseline LDL-C ≥130 mg/dL).

RESULTS

Bococizumab pharmacokinetics were well characterized following single IV or SC doses and following multiple IV doses. Exposure to single-dose bococizumab increased slightly greater than dose-proportionally and clearance decreased with increasing dose. In the single-dose studies, maximal mean percent reductions from baseline in LDL-C ranged from 43% (0.3 mg/kg) to 84% (18 mg/kg) in bococizumab-treated subjects, compared with 2% for placebo. For the multiple-dose study, maximal reductions in LDL-C ranged from 55% (0.25 mg/kg) to 66% (1 mg/kg) in bococizumab-treated subjects, compared with 9% for placebo. In all studies, adverse events were infrequent, transient, and not dose-related.

CONCLUSIONS

Bococizumab was generally safe and well tolerated. Bococizumab lowered LDL-C levels substantially in all four studies.

Systematic Review and Network Meta-Analysis on the Efficacy of Evolocumab and Other Therapies for the Management of Lipid Levels in Hyperlipidemia

Background

The proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors evolocumab and alirocumab substantially reduce low‐density lipoprotein cholesterol (LDL‐C) when added to statin therapy in patients who need additional LDL‐C reduction.

Methods and Results

We conducted a systematic review and network meta‐analysis of randomized trials of lipid‐lowering therapies from database inception through August 2016 (45 058 records retrieved). We found 69 trials of lipid‐lowering therapies that enrolled patients requiring further LDL‐C reduction while on maximally tolerated medium‐ or high‐intensity statin, of which 15 could be relevant for inclusion in LDL‐C reduction networks with evolocumab, alirocumab, ezetimibe, and placebo as treatment arms. PCSK9 inhibitors significantly reduced LDL‐C by 54% to 74% versus placebo and 26% to 46% versus ezetimibe. There were significant treatment differences for evolocumab 140 mg every 2 weeks at the mean of weeks 10 and 12 versus placebo (−74.1%; 95% credible interval −79.81% to −68.58%), alirocumab 75 mg (−20.03%; 95% credible interval −27.32% to −12.96%), and alirocumab 150 mg (−13.63%; 95% credible interval −22.43% to −5.33%) at ≥12 weeks. Treatment differences were similar in direction and magnitude for PCSK9 inhibitor monthly dosing. Adverse events were similar between PCSK9 inhibitors and control. Rates of adverse events were similar between PCSK9 inhibitors versus placebo or ezetimibe.

Conclusions

PCSK9 inhibitors added to medium‐ to high‐intensity statin therapy significantly reduce LDL‐C in patients requiring further LDL‐C reduction. The network meta‐analysis showed a significant treatment difference in LDL‐C reduction for evolocumab versus alirocumab.

Proprotein convertase inhibition: Paralyzing the cell's master switches

Proprotein convertases are serine proteases responsible for the cleavage and subsequent activation of protein substrates, many of them relevant for the development of an ample variety of diseases. Seven of the PCs, including furin and PACE4, recognize and hydrolyze the C-terminal end of the general sequence RXRR/KXR, whereas PCSK-9 recognizes a series of non-basic amino acids. In some systems, PC-mediated substrate activation results in the development of pathological processes, such as cancer, endocrinopathies, and cardiovascular and infectious diseases. After establishing PCs as relevant contributors to disease processes, research efforts were directed towards the development of inhibition strategies, including small and large molecules, anti-sense therapies, and antibody-based therapies. Most of these inhibitors mimic the consensus sequence of PCs, blocking the active site in a competitive manner. The most promising inhibitors were designed as bioengineered proteins; however, some non-protein and peptidomimetic agents have also proved to be effective. These efforts led to the design of pre-clinical studies and clinical trials utilizing inhibitors to PCs. Although the initial studies were performed using non-selective PCs inhibitors, such as CMK, the search for more specific, and compartmentalized selective inhibitors resulted in specific activities ascribed to some, but not all of the PCs. For instance, PACE4 inhibitors were effective in decreasing prostate cancer cell proliferation, and neovascularization. Decreased metastatic ovarian cancer utilizing furin inhibitors represents one of the major endeavors, currently in a phase II trial stage. Antibodies targeting PCSK-9 decreased significantly the levels of HDL-cholesterol, in a phase III trial. The study of Proprotein convertases has reached a stage of maturity. New strategies based on the alteration of their activity at the cellular and clinical level represent a promising experimental pharmacology field. The development of allosteric inhibitors, or specific agents directed against individual PCs is one of the challenges to be unraveled in the future.

Retargeting the management of hypercholesterolemia - focus on evolocumab

Hypercholesterolemia is one of the main risk factors for atherosclerosis and cardiovascular diseases. The treatment is based on the modification of the diet and lifestyle and if necessary on a pharmacological therapy. The most widely used drugs are the inhibitors of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (statins); nevertheless, many patients do not reach optimal levels of low-density lipoprotein-cholesterol (LDL-C) even with maximal dosage of statins (eventually associated to ezetimibe) or present side effects, which do not allow them to continue the treatment. Inhibitors of PCSK9 represent a new therapeutic approach for lowering LDL-C. Evolocumab and alirocumab are human monoclonal antibodies, which bind to extracellular PCSK9 and thus interfere with the degradation of low-density lipoprotein receptor. Evolocumab use is approved for the treatment of patients with heterozygous familial hypercholesterolemia (FH) and homozygous FH as an adjunct to diet and maximally tolerated statin therapy or for subjects with clinical atherosclerotic cardiovascular disease who require additional lowering of LDL-C. Phase III clinical trials have demonstrated the effectiveness of evolocumab (140 mg/every 2 weeks or 420 mg/month, via subcutaneous injection) in monotherapy and in combination with statins, in the treatment of patients intolerant to statins or with FH. In monotherapy, it reduces LDL-C by 55%, and its association with statins leads to a reduction of LDL-C by up to 63%–75%. Evolocumab has been demonstrated to be safe and well tolerated. Ongoing clinical trials are assessing the long-term effects of evolocumab on the incidence of cardiovascular risk, safety, and tolerability. This review resumes the available clinical evidence on the efficacy and safety of evolocumab, for which a relatively large amount of clinical data are currently available, and discusses the retargeting of cholesterol-lowering therapy in clinical practice.