Cardiovascular Efficacy and Safety of Bococizumab in High-Risk Patients

On P values and effect modification

AIM

A crucial element of evidence-based healthcare is the sound understanding and use of statistics. As part of instilling sound statistical knowledge and practice, it seems useful to highlight instances of unsound statistical reasoning or practice, not merely in captious or vitriolic spirit, but rather, to use such error as a springboard for edification by giving tangibility to the concepts at hand and highlighting the importance of avoiding such error. This article aims to provide an instructive overview of two key statistical concepts: effect modification and P values.

METHODS AND RESULTS

A recent article published in the Journal of the American College of Cardiology on side effects related to statin therapy offers a notable example of errors in understanding effect modification and P values, and although not so critical as to entirely invalidate the article, the errors still demand considerable scrutiny and correction. In doing so, this article serves as an instructive overview of the statistical concepts of effect modification and P values.

CONCLUSION

Judicious handling of statistics is imperative to avoid muddying their utility. This article contributes to the body of literature aiming to improve the use of statistics, which in turn will help facilitate evidence appraisal, synthesis, translation, and application.

Incorporation of PCSK9 inhibitors into prevention of atherosclerotic cardiovascular disease

Primary and secondary prevention of atherosclerotic cardiovascular disease (ASCVD) has become recently more complex than ever, leaving the clinicians perplexed with outdated guidelines and emerging evidence about new LDL-C lowering therapies. 2013 American College of Cardiology (ACC)/American Heart Association (AHA) guidelines have focused on high intensity statin therapy for specific groups of patients, while abandoning long established LDL-C goals, a strategy which no longer seems valid. PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitors have emerged as the add-on therapy on top of statins and/or ezetimibe for the treatment of hypercholesterolemia and ASCVD prevention. In several clinical trials, PCSK9 inhibitors have demonstrated their safety and robust LDL-C-lowering power. One completed cardiovascular (CV) outcomes trial (FOURIER; Further Cardiovascular Outcomes Research with PCSK9 Inhibitions in Subjects with Elevated Risk) has demonstrated that PCSK9 inhibition reduces rates of CV death as well as non-fatal stroke and MI, while another major CV outcome trial is under way (ODYSSEY-OUTCOMES). Several trials studying CV benefits of novel LDL-C-lowering therapies are also being conducted. Prompt revision of ACC/AHA guidelines is necessary. In the meantime, physicians need to use clinical judgment integrating the most recent evidence into their practice.

Low-Density Lipoprotein Cholesterol Lowering for the Primary Prevention of Cardiovascular Disease Among Men With Primary Elevations of Low-Density Lipoprotein Cholesterol Levels of 190 mg/dL or Above: Analyses From the WOSCOPS (West of Scotland Coronary Prevention Study) 5-Year Randomized Trial and 20-Year Observational Follow-Up

BACKGROUND

Patients with primary elevations of low-density lipoprotein cholesterol (LDL-C) ≥190 mg/dL are at a higher risk of atherosclerotic cardiovascular disease as a result of long-term exposure to markedly elevated LDL-C levels. Therefore, initiation of statin therapy is recommended for these individuals. However, there is a lack of randomized trial evidence supporting these recommendations in primary prevention. In the present analysis, we provide hitherto unpublished data on the cardiovascular effects of LDL-C lowering among a primary prevention population with LDL-C ≥190 mg/dL.

METHODS

We aimed to assess the benefits of LDL-C lowering on cardiovascular outcomes among individuals with primary elevations of LDL-C ≥190 mg/dL without preexisting vascular disease at baseline. We performed post hoc analyses from the WOSCOPS (West of Scotland Coronary Prevention Study) randomized, placebo-controlled trial, and observational posttrial long-term follow-up, after excluding individuals with evidence of vascular disease at baseline. WOSCOPS enrolled 6595 men aged 45 to 64 years, who were randomly assigned to pravastatin 40 mg/d or placebo. In the present analyses, 5529 participants without evidence of vascular disease were included, stratified by LDL-C levels into those with LDL-C <190 mg/dL (n=2969; mean LDL-C 178±6 mg/dL) and those with LDL-C ≥190 mg/dL (n=2560; mean LDL-C 206±12 mg/dL). The effect of pravastatin versus placebo on coronary heart disease and major adverse cardiovascular events were assessed over the 4.9-year randomized controlled trial phase and on mortality outcomes over a total of 20 years of follow-up.

RESULTS

Among 5529 individuals without vascular disease, pravastatin reduced the risk of coronary heart disease by 27% (P=0.002) and major adverse cardiovascular events by 25% (P=0.004) consistently among those with and without LDL-C ≥190 mg/dL (P-interaction >0.9). Among individuals with LDL-C ≥190 mg/dL, pravastatin reduced the risk of coronary heart disease by 27% (P=0.033) and major adverse cardiovascular events by 25% (P=0.037) during the initial trial phase and the risk of coronary heart disease death, cardiovascular death, and all-cause mortality by 28% (P=0.020), 25% (P=0.009), and 18% (P=0.004), respectively, over a total of 20 years of follow-up.

CONCLUSIONS

The present analyses provide robust novel evidence for the short- and long-term benefits of lowering LDL-C for the primary prevention of cardiovascular disease among individuals with primary elevations of LDL-C ≥190 mg/dL.

2017 Focused Update of the 2016 ACC Expert Consensus Decision Pathway on the Role of Non-Statin Therapies for LDL-Cholesterol Lowering in the Management of Atherosclerotic Cardiovascular Disease Risk: A Report of the American College of Cardiology Task Force on Expert Consensus Decision Pathways

In 2016, the American College of Cardiology published the first expert consensus decision pathway (ECDP) on the role of non-statin therapies for low-density lipoprotein (LDL)-cholesterol lowering in the management of atherosclerotic cardiovascular disease (ASCVD) risk. Since the publication of that document, additional evidence and perspectives have emerged from randomized clinical trials and other sources, particularly considering the longer-term efficacy and safety of proprotein convertase subtilisin/kexin 9 (PCSK9) inhibitors in secondary prevention of ASCVD. Most notably, the FOURIER (Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk) trial and SPIRE-1 and -2 (Studies of PCSK9 Inhibition and the Reduction of Vascular Events), assessing evolocumab and bococizumab, respectively, have published final results of cardiovascular outcomes trials in patients with clinical ASCVD and in a smaller number of high-risk primary prevention patients. In addition, further evidence on the types of patients most likely to benefit from the use of ezetimibe in addition to statin therapy after acute coronary syndrome has been published. Based on results from these important analyses, the ECDP writing committee judged that it would be desirable to provide a focused update to help guide clinicians more clearly on decision making regarding the use of ezetimibe and PCSK9 inhibitors in patients with clinical ASCVD with or without comorbidities. In the following summary table, changes from the 2016 ECDP to the 2017 ECDP Focused Update are highlighted, and a brief rationale is provided. The content of the full document has been changed accordingly, with more extensive and detailed guidance regarding decision making provided both in the text and in the updated algorithms. Revised recommendations are provided for patients with clinical ASCVD with or without comorbidities on statin therapy for secondary prevention. The ECDP writing committee judged that these new data did not warrant changes to the decision pathways and algorithms regarding the use of ezetimibe or PCSK9 inhibitors in primary prevention patients with LDL-C <190 mg/dL with or without diabetes mellitus or patients without ASCVD and LDL-C ≥190 mg/dL not due to secondary causes. Based on feedback and further deliberation, the ECDP writing committee down-graded recommendations regarding bile acid sequestrant use, recommending bile acid sequestrants only as optional secondary agents for consideration in patients intolerant to ezetimibe. For clarification, the writing committee has also included new information on diagnostic categories of heterozygous and homozygous familial hypercholesterolemia, based on clinical criteria with and without genetic testing. Other changes to the original document were kept to a minimum to provide consistent guidance to clinicians, unless there was a compelling reason or new evidence, in which case justification is provided.

Anti-PCSK9 antibodies for the treatment of heterozygous familial hypercholesterolemia: patient selection and perspectives

Heterozygous familial hypercholesterolemia (FH) is a genetic disorder characterized by high low-density lipoprotein cholesterol levels from birth, which exposes the arteries to high levels of atherogenic lipoproteins lifelong and results in a significantly increased risk of premature cardiovascular events. The diagnosis of FH, followed by an appropriate and early treatment is critical to reduce the cardiovascular burden in this population. Phase I–III clinical trials showed the benefit of proprotein convertase subtilisin kexin 9 inhibitors, both alirocumab and evolocumab, in these patients with an average low-density lipoprotein cholesterol reduction ranging from −40% to −60%. The aim of this review is to address the unmet needs in cholesterol management, elucidate the biology and the clinical benefit of proprotein convertase subtilisin kexin 9 inhibition and finally discuss the open gaps and future directions in the treatment of patients with heterozygous FH.

Effects of PCSK9 Inhibitors on Other than Low-Density Lipoprotein Cholesterol Lipid Variables

Low-density lipoprotein cholesterol (LDL-C) is a major cardiovascular risk factor, but other lipid variables such as triglycerides (TRGs), high-density lipoprotein cholesterol (HDL-C) and lipoprotein a [Lp(a)] also affect cardiovascular risk. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors significantly lower LDL-C concentration but also modestly improve the concentrations of TRGs and HDL-C and more robustly decrease Lp(a) levels. The review presents the associated mechanisms of the beneficial effects of PCSK9 inhibitors on the other than LDL-C lipid variables, including the effects on lipid/apolipoprotein secretion and clearance and the heteroexchange between lipoproteins, as well as the possible effects on other variables involved in lipid metabolism such as sortilin. Proprotein convertase subtilisin/kexin type 9 inhibitors improve the overall lipid profile, and these beneficial effects may play a role in the reduction of cardiovascular risk.

Evolocumab for the treatment of hypercholesterolemia

INTRODUCTION

Evolocumab is a fully human monoclonal immunoglobulin G2 directed against human proprotein convertase subtilisin/kexin type 9 (PCSK9). It is administered by subcutaneous injection every 2 weeks or once monthly. Area covered: Herein, the authors discuss the rationale for inhibiting PCSK9 and describe the pharmacodynamics, pharmacokinetics and clinical trials with evolocumab. Evolocumab reduces low density lipoprotein cholesterol (LDL-C) levels by 50 to 60% in most patients with and without background treatment with statins or other lipid lowering agents. The safety profile appears satisfactory from the completed clinical studies and concerns regarding the risk of neurocognitive events have largely been dispelled. Expert opinion: The reduction of LDL-C with evolocumab to previously unattainable levels has resulted in a reduction in the composite cardiovascular event endpoint in the FOURIER trial and this is likely to impact on future lipid management guidelines. The clinical outcome data and excellent tolerability profile clearly support the use of evolocumab in patients at high cardiovascular risk, including those with heterozygous or homozygous familial hypercholesterolemia, who are unable to achieve LDL-C targets with statins with or without other lipid-lowering drugs. The high cost of evolocumab will restrict its use, however.

PCSK9 signaling pathways and their potential importance in clinical practice

In the following review, authors described the structure and biochemical pathways of PCSK9, its involvement in LDL metabolism, as well as significances of proprotein convertase subtilisin/kexin type 9 targeted treatment. PCSK9 is a proprotein convertase, which plays a crucial role in LDL receptor metabolism. Transcription and translation of PCSK9 is controlled by different nuclear factors, such as, SREBP and HNF1α. This review focuses on interactions between PCSK9 and LDL receptor, VLDLR, ApoER2, CD36, CD81, and others. The role of PCSK9 in the inflammatory process is presented and its influence on cytokine profile (IL-1, IL-6, IL-10, TNF) in atherosclerotic plaque. Cholesterol metabolism converges also with diabetes by mTORC1 pathways. PCSK9 can be altered by oncologic pathways with utilization of kinases, such as Akt, JNK, and JAK/STAT. Finally, the article shows that blocking PCSK9 has proapoptotic capabilities. Administration of monoclonal antibodies against PCSK9 reduced mortality rate and cardiovascular events in randomized trials. On the other hand, immunogenicity of new drugs may play a crucial role in their efficiency. Bococizumab ended its career following SPIRE-1,2 outcome. PCSK9 inhibitors have enormous potential, which had been reflected by introducing them (as a new class of drugs reducing LDL concentration cholesterol) into New Lipid Guidelines from Rome 2016. Discoveries in drugs development are focused on blocking PCSK9 on different levels. For example, silencing messenger RNA (mRNA of PCSK9) is a new alternative against hypercholesterolemia. Peptides mimicking EGF-A domain of the LDL receptor are gaining significance and hopefully they will soon join others. The significance of PCSK9 has just been uncovered and further data is still required to understand their activity.

Clinical trials. A pending subject

Clinical trials are essential tools for the progress of clinical medicine in its diagnostic and therapeutic aspects. Since the first trial in 1948, which related tobacco use with lung cancer, there have been more than 150,000 clinical trials to date in various areas (paediatrics, cardiology, oncology, endocrinology, etc.). This article highlights the importance for all physicians to participate, over the course of their professional career, in a clinical trial, due to the inherent benefits for patients, the progress of medicine and for curricular prestige. The authors have created a synthesis of their experience with clinical trials on hypertension, diabetes, dyslipidaemia and ischaemic heart disease over the course of almost 3 decades. Furthermore, a brief reference has been made to the characteristics of a phase I unit, as well as to a number of research studies currently underway.

Novel lipid modifying drugs to lower LDL cholesterol

PURPOSE OF REVIEW

Statins have long been the cornerstone for the prevention of cardiovascular disease (CVD). However, because of perceived adverse effects and insufficient efficacy in certain groups of patients, considerable interest exists in the search for alternatives to lower LDL-cholesterol (LDL-C), and the recent approvals of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors underlines the success of this quest. Here, we give an updated overview on the most recent developments in the area of LDL-C lowering agents.

RECENT FINDINGS

The clinical effects of the PCSK9 inhibitors are promising, especially now that the FOURIER and SPIRE programmes are published. Most cholesterylester-transfer protein inhibitors, however, except anacetrapib, have been discontinued because of either toxicity or lack of efficacy in large cardiovascular outcome trials. Other agents - like mipomersen, lomitapide, ETC-1002, and gemcabene - aim to lower LDL-C in different ways than solely through the LDL receptor, opening up possibilities for treating patients not responding to conventional therapies. New discoveries are also being made at the DNA and RNA level, with mipomersen being the first approved therapy based on RNA intervention in the United States for homozygous familial hypercholesterolemia.

SUMMARY

Recent years have witnessed a new beginning for cholesterol-lowering compounds. With increased knowledge of lipid metabolism a score of new therapeutic targets has been identified. Mechanisms for modulation of those targets are also becoming more diverse while statins remain the backbone of CVD prevention, the new alternatives, such as PCSK9 monoclonals will probably play an important additional role in treatment of patients at risk for CVD.

Therapeutic targeting in nanomedicine: the future lies in recombinant antibodies

The unique chemical and functional properties of nanoparticles can be harnessed for the delivery of large quantities of various therapeutic biomolecules. Active targeting of nanoparticles by conjugating ligands that bind to target cells strongly facilitates accumulation, internalization into target cells and longer retention at the target site, with consequent enhanced therapeutic effects. Recombinant antibodies with high selectivity and availability for a vast range of targets will dominate the future. In this review, we systematically outline the tremendous progress in the conjugation of antibodies to nanoparticles and the clear advantages that recombinant antibodies offer in the therapeutic targeting of nanoparticles. The demonstrated flexibility of recombinant antibody coupling to nanoparticles highlights the bright future of this technology for modern therapeutic nanomedicine.

Dyslipidaemia: PCSK9 inhibitors and foamy monocytes in familial hypercholesterolaemia

Accumulation of foam cells — macrophages with intracellular lipid droplets — in arterial walls is a hallmark of atherosclerosis. Bernelot Moens and colleagues report increases in circulating monocytes with intracellular lipid accumulation, associated CCR2 expression, and enhanced monocyte migration in patients with familial hypercholesterolaemia. These changes could be reversed by PCSK9-inhibitor treatment.

Update on the use of PCSK9 inhibitors in adults: Recommendations from an Expert Panel of the National Lipid Association

An Expert Panel convened by the National Lipid Association was charged with updating the recommendations on the use of proprotein convertase subtilisin/kexin type 9 (PCSK9) antibody therapy that were provided by the 2015 National Lipid Association Recommendations for the Patient-Centered Management of Dyslipidemia: Part 2. Recent studies have demonstrated the efficacy of these agents in reducing low-density lipoprotein cholesterol and non-high-density lipoprotein cholesterol and have confirmed their excellent safety profile. A cardiovascular outcomes study has shown that these agents reduce incident atherosclerotic cardiovascular disease (ASCVD) events in patents with stable ASCVD and concomitant risk factors. The current update provides the Expert Panel's evidence-based recommendations on the clinical utility of PCSK9 inhibitors in patients with stable ASCVD, progressive ASCVD, LDL-C ≥ 190 mg/dL (including polygenic hypercholesterolemia, heterozygous familial hypercholesterolemia and the homozygous familial hypercholesterolemia phenotype) and very-high-risk patients with statin intolerance.

PCSK9 Inhibitors: Treating the Right Patients in Daily Practice

PURPOSE OF REVIEW

Monoclonal antibodies that inhibit proprotein convertase subtilisin/kexin type 9 (PCSK9) have emerged as a novel approach to low-density lipoprotein cholesterol (LDL-C) lowering. The potential role of PCSK9 inhibitors in clinical practice will be reviewed.

RECENT FINDINGS

Clinical trials have demonstrated that PCSK9 inhibitors produce robust LDL-C lowering when administered either as monotherapy or in combination with statins. This provides the opportunity to achieve effective lipid lowering in familial hypercholesterolemia, patients with either established atherosclerotic cardiovascular disease or high risk primary prevention and an important opportunity to treat patients with statin intolerance. The findings from plaque imaging and patients with established atherosclerotic cardiovascular disease suggest that PCSK9 inhibition has favorable outcomes beyond improving lipid profiles, which has the opportunity to expand their use. PCSK9 inhibitors represent a new approach to achieving effective cardiovascular risk reduction in a broader number of patients. How these agents will be taken up in clinical practice remains to be determined.

Prevention of cardiovascular disease in patients with familial hypercholesterolaemia: The role of PCSK9 inhibitors

Familial hypercholesterolaemia is an autosomal dominant inherited disorder characterised by elevated low-density lipoprotein cholesterol levels and consequently an increased risk of atherosclerotic cardiovascular disease (ASCVD). Familial hypercholesterolaemia is relatively common, but is often underdiagnosed and undertreated. Cardiologists are likely to encounter many individuals with familial hypercholesterolaemia; however, patients presenting with premature ASCVD are rarely screened for familial hypercholesterolaemia and fasting lipid levels are infrequently documented. Given that individuals with familial hypercholesterolaemia and ASCVD are at a particularly high risk of subsequent cardiac events, this is a missed opportunity for preventive therapy. Furthermore, because there is a 50% chance that first-degree relatives of individuals with familial hypercholesterolaemia will also be affected by the disorder, the underdiagnosis of familial hypercholesterolaemia among patients with ASCVD is a barrier to cascade screening and the prevention of ASCVD in affected relatives. Targeted screening of patients with ASCVD is an effective strategy to identify new familial hypercholesterolaemia index cases. Statins are the standard treatment for individuals with familial hypercholesterolaemia; however, low-density lipoprotein cholesterol targets are not achieved in a large proportion of patients despite treatment. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have been shown to reduce low-density lipoprotein cholesterol levels considerably in individuals with familial hypercholesterolaemia who are concurrently receiving the maximal tolerated statin dose. The clinical benefit of PCSK9 inhibitors must, however, also be considered in terms of their cost-effectiveness. Increased awareness of familial hypercholesterolaemia is required among healthcare professionals, particularly cardiologists and primary care physicians, in order to start early preventive measures and to reduce the mortality and morbidity associated with familial hypercholesterolaemia and ASCVD.

Inhibition of PCSK9 does not improve lipopolysaccharide-induced mortality in mice

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secreted protein that targets LDL receptors (LDLRs) for degradation in liver. Blocking the interaction of PCSK9 with the LDLR potently reduces plasma LDL cholesterol levels and cardiovascular events. Recently, it has been suggested that inhibition of PCSK9 might also improve outcomes in mice and humans with sepsis, possibly by increasing LDLR-mediated clearance of endotoxins. Sepsis is a complication of a severe microbial infection that has shared pathways with lipid metabolism. Here, we tested whether anti-PCSK9 antibodies prevent death from lipopolysaccharide (LPS)-induced endotoxemia. Mice were administered PCSK9 antibodies prior to, or shortly after, injecting LPS. In both scenarios, the administration of PCSK9 antibodies did not alter endotoxemia-induced mortality. Afterward, we determined whether the complete absence of PCSK9 improved endotoxemia-induced mortality in mice with the germ-line deletion of Pcsk9. Similarly, PCSK9 knockout mice were not protected from LPS-induced death. To determine whether low LDLR expression increased LPS-induced mortality, Ldlr^−/− mice and PCSK9 transgenic mice were studied after injection of LPS. Endotoxemia-induced mortality was not altered in either mouse model. In a human cohort, we observed no correlation between plasma inflammation markers with total cholesterol levels, LDL cholesterol, and PCSK9. Combined, our data demonstrate that PCSK9 inhibition provides no protection from LPS-induced mortality in mice.

How many familial hypercholesterolemia patients are eligible for PCSK9 inhibition?

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is a high cardiovascular risk condition. Less than 20% of patients achieve the LDL targets. Although PCSK9 inhibitors improve control and reduce cardiovascular events, official recommendations for their use are restrictive. We aim to assess the number of FH patients suitable for PCSK9 inhibition according to the European guidelines.

METHODS

A total of 2685 FH patients, with a minimum follow-up of 6 months, included in the Dyslipidemia Registry of the Spanish Arteriosclerosis Society, were sorted according to the intensity of their lipid-lowering therapy (LLT) and LDL cholesterol levels achieved. The number of patients who met the recommendations for PCSK9 inhibition treatment according to the European Atherosclerosis Society (ESC/EAS), Spanish Arteriosclerosis Society and the European Medicines Agency was calculated.

RESULTS

In total, 1573 patients were on high-intensity LLT; 607 were on moderate-intensity statins; 82 were on low-intensity LLT, and 423 were neither on statins nor on ezetimibe in the last visit registered. The mean LDL reduction among those on high-intensity LLT was 54%. Ninety-one percent of patients on high-intensity LLT had an LDL below 5.2 mmol/L, 53% below 3.4 mmol/L, and 23% below 2.6 mmol/L. Only 12% of FH patients with cardiovascular disease achieved 1.8 mmol/L. Despite this, only 17% of patients qualified for PCSK9 inhibition according to ESC/EAS guidelines.

CONCLUSIONS

For patients with a condition that exposes them to high cardiovascular risk and who have extreme difficulties in achieving LDL targets, wider access to PCSK9 inhibitor therapy is warranted.

PCSK9 monoclonal antibodies for the primary and secondary prevention of cardiovascular disease

BACKGROUND

Despite the availability of effective drug therapies that reduce low-density lipoprotein (LDL)-cholesterol (LDL-C), cardiovascular disease (CVD) remains an important cause of mortality and morbidity. Therefore, additional LDL-C reduction may be warranted, especially for patients who are unresponsive to, or unable to take, existing LDL-C-reducing therapies. By inhibiting the proprotein convertase subtilisin/kexin type 9 (PCSK9) enzyme, monoclonal antibodies (PCSK9 inhibitors) may further reduce LDL-C, potentially reducing CVD risk as well.

OBJECTIVES

Primary To quantify short-term (24 weeks), medium-term (one year), and long-term (five years) effects of PCSK9 inhibitors on lipid parameters and on the incidence of CVD. Secondary To quantify the safety of PCSK9 inhibitors, with specific focus on the incidence of type 2 diabetes, cognitive function, and cancer. Additionally, to determine if specific patient subgroups were more or less likely to benefit from the use of PCSK9 inhibitors.

SEARCH METHODS

We identified studies by systematically searching the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and Web of Science. We also searched Clinicaltrials.gov and the International Clinical Trials Registry Platform and screened the reference lists of included studies. We identified the studies included in this review through electronic literature searches conducted up to May 2016, and added three large trials published in March 2017.

SELECTION CRITERIA

All parallel-group and factorial randomised controlled trials (RCTs) with a follow-up time of at least 24 weeks were eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed and extracted data. When data were available, we calculated pooled effect estimates.

MAIN RESULTS

We included 20 studies with data on 67,237 participants (median age 61 years; range 52 to 64 years). Twelve trials randomised participants to alirocumab, three trials to bococizumab, one to RG7652, and four to evolocumab. Owing to the small number of trials using agents other than alirocumab, we did not differentiate between types of PCSK9 inhibitors used. We compared PCSK9 inhibitors with placebo (thirteen RCTs), ezetimibe (two RCTs) or ezetimibe and statins (five RCTs).Compared with placebo, PCSK9 inhibitors decreased LDL-C by 53.86% (95% confidence interval (CI) 58.64 to 49.08; eight studies; 4782 participants; GRADE: moderate) at 24 weeks; compared with ezetimibe, PCSK9 inhibitors decreased LDL-C by 30.20% (95% CI 34.18 to 26.23; two studies; 823 participants; GRADE: moderate), and compared with ezetimibe and statins, PCSK9 inhibitors decreased LDL-C by 39.20% (95% CI 56.15 to 22.26; five studies; 5376 participants; GRADE: moderate).Compared with placebo, PCSK9 inhibitors decreased the risk of CVD events, with a risk difference (RD) of 0.91% (odds ratio (OR) of 0.86, 95% CI 0.80 to 0.92; eight studies; 59,294 participants; GRADE: moderate). Compared with ezetimibe and statins, PCSK9 inhibitors appeared to have a stronger protective effect on CVD risk, although with considerable uncertainty (RD 1.06%, OR 0.45, 95% CI 0.27 to 0.75; three studies; 4770 participants; GRADE: very low). No data were available for the ezetimibe only comparison. Compared with placebo, PCSK9 probably had little or no effect on mortality (RD 0.03%, OR 1.02, 95% CI 0.91 to 1.14; 12 studies; 60,684 participants; GRADE: moderate). Compared with placebo, PCSK9 inhibitors increased the risk of any adverse events (RD 1.54%, OR 1.08, 95% CI 1.04 to 1.12; 13 studies; 54,204 participants; GRADE: low). Similar effects were observed for the comparison of ezetimibe and statins: RD 3.70%, OR 1.18, 95% CI 1.05 to 1.34; four studies; 5376 participants; GRADE: low. Clinical event data were unavailable for the ezetimibe only comparison.

AUTHORS' CONCLUSIONS

Over short-term to medium-term follow-up, PCSK9 inhibitors reduced LDL-C. Studies with medium-term follow-up time (longest median follow-up recorded was 26 months) reported that PCSK9 inhibitors (compared with placebo) decreased CVD risk but may have increased the risk of any adverse events (driven by SPIRE-1 and -2 trials). Available evidence suggests that PCSK9 inhibitor use probably leads to little or no difference in mortality. Evidence on relative efficacy and safety when PCSK9 inhibitors were compared with active treatments was of low to very low quality (GRADE); follow-up times were short and events were few. Large trials with longer follow-up are needed to evaluate PCSK9 inhibitors versus active treatments as well as placebo. Owing to the predominant inclusion of high-risk patients in these studies, applicability of results to primary prevention is limited. Finally, estimated risk differences indicate that PCSK9 inhibitors only modestly change absolute risks (often to less than 1%).

Physiological and therapeutic regulation of PCSK9 activity in cardiovascular disease

Ischemic heart disease is the main cause of death worldwide and is accelerated by increased levels of low-density lipoprotein cholesterol (LDL-C). Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a potent circulating regulator of LDL-C through its ability to induce degradation of the LDL receptor (LDLR) in the lysosome of hepatocytes. Only in the last few years, a number of breakthroughs in the understanding of PCSK9 biology have been reported illustrating how PCSK9 activity is tightly regulated at several levels by factors influencing its transcription, secretion, or by extracellular inactivation and clearance. Two humanized antibodies directed against the LDLR-binding site in PCSK9 received approval by the European and US authorities and additional PCSK9 directed therapeutics are climbing up the phases of clinical trials. The first outcome data of the PCSK9 inhibitor evolocumab reported a significant reduction in the composite endpoint (cardiovascular death, myocardial infarction, or stroke) and further outcome data are awaited. Meanwhile, it became evident that PCSK9 has (patho)physiological roles in several cardiovascular cells. In this review, we summarize and discuss the recent biological and clinical data on PCSK9, the regulation of PCSK9, its extra-hepatic activities focusing on cardiovascular cells, molecular concepts to target PCSK9, and finally briefly summarize the data of recent clinical studies.

Lipid-Reduction Variability and Antidrug-Antibody Formation with Bococizumab

BACKGROUND

Bococizumab, a humanized monoclonal antibody targeting proprotein convertase subtilisin-kexin type 9 (PCSK9), reduces levels of low-density lipoprotein (LDL) cholesterol. However, the variability and durability of this effect are uncertain.

METHODS

We conducted six parallel, multinational lipid-lowering trials enrolling 4300 patients with hyperlipidemia who were randomly assigned to receive 150 mg of bococizumab or placebo subcutaneously every 2 weeks and who were followed for up to 12 months; 96% were receiving statin therapy at the time of enrollment. The patients were assessed for lipid changes over time, stratified according to the presence or absence of antidrug antibodies detected during the treatment period.

RESULTS

At 12 weeks, patients who received bococizumab had a reduction of 54.2% in the LDL cholesterol level from baseline, as compared with an increase of 1.0% among those who received placebo (absolute between-group difference, -55.2 percentage points). Significant between-group differences were also observed in total cholesterol, non-high-density lipoprotein cholesterol, apolipoprotein B, and lipoprotein(a) (P<0.001 for all comparisons). However, high-titer antidrug antibodies developed in a substantial proportion of the patients who received bococizumab, which markedly diminished the magnitude and durability of the reduction in LDL cholesterol levels. In addition, among patients with no antidrug antibodies, there was wide variability in the reduction in LDL cholesterol levels at both 12 weeks and 52 weeks. Major cardiovascular events occurred in 57 patients (2.5%) who received bococizumab and in 55 (2.7%) who received placebo (hazard ratio, 0.96; 95% confidence interval, 0.66 to 1.39; P=0.83). The most common adverse event among patients who received bococizumab was injection-site reaction (12.7 per 100 person-years).

CONCLUSIONS

In six multinational trials evaluating bococizumab, antidrug antibodies developed in a large proportion of the patients and significantly attenuated the lowering of LDL cholesterol levels. Wide variation in the relative reduction in cholesterol levels was also observed among patients in whom antidrug antibodies did not develop. (Funded by Pfizer; SPIRE ClinicalTrials.gov numbers, NCT01968954 , NCT01968967 , NCT01968980 , NCT02100514 , NCT02135029 , and NCT02458287 .).