Application of PCSK9 Inhibitors in Practice

Effect of PCSK9 inhibition on plasma levels of small dense low density lipoprotein-cholesterol and 7-ketocholesterol

BACKGROUND

Oxidized forms of cholesterol (oxysterols) are implicated in atherogenesis and can accumulate in the body via direct absorption from food or through oxidative reactions of endogenous cholesterol, inducing the formation of LDL particles loaded with oxidized cholesterol. It remains unknown whether drastic reductions in LDL-cholesterol (LDL-C) are associated with changes in circulating oxysterols and whether small dense LDL (sdLDL) are more likely to carry these oxysterols and susceptible to the effects of PCSK9 inhibition (PCSK9i).

OBJECTIVE

We investigate the effect of LDL-C reduction accomplished via PCSK9i on changes in plasma levels of sdLDL-cholesterol (sdLDL-C) and a common, stable oxysterol, 7-ketocholesterol (7-KC), among 134 patients referred to our Preventive Cardiology clinic.

METHODS

Plasma lipid panel, sdLDL-C, and 7-KC measurements were obtained from patients before and after initiation of PCSK9i.

RESULTS

The intervention caused a significant lowering of LDL-C (-55.4 %). The changes in sdLDL-C levels (mean reduction 51.4 %) were highly correlated with the reductions in LDL-C levels (R = 0.829, p < 0.001). Interestingly, whereas changes in plasma free 7-KC levels with PCSK9i treatment were much smaller than (-6.6 %) and did not parallel those of LDL-C and sdLDL-C levels, they did significantly correlate with changes in triglycerides and very low-density lipoprotein-cholesterol (VLDL-C) levels (R = 0.219, p = 0.025).

CONCLUSION

Our findings suggest a non-preferential clearance of LDL subparticles as a consequence of LDL receptor upregulation caused by PCSK9 inhibition. Moreover, the lack of significant reduction in 7-KC with PCSK9i suggests that 7-KC may be in part carried by VLDL and lost during lipoprotein processing leading to LDL formation.

The Questions on Everyone's Mind: What is and Why Do We Need Preventive Cardiology?

Despite being largely preventable, atherosclerotic cardiovascular disease (ASCVD) continues to be the leading source of morbidity and mortality worldwide. While the past few decades have seen a substantial reduction in ASCVD mortality, much of this is due to significant improvements in treatment of already manifest disease, with its attendant morbidity and impact on quality of life. Moreover, evidence now suggests that ASCVD mortality in the United States has hit a nadir and is likely to start increasing again. It is now time to shift our attention from intervention to prevention. In this review, we explore the tremendous opportunity to define and implement the discipline of preventive cardiology.

Factors associated with time to initiation of a PCSK9 inhibitor after hospital discharge for acute myocardial infarction

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) lower atherosclerotic cardiovascular disease (ASCVD) event risk.

OBJECTIVE

Analyze patient characteristics associated with time to PCSK9i initiation following an acute myocardial infarction (AMI).

METHODS

We analyzed characteristics of patients ≥21 years of age in the Marketscan or Medicare databases who initiated a PCSK9i 0-89 days, 90-179 days, or 180-365 days after an AMI between July 2015 and December 2018 (n=1,705). We estimated the cumulative incidence of recurrent ASCVD events before PCSK9i initiation.

RESULTS

Overall, 42%, 25%, and 33% of patients who initiated a PCSK9i did so 0-89 days, 90-179 days, and 180-365 days following AMI hospital discharge, respectively. Taking ezetimibe prior to AMI hospitalization and initiating ezetimibe within 30 days after AMI hospital discharge were each associated with a higher likelihood of PCSK9i initiation in the 0-89 days versus 180-365 days post-discharge (adjusted odds ratio [OR] 1.83, 95% confidence interval [95%CI] 1.35-2.49 and 1.76, 95%CI 1.11-2.80, respectively). Statin use before and statin initiation within 30 days after AMI hospitalization were associated with a lower likelihood of PCSK9i initiation 0-89 days versus 180-365 days post-discharge (adjusted OR 0.64, 95%CI 0.49-0.84 and 0.39, 95%CI 0.28-0.54, respectively). Overall, 8.0%, 10.5%, and 12.5% of patients had an ASCVD event at 90, 180, and 365 days following AMI hospital discharge and before initiating a PCSK9i, respectively.

CONCLUSION

Among patients initiating a PCSK9i after AMI, a low proportion did so within 89 days of hospital discharge. Many patients had a recurrent ASCVD event before treatment initiation.

Hepatic Sensing Loop Regulates PCSK9 Secretion in Response to Inhibitory Antibodies

BACKGROUND

Monoclonal antibodies against proprotein convertase subtilisin/kexin type 9 (PCSK9i) lower LDL-C by up to 60% and increase plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels by 10-fold.

OBJECTIVES

The authors studied the reasons behind the robust increase in plasma PCSK9 levels by testing the hypothesis that mechanisms beyond clearance via the low-density lipoprotein receptor (LDLR) contribute to the regulation of cholesterol homeostasis.

METHODS

In clinical cohorts, animal models, and cell-based studies, we measured kinetic changes in PCSK9 production and clearance in response to PCSK9i.

RESULTS

In a patient cohort receiving PCSK9i therapy, plasma PCSK9 levels rose 11-fold during the first 3 months and then plateaued for 15 months. In a cohort of healthy volunteers, a single injection of PCSK9i increased plasma PCSK9 levels within 12 hours; the rise continued for 9 days until it plateaued at 10-fold above baseline. We recapitulated the rapid rise in PCSK9 levels in a mouse model, but only in the presence of LDLR. In vivo turnover and in vitro pulse-chase studies identified 2 mechanisms contributing to the rapid increase in plasma PCSK9 levels in response to PCSK9i: 1) the expected delayed clearance of the antibody-bound PCSK9; and 2) the unexpected post-translational increase in PCSK9 secretion.

CONCLUSIONS

PCSK9 re-entry to the liver via LDLR triggers a sensing loop regulating PCSK9 secretion. PCSK9i therapy enhances the secretion of PCSK9, an effect that contributes to the increased plasma PCSK9 levels in treated subjects.

Optimizing sodium-glucose co-transporter 2 inhibitor use in patients with heart failure with reduced ejection fraction: A collaborative clinical practice statement

Heart failure with reduced ejection fraction (HFrEF) is a debilitating disease that is associated with substantial morbidity, mortality, and societal costs. The past three decades have brought about significant advancements in the pharmacologic management of HFrEF, and a corresponding reduction in morbidity and mortality. However, the progress to improve clinical outcomes in real-world settings has stalled in recent years, largely due to underutilization of guideline directed medical therapies (GDMT). The discovery of significant cardio-renal protection from sodium-glucose co-transporter 2 inhibitors (SGLT2i) has ushered in a new treatment paradigm for HFrEF management with SGLT2i therapy becoming an essential component of GDMT. Our Preventive Cardiology and Heart Failure services have established an innovative, multi-disciplinary, collaborative protocol to optimize management of cardiovascular risk factors and facilitation SGLT2i use in patients with HFrEF. The goal of this collaboration is to enhance utilization and safety of SGLT2i for HFrEF management by circumventing medication access issues, the major obstacle to therapy initiation. Within this protocol, our heart failure providers identify patients for the addition of SGLT2i to a background of heart failure GDMT. The patient is then referred to preventive cardiology where the team performs a comprehensive cardiovascular risk assessment, optimizes cardiovascular risk factors, and initiates SGLT2i with an emphasis on medication access, cost minimization, and mitigation of potential side effects. The heart failure team assumes responsibility for modification of heart failure-based therapies, and the preventive team manages diabetes, lipid, and metabolic-based therapies. The patient is followed by both cardiology services in a structured fashion, comparing outcome measures at regular intervals and utilizing our patient registry and bio-repository. This clinical practice statement provides a detailed evidentiary review on the cardiovascular and renal benefits of SGLT2i, outlines the rational for creation of a collaborative protocol, details a structured program that may serve as a template for enhanced heart failure management in other health systems, and addresses challenges encountered and recommendations for use.

Inclisiran: A Novel Agent for Lowering Apolipoprotein B-Containing Lipoproteins

ABSTRACT

Hypercholesterolemia is a leading cause of cardiovascular morbidity and mortality. Accordingly, efforts to lower apolipoprotein B-containing lipoproteins in plasma are the centerpiece of strategies for cardiovascular prevention and treatment in primary and secondary management. Despite the importance of this endeavor, many patients do not achieve appropriate low density lipoprotein cholesterol (LDL-C) and non-high density lipoprotein cholesterol (non-HDL-C) goals, even among those who have experienced atherosclerotic cardiovascular disease (ASCVD). The development of new LDL-C-lowering medications with alternative mechanisms of action will facilitate improved goal achievement in high risk patients. Inclisiran is a novel small interfering ribonucleic acid (siRNA)-based drug that is experimental in the US and approved for clinical use in the EU. It lowers LDL-C and other apolipoprotein B-containing lipoproteins by reducing production of Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9), a protein that normally contributes to LDL-receptor (LDLR) degradation, thereby increasing LDLR density and recycling in hepatocytes. Although the lipid-lowering efficacy of inclisiran is comparable to results achieved with PCSK9-blocking monoclonal antibodies (PCSK9i) (alirocumab and evolocumab), there are several important differences between the two drug classes. First, inclisiran reduces levels of PCSK9 both intracellularly and extracellularly by blocking translation of and degrading PCSK9 messenger RNA. Second, the long biological half-life of inclisiran produces sustained LDL-C-lowering with twice yearly dosing. Third, although PCSK9i drugs are proven to reduce ASCVD events, clinical outcomes trials with inclisiran are still in progress. In this manuscript, we review the clinical development of inclisiran, its mechanism of action, lipid-lowering efficacy, safety and tolerability, and potential clinical role of this promising new agent.

Low-density lipoprotein cholesterol lowering in real-world patients treated with evolocumab

Background

Low‐density lipoprotein cholesterol (LDL‐C) is a risk factor for atherosclerotic cardiovascular disease (ASCVD). There are limited real‐world data on LDL‐C lowering with evolocumab in United States clinical practice.

Hypothesis

We assessed LDL‐C lowering during 1 year of evolocumab therapy.

Methods

This retrospective cohort study used linked laboratory (Prognos) and medical claims (IQVIA Dx/LRx and PharMetrics Plus^®) data. Patients with a first fill for evolocumab between 7/1/2015 and 10/31/2019 (index event) and LDL‐C ≥ 70 mg/dL were included (overall cohort; N = 5897). Additionally, a patient subgroup with a recent myocardial infarction (MI) within 12 months (median 130 days) before the first evolocumab fill was identified (N = 152). Reduction from baseline LDL‐C was calculated based on the lowest LDL‐C value recorded during a 12‐month follow‐up period.

Results

The mean (SD) age was 65 (10) years; 61.9% of patients had ASCVD diagnoses and 70.7% of patients were in receipt of lipid‐lowering therapy. Following evolocumab treatment, changes in LDL‐C from baseline were −60% in the overall cohort (median [interquartile range (IQR)] 146 [115–180] mg/dL to 58 [36–84] mg/dL) and −65% in the recent MI subgroup (median [IQR] 137 [109–165] mg/dL to 48 [30–78] mg/dL). In the overall cohort and recent MI subgroup, 62.1% and 69.7% of patients achieved LDL‐C < 70 mg/dL, respectively.

Conclusions

In this real‐world analysis, evolocumab was associated with significant reductions in LDL‐C comparable to that seen in the FOURIER clinical trial, which were durable over 1 year of treatment.

Advances in biological therapies for dyslipidemias and atherosclerosis

Atherosclerosis is a multifactorial disease influenced by genetics, lifestyle and environmental factors. Despite therapeutic advances that reduce the risk of cardiovascular events, atherosclerosis-related diseases remain the leading cause of mortality worldwide. Precise targeting of genes involved in lipoprotein metabolism is an emerging approach for atherosclerosis prevention and treatment. This article focuses on the latest developments, clinical potential and current challenges of monoclonal antibodies, vaccines and genome/transcriptome modification strategies, including antisense oligonucleotides, genome/base editing and gene therapy. Multiple lipid lowering biological therapies have already been approved by the FDA with impressive results to date, while many more promising targets are being pursued in clinical trials or pre-clinical animal models.

Real-world utilization of pharmacotherapy with new evidence-based cardiovascular indications in an academic preventive cardiology practice

Objective

To determine the real-world use of pharmacotherapy with new evidence-based cardiovascular indications in an academic Preventive Cardiology Clinic.

Methods

A retrospective study of patients seen in our Center for Preventive Cardiology (CPC) and who received a new prescription, according to Food and Drug Administration (FDA) approved indications, for one of the following pharmacotherapies with new evidence-based cardiovascular indications from May 2019 to May 2020: proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i), eicosapentaenoic acid (EPA), sodium-glucose cotransporter 2 inhibitors (SGLT2i), and glucagon-like peptide-1 receptor agonists (GLP-1 RA). Treatment endpoints were prescription patterns, medication access, patient out-of-pocket expenses, medication tolerability, and clinical cardiovascular events while on these therapies.

Results

Of the 2390 patients seen in our CPC clinic over the observation period, 532 (22.3%) had already started and 291 (12.2%) were newly initiated on pharmacotherapy with new evidence-based cardiovascular indications with a median treatment duration of 9.1 months. Of these, 291 patients (for a total of 320 separate drug orders) – 93 (29.1%) were prescribed PCSK9i, 131 (40.9%) EPA, 46 (14.4%) SGLT2i, and 50 (15.6%) GLP-1 RA. Nearly 80% of cases required some form of provider intervention post-prescription (authorization, appeal, financial assistance, and/or side effect management). A total of 70% of adult patients with type 2 diabetes on metformin and with an HgbA1C >7% were treated with a SGLT2i and/or GLP-1 RA – either initiated prior to or during the study period. Median monthly drug cost for the total cohort was reduced from $595.00 pre-insurance approval to $70.50 post-insurance approval, to $7.00 post-financial assistance intervention. The medications were well tolerated with any side effect occurring in 28.3%, and discontinuation due to side effects in 5.8% of cases. Clinical cardiovascular events occurred in 2.7%, of which 1.9% was due to ASCVD and 0.8% to hospitalization for heart failure. Differences in medication access, cost, tolerability and clinical cardiovascular events varied widely between the medication classes.

Conclusions

Initiation and management of pharmacotherapy with new evidence-based cardiovascular indications in a real-world setting requires substantial provider intervention, a workflow amenable to a multi-disciplinary approach which allows for high rates of medication access and cost minimization, and low rates of medication side effects and clinical cardiovascular events.

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Over 12 months, PCSK9i, EPA, SGLT2i, and GLP-1 RA where prescribed in 291 patients.

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Nearly 80% of cases required some form of provider intervention post-prescription.

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Multi-disciplinary efforts reduced median monthly patient cost from $595 to $7.

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Cost was the leading factor for medication non-adherence.

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Drugs with new CV indications were well tolerated with low rates of CV events.

Evolving trend in the management of heterozygous familial hypercholesterolemia in Italy: A retrospective, single center, observational study

BACKGROUND AND AIMS

The effective reduction of LDL-C in patients with heterozygous familial hypercholesterolemia (HeFH) is crucial to reduce their increased cardiovascular risk. Diagnostic and therapeutic (PCSK9 inhibitors) tools to manage HeFH improved in recent years. However, the impact of these progresses in ameliorating the contemporary real-world care of these patients remains to be determined. Aim of this study was to assess the evolution of treatments and LDL-C control in a cohort of HeFH patients in Italy.

METHODS AND RESULTS

Four hundred six clinically diagnosed HeFH followed in a single, tertiary lipid centre were included in this survey. Data on lipid levels and medications were collected at baseline and during a median 3-year follow-up. At baseline, 19.8% of patients were receiving conventional high-potency lipid lowering therapies (LLT) and this percentage increased up to 50.8% at last visit. The knowledge of results of molecular diagnosis was associated with a significant increase in treatment intensity and LDL-C lowering. Nevertheless, the new LDL-C target (<70 mg/dl) was achieved only in 3.6% of HeFH patients under conventional LLTs and this proportion remained low (2.9%) also in those exposed to maximal conventional LLT. In 51 patients prescribed with PCSK9 inhibitors, 64.6% and 62.1% reached LDL-C<70 mg/dl at 3- and 12-month follow-up, respectively.

CONCLUSIONS

Although treatments of HeFH improved over time, LDL-C target achievement with conventional LLT remains poor, mainly among women. The use of molecular diagnosis and even more the prescription of PCSK9i may improve LDL-C control in these patients.

Preventive cardiology as a dedicated clinical service: The past, the present, and the (Magnificent) future

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Ischemic cardiovascular disease continues to be most common cause of death after age 55 everywhere in the world.

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As the average person is exposed over life to a variety of artery-damaging insults it is easy to predict that this trend will continue for decades.

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We face an unprecedented opportunity to consolidate, strengthen, and broaden the effort to prevent cardiovascular events, both ischemic and non ischemic.

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This effort requires professional lifestyle counseling, dietary interventions, use of natural supplements, pharmacotherapy, and efficient cross-referral strategies.

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The nascent subspecialty of preventive cardiology must reach uniformity in protocols of care, and must develop a system of training and certification for the next generation of expert providers.

Unusual responses to PCSK9 inhibitors in a clinical cohort utilizing a structured follow-up protocol

Objective

To characterize unusual responses to PCSK9 inhibitor (PCSK9i) therapy in a real-world setting, given their extremely low prevalence in clinical trials.

Methods

A retrospective study of patients seen in a structured academic PCSK9i clinic who had LDL-C measurements before and after initiation of PCSK9i (up to 12 months). Unusual response was defined as: (1) no response: no changes in LDL-C level at all time points; (2) delayed response: <30% LDL-C reduction by the third dose, but achieving this threshold at a later time; (3) reduced response: <30% LDL-C reduction at all time points; and (4) lost response: ≥30% LDL-C reduction by the third dose, but displaying <30% reduction at a later time.

Results

Of the 411 patients meeting inclusion criteria, 54 were initially classified as unusual responders. After excluding those not adherent to prescribed interventions, 31 patients (7.5%) were classified as true unusual responders. These included: 2 with no response, 12 with delayed response, 3 with reduced response, 6 with delayed or reduced response, 4 with lost response, and 4 with delayed and lost response. Response to PCSK9i therapy at all time points revealed higher on-treatment LDL-C values (94–100 vs. 47–51 ​mg/dL, p ​< ​0.001) and lower degree of percent reduction in LDL-C (23.3–34% vs. 61.1–64.5%, p ​< ​0.001) in the unusual versus usual responders. Lipoprotein (a) (Lp[a]) values were consistently higher in the unusual responders (81–92.5 vs. 28.5–52 ​mg/dL, p ​< ​0.01). Fold change in post-versus pre-treatment PCSK9 plasma results was similar between the two cohorts (p ​> ​0.05), suggesting that unusual responses were not due to insufficient plasma PCSK9 blockade. Multiple logistic regression analysis identified clinical FH (OR 2.9, 95% CI 1.27-7.24) and no ezetimibe therapy (OR 0.334, 95% CI 0.150-0.728) as factors related to true unusual response.

Conclusions

Unusual responses to PCSK9i in a clinical cohort are more common than reported in clinical trials. Of the suspected unusual responders, nearly half were the result of adherence issues, and thus careful medication reconciliation should be the first step in diagnosing an unusual response.

Application of PCSK9 Inhibitors in Practice

PCSK9i (protein convertase subtilisin/kexin type 9 inhibitors) are set to revolutionize the treatment of hypercholesterolemia in the management of atherosclerotic risk, but numerous reports have detailed unprecedented barriers to access for these drugs. To overcome these challenges, our group created a model to facilitate provision of this new therapy for patients who qualify according to Food and Drug Administration criteria. This report details the real-world follow-up experience of PCSK9i use in a large patient cohort structured to ensure rigor in data collection, analysis, and interpretation. The 271 patients approved and actively followed in our PCSK9i clinic between July 2015 and August 2018 represent a 97% approval rate from insurance, with 28% of prescriptions requiring at least one appeal. Over 50% of patients were statin intolerant. On average, there was a median lapse of 15 days between initial visit and insurance approval. PCSK9i therapy was affordable for most patients, with an average monthly out-of-pocket expense of $58.05 (median $0). Only 2.3% of patients were unable to initiate or continue therapy because of cost. Reductions from baseline in LDL (low-density lipoprotein) cholesterol and Lp(a) (lipoprotein [a])were comparable to published reports with median reductions of 60% and 23% at 1 year, respectively. PCSK9i therapy was well-tolerated overall, though 9% of patients reported adverse events, and 5% of patients discontinued due mostly to musculoskeletal and flu-like symptoms. Our practice model demonstrates that PCSK9i therapy can be accessed easily and affordably for the majority of eligible patients, resulting in dramatic improvement in lipid profile results. Moreover, our registry data suggest that results from the prospective clinical trials of PCSK9i on LDL and Lp(a) reduction and on tolerability are applicable to a real-world cohort.

The Role of the Clinical Pharmacist in a Preventive Cardiology Practice

Background: Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality worldwide. In response, a multidisciplinary team approach, which includes clinical pharmacists, is recommended to improve patient outcomes. The purpose of the study was to describe interventions associated with integration of a clinical pharmacist, with an emphasis on pharmacist-generated patient cost avoidance. Methods: This is a prospective observational study detailing pharmacist-initiated interventions within an academic preventive cardiology service. Interventions targeting pharmacotherapy optimization, side effect management, patient education, medication adherence, and cost avoidance were implemented during shared office visits with providers and/or on provider consultation for remote follow-up. Tabulation of cost avoidance was arranged into 2 formats: clinical interventions implemented by the pharmacist and direct patient out-of-pocket expense reduction. Money saved per clinical intervention was extrapolated from data previously published. Patient out-of-pocket expense prior to and after pharmacist involvement was calculated to assess aggregate yearly patient cost savings. Results: Over 12 months the pharmacist intervened on 974 patients, totaling 3725 interventions. Cost avoidance strategies resulted in yearly savings of $830 748 in aggregate—$149 566 from clinical interventions and $681 182 from patient out-of-pocket expense reduction. Monthly patient out-of-pocket expense was reduced from a median (interquartile range) of $217 ($83.5-$347) before to $5 ($0-$18) after pharmacist intervention. Conclusions: Addition of a clinical pharmacist within an academic preventive cardiology clinic generated substantial pharmacotherapy interventions, resulting in significant cost avoidance for patients. The resulting cost avoidance may result in improved medication adherence and clinical outcomes.

Future role of proprotein convertase subtilisin/kexin type 9 inhibitors in preventive cardiology

PURPOSE OF REVIEW

The use of therapeutic monoclonal antibodies to target proprotein convertase subtilisin/kexin type 9 (PCSK9) represents a novel approach to the management of hypercholesteremia and prevention of atherosclerotic cardiovascular disease. We review the most recent literature relevant to PCSK9 inhibition with emphasis on how recent results and ongoing trials have and will continue to shape the use of this new therapeutic class in preventive cardiology.

RECENT FINDINGS

PCSK9 inhibitors reduce plasma lipoprotein(a) concentrations but a mechanistic understanding remains elusive. Evaluation of evolocumab for use in patients without prior myocardial infarction or stroke is underway (NCT03872401). Concerns regarding the cost-effectiveness of PCSK9 inhibitors have continued to thwart access to these drugs, though innovative models of care delivery and price reductions have improved this situation. Inclisiran, a small interfering ribonucleic acid (siRNA), reduces translation of PCSK9 and demonstrates more durable reductions in low-density lipoprotein-cholesterol (LDL-C). It is currently evaluated in the context of a phase III cardiovascular outcome trial in patients with established vascular disease (NCT03705234).

SUMMARY

The current scope of PCSK9 inhibitor therapy in preventive cardiology is limited to patients with familial hypercholesterolemia and/or established atherosclerotic cardiovascular disease. Future cardiovascular outcome trial results with PCSK9 blocking antibodies in primary prevention and with siRNA to PCSK9 in secondary prevention, improved understanding of the drivers of lipoprotein(a) reduction with PCSK9 inhibition, and cost-effectiveness will determine the future role of this therapeutic class.

The PCSK9 revolution: Current status, controversies, and future directions

Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) has revolutionized our understanding of cholesterol homeostasis and added to our arsenal against atherosclerotic cardiovascular disease (ASCVD). In a span of approximately 15 years, PCSK9 has morphed from an esoteric and rare cause of familial hypercholesterolemia (FH) into the most efficient cholesterol-lowering target ever known, with the completion of two large scale cardiovascular outcome trials showing positive results. Current Food and Drug Administration (FDA) approved modalities to inhibit PCSK9 are in the form of monoclonal antibodies which display an unparalleled degree of low-density lipoprotein cholesterol (LDL-C) lowering and expand upon the notion that lower LDL-C is better for ASCVD risk reduction. However, the accelerated pace of discovery and therapeutic development has left large gaps in our knowledge regarding the physiology and function of PCSK9. The aim of this review is to provide context to the discovery, history, treatment and current status of PCSK9 and its therapeutic inhibitors and highlight areas of controversy and future directions.

PCSK9: From Basic Science Discoveries to Clinical Trials

Unknown 15 years ago, PCSK9 (proprotein convertase subtilisin/kexin type 9) is now common parlance among scientists and clinicians interested in prevention and treatment of atherosclerotic cardiovascular disease. What makes this story so special is not its recent discovery nor the fact that it uncovered previously unknown biology but rather that these important scientific insights have been translated into an effective medical therapy in record time. Indeed, the translation of this discovery to novel therapeutic serves as one of the best examples of how genetic insights can be leveraged into intelligent target drug discovery. The PCSK9 saga is unfolding quickly but is far from complete. Here, we review major scientific understandings as they relate to the role of PCSK9 in lipoprotein metabolism and atherosclerotic cardiovascular disease and the impact that therapies designed to inhibit its action are having in the clinical setting.

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.