A randomized study of the relative pharmacokinetics, pharmacodynamics, and safety of alirocumab, a fully human monoclonal antibody to PCSK9, after single subcutaneous administration at three different injection sites in healthy subjects

Role of PCSK9 inhibitors in the management of dyslipidaemia

Proprotein convertase subtilisin kexin9 (PCSK9) inhibitors are novel agents that lower LDL cholesterol and reduce cardio-vascular event rate. Being expensive, these agents are reserved for those with high risk or very high risk of CV events and with suboptimal response to statins and ezetimibe, with or without bempedoic acid or those intolerant to statins.

Genetics, Safety, Cost-Effectiveness, and Accessibility of Injectable Lipid-Lowering Agents: A Narrative Review

Cardiovascular disease causes significant personal, financial, and societal burden and is a major cause of mortality and morbidity globally. Dyslipidemia has proven to be a major factor that contributes to its increased incidence; thus, since a long time, low-density lipoprotein cholesterol-lowering therapies have been employed to reduce coronary artery disease-associated mortality. The first-line therapy for hyperlipidemia and dyslipidemia is statins. Evidence showed that statins decrease the level of LDL-C resulting in a lower risk of CVD (20-25% for every decrease of 1 mmol/L). However, due to statin intolerance in some patients and despite using maximal doses, they have not been successful in lowering cardiovascular-associated mortality. Moreover, bococizumab was recently suspended due to its higher immunogenicity with time, resulting in less efficacy with long-term use. Alternatives to statins are PCSK9 inhibitors which are administered subcutaneously every two or four weeks. They are injectables with considerable lipid-lowering properties. This narrative review discusses their genetics, safety, tolerability, and cost-effectiveness. It also quantifies their benefit in certain subgroups by analyzing the findings from recent randomized clinical trials. Current data from phase 2 and 3 trials (ORION, ODYSSEY, and FOURIER) suggest a favorable profile for evolocumab, alirocumab, and inclisiran with minimal tolerable side effects and superior efficacy in statin-intolerant patients. Their cost-effectiveness has not yet been established clearly, but future outcomes seem promising.

Pharmacological rationale for the very early treatment of acute coronary syndrome with monoclonal antibodies anti-PCSK9

Immediate and aggressive lipid lowering therapies after acute coronary syndromes (ACS) and percutaneous coronary interventions (PCI) are supported by the ESC/EAS dyslipidemia guidelines, recommending the initiation of high-intensity statin therapy within the first 1-4 days of hospitalization. However, whether non statin lipid-lowering agents, added to statin treatment, could produce a further reduction in the risk of major adverse cardiovascular events (MACE) is still unknown. Thus, the efficacy of early treatment post-ACS with monoclonal antibodies (mAbs) anti PCSK9, evolocumab and alirocumab, is under investigation. The rationale to explore the rapid and aggressive pharmacological intervention with PCSK9 mAbs is supported by at least five confirmatory data in ACS: 1) circulating PCSK9 levels are raised during ACS 2) PCSK9 may stimulate platelet reactivity, this last being pivotal in the recurrence of ischemic events; 3) PCSK9 is associated with intraplaque inflammation, macrophage activation and endothelial dysfunction; 4) PCSK9 concentrations are associated with inflammation in the acute phase of ACS; and 5) statins raise PCSK9 levels promptly and, at times, dramatically. In this scenario, appropriate pharmacodynamic characteristics of anti PCSK9 therapies are a prerequisite for an effective response. Monoclonal antibodies act on circulating PCSK9 with a direct and rapid binding by blocking the interaction with the low-density lipoprotein receptor (LDLR). Evolocumab and alirocumab show a very rapid (within 4 h) and effective suppression of circulating unbound PCSK9 (- 95 % ÷ - 97 %). This inhibition results in a significant reduction of LDL-cholesterol (LDL-C) after 48 h (- 35 %) post injection with a full effect after 7-10 days (55-75 %). The complete and swift inhibitory action by evolocumab and alirocumab could have a potential clinical impact in ACS patients, also considering their potential inhibition of PCSK9 within the atherosclerotic plaque. Thus, administration of evolocumab or alirocumab is effective in lowering LDL-C levels in ACS, although the efficacy to prevent further cardiovascular (CV) events is still undetermined. The answer to this question will be provided by the ongoing clinical trials with evolocumab and alirocumab in ACS. In the present review we will discuss the pharmacological and biological rationale supporting the potential use of PCSK9 mAbs in ACS patients and the emerging evidence of evolocumab and alirocumab treatment in this clinical setting.

Combined Semi-mechanistic Target-Mediated Drug Disposition and Pharmacokinetic-Pharmacodynamic Models of Alirocumab, PCSK9, and Low-Density Lipoprotein Cholesterol in a Pooled Analysis of Randomized Phase I/II/III Studies

BACKGROUND AND OBJECTIVES

Alirocumab is a cholesterol-lowering monoclonal antibody targeting proprotein convertase subtilisin kexin type 9 (PCSK9) indicated in the prevention of cardiovascular risk and exhibiting target-mediated drug disposition (TMDD). The aim of this work was to develop an integrated pharmacokinetic-pharmacodynamic model to describe the interaction of alirocumab with PCSK9 and its impact on the evolution of low-density lipoprotein cholesterol (LDL-C) levels and explore labeling specification for subpopulations.

METHODS

Using data collected from nine phase I/II/III clinical studies (n = 527, subcutaneous or intravenous administration), a TMDD model considering the quasi-steady-state approximation was developed to characterize the interaction dynamics of alirocumab and PCSK9, combined with an indirect pharmacodynamic model describing the inhibition of LDL-C by PCSK9 in a one-step approach using nonlinear-mixed effects modeling. A "full fixed effects modeling" strategy was implemented to quantify parameter-covariate relationships.

RESULTS

The model captures the interaction between alirocumab and its target PCSK9 and how this mechanism drives LDL-C depletion, with an estimation of the associated between-subject variability of model parameters and the quantification of clinically relevant parameter-covariate relationships. Co-administration of statins was found to increase the central volume of distribution of alirocumab by 1.75-fold (5.6 L versus 3.2 L) and allow for a 14% greater maximum lipid-lowering effect (88% versus 74%), highlighting the synergy of action between anti-PCSK9 therapeutic antibodies and statins toward lowering LDL-C plasma levels. Baseline levels of PCSK9 were found to be related to the amplitude of LDL-C variations by increasing the concentration of free PCSK9 necessary to reach half its capacity of inhibition of LDL-C degradation.

CONCLUSION

The maximum effect of alirocumab is achieved when free PCSK9 concentration is close to zero, as seen mostly after 150 mg every 2 weeks (Q2W) or 300 mg every 4 weeks (Q4W), indicating that there would be no additional clinical benefit of increasing the dose higher than these recommended dosing regimens.

The promising novel therapies for familial hypercholesterolemia

Background

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

Methods

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

Results

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

Conclusion

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

Impact of injection sites on clinical pharmacokinetics of subcutaneously administered peptides and proteins

For most approved subcutaneously (SC) administered drug products in the US, the recommended injection sites (i.e., abdomen, thigh, and upper arm) are usually based on experience from phase 3 trials. Relative bioavailability data directly comparing the pharmacokinetics (PK) of different SC injection sites are often not available and the underlying mechanisms that may affect SC absorption have not been systematically investigated. In this study, we surveyed clinical PK data (AUC, C_max, and T_max) for SC administered drug products including therapeutic proteins and peptides based on literature and FDA database. The PK data after abdominal injection was used as a reference to determine the relative bioavailability of SC injections to the arm and thigh. The survey retrieved 19 immunoglobulin G (IgGs), 18 peptides/small proteins (molecular weight < 16 kDa), and 8 non-IgG proteins that had available clinical PK data from multiple SC injection sites. Among these, 5 (26%) IgGs, 9 (50%) peptides/small proteins, and 3 (38%) non-IgG proteins, exhibited injection site-dependent PK (i.e. PK differed by injection sites). Correlation analyses revealed that the PK of peptides/small proteins undergoing rapid SC absorption (T_max ≤ 2 h), elimination (CL/F ≥ 39 L/h) or low plasma protein binding were more sensitive to injection sites. Similarly, non-IgG proteins (molecular weight ≥ 16 kDa) with high CL/F and low T_max are associated with high risk of injection site-dependent SC absorption. IgGs with T_1/2 < 15 days or T_max < 5 days are more likely to show injection site-dependent SC absorption. Positive charge of the drug molecule (isoelectric point ≥8) may reduce SC absorption from all three injection sites but is not associated with high risk of injection site-dependent SC absorption. In summary, the results suggested that regional differences in pre-systemic catabolism and local SC blood flow potentially contribute injection site-dependent SC absorption of peptides/small proteins while local lymphatic flow and FcRn binding likely contribute to site-dependent SC absorption of IgGs.

An update on PCSK9 inhibitors- pharmacokinetics, drug interactions, and toxicity

INTRODUCTION

While atherosclerotic cardiovascular disease is affecting growing numbers of patients, lipid-lowering therapies have been continuously improving to achieve prevention of cardiovascular events. Thus, the appearance of a novel therapeutic class, PCSK9 inhibitors, has raised both high expectations as well as concern over possible adverse effects.

AREAS COVERED

This current review aims to analyze adverse events of special interest linked to PCSK9 inhibitors and give recommendations regarding further conduct when dealing with patients on this therapy. The most stringent adverse effect, neurocognitive impairment has been investigated in several studies, concluding that PCSK9 inhibitors neither improved nor worsened cognitive function. While new onset diabetes mellitus has also been a cause of concern due to its possible association with lipid lowering therapies, studies conducted so far have dispelled this possibility by showing that PCSK9 inhibitors do not increase this risk. Also, statin-associated muscle symptoms have not been proven to arise after the use of PCSK9 inhibitors, even in statin-intolerant patients.

EXPERT OPINION

In conclusion, it can be safely stated that so far, no compelling evidence links PCSK9 inhibitors to these adverse events; however, long-term trials are always welcome to further assess potential adverse effects.

Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Alirocumab in Healthy Chinese Subjects: A Randomized, Double-Blind, Placebo-Controlled, Ascending Single-Dose Study

BACKGROUND

The addition of alirocumab (a fully human monoclonal antibody to proprotein convertase subtilisin/kexin type 9 [PCSK9]) to background statin therapy provides significant incremental low-density lipoprotein cholesterol (LDL-C) lowering and cardiovascular event risk reduction.

OBJECTIVES

Our objectives were to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of single ascending doses of alirocumab in healthy Chinese subjects.

METHODS

In this double-blind, placebo-controlled, phase I study, 35 Chinese subjects (aged 21-45 years) with baseline LDL-C > 100 mg/dL (2.59 mmol/L) were randomized to receive a single 1 mL subcutaneous injection of alirocumab 75, 150, or 300 mg, or placebo, and followed up for ~ 12 weeks.

RESULTS

Treatment-emergent adverse events, most frequently nasal congestion and dry throat, were reported in three of seven or eight subjects in each alirocumab dose group (two of seven in the placebo group). One patient receiving alirocumab 300 mg had a mild local injection-site reaction. No alirocumab recipients demonstrated antidrug antibodies. Maximum alirocumab serum concentrations (6-34 mg/dL) occurred at a median of 3-7 days across the dose groups. Maximum mean LDL-C reductions from baseline were observed on days 8, 15, and 22 with alirocumab 75 (55.3%), 150 (63.7%), and 300 mg (73.7%), respectively. Mean free PCSK9 levels were reduced to below the lower limit of quantification within 4 h of dosing. Total cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B were reduced with alirocumab.

CONCLUSIONS

In Chinese subjects, alirocumab 75, 150, and 300 mg was safe and well-tolerated. Pharmacokinetic/pharmacodynamic parameters, including clinically meaningful reductions in LDL-C and other lipids/lipoproteins, were consistent with data from Japanese and Western populations. Clinicaltrials.gov identifier: NCT02979015.

Dyslipidaemias and Cardiovascular Disease: Focus on the Role of PCSK9 Inhibitors

Genetic, experimental and clinical studies have consistently confirmed that inhibition of Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) can result in significant lowering of LDL-C and two fully human PCSK9 monoclonal antibodies have received regulatory approval for use in highrisk patients. Co-administration of PCSK9 with statins has resulted in extremely low LDL-C levels with excellent short-term safety profiles. While results from Phase III clinical trials provided significant evidence about the role of PCSK9 inhibitors in reducing cardiovascular event rates, their impact on mortality remains less clear. PCSK9 inhibitor therapy can be considered for high-risk patients who are likely to experience significant cardiovascular risk reduction.

Clopidogrel drug interactions: a review of the evidence and clinical implications

INTRODUCTION

Patients with cardiovascular disease are commonly affected by a number of comorbidities leading to a high prevalence of polypharmacy. Polypharmacy increases the probability of drug-drug interactions (DDIs). Amongst these, DDIs involving clopidogrel, the most commonly utilized platelet P2Y₁₂ inhibitor, is a topic of potential clinical concern.

AREAS COVERED

This article reviews DDIs between clopidogrel and drugs which are widely used in clinical practice. In particular, drugs shown to interfere with the pharmacodynamic and pharmacokinetic effects of clopidogrel and the clinical implications of these findings are reviewed. These drugs include inhibitors of gastric acid secretion, statins, calcium channel blockers, antidiabetic agents, and antimicrobial agents. For the references, we searched PubMed, EMBASE, or the Cochrane Library.

EXPERT OPINION

Clopidogrel-drug interactions are common. Most of these DDIs are limited to laboratory findings showing an impact on clopidogrel-induced antiplatelet effects. While variability in clopidogrel-induced antiplatelet effects is known to affect clinical outcomes, with high platelet reactivity being associated with thrombotic complications among patients undergoing coronary stenting, most studies assessing the clinical implications of clopidogrel-drug interactions have not shown to significantly affect outcomes. However, awareness of these DDIs remains important for optimizing the selection of concomitant therapies.

Pharmacokinetics and Pharmacodynamics of Garetosmab (Anti-Activin A): Results From a First-in-Human Phase 1 Study

We describe outcomes from the first‐in‐human study of garetosmab (a fully human monoclonal antibody that inhibits activin A) under development for the treatment of fibrodysplasia ossificans progressiva (FOP). In a double‐blind, placebo‐controlled phase 1 study, 40 healthy women of nonchildbearing potential were randomized to receive a single dose of intravenous garetosmab 0.3, 1, 3, or 10 mg/kg; subcutaneous garetosmab 300 mg; or placebo. Serum concentrations of functional garetosmab (with ≥1 arm free to bind to target), total activin A, and antidrug antibodies were measured predose and up to 113 days post–first dose. Garetosmab demonstrated an acceptable safety profile with no dose‐limiting toxicities. Garetosmab displayed nonlinear pharmacokinetics with target‐mediated elimination. With increasing doses of intravenous garetosmab, mean peak concentration increased in a dose‐proportional manner; mean steady‐state estimates ranged from 41.4 to 47.8 mL/kg. A greater than dose‐proportional increase in mean area under the concentration‐time curve from time zero extrapolated to infinity (range, 72.2‐7520 mg*day/L) was observed, consistent with decreasing mean clearance (range, 4.35‐1.34 mL/day/kg). Following administration of intravenous garetosmab, mean concentrations of total activin A increased in a dose‐dependent manner. At 10 mg/kg, total activin A levels reached a state of little or no change between weeks 4 and 12, suggesting saturation of the target‐mediated pathway. No safety signals were seen in this study to preclude investigation in patients. Following intravenous administration, garetosmab concentrations decreased quickly, then decreased over time (reflecting linear elimination), and finally decreased in a nonlinear phase, reflecting target‐mediated elimination. Results here support further investigation. Garetosmab 10 mg/kg every 4 weeks intravenously is being evaluated in patients with FOP (NCT03188666).

Statins and PCSK9 inhibitors: A new lipid-lowering therapy

The clinical benefit of lipid-lowering therapies is to reduce circulating levels of atherogenic particles and to ameliorate the risk of atherosclerotic cardiovascular disease (ASCVD). The completion of two major clinical trials on PCSK9 inhibitors (PCSK9i), the FOURIER and the ODYSSEY outcome trials, has marked the beginning of a new era of lipid-lowering drugs. PCSK9i, evolocumab and alirocumab, are monoclonal antibodies that inactivate the liver proprotein convertase subtilisin kexin 9 (PCSK9). Inhibition of PCSK9 increases the number of low-density lipoprotein (LDL) receptors available leading to a profound reduction in circulating LDL particles. By preventing LDL receptor destruction, PCSK9i as adjunct to statin therapy can reduce LDL-C by 50-60% above that achieved by statin therapy alone. In addition, PCSK9i in combination with high-dose statins may reduce cardiovascular events and all-cause mortality in patients with clinical ASCVD. Based on evidence from clinical trials, the 2019 European Society of Cardiology (ESC)/European Atherosclerosis Society (EAS) guidelines for the management of dyslipidemias now include the use of PCSK9i to very high-risk ASCVD patients who are not achieving treatment goals on a maximum tolerated dose of a statin and ezetimibe. However, the cost-effectiveness of PCSK9i therapy is limited to secondary prevention in high-risk patients. This review outlines the main clinical trials leading to a change in the guidelines, clinical practice as well as the future challenges of PCSK9i therapy.

Population Pharmacokinetic Analysis of Alirocumab in Healthy Volunteers or Hypercholesterolemic Subjects Using a Michaelis-Menten Approximation of a Target-Mediated Drug Disposition Model-Support for a Biologics License Application Submission: Part I

Background

Alirocumab, a human monoclonal antibody, inhibits proprotein convertase subtilisin/kexin type 9 (PCSK9) to significantly reduce low-density lipoprotein cholesterol levels; pharmacokinetics (PK) are governed by non-linear, target-mediated drug disposition (TMDD).

Objectives

We aimed to develop and qualify a population PK (PopPK) model to characterize the PK profile of alirocumab, evaluate the impact of covariates on alirocumab PK and on individual patient exposures, and estimate individual predicted concentrations for a subsequent PK/pharmacodynamic (PD) analysis.

Methods

Data from 13 phase I–III trials of 2799 healthy volunteers or patients with hypercholesterolemia treated with intravenous or subcutaneous alirocumab (13,717 alirocumab concentrations) were included; a Michaelis–Menten approximation of the TMDD model was used to estimate PK parameters and exposures. The final model comprised two compartments with first-order absorption. Elimination from the central compartment was described by linear (CLL) and non-linear Michaelis–Menten clearance (Vm and Km). The model was validated using visual predictive check and bootstrap methods. Patient exposures to alirocumab were computed using individual PK parameters.

Results

The PopPK model was well-qualified, with the majority of observed alirocumab concentrations in the 2.5th–97.5th predicted percentiles. Covariates responsible for interindividual variability were identified. Body weight and concomitant statin administration impacted CLL, whereas time-varying free PCSK9 concentrations and age affected Km and peripheral distribution volume (V3), respectively. No covariates were clinically meaningful, therefore no dose adjustments were needed.

Conclusions

The model explained the between-subject variability, quantified the impact of covariates, and, finally, predicted alirocumab concentrations (subsequently used in a PopPK/PD model, see Part II) and individual exposures.

Electronic supplementary material

The online version of this article (10.1007/s40262-018-0669-y) contains supplementary material, which is available to authorized users.

PCSK9 Inhibition and Atherosclerosis: Current Therapeutic Option and Prospection

Low-density lipoprotein cholesterol (LDL-C) is a pivotal factor in atherosclerotic cardiovascular disease (ASCVD), the leading cause of worldwide mortality. The limitations of statin therapy require alternative treatment strategies to achieve target LDL-C level. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays an important role in LDLR recycling, consequently regulating plasma cholesterol levels. Monoclonal antibodies targeting PCSK9 increased expression of LDLRs at the cell surface and therefore decreased circulating LDL-C. PCSK9 inhibitors have shown great efficacy in reducing plasma LDL-C levels, which needs to inject once or twice monthly. Though SPIRE sponsors concern the immunogenicity and terminate trials early, FOURIER and ODYSSER OUTCOME trials improved the efficacy of PCSK9 inhibitors in LDL-C reduction. Inclisiran actually is a small interfering RNA (siRNA) developed to inhibit PCSK9 messenger RNA, leading to reduced concentrations of the PCSK9 protein and thereby lower concentrations of LDL-C. Inclisiran is a latest alternative treatment to cholesterol-lowering therapeutics. Twice injections of inclisiran durably reduced LDL-C levels over 1 year. siRNA therapeutics provided a simple, novel, and less frequent approach to LDL-C reduction in phase I and II trials, which may be used either as in combination with statin therapeutics or a stand-alone therapy in the future.

Anti-PCSK9 treatment: is ultra-low low-density lipoprotein cholesterol always good?

Anti-PCSK9 (proprotein convertase subtilisin kexin 9) monoclonal antibodies (Mab) are novel, potent lipid-lowering drugs. They demonstrated to improve the lipid profile in high cardiovascular risk patients. Anti-PCSK9 Mab inhibit the targeted low-density lipoprotein (LDL)-receptor degradation induced by PCSK9 protein and are able to reduce LDL cholesterol (LDL-C) levels on top of conventional lipid-lowering therapy. Though these drugs proved to be very safe in the short-term, little is known about the possible long-term effects, due to the short period of their marketing. The genetic low cholesterol syndromes (LCS) represent the natural models of the lipid-lowering anti-PCSK9 therapy, and a valuable opportunity to predict the long-term effects of these drugs. By looking at the clinical features of such models, we could be able to foresee possible drug-induced side effects. In the present review, the correspondences and discordances between the side effects of anti-PCSK9 therapy and the corresponding LCS models will be examined in the attempt to forecast possible long-term consequences of these novel lipid-lowering agents.

A Review of PCSK9 Inhibitors and their Effects on Cardiovascular Diseases

BACKGROUND

Cardiovascular diseases remain the leading cause of morbidity and mortality in the world, with elevated Low-Density Lipoprotein-Cholesterol (LDL-C) levels as the major risk factor. Lower levels of LDL-C can effectively reduce the risk of cardiovascular diseases. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays an important role in regulating the degradation of hepatic LDL receptors that remove LDL-C from the circulation. PCSK9 inhibitors are a new class of agents that are becoming increasingly important in the treatment to reduce LDL-C levels. Two PCSK9 inhibitors, alirocumab and evolocumab, have been approved to treat hypercholesterolemia and are available in the United States and the European Union. Through the inhibition of PCSK9 and increased recycling of LDL receptors, serum LDL-C levels can be significantly reduced.

OBJECTIVE

This review will describe the chemistry, pharmacokinetics, and pharmacodynamics of PCSK9 inhibitors and their clinical effects.

Comparative quantitative systems pharmacology modeling of anti-PCSK9 therapeutic modalities in hypercholesterolemia

Since the discovery of proprotein convertase subtilisin/kexin type 9 (PCSK9) as an attractive target in the treatment of hypercholesterolemia, multiple anti-PCSK9 therapeutic modalities have been pursued in drug development. The objective of this research is to set the stage for the quantitative benchmarking of two anti-PCSK9 pharmacological modality classes, monoclonal antibodies (mAbs) and small interfering RNA (siRNA). To this end, we developed an integrative mathematical model of lipoprotein homeostasis describing the dynamic interplay between PCSK9, LDL-cholesterol (LDL-C), VLDL-cholesterol, HDL-cholesterol (HDL-C), apoB, lipoprotein a [Lp(a)], and triglycerides (TGs). We demonstrate that LDL-C decreased proportionally to PCSK9 reduction for both mAb and siRNA modalities. At marketed doses, however, treatment with mAbs resulted in an additional ∼20% LDL-C reduction compared with siRNA. We further used the model as an evaluation tool and determined that no quantitative differences were observed in HDL-C, Lp(a), TG, or apoB responses, suggesting that the disruption of PCSK9 synthesis would provide no additional effects on lipoprotein-related biomarkers in the patient segment investigated. Predictive model simulations further indicate that siRNA therapies may reach reductions in LDL-C levels comparable to those achieved with mAbs if the current threshold of 80% PCSK9 inhibition via siRNA could be overcome.

Keep recycling going: New approaches to reduce LDL-C

Hypercholesterolemia represents a leading cause in the development of atherosclerotic plaques, increasing the risk for ACVS. It actually counts as a major cause of cardiovascular disease etiopathogenesis. The causes of hypercholesterolemia are multifactorial, spanning from genetic constitution, age, sex, to sedentary lifestyle and diets rich in sugars and lipids. Although dietary restriction in saturated fats, increased exercise, and other modification in lifestyle represent a first-line approach to treat very initial stages in hypercholesterolemia, most patients will require the addition of pharmacological agents. Pharmacological approaches include inhibition of cholesterol synthesis, decreased fat absorption from the GI tract, and increased degradation of FA. These strategies present a series of side effects, low therapeutic efficiency in some patients, and reduced tolerability. One of the major goals in treatment for hypercholesterolemia is to decrease the levels of low density lipoproteins (LDL), while maintaining those of high density lipoproteins (HDL). LDL particles contain about 80% of lipids, most of it cholesterol and cholesteryl esters, and 20% of the ApoB-100 protein. LDL carries cholesterol to the tissues, to be incorporated to biological membranes, or to be transformed to steroids. Excess of LDL translates into increased levels of circulating cholesterol particles and accumulation in certain tissues, especially vascular tissue, initiating a fatty streak, which may evolve to an atheroma, causing a series of cardiovascular problems, including impaired circulation, high blood pressure, increased cardiac workload, and coronary artery disease. It is essential to prevent LDL accumulation into the bloodstream to avoid the formation of these fatty streaks and the initiation of a cascade that will lead to the development of atherosclerosis. In healthy individuals. Under physiological conditions, LDL is effectively removed from circulation through receptor-mediated endocytosis. LDL clearance involves binding to its receptor, LDLR, which enables the internalization of the LDL particle and drives its degradation in lysosomes. Once the LDL particle is degraded, the free receptor recycles to the plasma membrane, and captures new LDL particles. Adequate levels of LDLR are essential to remove the excess of cholesterol-laden LDL. Proprotein convertase, subtilysin kexin type 9 (PCSK-9), expressed in liver and intestine, binds to LDLR, and internalized. Once inside the cell, PCSK-9 catalyzes the proteolysis of LDLR, preventing its recycling to the cell surface, and effectively decreasing the number of LDLR, notoriously decreasing the ability to clear LDL from circulation. Levels of PCSK-9 varies with age, gender, and levels of insulin, glucose, and triglycerides. Loss-of-function mutations in PCSK-9 gene invariably translates into lower levels of LDL, and decreased risk of developing coronary artery disease. Conversely, increased activity or expression of this enzyme leads to hypercholesterolemia. Inhibition of PCSK9 has proven to be successful in decreasing LDL levels and risk of the development of hypercholesterolemia with its associated higher risk for ASCVD. Patient with gain-of-function mutations in the PCSK9 undoubtedly benefit from therapies based on PCSK-9 inhibitors. However, millions of patients show statin intolerance, or cannot be efficiently controlled by statins alone- the most prevalent therapy for hypeprcholesterolemia. This commentary will evaluate the possibilities, caveats and future directions in the treatment of hypercholesterolemia, and therapies with combination of drugs.

Target-Mediated Drug Disposition Population Pharmacokinetics Model of Alirocumab in Healthy Volunteers and Patients: Pooled Analysis of Randomized Phase I/II/III Studies

Background and Objective

Proprotein convertase subtilisin/kexin type 9 inhibition with monoclonal antibodies such as alirocumab significantly reduces low-density lipoprotein-cholesterol levels ± other lipid-lowering therapies. We aimed to develop and qualify a population pharmacokinetics (PopPK) model for alirocumab in healthy subjects and patients, taking into account the mechanistic target-mediated drug disposition (TMDD) process.

Methods

This TMDD model was developed using a subset of the alirocumab clinical trial database, including nine phase I/II/III studies (n = 527); the model was subsequently expanded to a larger data set of 13 studies (n = 2870). Potential model parameters and covariate relationships were explored, and predictive ability was qualified using a visual predictive check.

Results

The TMDD model was built using the quasi-steady-state approximation. The final TMDD–quasi-steady-state model included a significant relationship between distribution volume of the central compartment and disease state: distribution volume of the central compartment was 1.56-fold higher in patients vs. healthy subjects. Separately, application of the model to the expanded data set revealed a significant relationship between linear clearance and statin co-administration: linear clearance was 1.27-fold higher with statins. The good predictive performance of the TMDD model was assessed based on graphical and numerical quality criteria, together with the visual predictive check and comparison of the predictions to those from a PopPK model with parallel linear and Michaelis–Menten clearances (i.e., simplification of the TMDD PopPK model).

Conclusions

This mechanistic TMDD PopPK model integrates the interaction of alirocumab with its target and accurately predicts both alirocumab and total proprotein convertase subtilisin/kexin type 9 concentrations in healthy subjects and patients.

Electronic supplementary material

The online version of this article (doi:10.1007/s40262-016-0505-1) contains supplementary material, which is available to authorized users.

PCSK9 in cholesterol metabolism: from bench to bedside

Dyslipidemia, and specifically elevated low-density lipoprotein (LDL) cholesterol, is one of the most important cardiovascular risk factors. Statins are considered first line therapy for the primary and secondary prevention of cardiovascular disease. However, statins may not be adequate treatment for elevated circulating LDL levels and are ineffective in certain familial hypercholesterolemias. The discovery of proprotein convertase subtilisin/kexin type 9 (PCSK9), a regulatory protein that affects LDL receptors, offers a new alternative for these patients. Moreover, gain-of-function PCSK9 mutations were discovered to be the root cause of familial autosomal dominant hypercholesterolemia. Inhibition of PSCK9 reduces plasma LDL levels, even in patients for whom statins are ineffective or not tolerated. Alirocumab and evolocumab, human monoclonal antibodies that inhibit PCSK9, have been approved to lower LDL levels. While there are drawbacks to these treatments, including adverse events, administration by subcutaneous injection, and high cost, these drugs are indicated for the treatment of atherosclerotic cardiovascular disease and familial hypercholesterolemia as adjunct to diet and maximally tolerated statin therapy. PCSK9 inhibitors may work synergistically with statins to lower LDL. Novel approaches to PCSK9 inhibition are currently in development with the aim of providing safe and effective treatment options to decrease cardiovascular event burden, ideally at lower cost and with oral bioavailability.

Pediatric physiology in relation to the pharmacokinetics of monoclonal antibodies

INTRODUCTION

Dose design for pediatric trials with monoclonal antibodies (mAbs) is often extrapolated from the adult dose according to weight, age, or body surface area. While these methods account for the size differences between adults and children, they do not account for the maturation of processes that may play a key role in the pharmacokinetics and/or pharmacodynamics of mAbs. With the same weight-based dose, infants and young children typically receive lower plasma exposures when compared to adults. Areas covered: The mechanistic features of mAb distribution, elimination, and absorption are explored in detail and literature-based hypotheses are generated to describe their age-dependence. This knowledge can be incorporated into a physiologically based pharmacokinetic (PBPK) modeling approach to pediatric dose determination. Expert opinion: As data from pediatric clinical trials become increasingly available, we have the opportunity to reflect on the physiologic drivers of pharmacokinetics, safety, and efficacy in children with mathematical models. A modeling approach that accounts for the age-related features of mAb disposition can be used to derive first-in-pediatric doses, design optimal sampling schemes for children in clinical trials and even explore new pharmacokinetic end-points as predictors of safety and efficacy in children.

Pharmacokinetics and pharmacodynamics of bococizumab, a monoclonal antibody to PCSK9, after single subcutaneous injection at three sites [NCT 02043301]

AIM

To characterize the single-dose pharmacokinetics (PK) and pharmacodynamics (PD) of bococizumab, a monoclonal antibody inhibiting proprotein convertase subtilisin/kexin type 9 (PCSK9), administered subcutaneously (s.c.) to the abdomen, thigh, or upper arm (NCT02043301).

METHODS

Seventy-five adults with low-density lipoprotein cholesterol (LDL-C) ≥130 mg/dL and not on background lipid-lowering therapy were randomized (1:1:1) to a single 150-mg s.c. dose of bococizumab administered to the abdomen, thigh, or upper arm. Blood samples for bococizumab and lipids were collected for 12 weeks postdose.

RESULTS

Plasma bococizumab concentration-time profiles and PK parameters were generally similar across injection sites. Mean maximum observed concentration (C_max ) ranged from 8.14 to 11.9 μg/mL, and area under the concentration-time curve (AUC_inf ) ranged from 160.3 to 198.9 µg∙day/mL. The median time to C_max (T_max ) ranged from 4.25 to 6.93 days. Similar LDL-C concentration-time profiles were observed across injection sites, with mean (% coefficient of variation) maximum reductions in LDL-C of -57.5% (15.8), -57.0% (25.9), and -55.0% (24.1) for the abdomen, thigh, and upper arm, respectively. Adverse events (AEs) were mostly mild and generally similar across injection sites. Commonly reported AEs were upper respiratory tract infection (9.3%), headache (6.7%), and injection site reaction (6.7%). One serious AE was reported (ischemic colitis), which was not considered related to study drug.

CONCLUSIONS

Similar PK profiles and robust LDL-C reductions were observed following a single 150-mg s.c. injection of bococizumab administered to the abdomen, thigh, or upper arm in untreated subjects with LDL-C ≥130 mg/dL. Bococizumab was generally well tolerated following a single 150-mg s.c. administration in this subject population.

Advances in the field of proprotein convertase subtilisin kexin type 9 inhibitors

PURPOSE OF REVIEW

Proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitors are promising therapies that inhibit the degradation of low-density lipoprotein (LDL) receptors in the hepatocyte and thus increase LDL cholesterol (LDL-C) uptake from the blood. This review summarizes main findings in the field of PCSK9 inhibitors, from basic mechanism to clinical studies, and aims to provide a contemporary and practical overview of the clinical implication and future directions with PCSK9 inhibitors.

RECENT FINDINGS

Monoclonal antibodies that inhibit PCSK9 reduce LDL-C levels by 40-70% across a wide range of patients with various LDL-C levels, and with different lipid-lowering regimens. These agents significantly reduce apolipoprotein B and lipoprotein (a), may have a potential role in plaque stabilization in acute coronary syndromes, and are safe and tolerable, even among statin-intolerant patients. Preliminary data with evolocumab and alirocumab demonstrate the potential reduction of cardiovascular (CV) events. These PCSK9 inhibitors were recently approved for clinical use, and recommended in the 2016 American College of Cardiology expert consensus document for nonstatin therapy for LDL-C lowering.

SUMMARY

PCSK9 inhibitors are novel promising therapies to reduce LDL-C. Ongoing phase 3 clinical trials with more than 70 000 high-risk patients will examine their safety and efficacy in reducing cardiovascular disease.

Comparative Pharmacokinetics and Pharmacodynamics of Bococizumab Following a Single Subcutaneous Injection Using Drug Substance Manufactured at Two Sites or Administration via Two Different Devices

The pharmacokinetics (PK) and pharmacodynamics (PD) of bococizumab, a proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor, were compared following a single 150-mg subcutaneous dose administered to healthy subjects (n = 156-158/arm) via: (1) a prefilled syringe (PFS) using drug substance (DS) manufactured by Pfizer, (2) a PFS using DS manufactured by Boehringer Ingelheim Pharma, (3) a prefilled pen using DS manufactured by Pfizer (NCT02458209). Blood samples were collected for 12 weeks postdose. Safety was monitored throughout. Mean maximum plasma concentration (C_max ) ranged between 11.0 and 11.3 μg/mL, and area under the plasma concentration-time curve (AUC_inf ) ranged between 177.6 and 185.0 μg·day/mL across treatments. The 90% confidence intervals for the ratios of adjusted geometric means for C_max and AUC_inf fell within the 80%-125% range for both DS and delivery device comparisons. Comparable low-density lipoprotein cholesterol profiles were observed, with nadir values of 54.3-56.1 mg/dL across treatments. Similar PCSK9 responses were also observed. Safety profiles were similar across treatments, and the majority of adverse events (AEs) were mild. Three subjects reported serious AEs. The most frequently reported AEs were headache, injection-site reaction, and upper respiratory tract infection, with no clear differences across treatments. Comparable PK, PD, and safety were observed following a single bococizumab 150-mg subcutaneous injection regardless of site of DS manufacture or delivery device used.

Cardiovascular Outcomes of PCSK9 Inhibitors: With Special Emphasis on Its Effect beyond LDL-Cholesterol Lowering

PCSK9 inhibitors, monoclonal antibodies, are novel antihypercholesterolemic drugs. FDA first approved them in July 2015. PCSK9 protein (692-amino acids) was discovered in 2003. It plays a major role in LDL receptor degradation and is a prominent modulator in low-density lipoprotein cholesterol (LDL-C) metabolism. PCSK9 inhibitors are monoclonal antibodies that target PCSK9 protein in liver and inhibiting this protein leads to drastically lowering harmful LDL-C level in the bloodstream. Despite widespread use of the statin, not all the high-risk patients were able to achieve targeted level of LDL-C. Using PCSK9 inhibitors could lead to a substantial decrement in LDL-C plasma level ranging from 50% to 70%, either as a monotherapy or on top of statins. A large number of trials have shown robust reduction of LDL-C plasma level with the use of PCSK9 inhibitors as a monotherapy or in combination with statins in familial and nonfamilial forms of hypercholesterolemia. Moreover, PCSK9 inhibitors do not appear to increase the risk of hepatic and muscle-related side effects. PCSK9 inhibitors proved to be a highly potent and promising antihypercholesterolemic drug by decreasing LDL-R lysosomal degradation by PCSK9 protein. Statin drugs are known to have some pleiotropic effects. In this article, we are also focusing on the effects of PCSK9 inhibitor beyond LDL-C reduction like endothelial inflammation, atherosclerosis, its safety in patients with diabetes, obesity, and chronic kidney disease, and its influence on neurocognition and stroke.

PCSK9 inhibitors - from discovery of a single mutation to a groundbreaking therapy of lipid disorders in one decade

Hypercholesterolemia is one of the main risk factors for coronary heart disease and significantly contributes to the high mortality associated with cardiovascular diseases. Statin therapy represents the gold standard in the reduction of low-density lipoprotein cholesterol concentration. Nevertheless, many patients still cannot achieve the recommended target levels, due to either inadequate effectiveness or intolerance of these drugs. Monoclonal antibodies that inhibit proprotein convertase subtilisin/kexin type 9 (PCSK9) have emerged as a promising option in lipid-lowering treatment. After confirmation of their efficacy and safety in clinical trials, evolocumab and alirocumab received approval from the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) for introduction into clinical practice. In this review, we present a history of the development and mechanisms of action, as well as the results of the most important studies concerning PCSK9 inhibitors.

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%).

Alirocumab for the treatment of hypercholesterolaemia

INTRODUCTION

Prescription of statins for low-density lipoprotein cholesterol (LDL-C) reduction is the standard of care in primary and secondary prevention of cardiovascular disease; nevertheless, a large number of patients treated with statins are unable to reach the recommended LDL-C targets. Therefore, there is need for safe and effective novel therapies for the pharmacological management of hypercholesterolaemia, in addition or as alternative to lipid-lowering therapies (LLT) currently in use. Areas covered: In 2015, the Food and Drug Administration and the European Medicines Agency approved alirocumab (Praluent®; Sanofi), a fully human monoclonal antibody against proprotein convertase subtilisin/kexin type 9 (PCSK9), for the treatment of hypercholesterolaemic patients unable to meet LDL-C targets, as an adjunct to diet in addition/alternative to LLT. The authors review the pharmacological features, clinical efficacy, and safety of alirocumab in lowering LDL-C, and discuss its therapeutic perspectives based on the most recent clinical trials. Expert commentary: Alirocumab causes a marked reduction in LDL-C, presents good safety and tolerability, and represents a promising approach for LDL-C lowering, particularly in patients with intolerance to statin or elevated LDL-C despite maximal statin therapy; nevertheless, further long-term data on safety and efficacy are necessary, such as data on the improvement of cardiovascular outcomes.

PCSK9 inhibitors: A new era of lipid lowering therapy

Hyperlipidemia is a well-established risk factor for developing cardiovascular disease (CVD). The recent American College of Cardiology and American Heart Association guidelines on lipid management emphasize treatment of individuals at increased risk for developing CVD events with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) at doses proven to reduce CVD events. However, there are limited options for patients who are either intolerant to statin therapy, develop CVD despite being on maximally tolerated statin therapy, or have severe hypercholesterolemia. Recently the Food and Drug Administration approved two novel medications for low-density lipoprotein (LDL)-cholesterol reduction: Evolocumab and Alirocumab. These agents target and inactivate proprotein convertase subtilsin-kexin type 9 (PCSK9), a hepatic protease that attaches and internalizes LDL receptors into lysosomes hence promoting their destruction. By preventing LDL receptor destruction, LDL-C levels can be lowered 50%-60% above that achieved by statin therapy alone. This review explores PCSK-9 biology and the mechanisms available to alter it; clinical trials targeting PCSK9 activity, and the current state of clinically available inhibitors of PCSK9.

PCSK9 Inhibitors: An Innovative Approach to Treating Hyperlipidemia

Proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitors are novel agents indicated for the treatment of hyperlipidemia. Inhibition of PCSK9 produces an increase in surface low-density lipoprotein (LDL) receptors and increases removal of LDL from the circulation. Alirocumab (Praluent; Sanofi/Regeneron, Bridgewater, NJ) and evolocumab (Repatha; Amgen, Thousand Oaks, CA) are currently available and approved for use in patients with heterozygous familial hypercholesterolemia, homozygous familial hypercholesterolemia, and clinical atherosclerotic cardiovascular disease. Bococizumab (RN316; Pfizer, New York, NY) is currently being studied in similar indications, with an estimated approval date in late 2016. The pharmacodynamic effects of PCSK9 inhibitors have been extensively studied in various patient populations. They have been shown to produce significant reductions in LDL and are well tolerated in clinical studies, but they are very costly when compared with statins, the current mainstay of hyperlipidemia treatment. Clinical outcome studies are underway, but not yet available; however, meta-analyses have pointed to a reduction in cardiovascular death and cardiovascular events with the use of PCSK9 inhibitors. This review will discuss the novel mechanism of action of PCSK9 inhibitors, the results of clinical studies, and the clinical considerations of these agents in current therapy.

A Phase I Randomized Study of a Specifically Engineered, pH-Sensitive PCSK9 Inhibitor RN317 (PF-05335810) in Hypercholesterolemic Subjects on Statin Therapy

This phase I study assessed the safety, tolerability, pharmacokinetics, and pharmacodynamics of RN317 (PF-05335810), a specifically engineered, pH-sensitive, humanized proprotein convertase subtilisin kexin type 9 (PCSK9) monoclonal antibody, in hypercholesterolemic subjects (low-density lipoprotein cholesterol (LDL-C) ≥ 80 mg/dl) 18-70 years old receiving statin therapy. Subjects were randomized to: single-dose placebo, RN317 (subcutaneous (s.c.) 0.3, 1, 3, 6, or intravenous (i.v.) 1, 3, 6 mg/kg), or bococizumab (s.c. 1, 3, or i.v. 1 mg/kg); or multiple-dose RN317 (s.c. 300 mg every 28 days; three doses). Of 133 subjects randomized, 127 completed the study. RN317 demonstrated a longer half-life, greater exposure, and increased bioavailability vs. bococizumab. RN317 was well tolerated, with no subjects discontinuing because of treatment-related adverse events. RN317 lowered LDL-C by up to 52.5% (day 15) following a single s.c. dose of 3.0 mg/kg vs. a maximum of 70% with single-dose bococizumab s.c. 3.0 mg/kg. Multiple dosing of RN317 produced LDL-C reductions of ∼50%, sustained over an 85-day dosing interval.

New directions for pharmacotherapy in the treatment of acute coronary syndrome

INTRODUCTION

Acute coronary syndromes (ACS) are one of the leading causes of death worldwide. Several landmark trials, followed by a widespread introduction of new agents, have significantly improved ACS outcomes in recent years. However, despite the use of contemporary therapy, a substantial number of ACS patients continue to suffer from cardiovascular events. Areas covered: The aim of this review was to summarize available data on innovative drugs and pharmacological strategies that have potential to amend the current ACS therapy. We present the results of recent large clinical trials, as well as insights from ongoing phase III and phase IV studies, exploring the value of new strategies for the improvement of outcomes in ACS. Expert opinion: More potent platelet inhibition, more profound lipid reduction and possibly anti-inflammatory action are considered to have potential to further reduce the rates of adverse cardiovascular and thrombotic events in ACS patients. 'Hit fast, hit hard' approach regarding novel antiplatelet and lipid-lowering therapy seems attractive, but it has to be considered that these strategies may be associated with increased adverse events rate. Introduction of cangrelor and ezetimibe, and potentially future recognition of proprotein convertase subtilisin/kexin type 9 antibodies, are likely to alter the landscape of ACS pharmacotherapy.

PCSK9 Inhibitors

Objective: To evaluate the safety and efficacy of 2 human monoclonal antibodies, alirocumab and evolocumab, on reduction of low-density lipoprotein cholesterol (LDL-C), cardiovascular benefits, and their place in current practice. Data Sources: A search of MEDLINE and Scopus databases (1966 to May 2016) with search terms “alirocumab,” “evolocumab,” “LDL,” and “PCSK9.” Study Selection and Data Extraction: The search identified phase 3 randomized control trials in English language in the past 10 years that studied LDL-C reduction of alirocumab or evolocumab. The studies were assessed for all efficacy and safety endpoints. Data Synthesis: Twelve total studies were identified evaluating alirocumab or evolocumab. These monoclonal antibodies have been shown to significantly decrease LDL-C as monotherapy and in combination with statins in phase 3 clinical trials in patients with primary hypercholesterolemia as well as familial hypercholesterolemia by inhibiting PCSK9. Alirocumab significantly reduced LDL-C by up to 61%, while evolocumab significantly reduced LDL-C by up to 66%. Adverse effects of these medications have been low and overall well tolerated. Conclusion: Although these monoclonal antibodies have shown to significantly reduce LDL-C, their effect on cardiovascular outcomes has not yet been determined. Further studies are being conducted to assess the cardiovascular benefit of both alirocumab and evolocumab. Until these studies demonstrate a reduction in atherosclerotic cardiovascular disease risk, statins should remain first-line therapy for most patients. However, alirocumab and evolocumab can be used as an effective adjunctive therapy option to lower LDL-C or in patients who are statin intolerant.

Alirocumab: First Global Approval

Alirocumab (Praluent®) is a fully human monoclonal antibody developed by Regeneron Pharmaceuticals and Sanofi that has been approved in the US as an adjunct to diet and maximally tolerated statin therapy for the treatment of adults with heterozygous familial hypercholesterolaemia (HeFH) or clinical atherosclerotic cardiovascular disease, who require additional lowering of LDL-C. It specifically binds proprotein convertase subtilisin/kexin type 9 (PCSK9)-a down regulator of liver low-density lipoprotein (LDL)-receptors-thereby increasing the ability of the liver to bind LDL-cholesterol (LDL-C) and reducing levels of LDL-C in blood. It has been shown to reduce LDL-C levels in patients with hypercholesterolaemia, including HeFH, both as monotherapy and in conjunction with statin therapy. This article summarizes the milestones in the development of alirocumab leading to this first approval.

Alirocumab: A Review in Hypercholesterolemia

Alirocumab (Praluent(®)) is a monoclonal antibody against proprotein convertase subtilisin/kexin type 9 (PCSK9) that is administered via subcutaneous injection every 2 weeks. Across ten phase III studies from the ODYSSEY clinical trial program in patients with heterozygous familial hypercholesterolemia (heFH) or nonfamilial hypercholesterolemia (nonFH), including some with mixed dyslipidemia, subcutaneous alirocumab 75 or 150 mg every 2 weeks was significantly more effective with regard to reducing low-density lipoprotein-cholesterol (LDL-C) over 24 weeks than comparator agents (i.e. matching placebo, once-daily oral ezetimibe, or modified oral statin therapy), including when administered as monotherapy or in combination with statin therapy, and when administered with non-statin lipid-lowering therapy (LLT) in patients with statin intolerance. Alirocumab provided sustained LDL-C-lowering efficacy over 52-78 weeks' treatment in longer-term trials, and was associated with significantly favorable effects on several other lipid parameters, including non-high-density lipoprotein-cholesterol (non-HDL-C) and lipoprotein (a) [Lp(a)]. Alirocumab was generally well tolerated in phase III trials, with no apparent increase in muscle-related adverse events compared with placebo. Thus, alirocumab is a valuable emerging option for use in patients with hypercholesterolemia, particularly patients with statin intolerance or inadequately-controlled LDL-C despite statin therapy; however, more data are needed to establish its potential cardiovascular benefits.

New developments in atherosclerosis: clinical potential of PCSK9 inhibition

Pro-protein convertase subtilisin/kexin type 9 (PCSK9) is a secreted 692-amino acid protein that binds surface low-density lipoprotein (LDL) receptor (LDLR) and targets it toward lysosomal degradation. As a consequence, the number of LDLRs at the cell surface is decreased, and LDL-cholesterol (LDL-C) clearance is reduced, a phenomenon that is magnified by gain-of-function mutations of PCSK9. In contrast, loss-of-function mutations of PCSK9 result in increased surface LDLR and improved LDL-C clearance. This provides the rationale for targeting PCSK9 in hypercholesterolemic subjects as a means to lower LDL-C levels. Monoclonal antibodies (mAbs) against PCSK9 that block its interaction with the LDLR have been developed in the past decade. Two companies have recently received the approval for their anti-PCSK9 mAbs by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) Regeneron/Sanofi, with alirocumab (commercial name – PRALUENT^®) and, Amgen with evolocumab (commercial name – Repatha™). The introduction of anti-PCSK9 mAbs will provide an alternative therapeutic strategy to address many of the unmet needs of current lipid-lowering therapies, such as inability to achieve goal LDL-C level, or intolerance and aversion to statins. This review will focus on the kinetics of PCSK9, pharmacokinetics and pharmacodynamics of anti-PCSK9 mAbs, and recent data linking PCSK9 and anti-PCSK9 mAbs to cardiovascular events. Moreover, it will highlight the unanswered questions that still need to be addressed in order to understand the physiologic function, kinetics, and dynamics of PCSK9.