Pharmacokinetics of the novel PAR-1 antagonist vorapaxar in patients with hepatic impairment

Proteinase-activated receptor 1: A target for repurposing in the treatment of COVID-19?

In the search to rapidly identify effective therapies that will mitigate the morbidity and mortality of COVID‐19, attention has been directed towards the repurposing of existing drugs. Candidates for repurposing include drugs that target COVID‐19 pathobiology, including agents that alter angiotensin signalling. Recent data indicate that key findings in COVID‐19 patients include thrombosis and endotheliitis. Activation of proteinase‐activated receptor 1 (PAR1), in particular by the serine protease thrombin, is a critical element in platelet aggregation and coagulation. PAR1 activation also impacts on the actions of other cell types involved in COVID‐19 pathobiology, including endothelial cells, fibroblasts and pulmonary alveolar epithelial cells. Vorapaxar is an approved inhibitor of PAR1, used for treatment of patients with myocardial infarction or peripheral arterial disease. We discuss evidence for a possible beneficial role for vorapaxar in the treatment of COVID‐19 patients and other as‐yet non‐approved antagonists of PAR1 and proteinase‐activated receptor 4 (PAR4).

Linked Articles

This article is part of a themed issue on The Pharmacology of COVID‐19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc

Effect of Hepatic Impairment on Cobimetinib Pharmacokinetics: The Complex Interplay Between Physiological Changes and Drug Characteristics

Cobimetinib is a kinase inhibitor indicated for use in combination with vemurafenib for treatment of unresectable/metastatic melanoma with specific BRAF mutations. Cobimetinib is extensively metabolized in liver; thus, patients with hepatic impairment (HI) might have increased cobimetinib exposure. In this study, we investigated the impact of HI on the pharmacokinetics (PK) and safety of cobimetinib. Subjects with normal hepatic function and mild to severe HI were enrolled. All subjects received a single oral dose of 10 mg cobimetinib, and serial blood samples were collected at specified times. Cobimetinib PK in subjects with mild and moderate HI was similar to that in those with normal liver function. However, subjects with severe HI, on average, showed ∼30% lower total AUC_0-∞ and ∼2-fold higher unbound AUC_0-∞ compared with those with normal hepatic function. These exposure differences can be explained by lower albumin levels observed in subjects with severe HI, the strong correlation between albumin level and the unbound fraction and the general PK variability of cobimetinib. In addition, previous studies with cobimetinib showed a lack of an exposure-response relationship for efficacy and safety. Therefore, collectively, our results suggest that the starting dose for patients with hepatic impairment can be the same as that for those with normal hepatic function.

Effect of Mild and Moderate Hepatic Impairment on the Pharmacokinetics, Safety, and Tolerability of a Single Dose of Oral Ivosidenib in Otherwise Healthy Participants

Ivosidenib, a small-molecule inhibitor of mutant isocitrate dehydrogenase 1, is primarily cleared by hepatic metabolism. This open-label study investigated the impact of hepatic impairment on ivosidenib pharmacokinetics (ClinicalTrials.gov: NCT03282513). Otherwise healthy participants with mild (n = 9) or moderate (n = 8) hepatic impairment (Child-Pugh score) and matched participants with normal hepatic function (n = 16) received 1 oral dose of 500-mg ivosidenib. Mild hepatic impairment had a negligible effect on total ivosidenib plasma exposure, with geometric mean ratios (90% confidence interval [CI]) of 0.933 (0.715-1.22) for maximum concentration (C_max ) and 0.847 (0.624-1.15) for area under the plasma concentration-time curve (AUC) in participants with mild hepatic impairment versus matched controls. Moderate hepatic impairment reduced total ivosidenib exposure by 28% to 44%, with geometric mean ratios (90%CI) of 0.565 (0.419-0.763) for C_max and 0.716 (0.479-1.07) for AUC, although the 90%CI for AUC included 1.00. The ivosidenib unbound fraction was concentration dependent and higher in participants with mild/moderate hepatic impairment compared with matched controls. There was no apparent trend to increasing unbound C_max with increased hepatic impairment severity. A single 500-mg ivosidenib dose was well tolerated, with no serious or severe adverse events and no adverse events leading to discontinuation. We conclude that mild/moderate hepatic impairment did not lead to clinically relevant changes in ivosidenib exposure following a single 500-mg dose.

Progress in the development of antiplatelet agents: Focus on the targeted molecular pathway from bench to clinic

Antiplatelet drugs serve as a first-line antithrombotic therapy for the management of acute ischemic events and the prevention of secondary complications in vascular diseases. Numerous antiplatelet therapies have been developed; however, currently available agents are still associated with inadequate efficacy, risk of bleeding, and variability in individual response. Understanding the mechanisms of platelet involvement in thrombosis and the clinical development process of antiplatelet agents is critical for the discovery of novel agents. The functions of platelets in thrombosis are regulated by two major mechanisms: the interaction between surface receptors and their ligands, and the downstream intracellular signaling pathways. Recently, most of the progress made in antiplatelet drug development has been achieved with P2Y receptor antagonists. Additionally, the usage of GP IIb/IIIa receptor antagonists has decreased, because it is associated with a higher risk of bleeding and thrombocytopenia. Agents targeting other platelet surface receptors such as PARs, TP receptor, EP3 receptor, GPIb-IX-V receptor, P-selectin, as well as intracellular signaling factors, such as PI3Kβ, have been evaluated in an attempt to develop the next generation of antiplatelet drugs, reduce or eliminate interpatient variability of drug efficacy and significantly lower the risk of drug-induced bleeding. The aim of this review is to describe the pathways of platelet activation in thrombosis, and summarize the development process of antiplatelet agents, as well as the preclinical and clinical evaluations performed on these agents.

Role for Thrombin Receptor Antagonism With Vorapaxar in Secondary Prevention of Atherothrombotic Events: From Bench to Bedside

In spite of treatment with the current standard of care antiplatelet regimens including dual antiplatelet therapy, recurrence rates of ischemic events remain elevated for high-risk patients with atherosclerotic disease. This may be in part attributed to the fact that other key platelet activation pathways remain uninhibited and can thus continue to trigger platelet activation and lead to thrombotic complications. Thrombin is a powerful inducer of platelet activation and mediates its effects directly on platelets through protease activator receptors (PARs), particularly the PAR-1 subtype, making PAR-1 inhibition an attractive approach for reducing atherothrombotic events. These observations have led to the development of several PAR-1 antagonists. Vorapaxar is a direct inhibitor of PAR-1 and the only agent of this class approved for the prevention of recurrent ischemic events in patients with prior myocardial infarction or peripheral artery disease. In the present manuscript, we present a review of the pathophysiologic role of thrombin on thrombotic complications, the impact of vorapaxar on outcomes, including the most recent updates deriving from clinical trials, as well as future perspectives in the field.

Vorapaxar: The Current Role and Future Directions of a Novel Protease-Activated Receptor Antagonist for Risk Reduction in Atherosclerotic Disease

Introduction

Despite the current standard of care, patients with cardiovascular disease remain at a high risk for recurrent events. Inhibition of thrombin-mediated platelet activation through protease-activated receptor-1 antagonism may provide reductions in atherosclerotic disease beyond those achievable with the current standard of care.

Objective

Our primary objective is to evaluate the clinical literature regarding the role of vorapaxar (Zontivity™) in the reduction of cardiovascular events in patients with a history of myocardial infarction and peripheral artery disease. In particular, we focus on the potential future directions for protease-activating receptor antagonists in the treatment of a broad range of atherosclerotic diseases.

Data Sources

A literature search of PubMed and EBSCO was conducted to identify randomized clinical trials from August 2005 to June 2016 using the search terms: ‘vorapaxar’, ‘SCH 530348’, ‘protease-activated receptor-1 antagonist’, and ‘Zontivity™’. Bibliographies were searched and additional resources were obtained.

Results

Vorapaxar is a first-in-class, protease-activated receptor-1 antagonist. The Thrombin Receptor Antagonist for Clinical Event Reduction (TRACER) trial did not demonstrate a significant reduction in a broad primary composite endpoint. However, the Thrombin-Receptor Antagonist in Secondary Prevention of Atherothrombotic Ischemic Events (TRA 2°P-TIMI 50) trial examined a more traditional composite endpoint and found a significant benefit with vorapaxar. Vorapaxar significantly increased bleeding compared with standard care. Ongoing trials will help define the role of vorapaxar in patients with peripheral arterial disease, patients with diabetes mellitus, and other important subgroups. The use of multivariate modeling may enable the identification of subgroups with maximal benefit and minimal harm from vorapaxar.

Conclusion

Vorapaxar provides clinicians with a novel mechanism of action to further reduce the burden of ischemic heart disease. Identification of patients with a high ischemic risk and low bleeding risk would enable clinicians to maximize the utility of this unique agent.

Electronic supplementary material

The online version of this article (doi:10.1007/s40268-016-0158-4) contains supplementary material, which is available to authorized users.

Pharmacokinetic drug evaluation of vorapaxar for secondary prevention after acute coronary syndrome

INTRODUCTION

Vorapaxar is the first protease-activated receptor-1 inhibitor approved for clinical use. Its main indication is the reduction in thrombotic cardiovascular events in patients with previous myocardial infarction or symptomatic peripheral artery disease. Areas covered: This article reviews the pharmacokinetics of vorapaxar and its potential use in secondary prevention after an acute coronary syndrome. Expert opinion: Vorapaxar inhibits platelet aggregation mediated by thrombin. This effect is carried out without affecting to coagulation parameters and bleeding times. This drug has showed a significant reduction of cardiovascular events in patients with chronic atherosclerosis but not during the admission for an acute coronary syndrome. The rate of major bleeding found in patients treated with vorapaxar in randomized trials was consistently higher than placebo in most of the analyzed subgroups. For this reason, cautious evaluation of risk-benefit profiles should be required before prescribing this drug.

Impact of selective platelet inhibition in reducing cardiovascular risk - role of vorapaxar

This article reviews the pharmacology, clinical efficacy, and safety of vorapaxar in reducing cardiovascular risk. Vorapaxar is a tricyclic himbacine-derived reversible inhibitor of platelet surface protease activator receptor-1, which prevents thrombin from activating platelets. Two Phase III clinical trials and multiple subanalyses from the two trials with vorapaxar have been published. In patients with recent acute coronary syndrome, vorapaxar, when added to standard therapy, did not reduce the composite cardiovascular end point. In contrary, in a study of secondary prevention for patients with cardiovascular diseases, vorapaxar reduced the risk of cardiovascular death or ischemic events (myocardial infarction, stroke) in patients with stable atherosclerosis who were receiving standard therapy. Vorapaxar is approved in the US for use with aspirin and/or clopidogrel in the secondary prevention of thrombogenic cardiovascular events in stable patients with peripheral arterial disease or a history of myocardial infarction. Vorapaxar increases risk of bleeding and is contraindicated in patients with previous cerebrovascular events. It is essential to balance individual patient’s bleeding risk to any further cardiovascular benefits that they may get. Future investigation is also needed to evaluate use of vorapaxar with newer antiplatelet agents such as ticagrelor and cangrelor, as well as its role as monotherapy.

Vorapaxar: A Protease-Activated Receptor Antagonist for the Prevention of Thrombotic Events

Antiplatelet therapy reduces the risks for cardiovascular morbidity and mortality in patients with atherosclerotic disease, and it is also beneficial in managing peripheral arterial disease (PAD). These agents work through various therapeutic pathways to achieve antithrombotic effects. Although single- or two-drug regimens have been deployed to prevent vascular events, approximately 10% of the patients with acute coronary syndrome remain at risk for recurrent thrombotic events and may need a more aggressive preventative strategy. Vorapaxar offers a unique mechanism for platelet inhibition via the antagonism of protease-activated receptor-1. It is approved for the reduction of thrombotic cardiovascular events in patients with a history of myocardial infarction (MI) or PAD. This new drug approval was mainly based on the results from subgroup analyses from a large landmark trial (Thrombin Receptor Antagonist in Secondary Prevention of Atherothrombotic Ischemic Events-Thrombolysis in Myocardial Infarction 50), which found that vorapaxar reduces the rate of the combined end point of cardiovascular death, MI, stroke, and urgent coronary revascularization when used in addition to aspirin and/or clopidogrel in patients without a history of stroke. In this study, vorapaxar was discontinued in patients with a history of stroke due to excessive risk for intracranial hemorrhage after 2 years of therapy. As an adjunctive therapy to standard regimens, vorapaxar provides a greater net clinical benefit in MI patients who are at a lower risk for bleeding. In patients with PAD, it reduces the rates of recurrent acute limb ischemia with rehospitalization or peripheral revascularization. The most concerning adverse effect is bleeding. Vorapaxar should not be used in patients with a history of stroke, transient ischemic attack, intracranial hemorrhage, or active pathological bleeding. The risks and benefits of adding vorapaxar to intensify antiplatelet regimens should be assessed in individual patients to aim for additional therapeutic outcomes with minimal bleeding risks.

Vorapaxar: A novel agent to be considered in the secondary prevention of myocardial infarction

Patients receiving therapy for the secondary prevention of myocardial infarction (MI) are still at high risk of a major cardiovascular event or death despite the use of currently available treatment strategy. Vorapaxar, an oral protease-activated receptor antagonist, is a novel antiplatelet drug that has been recently approved to provide further risk reduction. The results of two Phase III trials (thrombin receptor antagonists for clinical event reduction and the TRA 2°P-TIMI 50) have showed that vorapaxar, in addition to standard of care therapy, has the potential to provide further risk reduction in patients with prior MI. A search was made on PubMed on articles related to clinical trials and clinical consideration with the use of vorapaxar. This review article summarizes the results of Phase II trials, Phase III trials, subgroup analysis, precautions, and drug interaction with the use of vorapaxar.

Review of vorapaxar for the prevention of atherothrombotic events

INTRODUCTION

Atherosclerosis is frequently caused by clot blockage of the coronary or peripheral arteries, and may lead to myocardial infarction (MI) or peripheral arterial disease (PAD). Despite advancements in management of atherosclerosis, mortality and ischemic rates remain high. Vorapaxar is a protease activated receptor-1 (PAR-1) antagonist, and prevents thrombin activation of PAR-1 receptors on platelets.

AREAS COVERED

Vorapaxar was studied in 2 landmark trials in patients with acute coronary syndrome (ACS) and in those with history of atherosclerosis. For patients with ACS, vorapaxar did not significantly reduce rates of the primary efficacy outcome as compared to placebo. For patients with a history of atherosclerosis, vorapaxar significantly reduced rates of primacy outcome. However, in both landmark trials, vorapaxar significantly increased risks of bleeding, and significantly increases risks of intracranial hemorrhage in patients with a history of stroke. Vorapaxar was approved in 2014 in the US for patients with a history of MI or PAD, and in the European Union for patients with a history of MI.

EXPERT OPINION

Use of vorapaxar may be limited due to its high potential for causing bleeding. Efficacy of vorapaxar in addition to aspirin and prasugrel or ticagrelor for the management of ACS should be studied in the future.

Platelet thrombin receptor antagonism with vorapaxar: pharmacology and clinical trial development

Oral antiplatelet therapies for secondary prevention of ischemic recurrences in patients with atherosclerotic disease manifestations include aspirin and P2Y12 receptor antagonists. Despite the use of these therapies, patients remain at risk for recurrent ischemic events, which may be attributed to other platelet signaling pathways which continue to be activated. More intense antithrombotic strategies have been investigated, including identifying additional targets to modulate platelet activation. Among these, thrombin-mediated platelet activation through PAR-1 has been subject to broad clinical investigation. Vorapaxar is the only PAR-1 receptor antagonists that completed large-scale clinical investigations and is approved for clinical use. This manuscript provides an overview of the pharmacology and clinical trial development of vorapaxar as well as its role in clinical practice.

Vorapaxar: first global approval

Vorapaxar [Zontivity(®) (US)], an orally active protease-activated receptor-1 (PAR-1) receptor antagonist, has been developed by Merck & Co for the reduction of thrombotic cardiovascular events in patients with a history of myocardial infarction (MI) or peripheral arterial disease (PAD). Vorapaxar has received its first global approval for this indication in the US. This article summarizes the milestones in the development of vorapaxar leading to this first approval for the reduction of thrombotic cardiovascular events in patients with a prior MI or PAD.

Platelet transfusion reverses bleeding evoked by triple anti-platelet therapy including vorapaxar, a novel platelet thrombin receptor antagonist

Vorapaxar is a novel protease-activated receptor-1 (PAR-1) antagonist recently approved for the reduction of thrombotic cardiovascular events in patients with a history of myocardial infarction or with peripheral arterial disease. Patients who received vorapaxar in addition to standard of care antiplatelet therapy had an increased incidence of major bleeding events compared with placebo. To assess whether platelet transfusion can restore hemostasis in primates on triple antiplatelet therapy, template bleeding times were assessed concurrently in the buccal mucosa, finger pad, and distolateral tail of anesthetized cynomolgus macaques to evaluate bleeding with vorapaxar as either monotherapy or in combination with aspirin or aspirin and clopidogrel. Aspirin (5mg/kg, IV) or vorapaxar (1mg/kg, PO) alone had no significant effect on bleeding times in the three vascular beds examined. A modest (<2-fold) increase in bleeding time was achieved in the three beds with the dual combination of aspirin and vorapaxar. Major increases in bleeding time were achieved in the three beds with the triple combination of aspirin (5mg/kg, IV), vorapaxar (1mg/kg, PO), and clopidogrel (1mg/kg, PO). Transfusion of fresh human platelet rich plasma, but not platelet poor plasma, reversed the increase in bleeding time in the triple therapy group. Transfusion of human platelets may be a viable approach in situations requiring a rapid reversal of platelet function in individuals treated with triple anti-platelet therapy that includes vorapaxar.

Vorapaxar in atherosclerotic disease management

OBJECTIVE

To review the pharmacology, efficacy, and safety of vorapaxar, a protease activator receptor-1 (PAR-1) antagonist, in the management of atherosclerotic diseases.

DATA SOURCES

Peer-reviewed clinical trials and review articles were identified from MEDLINE and Current Content database (both 1966 to December 31, 2014) using the search terms vorapaxar and protease activator receptor antagonist.

STUDY SELECTION AND DATA EXTRACTION

A total of 30 clinical studies were identified (16 clinical trials, including subanalyses, 14 related to pharmacology, pharmacokinetics, and pharmacodynamics and drug interactions).

DATA SYNTHESIS

Two phase III clinical trials with vorapaxar have been published. In patients with non-ST segment elevation myocardial infarction (MI), vorapaxar failed to significantly reduce the primary efficacy end point (composite of cardiovascular death, MI, stroke, recurrent ischemia with hospitalization, and urgent coronary revascularization). Conversely, in a study of secondary prevention for patients with cardiovascular disease, the composite end point of cardiovascular death, MI, or stroke was significantly reduced. In both trials, the safety end points of major/minor bleeding were increased compared with placebo. In the secondary prevention trial, an increased incidence of intracranial hemorrhage led to the exclusion of patients with a prior history of stroke.

CONCLUSION

Vorapaxar is approved for use with aspirin and/or clopidogrel in the secondary prevention of cardiovascular events in stable patients with peripheral arterial disease or a history of MI. However, the addition of vorapaxar to other antiplatelets can significantly increase the risk of bleeding. It is, therefore, essential to balance the need for further reduction of risk of thrombotic event with patient's individual bleeding risk.

Vorapaxar, an oral PAR-1 receptor antagonist, does not affect the pharmacokinetics of rosiglitazone

PURPOSE

To evaluate the potential effects of vorapaxar on the pharmacokinetics and safety of rosiglitazone.

METHODS

This was an open-label, two-period, two-treatment, fixed-sequence study in 18 healthy subjects. On Day 1, Period 1, subjects received a single dose of rosiglitazone 8 mg. In Period 2, subjects received vorapaxar 40 mg on Day 1, vorapaxar 7.5 mg once-daily on Days 2-7, and a single dose of rosiglitazone 8 mg on Day 7. Rosiglitazone and N-desmethylrosiglitazone pharmacokinetics were assessed alone (Period 1) and after coadministration with vorapaxar (Period 2). Vorapaxar and its M20 metabolite pharmacokinetics were assessed on Day 7, Period 2. Safety and tolerability were assessed throughout the study.

RESULTS

Coadministration of rosiglitazone with vorapaxar had no effect on rosiglitazone or N-desmethylrosiglitazone pharmacokinetics. The ratio of geometric means (GMR) and 90% confidence intervals (CI) of the coadministration versus monotherapy for Cmax (GMR 95; 90% CI 88, 103) and AUC0-24 h (GMR 103; 90% CI 98, 108) were within the 80-125% bioequivalence criteria. The metabolite-to-parent exposure ratio with and without vorapaxar was unaltered. Coadministration of vorapaxar with rosiglitazone was generally well tolerated.

CONCLUSION

Coadministration of vorapaxar with rosiglitazone or drugs metabolized via CYP2C8 is unlikely to cause a significant pharmacokinetic interaction.