Usefulness and safety of vorapaxar in patients with non-ST-segment elevation acute coronary syndrome undergoing percutaneous coronary intervention (from the TRACER Trial)

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.

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.

Protease-Activated Receptor-1 Antagonists Post-Percutaneous Coronary Intervention

Thrombin is a potent platelet agonist, and protease-activated receptor-1 (PAR-1) is the main thrombin receptor in human platelets and thrombin. PAR-1 antagonism has attracted interest as a potential therapeutic target to reduce atherothrombotic events in patients with atherosclerotic disease, especially coronary artery disease. In this review, the author describes the rationale of PAR-1 antagonism for the reduction of atherothrombotic events and reviews the key phase 3 trial results, with special attention to analyses in percutaneous coronary intervention patients.

Vorapaxar: emerging evidence and clinical questions in a new era of PAR-1 inhibition

Despite the use of therapies recommended in practice guidelines for secondary prevention in patients with atherosclerotic coronary artery disease, the residual risk for cardiovascular events remains high. Some of the residual risk is believed to result from incomplete platelet inhibition with current therapy. Vorapaxar is a first-in-class, novel antiplatelet agent that acts by antagonizing the PAR-1 receptor, inhibiting thrombin-mediated platelet activation. Vorapaxar was recently approved by the Food and Drug Administration for secondary prevention of cardiovascular events in patients with a history of myocardial infarction or peripheral artery disease who do not have a history of transient ischemic attack or stroke. We review the data from two key phase III cardiovascular outcome trials with vorapaxar: TRACER and TRA 2P-TIMI 50. We will focus on identifying the key patient populations that should be identified for treatment, highlight practical clinical issues when prescribing vorapaxar, and review unanswered questions. Vorapaxar should be considered in patients at high risk for recurrent ischemic events and low risk of bleeding.

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.

Efficacy and safety of vorapaxar for the prevention of adverse cardiac events in patients with coronary artery disease: a meta-analysis

BACKGROUND

Coronary artery disease (CAD) is the leading cause of morbidity and mortality worldwide. Vorapaxar, a protease-activated receptor-1 (PAR-1) antagonist, is a novel antiplatelet agent that may provide us a new way in antithrombotic therapy. Several studies had been conducted to evaluate the efficacy of vorapaxar in the treatment of CAD, but the results were inconsistent. Here a meta-analysis was made to assess the efficacy and safety of vorapaxar in reducing adverse cardiac events in patients with CAD.

METHODS

A comprehensive literature search was conducted. The primary efficacy endpoint was the major adverse cardiac events, which was defined as a composite of cardiovascular death, myocardial infarction (MI), stroke, urgent coronary revascularization, or recurrent ischemia with rehospitalization. The primary safety endpoint was the composite of major or minor bleeding events. Pooled effects were measured by odds ratios (ORs) with 95% confidence intervals (CIs). A random-effect or fixed model was used in this meta-analysis.

RESULTS

Totally, 31,388 patients from four randomized controlled trials (RCTs) were included in this meta-analysis. Patients who took vorapaxar combined with standard dual anti-platelet therapy (aspirin and thienopyridine) showed a lower incidence in major adverse cardiac events (OR, 0.86, 95% CI: 0.75-0.99, P=0.03), MI (OR, 0.79, 95% CI: 0.67-0.95, P=0.01) and ischemic stroke (OR, 0.72, 95% CI: 0.58-0.89, P=0.003) than those who only took placebo instead. But there was no significant reduction in cardiovascular death (OR, 0.95, 95% CI: 0.82-1.09, P=0.45). Nevertheless, the vorapaxar group were associated with a higher risk of bleeding events (P<0.001).

CONCLUSIONS

The result of this meta-analysis indicated that adding vorapaxar to the standard dual anti-platelet therapy may be efficient in reducing the incidence of major adverse cardiac events at the cost of increasing risk of bleeding events.

Role of Vorapaxar After Coronary Revascularization

We aim to evaluate the potential benefit and risk of addition of vorapaxar to standard medical therapy in patients who underwent coronary revascularization with either percutaneous coronary revascularization or coronary artery bypass graft surgery. We searched PubMed, EMBASE, the Cochrane Central Register of Controlled trials, and the clinical trial registry maintained at clinicaltrials.gov for randomized control trials evaluating the safety and efficacy of vorapaxar in patients who underwent coronary revascularization procedures with either percutaneous coronary revascularization or coronary artery bypass graft surgery. Event rates were compared using a Forest plot of relative risk using a random-effects model. The 5 studies (n = 24,025) that met all criteria were included in the final analysis. After coronary revascularization procedures, addition of vorapaxar to standard medical therapy was associated with reduction in the risk of myocardial infarction (MI; risk ratio 0.83 [0.75 to 0.92]) and ischemic stroke (0.011 [0.007 to 0.016]); however, it also resulted in significant increase risk of hemorrhagic stroke (1.57 [1.01 to 2.44]) and Thrombolysis In Myocardial Infarction major and minor bleeds (1.36 [1.07 to 1.70]). There was no significant difference in the risk of cardiovascular mortality (0.90 [0.73 to 1.09]), repeat revascularization (0.78 [0.23 to 2.70]), and stent thrombosis (0.95 [0.62 to 1.45]) in the vorapaxar and control groups. In conclusion, after coronary revascularization procedures, addition of vorapaxar to standard medical therapy was associated with reduction in the risk of MI and ischemic stroke and increase in risk of hemorrhagic stroke and Thrombolysis In Myocardial Infarction major and minor bleeds.

Vorapaxar in the secondary prevention of atherothrombosis

Dual antiplatelet therapy with aspirin, a platelet cyclooxygenase-1 inhibitor and P2Y12 receptor blockers, remains the major drug strategy to prevent ischemic event occurrence in patients with acute coronary syndromes and in patients undergoing coronary stenting, but there some limitations that can be overcome by targeting novel targets. Unlike direct thrombin inhibitors that bind directly to thrombin, targeting the platelet thrombin receptor, protease activated receptor (PAR)-1, may offer a better choice for the attenuation of atherosclerosis progression, thrombus-mediated ischemic events and restenosis without interfering with primary hemostasis. Vorapaxar - a synthetic analogue of himbacine, is a high affinity and highly selective PAR-1 antagonist that can effectively inhibit thrombin-induced platelet aggregation. In the TRACER trial, the addition of vorapaxar to standard therapy in patients with non-stent thrombosis-elevation- acute coronary syndromes did not significantly reduce the primary composite end point occurrence of cardiovascular (CV) death, myocardial infarction (MI), stroke, hospitalization for ischemia, or urgent revascularization, but significantly increased the GUSTO moderate and severe bleeding (p < 0.001) and intracranial hemorrhage (ICH). In the TRA 2°P-TIMI 50 trial, in patients with a history of MI and peripheral arterial disease (PAD) (67% of the total population), the end point of CV death, MI, or stroke was significantly (20%) reduced with vorapaxar whereas GUSTO moderate or severe bleeding was increased (1.5-fold), but not ICH or fatal bleeding and the net clinical outcome favoring the vorapaxar therapy. Based on these favorable results, the FDA approved vorapaxar for the reduction of thrombotic cardiovascular events in patients with prior MI or with PAD for long term therapy. A careful patient selection is needed to balance efficacy versus safety. At this time, patients with high risk for recurrent ischemic event occurrence such as patients with diabetes mellitus and previous MI can be safely treated with vorapaxar for long-term therapy.

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.

Current antiplatelet agents: place in therapy and role of genetic testing

Antiplatelet therapies play a central role in reducing the risk of cardiovascular events such as myocardial infarction and stroke. While aspirin, a cyclo-oxygenase-1 inhibitor has been the cornerstone of antithrombotic treatment for several decades, P2Y12 receptor inhibitors cangrelor, clopidogrel, prasugrel, and ticagrelor and protease-activated receptor-1 antagonist vorapaxar, have emerged as additional therapies to reduce the risk of recurrent cardiovascular events in high-risk patients. Recent clinical trials evaluating the role of these agents and major society guideline updates for use of antiplatelet therapies for secondary prevention of cardiovascular events will be examined. The latest studies regarding the appropriate duration of dual antiplatelet therapy after percutaneous coronary intervention will be presented. The current state of genetic and platelet function testing will be reviewed.