New Ischemic Stroke and Outcomes With Vorapaxar Versus Placebo

Pharmacological management of cerebral ischemia in the elderly

Introduction: For elderly adults in the United States, stroke is the fifth leading cause of death of which ischemic strokes comprise a vast majority. Optimal pharmacological management of elderly ischemic stroke patients involves both reperfusion and supportive care. Recent research into pharmacological management has focused on vascular, immunomodulatory, cytoprotective, and alternative agents, some of which have shown limited success in clinical trials. However, no treatments have been established as a reliable mode for management of cerebral ischemia for elderly adults beyond acute thrombolysis.Areas covered: The authors conducted a literature search for ischemic stroke management in the elderly and a search for human drug studies for managing ischemic stroke on clinicaltrials.gov. Here, they describe recent progress in the pharmacological management of cerebral ischemia in the elderly.Expert opinion: Many drug classes (antihypertensive, cytoprotective and immunomodulatory, and alternative agents) have been explored with limited success in managing ischemic stroke, though some have shown preventative benefits. We generally observed a broad gap in evidence on elderly patients from studies across all drug classes, necessitating further studies to gain an understanding of effective management of ischemic stroke in this large demographic of patients.

The Role of Thrombin in Brain Injury After Hemorrhagic and Ischemic Stroke

Thrombin is increased in the brain after hemorrhagic and ischemic stroke primarily due to the prothrombin entry from blood either with a hemorrhage or following blood-brain barrier disruption. Increasing evidence indicates that thrombin and its receptors (protease-activated receptors (PARs)) play a major role in brain pathology following ischemic and hemorrhagic stroke (including intracerebral, intraventricular, and subarachnoid hemorrhage). Thrombin and PARs affect brain injury via multiple mechanisms that can be detrimental or protective. The cleavage of prothrombin into thrombin is the key step of hemostasis and thrombosis which takes place in every stroke and subsequent brain injury. The extravascular effects and direct cellular interactions of thrombin are mediated by PARs (PAR-1, PAR-3, and PAR-4) and their downstream signaling in multiple brain cell types. Such effects include inducing blood-brain-barrier disruption, brain edema, neuroinflammation, and neuronal death, although low thrombin concentrations can promote cell survival. Also, thrombin directly links the coagulation system to the immune system by activating interleukin-1α. Such effects of thrombin can result in both short-term brain injury and long-term functional deficits, making extravascular thrombin an understudied therapeutic target for stroke. This review examines the role of thrombin and PARs in brain injury following hemorrhagic and ischemic stroke and the potential treatment strategies which are complicated by their role in both hemostasis and brain.

Vorapaxar in the treatment of cardiovascular diseases

Vorapaxar specifically and effectively inhibits protease activated receptor-1 and may reduce thrombin-mediated ischemic events without interfering primary hemostasis. In the TRA-2P-TIMI 50 trial, vorapaxar reduced the risk of primary ischemic outcome but with increased bleeding risk. In the post hoc analysis, in patients with a history of myocardial infarction, peripheral artery disease, the net clinical outcome favored vorapaxar therapy with 10% reduction in cardiovascular death, myocardial infarction, stroke, urgent coronary revascularization and moderate or severe bleeding. Based on these favorable results, vorapaxar was approved for the reduction of thrombotic cardiovascular events in patients with prior myocardial infarction or with peripheral artery disease on top of standard antiplatelet therapy. A careful patient selection is needed to balance efficacy versus safety.

Pharmacological Inhibition of Serine Proteases to Reduce Cardiac Inflammation and Fibrosis in Atrial Fibrillation

Systemic inflammation correlates with an increased risk of atrial fibrillation (AF) and thrombogenesis. Systemic inflammation alters vessel permeability, allowing inflammatory and immune cell migration toward target organs, including the heart. Among inflammatory cells infiltrating the atria, macrophages and mast cell have recently attracted the interest of basic researchers due to the pathogenic mechanisms triggered by their activation. This chemotactic invasion is likely implicated in short- and long-term changes in cardiac cell-to-cell communication and in triggering fibrous tissue accumulation in the atrial myocardium and electrophysiological re-arrangements of atrial cardiomyocytes, thus favoring the onset and progression of AF. Serine proteases are a large and heterogeneous class of proteases involved in several processes that are important for cardiac function and are involved in cardiac diseases, such as (i) coagulation, (ii) fibrinolysis, (iii) extracellular matrix degradation, (iv) activation of receptors (i.e., protease-activated receptors [PPARs]), and (v) modulation of the activity of endogenous signals. The recognition of serine proteases substrates and their involvement in inflammatory/profibrotic mechanisms allowed the identification of novel cardio-protective mechanisms for commonly used drugs that inhibit serine proteases. The aim of this review is to summarize knowledge on the role of inflammation and fibrosis as determinants of AF. Moreover, we will recapitulate current findings on the role of serine proteases in the pathogenesis of AF and the possible beneficial effects of drugs inhibiting serine proteases in reducing the risk of AF through decrease of cardiac inflammation and fibrosis. These drugs include thrombin and factor Xa inhibitors (used as oral anticoagulants), dipeptidyl-peptidase 4 (DPP4) inhibitors, used for type-2 diabetes, as well as novel experimental inhibitors of mast cell chymases.

Stroke Outcomes With Vorapaxar Versus Placebo in Patients With Acute Coronary Syndromes: Insights From the TRACER Trial

Background

Vorapaxar, a protease‐activated receptor‐1 antagonist, is approved for secondary prevention of cardiovascular events but is associated with increased intracranial hemorrhage.

Methods and Results

TRACER (Thrombin Receptor Antagonist for Clinical Event Reduction in Acute Coronary Syndrome) was a trial of vorapaxar versus placebo among patients with acute coronary syndrome. Strokes were adjudicated by a central events committee. Of 12 944 patients, 199 (1.5%) had ≥1 stroke during the study period (median follow‐up, 477 days). Four patients had a single stroke of unknown type; 195 patients had ≥1 stroke classified as hemorrhagic or nonhemorrhagic (165 nonhemorrhagic, 28 hemorrhagic, and 2 both). Strokes occurred in 96 of 6473 patients (1.5%) assigned vorapaxar and 103 of 6471 patients (1.6%) assigned placebo. Kaplan‐Meier incidence of stroke for vorapaxar versus placebo was higher for hemorrhagic stroke (0.45% versus 0.14% [hazard ratio, 2.74; 95% confidence interval, 1.22–6.15]), lower but not significantly different for nonhemorrhagic stroke (1.53% versus 1.98% at 2 years [hazard ratio, 0.79; 95% confidence interval, 0.58–1.07]), and similar for stroke overall (1.93% versus 2.13% at 2 years [hazard ratio, 0.94; 95% confidence interval, 0.71–1.24]).

Conclusions

Stroke occurred in <2% of patients. Vorapaxar‐assigned patients had increased hemorrhagic stroke but a nonsignificant trend toward lower nonhemorrhagic stroke. Overall stroke frequency was similar with vorapaxar versus placebo.

Global Vascular Guidelines on the Management of Chronic Limb-Threatening Ischemia

GUIDELINE SUMMARY

Chronic limb-threatening ischemia (CLTI) is associated with mortality, amputation, and impaired quality of life. These Global Vascular Guidelines (GVG) are focused on definition, evaluation, and management of CLTI with the goals of improving evidence-based care and highlighting critical research needs. The term CLTI is preferred over critical limb ischemia, as the latter implies threshold values of impaired perfusion rather than a continuum. CLTI is a clinical syndrome defined by the presence of peripheral artery disease (PAD) in combination with rest pain, gangrene, or a lower limb ulceration >2 weeks duration. Venous, traumatic, embolic, and nonatherosclerotic etiologies are excluded. All patients with suspected CLTI should be referred urgently to a vascular specialist. Accurately staging the severity of limb threat is fundamental, and the Society for Vascular Surgery Threatened Limb Classification system, based on grading of Wounds, Ischemia, and foot Infection (WIfI) is endorsed. Objective hemodynamic testing, including toe pressures as the preferred measure, is required to assess CLTI. Evidence-based revascularization (EBR) hinges on three independent axes: Patient risk, Limb severity, and ANatomic complexity (PLAN). Average-risk and high-risk patients are defined by estimated procedural and 2-year all-cause mortality. The GVG proposes a new Global Anatomic Staging System (GLASS), which involves defining a preferred target artery path (TAP) and then estimating limb-based patency (LBP), resulting in three stages of complexity for intervention. The optimal revascularization strategy is also influenced by the availability of autogenous vein for open bypass surgery. Recommendations for EBR are based on best available data, pending level 1 evidence from ongoing trials. Vein bypass may be preferred for average-risk patients with advanced limb threat and high complexity disease, while those with less complex anatomy, intermediate severity limb threat, or high patient risk may be favored for endovascular intervention. All patients with CLTI should be afforded best medical therapy including the use of antithrombotic, lipid-lowering, antihypertensive, and glycemic control agents, as well as counseling on smoking cessation, diet, exercise, and preventive foot care. Following EBR, long-term limb surveillance is advised. The effectiveness of nonrevascularization therapies (eg, spinal stimulation, pneumatic compression, prostanoids, and hyperbaric oxygen) has not been established. Regenerative medicine approaches (eg, cell, gene therapies) for CLTI should be restricted to rigorously conducted randomizsed clinical trials. The GVG promotes standardization of study designs and end points for clinical trials in CLTI. The importance of multidisciplinary teams and centers of excellence for amputation prevention is stressed as a key health system initiative.

Global vascular guidelines on the management of chronic limb-threatening ischemia

Chronic limb-threatening ischemia (CLTI) is associated with mortality, amputation, and impaired quality of life. These Global Vascular Guidelines (GVG) are focused on definition, evaluation, and management of CLTI with the goals of improving evidence-based care and highlighting critical research needs. The term CLTI is preferred over critical limb ischemia, as the latter implies threshold values of impaired perfusion rather than a continuum. CLTI is a clinical syndrome defined by the presence of peripheral artery disease (PAD) in combination with rest pain, gangrene, or a lower limb ulceration >2 weeks duration. Venous, traumatic, embolic, and nonatherosclerotic etiologies are excluded. All patients with suspected CLTI should be referred urgently to a vascular specialist. Accurately staging the severity of limb threat is fundamental, and the Society for Vascular Surgery Threatened Limb Classification system, based on grading of Wounds, Ischemia, and foot Infection (WIfI) is endorsed. Objective hemodynamic testing, including toe pressures as the preferred measure, is required to assess CLTI. Evidence-based revascularization (EBR) hinges on three independent axes: Patient risk, Limb severity, and ANatomic complexity (PLAN). Average-risk and high-risk patients are defined by estimated procedural and 2-year all-cause mortality. The GVG proposes a new Global Anatomic Staging System (GLASS), which involves defining a preferred target artery path (TAP) and then estimating limb-based patency (LBP), resulting in three stages of complexity for intervention. The optimal revascularization strategy is also influenced by the availability of autogenous vein for open bypass surgery. Recommendations for EBR are based on best available data, pending level 1 evidence from ongoing trials. Vein bypass may be preferred for average-risk patients with advanced limb threat and high complexity disease, while those with less complex anatomy, intermediate severity limb threat, or high patient risk may be favored for endovascular intervention. All patients with CLTI should be afforded best medical therapy including the use of antithrombotic, lipid-lowering, antihypertensive, and glycemic control agents, as well as counseling on smoking cessation, diet, exercise, and preventive foot care. Following EBR, long-term limb surveillance is advised. The effectiveness of nonrevascularization therapies (eg, spinal stimulation, pneumatic compression, prostanoids, and hyperbaric oxygen) has not been established. Regenerative medicine approaches (eg, cell, gene therapies) for CLTI should be restricted to rigorously conducted randomizsed clinical trials. The GVG promotes standardization of study designs and end points for clinical trials in CLTI. The importance of multidisciplinary teams and centers of excellence for amputation prevention is stressed as a key health system initiative.

Targeting von Willebrand Factor in Ischaemic Stroke: Focus on Clinical Evidence

Despite great efforts in stroke research, disability and recurrence rates in ischaemic stroke remain unacceptably high. To address this issue, one potential target for novel therapeutics is the glycoprotein von Willebrand factor (vWF), which increases in thrombogenicity especially under high shear rates as it bridges between vascular sub-endothelial collagen and platelets. The rationale for vWF as a potential target in stroke comes from four bodies of evidence. (1) Animal models which recapitulate the pathogenesis of stroke and validate the concept of targeting vWF for stroke prevention and the use of the vWF cleavage enzyme ADAMTS13 in acute stroke treatment. (2) Extensive epidemiologic data establishing the prognostic role of vWF in the clinical setting showing that high vWF levels are associated with an increased risk of first stroke, stroke recurrence or stroke-associated mortality. As such, vWF levels may be a suitable marker for further risk stratification to potentially fine-tune current risk prediction models which are mainly based on clinical and imaging data. (3) Genetic studies showing an association between vWF levels and stroke risk on genomic levels. Finally, (4) studies of patients with primary disorders of excess or deficiency of function in the vWF axis (e.g. thrombotic thrombocytopenic purpura and von Willebrand disease, respectively) which demonstrate the crucial role of vWF in atherothrombosis. Therapeutic inhibition of VWF by novel agents appears particularly promising for secondary prevention of stroke recurrence in specific sub-groups of patients such as those suffering from large artery atherosclerosis, as designated according to the TOAST classification.

Impact of Cerebrovascular Events Older Than One Year on Ischemic and Bleeding Outcomes With Cangrelor in Percutaneous Coronary Intervention

BACKGROUND

Cangrelor is a potent intravenous adenosine diphosphate-receptor antagonist that in the CHAMPION trials reduced the 48-hour and 30-day rates of ischemic events during percutaneous coronary intervention without an increase in severe bleeding.

METHODS AND RESULTS

CHAMPION PCI (A Clinical Trial to Demonstrate the Efficacy of Cangrelor), CHAMPION PLATFORM (Cangrelor Versus Standard Therapy to Achieve Optimal Management of Platelet Inhibition), and CHAMPION PHOENIX (A Clinical Trial Comparing Cangrelor to Clopidogrel Standard Therapy in Subjects Who Require Percutaneous Coronary Intervention) were 3 randomized, double-blind, double-dummy trials in which cangrelor was compared with clopidogrel during percutaneous coronary intervention. The effect of cangrelor on ischemic events and bleeding was analyzed in the subgroup of patients with a history of cerebrovascular events at least 1 year prior to randomization; the Breslow-Day test was used to test for interaction of treatment effect in subgroups with and without such a history. The primary efficacy end point was a composite of death, myocardial infarction, ischemia-driven revascularization, or stent thrombosis at 48 hours. Among 24 910 randomized patients, 1270 patients (5.1%) had a cerebrovascular event >1 year old, including 650 assigned to cangrelor and 620 assigned to clopidogrel. Consistent with the overall trial results, the rate of the primary efficacy end point was 4.3% in the cangrelor group versus 5.3% in the clopidogrel group (odds ratio 0.80; 95% confidence interval 0.48-1.34; P=0.40; P for interaction =0.97), and the rate of GUSTO (Global Use of Strategies to Open Occluded Coronary Arteries) severe bleeding was 0.3% in both groups (P=0.97; P for interaction =0.81).

CONCLUSIONS

Among patients in the CHAMPION trials with a prior cerebrovascular event at least 1 year before the percutaneous coronary intervention, the efficacy and bleeding profile of cangrelor compared with clopidogrel was similar to that in the overall trial.

Changes in Treatment Patterns and Incremental Health Care Utilization Due to P2Y12-Associated Complications in Patients with Acute Coronary Syndrome

BACKGROUND

P2Y12 antiplatelet therapy (APT) is highly efficacious in reducing the incidence of ischemic events in patients with acute coronary syndrome (ACS); however, it is associated with several adverse complications. Data on P2Y12-associated complications and adherence to APT are sparse.

OBJECTIVE

To describe the characteristics, frequency of P2Y12-associated complications, adherence and persistence to P2Y12 APT, and health care utilization among ACS patients on P2Y12 APT.

METHODS

This retrospective observational study of the MarketScan Commercial Claims and Encounters Database identified patients aged ≥ 18 years who were discharged from an ACS hospitalization in 2012-2014 and initiated P2Y12 APT (ticagrelor, prasugrel, or clopidogrel). The proportion of patients within each treatment group who experienced P2Y12-associated complications within 1 year and who were adherent to APT were determined. Frequencies of all-cause health care utilization (i.e., hospitalization, length of stay, emergency room [ER] visits, outpatient visits, cardiac events, and transfusions) were evaluated for each treatment group. Poisson regressions were conducted to evaluate the association between nonad-herence with P2Y12 APT and health care utilization, after adjusting for demographics (age and gender), health insurance type, and comorbidities.

RESULTS

Among 11,629 ACS patients, most were male; 44.6% had hypertension; 20.6% had diabetes; and 53.4% had hyperlipidemia. Clopidogrel use was common (62.6%), with ticagrelor use less common (9.0%). Among all groups, approximately one third experienced P2Y12-associated complications. One-year adherence to APT was suboptimal (68% overall), with 73.3% adherence among prasugrel users, followed by 71.4% adherence among ticagrelor users and 65.6% adherence among clopidogrel users. Switching was most common with ticagrelor users. Inpatient hospitalizations, cardiac events, and transfusions were more common in clopidogrel users compared with prasugrel and ticagrelor users. Nonadherent patients experienced significantly more hospitalizations, ER visits, and transfusions (1.34, 1.09, and 1.85 [P < 0.05], respectively) compared with adherent patients. These trends of association remained consistent across all treatment groups. Also, patients not adherent to ticagrelor experienced 1.9 times as many cardiac events as adherent patients. However, this association was not significant for clopidogrel and prasugrel users. Patients not adherent to P2Y12 APT experienced significantly lower outpatient visits compared with adherent patients.

CONCLUSIONS

Complications associated with P2Y12 in ACS patients treated with P2Y12 APT were common, with dyspnea, heart block, and major or life-threatening bleeding as the most common. Adherence was significantly associated with lower health care utilization. Increased adherence to secondary prevention therapy among these very high-risk patients is crucial. Disease management strategies to improve adherence and reduce treatment-associated adverse events through individualized patient care, alternative secondary treatment options, and physician awareness should be designed, implemented, and sustained.

DISCLOSURES

Data analysis was conducted by Merck & Co., the manufacturer of vorapaxar (ZONTIVITY). At the time of this study, Vyas was an employee of Rutgers University, which received grant funding from Merck & Co. for this study, and is now employed with the University of Rhode Island. Patel was employed by Symphony Solutions and the University of North Carolina during the drafting and revising of the manuscript. Bash is employed by Merck & Co. Simpson received consulting fees from Merck & Co. for work on this study and has received fees for research from Amgen and Pfizer. Study concept and design were contributed by Vyas, Bash, Patel, and Simpson. Patel took the lead in data collection, assisted by the other authors. All the authors contributed equally to data analysis and manuscript preparation. The abstract for this study was presented as a poster at the American Heart Association Scientific Sessions 2016; November 12-16, 2016; New Orleans, Louisiana.

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.

Antithrombotic therapy for secondary prevention of atherothrombotic events in cerebrovascular disease

Atherothrombosis is the common underlying process for numerous progressive manifestations of cardiovascular disease, including coronary artery disease (CAD) and cerebrovascular disease (CVD). Antiplatelet therapy is the cornerstone of pharmacological management in patients with atherothrombosis. Over the past 20 years, major advances in antiplatelet pharmacotherapy have been made, particularly for the treatment of patients with CAD. The treatment of patients with concomitant CAD and CVD is complex, owing to their increased risk of both ischaemia and bleeding. When CVD arises from large artery atherosclerosis, antithrombotic therapies are essential to prevent stroke or transient ischaemic attack (TIA). However, the use of antithrombotic medications in patients with CVD can put them at high risk of intracranial haemorrhage. As such, the risk-benefit profile of various combinations of antiplatelet agents in patients with both CAD and CVD is uncertain. This Review provides a state-of-the-art account of the available evidence on antithrombotic therapies for the secondary prevention of atherothrombotic events in patients with concomitant CAD and CVD, particularly those with a history of noncardioembolic stroke or TIA.

Antithrombotic therapy for secondary prevention of atherothrombotic events in cerebrovascular disease

Atherothrombosis is the common underlying process for numerous progressive manifestations of cardiovascular disease, including coronary artery disease (CAD) and cerebrovascular disease (CVD). Antiplatelet therapy is the cornerstone of pharmacological management in patients with atherothrombosis. Over the past 20 years, major advances in antiplatelet pharmacotherapy have been made, particularly for the treatment of patients with CAD. The treatment of patients with concomitant CAD and CVD is complex, owing to their increased risk of both ischaemia and bleeding. When CVD arises from large artery atherosclerosis, antithrombotic therapies are essential to prevent stroke or transient ischaemic attack (TIA). However, the use of antithrombotic medications in patients with CVD can put them at high risk of intracranial haemorrhage. As such, the risk-benefit profile of various combinations of antiplatelet agents in patients with both CAD and CVD is uncertain. This Review provides a state-of-the-art account of the available evidence on antithrombotic therapies for the secondary prevention of atherothrombotic events in patients with concomitant CAD and CVD, particularly those with a history of noncardioembolic stroke or TIA.

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.

Expert position paper on prolonged dual antiplatelet therapy in secondary prevention following myocardial infarction

The protective effect of dual antiplatelet therapy (DAPT) following acute coronary syndrome is undisputed, but its duration is subject of debate. Several studies show that prolonged therapy provides a clinical benefit in patients following acute coronary syndrome. The aim of this position paper authored by Austrian experts is to outline the current evidence and provide an overview of recent studies. It is also intended to serve as a practical guide to identify those patients who may benefit from prolonged DAPT.

Diabetes Mellitus and Prevention of Late Myocardial Infarction After Coronary Stenting in the Randomized Dual Antiplatelet Therapy Study

Background—

Patients with diabetes mellitus (DM) are at high risk for recurrent ischemic events after coronary stenting. We assessed the effects of continued thienopyridine among patients with DM participating in the Dual Antiplatelet Therapy (DAPT) Study as a prespecified analysis.

Methods and Results—

After coronary stent placement and 12 months treatment with open-label thienopyridine plus aspirin, 11 648 patients free of ischemic or bleeding events and who were medication compliant were randomly assigned to continued thienopyridine or placebo, in addition to aspirin, for 18 more months. After randomization, patients with DM (n=3391), in comparison with patients without DM (n=8257), had increased composite outcome of death, myocardial infarction (MI), or stroke (6.8% versus 4.3%, P <0.001), increased death (2.5% versus 1.4%, P <0.001), and MI (4.2% versus 2.6%, P <0.001). Among patients with DM, in a comparison of continued thienopyridine versus placebo, rates of stent thrombosis were 0.5% versus 1.1%, P =0.06, and rates of MI were 3.5% versus 4.8%, P =0.058; and among patients without DM the rates were 0.4% versus 1.4%, P <0.001 (stent thrombosis, P interaction=0.21) and 1.6% versus 3.6%, P <0.001 (MI, P interaction=0.02). Bleeding risk with continued thienopyridine was similar among patients with or without DM (interaction P =0.61).

Conclusions—

In patients with DM, continued thienopyridine beyond 1 year after coronary stenting is associated with reduced risk of MI, although this benefit is attenuated in comparison with patients without DM.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00977938.

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.

Vorapaxar monotherapy for secondary stroke prevention: A call for randomized trial

BACKGROUND AND PURPOSE

Vorapaxar, a novel platelet thrombin protease-activated receptor 1 blocker, is currently approved for post-myocardial infarction and peripheral artery disease indications on top of clopidogrel or/and aspirin. We sought to summarize the conflicting stroke data after vorapaxar for justifying a secondary stroke prevention trial.

METHODS

Analyses of the stroke data after vorapaxar yielded from thrombin-receptor antagonist vorapaxar in acute coronary syndromes (TRACER) and TRA2P clinical trials, and affiliated Food and Drug Administration (FDA) reviews.

RESULTS

The stroke data are mixed, with catastrophic 2.5 excess of intracranial bleeding risks (HR = 2.52; 95% CI = 1.46-4.36, p < 0.0001); trend to worsened second stroke rates (13.0% vs. 11.7%; HR = 1.03; 95% CI = 0.85-1.25, p = NS), but a hint towards less primary ischemic strokes in vorapaxar indicated population (HR = 0.57; 95% CI = 0.43 to 0.75; p < 0.001). These conflicting data are not solely attributed to vorapaxar, but rather reflect unreasonably aggressive triple antiplatelet strategies utilized frequently in TRA2P and dominant in TRACER. Overall, the FDA-confirmed evidence advocates future vorapaxar secondary stroke prevention trial due to being first-in-class agent, unique pharmakynetics, and exhibiting very mild "comfort zone" antiplatelet profile. The three arm trial testing head-to-head monotherapy with vorapaxar (Zontivity®), versus clopidogrel (Plavix®), and versus extended-released dipyridamole with very low dose aspirin (Aggrenox®) is warranted.

CONCLUSIONS

Vorapaxar may be superior to currently recommended antiplatelet strategies and should be tested as a monotherapy in a randomized outcome-driven secondary stroke prevention trial.

Vorapaxar for secondary stroke prevention: perspectives and obstacles

Vorapaxar, a novel antiplatelet thrombin protease-activated receptor 1 (PAR-1) inhibitor, has been evaluated in the successful TRA2P trial and failed TRACER trial. The drug is currently approved for post myocardial infarction and peripheral artery disease indications on top of clopidogrel and/or aspirin. The stroke data after vorapaxar are mixed, dominated with heavy excess of intracranial bleeding risks and slightly worsened second stroke rates, but show less primary ischemic strokes. Fortunately, these conflicting data do not belong purely to vorapaxar per se but rather, reflect unreasonably aggressive strategies, including predominantly triple antiplatelet therapy, utilized in both Trial to Assess the Effects of SCH 530348 in Preventing Heart Attack and Stroke in Patients with Arteriosclerosis (TRA2P) and especially in Thrombin-Receptor Antagonist Vorapaxar in Acute Coronary Syndromes (TRACER). The FDA-confirmed evidence strongly suggests that unique pharmacokinetics and a very mild "comfort zone" antiplatelet profile makes vorapaxar a good candidate for improved secondary stroke prevention. The outcome-driven, randomized trial should test head-to-head monotherapy with vorapaxar (Zontivity®) versus clopidogrel (Plavix®) and versus dipyridamole with very low dose aspirin (Aggrenox®). The advantages and potential pitfalls of such a trial are discussed in this article.

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.

Platelet function recovery following exposure to triple anti-platelet inhibitors using an in vitro transfusion model

INTRODUCTION

Dual anti-platelet therapy (DAPT) with aspirin and a P2Y12 antagonist is standard of care to reduce risk of thrombosis, but does not directly target thrombin-dependent platelet activation. Therefore, PAR-1 antagonist addition to DAPT (i.e., triple anti-platelet therapy; TAPT) may improve the efficacy of treatment, though at the expense of an increase in bleeding risk. Using an in vitro transfusion model, we evaluated if platelet function loss associated with TAPT can be remedied by the addition of drug-naïve platelets.

METHODS

To mimic TAPT, platelet-rich plasma (PRP) prepared from consented DAPT patients (DPRP) was incubated with a vorapaxar at therapeutic plasma levels (TPRP). To simulate platelet transfusions, TPRP was mixed with increasing proportions of drug-naïve PRP (NPRP). Platelet function recovery was assessed by light transmission aggregometry (LTA), aggregate morphology, and P-selectin expression.

RESULTS

LTA results demonstrated that 20% NPRP was required to restore the ADP aggregation response in TPRP to the response observed in DPRP and 40% NPRP recovered aggregation to >65%. Higher NPRP fractions (60%) were required to restore the platelet reactivity using TRAP-6 (SFLLRN) or arachidonic acid (AA). PAR-4 aggregation was unaffected by platelet antagonists. A decrease in single, free platelets and incorporation of mepacrine-labeled naïve platelets into aggregates occurred with increasing NPRP portions. Upon agonist activation, the surface density and percent of P-selectin positive platelets increased linearly upon addition of NPRP.

CONCLUSION

This in vitro model demonstrated that administration of drug-naïve platelets can be a useful strategy for reversing overall platelet inhibition observed with TAPT.

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.

Cerebrovascular events after a primary percutaneous coronary intervention strategy for acute ST-segment-elevation myocardial infarction: analysis from the HORIZONS-AMI Trial

BACKGROUND

Patients with ST-segment-elevation myocardial infarction are at increased risk of cerebrovascular events. We assessed the incidence, predictors, and implications of cerebrovascular events in patients with ST-segment-elevation myocardial infarction managed with a primary percutaneous coronary intervention strategy.

METHODS AND RESULTS

In the Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction (HORIZONS-AMI) trial, 72 of 3602 patients (2.0%) experienced at least 1 cerebrovascular event (stroke: 63 patients; transient ischemic attack: 12 patients) during the 3-year follow-up (40.3% within 30 days, 20.8% between 30 days and 1 year, and 38.9% between 1 and 3 years). Stroke was ischemic in 58 (92.1%) patients and hemorrhagic in 5 (7.9%) patients. More than half of all strokes (52.3%) were disabling. By principal management strategy, cerebrovascular events developed in 2.0%, 14.9%, and 1.9% of patients triaged to primary percutaneous coronary intervention, coronary artery bypass grafting, and medical therapy, respectively (P<0.0001). Cerebrovascular events were independently predicted by older age, creatinine clearance <60 mL/min, treatment with coronary artery bypass grafting, anemia, and diabetes mellitus. Cerebrovascular events were associated with significantly increased rates of 3-year mortality (20.5% versus 6.5%; P<0.0001), as well as reinfarction (14.3% versus 3.8%; P=0.0007), ischemia-driven target vessel revascularization (22.8% versus 13.0%; P=0.006), and major bleeding (23.5% versus 8.4%; P<0.0001).

CONCLUSIONS

In HORIZONS-AMI, cerebrovascular events within 3 years after ST-segment-elevation myocardial infarction in patients undergoing a primary percutaneous coronary intervention management strategy occurred in 2.0% of patients and were most frequent after coronary artery bypass grafting. Cerebrovascular events were often disabling and were strongly associated with high rates of death, reinfarction, recurrent ischemia, and major bleeding.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00433966.