Ticagrelor versus clopidogrel in patients with acute coronary syndromes intended for non-invasive management: substudy from prospective randomised PLATelet inhibition and patient Outcomes (PLATO) trial

Clopidogrel Response Variability: Review of the Literature and Practical Considerations

Dual antiplatelet therapy with aspirin and a P2Y12 inhibitor is standard therapy following acute coronary syndrome and percutaneous coronary intervention. Despite the use of potent antiplatelet agents, vascular events continue to occur. Lack of response to clopidogrel therapy has been widely investigated using various methods of platelet function testing. These studies have consistently found an association between poor clopidogrel response and an increased risk of vascular events. Strategies to overcome this problem include higher clopidogrel doses or the use of an alternative P2Y12 agent. To date, the majority of studies investigating tailored antiplatelet therapy have failed to show any reduction in clinical events likely due to the low-risk population studied. Despite this lack of benefit from altering therapy, platelet function testing may be done in certain patient populations. Patients at high risk of deleterious outcomes from stent thrombosis may be an appropriate patient population for platelet function testing to ensure adequate response to therapy. In addition, emerging data suggests a potential role for platelet function testing to assess for bleeding risk. The purpose of this article is to review the key studies demonstrating response variability to clopidogrel therapy, strategies to overcome variability, and practical considerations for the clinician.

Current approaches for the diagnosis, risk stratification and interventional treatment of patients with acute coronary syndromes without st-segment elevation

This article reviews current approaches to diagnosis and determination of the individual risk of patients with acute coronary syndrome without ST-segment elevation. Guidelines for determining the choice of treatment strategy and the time slots for its implementation are discussed. We describe the technical features of the implementation of interventional treatment in this group of patients; the choice of methods of myocardial revascularization is discussed.

Contemporary use of ticagrelor in patients with acute coronary syndrome: insights from Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies (SWEDEHEART)

AIMS

The platelet inhibitor ticagrelor is strongly recommended during 12 months post-acute coronary syndrome (ACS) in European guidelines. We analysed clinical characteristics of patients given ticagrelor for ACS in the real world.

METHODS AND RESULTS

We studied the use of ticagrelor in patients admitted for ACS in Sweden between 1 January 2012 and 31 December 2013 who were enrolled in the Swedish Web system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies (SWEDEHEART). Clinical characteristics were investigated for patients prescribed ticagrelor at discharge as well as for patients undergoing percutaneous coronary intervention who were prescribed ticagrelor. Independent factors associated with selecting ticagrelor were analysed in logistic regression. We found that 44.0% (n = 12 601) out of a total of 28 639 patients had been prescribed ticagrelor at discharge. After adjusting for age and sex, prior cardiovascular disease was less common in patients discharged on ticagrelor (myocardial infarction, ischaemic stroke, and peripheral vascular disease; P for all <0.001). The risk of death as predicted by GRACE score and the risk of major bleeding as predicted by CRUSADE score were both lower in ticagrelor-treated patients vs. others (median 99 vs. 126 and median 23 vs. 25, respectively; P for both < 0.001). The intended treatment duration at discharge was 12 months in 82.5% of patients and <12 months in 9.3%.

CONCLUSION

Ticagrelor is preferentially being used in patients at lower risk. A minority of patients are recommended ticagrelor during <12 months.

Practical experience with ticagrelor: an Australian and New Zealand perspective

OBJECTIVE

Ticagrelor is recommended in local and international guidelines as first-line therapy in combination with aspirin in patients presenting with acute coronary syndromes (ACS). The purpose of this article is to provide practical guidance regarding the use of ticagrelor in this setting.

METHODS AND RESULTS

Ticagrelor, a direct-acting, reversible P2Y12 receptor antagonist, has a faster onset, and a more potent and predictable antiplatelet effect compared with clopidogrel. The authors recommend considering the use of ticagrelor in moderate-to-high risk ACS patients treated with an invasive approach and those managed non-invasively who have elevated troponin levels. Consistent with outcomes observed in the PLATO trial overall, ticagrelor was superior to clopidogrel treatment in patients with chronic kidney disease, a history of stroke or transient ischemic attack, the elderly, and patients requiring surgical revascularization.

CONCLUSIONS

When switching from clopidogrel to ticagrelor, patients established on clopidogrel therapy can be switched directly without loading; patients not loaded with clopidogrel and not taking maintenance dose clopidogrel for at least 5 days should first be loaded with ticagrelor. Guidelines recommend discontinuing ticagrelor 5 days before surgery if antiplatelet effects are not desired and recommencing therapy as soon as safe following surgery. Ticagrelor should be avoided in individuals with a history of intracranial hemorrhage, moderate-to-severe hepatic impairment, high bleeding risk, within 24 hours of thrombolytic therapy, and in those treated with oral anticoagulants. Local, real-world experience suggests low bleeding rates with ticagrelor therapy. Dyspnoea is a common symptom in patients with ACS and is also a side-effect of ticagrelor therapy. Discontinuation of ticagrelor due to dyspnoea has been uncommon in clinical trials. However, local registry data suggest higher discontinuation rates (2-9%) related to dyspnoea in the real-world setting, indicating that clinicians may need to consider other potential causes of dyspnoea before discontinuing ticagrelor.

Clinical evidence for oral antiplatelet therapy in acute coronary syndromes

Platelet-mediated thrombosis is a major pathophysiological mechanism that underlies acute coronary syndromes, and therefore, antiplatelet therapy is an important foundation in the treatment and prevention of recurrence of these syndromes. Nearly 30 years ago, aspirin was the first agent to show a benefit for acute coronary syndromes and is still a key therapeutic agent. The landmark CURE trial showed that the addition of a P2Y12 antagonist, clopidogrel, to aspirin was beneficial in the treatment of acute coronary syndromes. Despite substantial benefits with clopidogrel, limitations include the slow speed of onset, variable response, and a modest antiplatelet effect. Next-generation P2Y12 antagonists, prasugrel and ticagrelor, overcome these limitations and have been shown, in large-scale clinical trials for acute coronary syndromes, to reduce ischaemic events more than clopidogrel, at the expense of an increase in bleeding. Additional agents that target platelets by alternate mechanisms, including the protease-activated receptor-1 antagonist vorapaxar, have shown ischaemic benefit. These large-scale trials inform treatment decisions that need to balance ischaemic benefit and bleeding risk in patients with acute coronary syndromes. This Series paper describes major trial results, implications for clinical practice, and summarises continuing controversy.

Updates and current recommendations for the management of patients with non-ST-elevation acute coronary syndromes: what it means for clinical practice

The American Heart Association (AHA) and the American College of Cardiology (ACC) have recently updated their joint guidelines for the management of patients with non-ST-elevation acute coronary syndromes (NSTE-ACS, including unstable angina [UA] and non-ST-elevation myocardial infarction [NSTEMI]). These guidelines replace the 2007 guidelines and the focused updates from 2011 and 2012 and now combine UA and NSTEMI into a new classification, NSTE-ACS, and updating the terminology around noninvasive management to ischemia-guided strategy. The latest guidelines include updated recommendations for the use of the oral antiplatelet agents (P2Y12 inhibitors) prasugrel and ticagrelor as part of dual-antiplatelet therapy-the cornerstone of treatment for these patients. This report provides a comprehensive overview of the new and modified recommendations for the management of patients with NSTE-ACS and the evidence supporting them. Also, where appropriate, similarities and differences between the current recommendations of the AHA/ACC and those of the European Society of Cardiology (ESC) are highlighted. For example, the AHA/ACC recommends the P2Y12 inhibitor ticagrelor over clopidogrel in all patients with NSTE-ACS and clopidogrel, prasugrel, or ticagrelor for patients in whom percutaneous coronary intervention is planned, whereas the ESC guidelines specifically recommend individual P2Y12 inhibitors for particular patient subgroups.

Challenges and solutions in medically managed ACS in the Asia-Pacific region: expert recommendations from the Asia-Pacific ACS Medical Management Working Group

Acute coronary syndromes (ACS) remain a leading cause of mortality and morbidity in the Asia-Pacific (APAC) region. International guidelines advocate invasive procedures in all but low-risk ACS patients; however, a high proportion of ACS patients in the APAC region receive solely medical management due to a combination of unique geographical, socioeconomic, and population-specific barriers. The APAC ACS Medical Management Working Group recently convened to discuss the ACS medical management landscape in the APAC region. Local and international ACS guidelines and the global and APAC clinical evidence-base for medical management of ACS were reviewed. Challenges in the provision of optimal care for these patients were identified and broadly categorized into issues related to (1) accessibility/systems of care, (2) risk stratification, (3) education, (4) optimization of pharmacotherapy, and (5) cost/affordability. While ACS guidelines clearly represent a valuable standard of care, the group concluded that these challenges can be best met by establishing cardiac networks and individual hospital models/clinical pathways taking into account local risk factors (including socioeconomic status), affordability and availability of pharmacotherapies/invasive facilities, and the nature of local healthcare systems. Potential solutions central to the optimization of ACS medical management in the APAC region are outlined with specific recommendations.

The potential role of anticoagulant therapy for the secondary prevention of ischemic events post-acute coronary syndrome

Abstract The use of dual antiplatelet therapy has led to a substantial reduction in ischemic events post-acute coronary syndrome (ACS). Despite this, recurrent event rates remain high. Recent research has combined antiplatelet with anticoagulant therapy to reduce recurrent event rates further. Compared with standard medical therapy, rivaroxaban demonstrated improved efficacy outcomes and significantly reduced mortality after an ACS. Although clear benefits of novel oral anticoagulants post-ACS have been proven, concerns regarding bleeding are still a barrier to widespread use. This review explores key trials of dual antiplatelet therapy and examines the latest research in anticoagulation aiming to optimize clinical outcomes post-ACS.

Prasugrel and ticagrelor: is there a winner?

Clopidogrel is a prodrug that undergoes extensive enteric clearance and requires two-stage hepatic activation by cytochrome P450 (CYP) enzymes. This metabolic pathway is susceptible to genetic polymorphisms, resulting in a variable platelet inhibitory effect. A growing number of studies have linked poor antiplatelet response to clopidogrel to adverse clinical outcomes, particularly coronary ischemic events and stent thrombosis. This has prompted the development of new ADP receptor antagonists that inhibit platelets more effectively. Two of these agents, prasugrel and ticagrelor, have been investigated in two large randomized clinical trials, and both have shown superiority versus clopidogrel in reducing ischemic endpoints, with an increase in bleeding events, but a favorable final net clinical outcome. Since the publication of the main articles, several sub-analyses have been performed on the same data, and Guideline recommendations have largely endorsed these subgroup findings. Most clinicians have accepted the concept that we might consider approaching the patient differently, deserving a specific agent for each different settings. However, subgroup analyses of randomized trials are often post hoc, underpowered and prone to bias. Weighing efficacy and safety of the most commonly used antiplatelet agents will represent a clinical challenge over the next few years. Furthermore, individuals and organizations involved in formulary decisions will have to face economic constraints, also taking into account the availability of low-cost generic clopidogrel. In the following review, we have performed a critical appraisal of the current literature in order to outline lights and shadows on the most relevant clinical scenarios.

Health economic analysis of ticagrelor in patients with acute coronary syndromes intended for non-invasive therapy

Objective

To investigate the cost effectiveness of ticagrelor versus clopidogrel in patients with acute coronary syndromes (ACS) in the Platelet Inhibition and Patient Outcomes (PLATO) study who were scheduled for non-invasive management.

Methods

A previously developed cost effectiveness model was used to estimate long-term costs and outcomes for patients scheduled for non-invasive management. Healthcare costs, event rates and health-related quality of life under treatment with either ticagrelor or clopidogrel over 12 months were estimated from the PLATO study. Long-term costs and health outcomes were estimated based on data from PLATO and published literature sources. To investigate the importance of different healthcare cost structures and life expectancy for the results, the analysis was carried out from the perspectives of the Swedish, UK, German and Brazilian public healthcare systems.

Results

Ticagrelor was associated with lifetime quality-adjusted life-year (QALY) gains of 0.17 in Sweden, 0.16 in the UK, 0.17 in Germany and 0.13 in Brazil compared with generic clopidogrel, with increased healthcare costs of €467, €551, €739 and €574, respectively. The cost per QALY gained with ticagrelor was €2747, €3395, €4419 and €4471 from a Swedish, UK, German and Brazilian public healthcare system perspective, respectively. Probabilistic sensitivity analyses indicated that the cost per QALY gained with ticagrelor was below conventional threshold values of cost effectiveness with a high probability.

Conclusions

Treatment of patients with ACS scheduled for 12 months’ non-invasive management with ticagrelor is associated with a cost per QALY gained below conventional threshold values of cost effectiveness compared with generic clopidogrel.

Trial registration number

NCT000391872.

Ticagrelor: pharmacokinetics, pharmacodynamics, clinical efficacy, and safety

Dual antiplatelet therapy, composed of aspirin plus a P2Y₁₂-receptor antagonist, is the cornerstone of treatment for patients with acute coronary syndrome (ACS). A number of U.S. Food and Drug Administration–approved P2Y₁₂-receptor antagonists are available for treating patients with ACS, including the thienopyridine compounds clopidogrel and prasugrel. Ticagrelor, the first of a new class of antiplatelet agents, is a noncompetitive, direct-acting P2Y₁₂-receptor antagonist. Unlike the thienopyridine compounds, ticagrelor does not require metabolism for activity. Also, whereas clopidogrel and prasugrel are irreversible inhibitors of the P2Y₁₂ receptor, ticagrelor binds reversibly to inhibit receptor signaling and subsequent platelet activation. In pharmacodynamic studies, ticagrelor demonstrated faster onset and more potent inhibition of platelet aggregation than clopidogrel. These properties of ticagrelor may contribute to reduced rates of thrombotic outcomes compared with clopidogrel, as demonstrated in a phase III clinical trial. However, in addition to bleeding, distinctive adverse effects of this new chemical entity have not been reported with the thienopyridine P2Y₁₂-receptor inhibitors. Although ticagrelor represents an advancement in P2Y₁₂-receptor inhibition therapy, a thorough understanding of this compound as an antiplatelet therapy remains to be elucidated.

World heart federation expert consensus statement on antiplatelet therapy in east asian patients with ACS or undergoing PCI

Guideline recommendations on the use of dual antiplatelet therapy (DAPT) in patients with acute coronary syndromes and in those undergoing percutaneous coronary intervention (PCI) have been formulated by both the ACC/AHA and the ESC. These recommendations are based primarily on large, phase III, randomized, controlled trials of the P2Y12 inhibitors clopidogrel, prasugrel, and ticagrelor. However, few East Asian patients have been included in the trials to assess the use of these agents, particularly the newer agents prasugrel and ticagrelor. Additionally, an increasing body of data suggests that East Asian patients have differing risk profiles for both thrombophilia and bleeding compared with white patients, and that a different 'therapeutic window' of on-treatment platelet reactivity might be appropriate in East Asian patients. Furthermore, a phenomenon referred to as the 'East Asian paradox' has been described, in which East Asian patients have a similar or even a lower rate of ischaemic events after PCI compared with white patients, despite a higher level of platelet reactivity during DAPT. Recognizing these concerns, the World Heart Federation has undertaken this evidence-based review and produced this expert consensus statement to determine the antiplatelet treatment strategies that are most appropriate for East Asian patients.

Expert consensus document: World Heart Federation expert consensus statement on antiplatelet therapy in East Asian patients with ACS or undergoing PCI

Guideline recommendations on the use of dual antiplatelet therapy (DAPT) in patients with acute coronary syndromes and in those undergoing percutaneous coronary intervention (PCI) have been formulated by both the ACC/AHA and the ESC. These recommendations are based primarily on large, phase III, randomized, controlled trials of the P2Y12 inhibitors clopidogrel, prasugrel, and ticagrelor. However, few East Asian patients have been included in the trials to assess the use of these agents, particularly the newer agents prasugrel and ticagrelor. Additionally, an increasing body of data suggests that East Asian patients have differing risk profiles for both thrombophilia and bleeding compared with white patients, and that a different 'therapeutic window' of on-treatment platelet reactivity might be appropriate in East Asian patients. Furthermore, a phenomenon referred to as the 'East Asian paradox' has been described, in which East Asian patients have a similar or even a lower rate of ischaemic events after PCI compared with white patients, despite a higher level of platelet reactivity during DAPT. Recognizing these concerns, the World Heart Federation has undertaken this evidence-based review and produced this expert consensus statement to determine the antiplatelet treatment strategies that are most appropriate for East Asian patients.

Management of acute coronary syndrome in the hospital: a focus on ACCF/AHA guideline updates to oral antiplatelet therapy

The 3 main clinical manifestations of acute coronary syndrome (ACS) are unstable angina, non-ST-segment myocardial infarction, and ST-segment myocardial infarction. Together they comprise a major cause of emergency care and hospitalization in the United States. Consequently, all hospital-based physicians should be familiar with current recommendations regarding the diagnosis and management of ACS. Effective inhibition of platelet activation and aggregation is central to the treatment of ACS, and dual antiplatelet therapy with aspirin and a P2Y12 inhibitor is recommended in all patients with ACS. Recently, the American Heart Association and American College of Cardiology Foundation published focused updates to their guidelines for the management of ACS patients. These updates included changes in antiplatelet therapy arising from the introduction of prasugrel and ticagrelor as alternatives to clopidogrel for the P2Y12 inhibitor component of dual antiplatelet therapy. Among the P2Y12 inhibitors recommended for each indication, the guidelines do not advocate any one P2Y12 inhibitor over another, but instead recommend that therapy is individualized based on each patient's demographic and clinical characteristics. This article presents a clinical case study to illustrate the hospital management of ST-segment myocardial infarction and unstable angina/non-ST-segment myocardial infarction with particular reference to the latest changes in antiplatelet therapy guidelines. This article outlines key differences in the indications and recommendations for P2Y12 inhibitors and summarizes clinical data from the pivotal studies of prasugrel and ticagrelor.

Updates in antiplatelet agents used in cardiovascular diseases

BACKGROUND

Antiplatelet therapy is a cornerstone in coronary artery disease management. However, patients with acute coronary syndrome still remain at risk of recurrent cardiovascular events despite the advance of medical therapy.

OBJECTIVE

This article provides a review of antiplatelet agents used in cardiovascular diseases and focus on updates in the past 5 years.

METHOD

Peer-reviewed clinical trials and relevant treatment guidelines were identified from MEDLINE and Current Content database (from 1966 to April 15, 2013) using search terms aspirin, clopidogrel, prasugrel, ticagrelor, glycoprotein IIb/IIIa inhibitors, antiplatelet agents, coronary artery disease, acute coronary syndrome, pharmacology, pharmacokinetics, and pharmacodynamics. Citations from the available articles were also reviewed for additional references.

RESULTS

In unstable angina and non-ST-segment elevation myocardial infarction (MI), dual antiplatelet therapy (aspirin and clopidogrel) demonstrated a reduction in death from cardiovascular causes, nonfatal MI, or stroke (relative risk 0.80; 95% confidence interval [CI], 0.72-0.90). In ST-segment elevation MI, dual antiplatelet therapy reduced the rate of occluded infarct-related artery/death or recurrent MI (95% CI, 24%-47%). Newer agents such as prasugrel, when compared to clopidogrel, reduced death from vascular causes, MI, or stroke in patients undergoing percutaneous coronary intervention (PCI; hazard ratio [HR], 0.81; 95% CI 0.73-0.90) but not in those receiving medical management only. When compared to clopidogrel, ticagrelor reduces death from vascular causes, MI, or stroke (HR: 0.84; 95% CI, 0.77-0.92) in patients undergoing PCI or receiving medical management only. Both the agents, however, increase the risk of bleeding in certain patient population.

CONCLUSIONS

In the last 5 years, newer antiplatelet agents, including prasugrel and ticagrelor, have been demonstrated to reduce recurrent cardiovascular events compared to standard therapy and, however, also caused increase bleeding in selected patient populations. Newer agents including shorter acting P2Y12 inhibitor or antiplatelets that target other receptors are being evaluated to improve/maintain therapeutic efficacy yet minimize the risk of bleeding.

Ticagrelor vs. clopidogrel in patients with non-ST-elevation acute coronary syndrome with or without revascularization: results from the PLATO trial

Aims

The optimal platelet inhibition strategy for ACS patients managed without revascularization is unknown.

We aimed to evaluate efficacy and safety of ticagrelor vs. clopidogrel in the non-ST-elevation acute coronary syndrome (NSTE-ACS) subgroup of the PLATO trial, in the total cohort, and in the subgroups managed with and without revascularization within 10 days of randomization.

Methods and results

We performed a retrospective analysis of the primary endpoint of cardiovascular death/myocardial infarction/stroke. Among 18 624 PLATO patients, 11 080 (59%) were categorized as NSTE-ACS at randomization. During the initial 10 days, 74% had angiography, 46% PCI, and 5% CABG. In NSTE-ACS patients, the primary endpoint was reduced with ticagrelor vs. clopidogrel [10.0 vs. 12.3%; hazard ratio (HR) 0.83; 95% confidence interval (CI) = 0.74–0.93], as was myocardial infarction (6.6 vs. 7.7%; HR 0.86; 95% CI = 0.74–0.99), cardiovascular death (3.7 vs. 4.9%; HR 0.77; 95% CI = 0.64–0.93), and all-cause death (4.3 vs. 5.8%; HR 0.76; 95% CI = 0.64–0.90). Major bleeding rate was similar between treatment groups (13.4 vs. 12.6%; HR 1.07; 95% CI = 0.95–1.19), but ticagrelor was associated with an increase in non-CABG major bleeding (4.8 vs. 3.8%; HR 1.28; 95% CI = 1.05–1.56). Within the first 10 days, 5366 (48.4%) patients were managed without revascularization. Regardless of revascularization or not, ticagrelor consistently reduced the primary outcome (HR 0.86 vs. 0.85, interaction P = 0.93), and all-cause death (HR 0.75 vs. 0.73, interaction P = 0.89) with no significant increase in overall major bleeding.

Conclusion

In patients with NSTE-ACS, benefit of ticagrelor over clopidogrel in reducing ischaemic events and total mortality was consistent with the overall PLATO trial, independent of actually performed revascularization during the initial 10 days.

New antiplatelet agents prescribed to patients with ischemic heart disease: implications for treatment of stroke

OPINION STATEMENT

Stroke continues to be a significant public health problem worldwide. Despite a number of clinical trials testing various therapeutic agents, we are still left with a small armamentarium of options. Aspirin, clopidogrel and combination aspirin-dipyridamole remain the mainstay for prevention of recurrent ischemic stroke. Tissue plasminogen activator (tPA) or alteplase is the sole agent used in the acute phase up to 4.5 h from the onset of stroke symptoms. A greater understanding of pathophysiologic mechanisms produced an array of acute experimental treatments including intravenous magnesium and free radical scavengers. However, they did not stand up to the scrutiny of phase III randomized clinical trials. Secondary prevention of stroke benefitted more from epidemiologic studies focusing on risk factor modifications, rather than antiplatelet or other stroke specific agents. One must ask if new treatments for stroke are exhausted. Despite the frustrations of stroke neurologists, new avenues for treatment continue to be explored. One comes from our colleagues in cardiology. Development of new medications for treating ischemic heart disease, acute or chronic, may provide opportunity to cross over into stroke. Cardiovascular trials usually encompass stroke as an outcome measure. As of yet, there have not been the data to support use of these agents in stroke. Recent medications for acute and chronic phases of ischemic heart diseases include desmoteplase, tenecteplase, tirofiban, prasugrel, and ticagrelor. Though some of these medications may fail to show a benefit in stroke patients, we feel there is always potential for a breakthrough.

New antiplatelet agents in the treatment of acute coronary syndromes

Effective antagonism of the P2Y12 platelet receptor is central to the treatment of acute coronary syndrome (ACS) patients, especially in the setting of percutaneous coronary intervention and stenting. According to consensus guidelines, early revascularization and intensive antiplatelet therapy are key to reducing the complications that arise from myocardial ischaemia and the recurrence of cardiovascular events. Until recently, clopidogrel was the key P2Y12 antagonist advocated, but due to several limitations as an antiplatelet agent, newer drugs with more predictable, rapid and potent effects have been developed. Prasugrel and ticagrelor are now the recommended first-line agents in patients presenting with non-ST-segment elevation ACS and ST-segment elevation ACS, due to large-scale randomized trials that demonstrated net clinical benefit of these agents over clopidogrel, as stated in the European guidelines. Although no study has directly compared the two agents, analysis of the data to date suggests that certain patient types, such as diabetics, those with ST-segment elevation myocardial infarction or renal failure and the elderly may have a better outcome with one agent over the other. Further studies are needed to confirm these differences and answer pending questions regarding the use of these drugs to optimize efficacy while minimizing adverse events, such as bleeding. The aim of this review is to provide an overview of the current P2Y12 receptor antagonists in the treatment of ACS, with a focus on issues of appropriate agent selection, timing of treatment, bleeding risk and the future role of personalized treatment using platelet function and genetic testing.

New antithrombotics for secondary prevention of acute coronary syndrome

Patients with acute coronary syndrome (ACS) usually receive acetylsalicylic acid plus an adenosine diphosphate (ADP) receptor inhibitor to reduce the long-term risk of recurrent events. However, patients receiving standard antiplatelet prophylaxis still face a substantial risk of recurrent events. Strategies involving 3 antithrombotic agents with different modes of action have now been tested. In Thrombin Receptor Antagonists for Clinical Event Reduction (TRA-CER), compared with standard care alone, bleeding complications including intracranial hemorrhage (ICH) were increased with the addition of vorapaxar, without efficacy benefit. In Trial to Assess the Effects of SCH 530348 in Preventing Heart Attack and Stroke in Patients With Atherosclerosis (TRA 2°P-TIMI 50), the addition of vorapaxar reduced recurrent events compared with standard care in stable patients with prior myocardial infarction. This study was terminated early in patients with prior stroke owing to excess ICH, though an increased risk of ICH or fatal bleeding was not detected in patients with prior myocardial infarction. The Apixaban for Prevention of Acute Ischemic and Safety Events 2 (APPRAISE-2) trial of standard-dose apixaban added to standard care in patients with ACS was also stopped early owing to excess serious bleeding. However, in Rivaroxaban in Combination With Aspirin Alone or With Aspirin and a Thienopyridine in Patients With Acute Coronary Syndromes (ATLAS ACS 2 TIMI 51), fatal bleeding or fatal ICH did not increase with low-dose rivaroxaban added to low-dose acetylsalicylic acid-based standard care compared with standard care alone. In that trial, a significant reduction of recurrent vascular events was shown with 3 antithrombotic regimens compared with standard care. Therefore, depending on drug dose and patient population, further reductions in recurrent vascular events after ACS may be possible in future clinical practice, with a favorable benefit-risk profile.

Randomized comparison of ticagrelor versus prasugrel in patients with acute coronary syndrome and planned invasive strategy--design and rationale of the iNtracoronary Stenting and Antithrombotic Regimen: Rapid Early Action for Coronary Treatment (ISAR-REACT) 5 trial

In acute coronary syndromes (ACS), a dual antiplatelet regimen with an adenosine diphosphate (ADP) receptor antagonist plus aspirin has become the cornerstone of treatment. The third-generation thienopyridine prasugrel and the cyclopentyl-triazolo-pyrimidine ticagrelor provide a greater, more rapid and consistent platelet inhibition compared to their predecessor clopidogrel. Based on their advantages over clopidogrel in two landmark studies, both drugs received a class I recommendation for their use in ACS patients with and without ST segment elevation. Due to differences in ACS populations and conditions investigated, the relative merits of ticagrelor versus prasugrel in the treatment of ACS patients with planned invasive strategy cannot be reliably estimated from independent trials. To date, no direct head-to-head comparison of ticagrelor and prasugrel in terms of clinical outcome exists. The aim of this multicenter, randomized, open-label trial is to assess whether ticagrelor is superior to prasugrel in ACS patients with planned invasive strategy.

Use of antiplatelet agents in patients with atherosclerotic disease

Platelets play a key role in the initiation of hemostatic mechanisms during vascular injury. When contemplating prescription of antiplatelet agents (APAs) for patients as primary prevention for cardiovascular events, the physician should carefully weigh the potential benefits of cardiovascular risk reduction with the likelihood of harm, related mostly to hemorrhagic complications. The role of APAs in secondary prevention of atherosclerosis and coronary artery disease is well established, however, optimal duration of therapy and intensity of patient treatment are not settled and probably need to be individualized per patient. We describe the data emerging from contemporary trials on the efficacy and safety of the use of oral APAs in various patient subpopulations. We also discuss the advantages and potential roles of new APAs during and following acute coronary syndromes, percutaneous coronary interventions, and symptomatic atherosclerosis. We propose certain strategies and directions for future research to enhance the safety and efficacy prevention by optimizing the beneficial effects of APAs along with other contemporary treatment modalities of primary and secondary prevention.

Synthesis and biological evaluation of cyclopentyl-triazolol-pyrimidine (CPTP) based P2Y12 antagonists

In this Letter we describe SAR investigation on the cyclopentyl-triazolol-pyrimidine scaffold in pursuit of new oral P2Y12 inhibitors. Different synthetic routes were developed for variations at the cyclopentyl core. Optimization finally led to compound 2d which was advanced into preclinical development based on better potency and safety profile in comparison to ticagrelor.

P2Y12-receptor-inhibiting antiplatelet strategies in acute coronary syndromes

Antiplatelet therapy in acute coronary syndromes is essential for preventing stent thrombosis and for reducing major adverse cardiovascular events. Treatment strategy has changed over the last years by frequent use of more active agents inhibiting the ADP mediated activation of platelets instead of clopidogrel, such as prasugrel and ticagrelor. Compared to clopidogrel these modern antiplatelet drugs showed a significant reduction of efficacy endpoints as well as an acceptable safety profile in large multicenter randomized trials (TRITON TIMI 38, PLATO). Going in with higher efficacy a generally higher bleeding risk of prasugrel could be reduced by optimizing the maintenance dose in elderly and underweight patients (TRILOGY-ACS). However even prasugrel and ticagrelor have shown a delayed onset of action in special patient populations (e.g. STEMI) suggesting that the optimal ADP inhibitor has not been found yet. Results of the CHAMPION PHOENIX trial indicate that cangrelor, an intravenous agent, might fulfill these high expectations of an ideal platelet inhibitor in the first hours of an ACS in special patient cohorts. This review summarizes the results of most important clinical studies investigating the novel P2Y12 receptor inhibiting antiplatelet drugs.

Clopidogrel, prasugrel, or ticagrelor? a practical guide to use of antiplatelet agents in patients with acute coronary syndromes

Aspirin is a cornerstone of therapy in the treatment of patients with acute coronary syndromes (ACS). However, dual antiplatelet therapy reduces the risk of stent thrombosis and cardiovascular events compared with aspirin alone in the treatment of patients with ACS. Recently, there has been debate as to which antiplatelet agent should be added to aspirin in the ACS treatment regimen. This review summarizes the pharmacologic and clinical data comparing clopidogrel, prasugrel, and ticagrelor, and provides a practical guide to clinicians for determining which antiplatelet to use for patients with ACS.

Assessing post-treatment platelet reactivity: a focus on patient selection and setting

Dual antiplatelet therapy is critical to inhibit platelet reactivity in order to prevent ischemic recurrences in stented patients. However, studies have observed a variable blockade of the P2Y12 adenosine diphosphate receptor between patients following clopidogrel intake. This interindividual variability in the biological response is not uncommon with clopidogrel (about 50%) and even prasugrel (20%). High on-treatment platelet reactivity (HTPR) is correlated with thrombotic events following percutaneous coronary intervention. Several studies suggested that tailoring of antiplatelet therapy based on platelet reactivity (PR) monitoring could safely reduce the rate of major adverse cardiovascular events in HTPR patients. In addition, low on-treatment PR was recently associated with bleeding events both in patients treated with prasugrel and clopidogrel. Of importance, bleedings are associated with a poor prognosis in stented patients. Overall, the potential of PR monitoring to individualize antiplatelet therapy might benefit stented patients by reducing both ischemic and bleeding risks. However, such strategies remain to be evaluated in adequately designed large-scale randomized clinical trials.

Prasugrel versus clopidogrel for patients with unstable angina or non-ST-segment elevation myocardial infarction with or without angiography: a secondary, prespecified analysis of the TRILOGY ACS trial

BACKGROUND

Treatment with prasugrel and aspirin improves outcomes compared with clopidogrel and aspirin for patients with acute coronary syndrome who have had angiography and percutaneous coronary intervention; however, no clear benefit has been shown for patients managed first with drugs only. We assessed outcomes from the TRILOGY ACS trial based on whether or not patients had coronary angiography before treatment was chosen.

METHODS

TRILOGY ACS (ClinicalTrials.gov number NCT00699998) was a randomised controlled trial, done at more than 800 sites worldwide. Patients with non-ST-elevation acute coronary syndrome who were selected for management without [corrected] revascularisation were randomly assigned to clopidogrel or prasugrel.The primary endpoint was cardiovascular death, myocardial infarction, or stroke at 30 months. In the present analysis we assessed differences in the primary endpoint by angiography status and whether the effects of treatment on the primary endpoint differed between patients who had angiography before enrolment and those who had not.

FINDINGS

7243 patients younger than 75 years were included in the TRILOGY ACS primary analysis. 3085 (43%) had angiography at baseline, 4158 (57%) had not. Fewer patients who had angiography reached the primary endpoint at 30 months compared with those who did not have angiography, according to Kaplan-Meier analysis (281/3085 [12·8%] vs 480/4158 [16·5%], adjusted hazard ratio [HR] 0·63, 95% CI 0·53-0·75; p<0·0001). The proportion of patients who reached the primary endpoint was lower in the prasugrel group than in the clopidogrel group for those who had angiography (122/1524 [10·7%] vs 159/1561 [14·9%], HR 0·77, 95% CI 0·61-0·98; p=0·032) but did not differ between groups in patients who did not have angiography (242/2096 [16·3%] vs 238/2062 [16·7%], HR 1·01, 0·84-1·20; p=0·94; pinteraction=0·08). Overall, TIMI major bleeding and GUSTO severe bleeding were rare. Bleeding outcomes tended to be higher with prasugrel but did not differ significantly between treatment groups in either angiography cohort.

INTERPRETATION

Among patients who had angiography who took prasugrel there were fewer cardiovascular deaths, myocardial infarctions, or strokes than in those who took clopidogrel. This result needs to be corroborated, but it is consistent with previous trials of more versus less intensive antiplatelet treatment. When angiography is done for acute coronary syndrome and anatomic coronary disease confirmed, the benefits and risks of intensive antiplatelet treatment exist whether the patient is treated with drugs or percutaneous coronary intervention.

FUNDING

Daiichi Sankyo, Eli Lilly.

Novel antiplatelet and anticoagulant agents in the cardiac care unit

This article reviews the pivotal studies of several novel antiplatelet (prasugrel and ticagrelor) and anticoagulant (dabigatran, rivaroxaban, and apixaban) agents. The clinical use of these drugs in cardiac intensive care is discussed, focusing on the management of acute coronary syndromes, ischemic stroke, atrial fibrillation, and venous thromboembolism.