Platelet function profiles in the elderly: Results of a pharmacodynamic study in patients on clopidogrel therapy and effects of switching to prasugrel 5 mg in patients with high platelet reactivity

Impact of Age on the Safety and Efficacy of Ticagrelor Monotherapy in Patients Undergoing PCI

OBJECTIVES

The aim of this study was to assess the impact of age on the safety and efficacy of ticagrelor monotherapy after percutaneous coronary intervention (PCI).

BACKGROUND

As the risk for bleeding and ischemic complications after PCI increases with age, the authors conducted a pre-specified analysis of the TWILIGHT (Ticagrelor With Aspirin or Alone in High-Risk Patients After Coronary Intervention) trial to evaluate the possible benefits of ticagrelor monotherapy according to age.

METHODS

The TWILIGHT trial enrolled patients undergoing PCI with drug-eluting stents who fulfilled at least 1 clinical and 1 angiographic high-risk criterion. Age ≥65 years was a clinical entry criterion. After 3 months of dual-antiplatelet therapy with ticagrelor, event-free patients were randomized to ticagrelor plus placebo or ticagrelor plus aspirin for an additional 12 months. The primary endpoint was Bleeding Academic Research Consortium type 2, 3, or 5 bleeding. The key secondary endpoint was the composite of all-cause death, myocardial infarction, or stroke.

RESULTS

A total of 3,113 patients (47.7%) were ≥65 years of age. At 1 year after randomization, ticagrelor monotherapy significantly reduced BARC type 2, 3, or 5 bleeding (4.5% vs. 8.2%; hazard ratio: 0.53; 95% confidence interval: 0.40 to 0.71) without increasing ischemic events (4.2% vs. 4.4%; hazard ratio: 0.96; 95% confidence interval: 0.68 to 1.35) compared with ticagrelor plus aspirin among patients ≥65 years of age. These findings were consistent in patients <65 years of age with respect to the primary (p_interaction = 0.62) and key secondary (p_interaction = 0.77) endpoints and across different age categories.

CONCLUSIONS

A strategy of ticagrelor monotherapy following 3 months of dual-antiplatelet therapy significantly reduced clinically relevant bleeding compared with ticagrelor plus aspirin without an increase in ischemic events, irrespective of age.

Age- and Weight-Adapted Dose of Prasugrel Versus Standard Dose of Ticagrelor in Patients With Acute Coronary Syndromes : Results From a Randomized Trial

BACKGROUND

The efficacy and safety of a reduced dose of prasugrel versus a standard dose of ticagrelor in elderly patients or those with a low body weight presenting with an acute coronary syndrome (ACS) are unknown.

OBJECTIVE

To investigate the effect of an age- and weight-adapted dose of prasugrel versus a standard dose of ticagrelor in patients with ACS. (ClinicalTrials.gov: NCT01944800).

DESIGN

Prespecified analysis of the multicenter, randomized ISAR-REACT 5 trial.

SETTING

23 centers in Germany and Italy.

PATIENTS

3997 patients with ACS planned for invasive management.

INTERVENTION

Participants were randomly assigned to receive a standard dose of ticagrelor or prasugrel (reduced dose in the elderly or low-weight group and standard dose in the neither elderly nor low-weight group).

MEASUREMENTS

The efficacy end point was a composite of death, myocardial infarction, or stroke, and the safety end point was bleeding, both at 12 months.

RESULTS

In the elderly or low-weight group, the efficacy end point occurred in 12.7% of patients assigned to receive prasugrel and 14.6% of those assigned to receive ticagrelor (hazard ratio [HR], 0.82 [95% CI, 0.60 to 1.14]); in the neither elderly nor low-weight group, the efficacy end point occurred in 4.8% of patients assigned to receive prasugrel and 7.3% of those assigned to receive ticagrelor (HR, 0.65 [CI, 0.48 to 0.88]; P for interaction > 0.2). In the elderly or low-weight group, Bleeding Academic Research Consortium type 3 to 5 bleeding occurred in 8.1% of patients assigned to receive prasugrel and 10.6% of those assigned to receive ticagrelor (HR, 0.72 [0.46 to 1.12]), and in 3.7% and 3.8%, respectively, of patients in the neither elderly nor low-weight group (HR, 0.98 [CI, 0.65 to 1.47]; P for interaction > 0.2).

LIMITATION

The study is a subgroup analysis.

CONCLUSION

In elderly or low-weight patients with ACS, a reduced dose of prasugrel compared with the standard dose of ticagrelor is associated with maintained anti-ischemic efficacy while protecting these patients against the excess risk for bleeding.

PRIMARY FUNDING SOURCE

German Center for Cardiovascular Research and Deutsches Herzzentrum München.

Anti-thrombotic strategies in elderly patients receiving platelet inhibitors

Acetyl-salicylic acid is the basic anti-thrombotic therapy used for single anti-platelet therapy in primary as well as secondary prevention of atherosclerotic disease. Dual anti-platelet therapy (DAPT) is the cornerstone of maintenance medication following elective percutaneous coronary intervention or acute coronary syndromes (ST elevation myocardial infarction, non-ST elevation myocardial infarction, unstable angina). DAPT duration has been frequently discussed. Currently, guideline recommendations strengthen the importance of individualized treatment to reduce bleeding risk based on clinical predictors, of which older age is an important one. Patients aged ≥75 years are often underrepresented in randomized clinical trials, but present a patient cohort deemed both at heightened ischaemic as well as bleeding risk. We aimed to summarize the evidence or the lack of evidence for anti-platelet treatment strategies in patients aged ≥75 years including combinations with anticoagulants in secondary prevention or coronary interventions in elderly patients with atrial fibrillation. This review article represents the author's interpretation of available data and is not discussed by a formal task force; it is intended to point out missing evidence and to provide age-specific data for individualized decision making, which is currently encouraged by the guidelines.

Stratified Approaches to Antiplatelet Therapies Based on Platelet Reactivity Testing

Antiplatelet therapy with P2Y₁₂ receptor inhibitors (clopidogrel, prasugrel, ticagrelor, cangrelor) is a cornerstone of medical therapy after percutaneous coronary interventions. Significant prevalence of high on-treatment platelet reactivity (HTPR) on clopidogrel treatment led to introduction of more potent P2Y₁₂ inhibitors: prasugrel (a third generation thienopyridine), ticagrelor, and cangrelor (cyclopentyl-triazolo-pyrimidines). Nevertheless, more potent platelet inhibition and resulting low on-treatment platelet reactivity (LTPR) has led to increased risk of major bleeding events. These limitations resulted in a need for an individualized antiplatelet therapy approach. This review discusses the current role and future perspectives of diagnostic tools such as platelet function testing to optimize antiplatelet therapy with a focus on deescalating therapies to reduce bleeding risks.

Tailoring P2Y12 Inhibiting Therapy in Elderly Patients With Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

See Article Schmucker et al

Pharmacodynamics During Transition Between Platelet P2Y12 Inhibiting Therapies

Several platelet P2Y₁₂ inhibiting agents, both oral and intravenous, are available for clinical use. The oral P2Y₁₂ inhibitors comprise clopidogrel, prasugrel, and ticagrelor. Cangrelor is the only intravenous P2Y₁₂ inhibitor. Numerous pharmacodynamic studies have been performed to assess the impact of P2Y₁₂ inhibitor switching on platelet reactivity profiles and to define the optimal strategy if switching is needed, with the goal of minimizing the risk of having inadequate platelet inhibition due to potential drug-drug interactions occurring during the drug overlap phase. This article provides an overview of pharmacodynamic studies assessing switching between P2Y₁₂ inhibitors and recommendations on switching modalities based on these findings.

Comparison of Reduced-Dose Prasugrel and Standard-Dose Clopidogrel in Elderly Patients With Acute Coronary Syndromes Undergoing Early Percutaneous Revascularization

Background:

Elderly patients are at elevated risk of both ischemic and bleeding complications after an acute coronary syndrome and display higher on-clopidogrel platelet reactivity compared with younger patients. Prasugrel 5 mg provides more predictable platelet inhibition compared with clopidogrel in the elderly, suggesting the possibility of reducing ischemic events without increasing bleeding.

Methods:

In a multicenter, randomized, open-label, blinded end point trial, we compared a once-daily maintenance dose of prasugrel 5 mg with the standard clopidogrel 75 mg in patients >74 years of age with acute coronary syndrome undergoing percutaneous coronary intervention. The primary end point was the composite of mortality, myocardial infarction, disabling stroke, and rehospitalization for cardiovascular causes or bleeding within 1 year. The study was designed to demonstrate superiority of prasugrel 5 mg over clopidogrel 75 mg.

Results:

Enrollment was interrupted, according to prespecified criteria, after a planned interim analysis, when 1443 patients (40% women; mean age, 80 years) had been enrolled with a median follow-up of 12 months, because of futility for efficacy. The primary end point occurred in 121 patients (17%) with prasugrel and 121 (16.6%) with clopidogrel (hazard ratio, 1.007; 95% confidence interval, 0.78–1.30; P =0.955). Definite/probable stent thrombosis rates were 0.7% with prasugrel versus 1.9% with clopidogrel (odds ratio, 0.36; 95% confidence interval, 0.13–1.00; P =0.06). Bleeding Academic Research Consortium types 2 and greater rates were 4.1% with prasugrel versus 2.7% with clopidogrel (odds ratio, 1.52; 95% confidence interval, 0.85–3.16; P =0.18).

Conclusions:

The present study in elderly patients with acute coronary syndromes showed no difference in the primary end point between reduced-dose prasugrel and standard-dose clopidogrel. However, the study should be interpreted in light of the premature termination of the trial.

Clinical Trial Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT01777503.

How to improve the concept of individualised antiplatelet therapy with P2Y12 receptor inhibitors – is an algorithm the answer?

Within the past decade, high on-treatment platelet reactivity (HTPR) on clopidogrel and its clinical implications have been frequently discussed. Although it has been previously assumed that HTPR is a phenomenon occurring only in patients treated with clopidogrel, recent data show that HTPR might also occur during treatment with prasugrel or ticagrelor in the acute phase of ST-elevation myocardial infarction. Moreover, it has been postulated that there is a therapeutic window for P2Y12 receptor blockers, thus indicating that HTPR is associated with thrombotic events whereas low on-treatment platelet reactivity (LTPR) is associated with bleeding events. The current paper focuses on tools to identify risk factors for HTPR (pharmacogenomic testing, clinical scoring and drug-drug interactions) and on the use of platelet function testing in order to identify patients who might not respond adequately to clopidogrel. The majority of recent clinical randomised trials have not supported the hypothesis that platelet function testing and tailored antiplatelet therapy are providing a favourable clinical outcome. These trials, mainly performed in low-to-moderate risk patients, will be reviewed and discussed. Finally, an algorithm based on current knowledge is suggested, which might be of use for design of clinical trials.

Platelet oxidative stress as a novel target of cardiovascular risk in frail older people

The average lifespan of humans and the percentage of people entering the 65 and older age group are growing rapidly. Within this age group, cardiovascular diseases (CVD) increase steeply and are the most common cause of death. During aging, experimental and clinical studies support the pivotal role played by reactive oxidant species in the mechanism of platelet activation. Frailty has been implicated as a causative and prognostic factor in patients with CVD. Oxidative stress is increased in frail older people, and may lead to accelerated aging and higher incidence of oxidative diseases such as CVD. The present article aims to highlight the relative contribution of platelet oxidative stress as a key target of frailty in elderly people with CVD.

The Rationale for and Clinical Pharmacology of Prasugrel 5 mg

Prasugrel is a third-generation thienopyridine platelet P2Y₁₂ adenosine diphosphate (ADP) receptor antagonist administered with aspirin for the treatment of patients with acute coronary syndrome (ACS) with planned percutaneous coronary intervention. Prasugrel is administered periprocedurally at an oral loading dose of 60 mg followed by daily maintenance doses (MDs) of 10 mg for most patients and 5 mg for patients weighing <60 kg or aged ≥75 years. Data from a prasugrel phase III study, TRITON-TIMI 38, suggested that a lower MD might be more suitable for patients weighing <60 kg or aged ≥75 years; subsequent pharmacokinetic and pharmacodynamic studies have indicated that prasugrel 5 mg reduced platelet reactivity in these populations to an extent similar to that of prasugrel 10 mg in heavier or younger patients. Clinical experience with prasugrel 5 mg is limited, and additional studies are needed to verify the clinical efficacy and safety of this dose in these challenging populations.

A comparison of reduced-dose prasugrel and standard-dose clopidogrel in elderly patients with acute coronary syndromes undergoing early percutaneous revascularization: Design and rationale of the randomized Elderly-ACS 2 study

BACKGROUND

Elderly patients display higher on clopidogrel platelet reactivity as compared with younger patients. Treatment with prasugrel 5mg has been shown to provide more predictable and homogenous antiplatelet effect, as compared with clopidogrel, suggesting the possibility of reducing ischemic events after an acute coronary syndrome (ACS) without increasing bleeding.

STUDY DESIGN

The Elderly-ACS 2 study is a multicenter, randomized, parallel-group, open-label trial designed to demonstrate the superiority of a strategy of dual antiplatelet treatment using a reduced 5-mg daily dose of prasugrel over a standard strategy with a daily clopidogrel dose of 75mg in patients older than 74years with ACS (either ST- or non-ST-elevation myocardial infarction) undergoing early percutaneous revascularization. The primary end point is the composite of all-cause mortality, myocardial reinfarction, disabling stroke, and rehospitalization for cardiovascular causes or bleeding within 1 year. Taking advantage of the planned size of 2,000 patients, the secondary objective is to assess the prognostic impact of selected prerandomization variables (age, sex, diabetic status, serum creatinine level, electrocardiogram changes, abnormal troponin levels, basal and residual SYNergy between percutaneous coronary intervention with TAXus and cardiac surgery [SYNTAX] score).

CONCLUSION

The Elderly-ACS 2 study is a multicenter, randomized trial comparing a strategy of dual antiplatelet therapy with a reduced dose of prasugrel with a standard dose of clopidogrel in elderly patients with ACS undergoing percutaneous revascularization (the Elderly ACS 2 trial: NCT01777503).

On-treatment platelet reactivity: State of the art and perspectives

High on-clopidogrel platelet reactivity (HcPR) during dual-antiplatelet therapy is a marker of vascular risk, in particular stent thrombosis, in patients with acute coronary syndromes (ACS). Genetic determinants (CYP2C19*2 polymorphism), advanced age, female gender, diabetes and reduced ventricular function are related to a higher risk to develop HcPR. In addition, inflammation and increased platelet turnover, as revealed by the elevated percentage of reticulated platelets in patients' blood, that characterize the acute phase of acute coronary syndromes, are associated with HcPR. To overcome the limitation of clopidogrel, new antiplatelet agents (prasugrel and ticagrelor) were developed and the demonstration of their superiority over clopidogrel was obtained in the two randomized trials, TRITON TIMI 38 and PLATO. Emerging evidence is accumulating on the role of high-on aspirin platelet reactivity (HaPR), especially in the clinical context of diabetes. Finally, the presence of new, potent antiplatelet drugs has shifted the focus from thrombotic to bleeding risk. Recent data document that low on-treatment platelet reactivity (LPR) is associated with a significantly higher bleeding risk. Due to the current possibility to choose between multiple antiplatelet strategies, the future perspective is to include in the management of ACS, in addition to clinical data and classical risk factors, the definition of platelet function during treatment in order to set a tailored therapy.

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.

In-hospital switching of oral P2Y12 inhibitor treatment in patients with acute coronary syndrome undergoing percutaneous coronary intervention: prevalence, predictors and short-term outcome

BACKGROUND

P2Y12 inhibitor switching has appeared in clinical practice as a consequence of prasugrel and ticagrelor availability, apart from clopidogrel, for use in patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI).

METHODS

In the context of the GReek AntiPlatelet REgistry (GRAPE) we assessed the prevalence, predictive factors and short-term outcome of in-hospital P2Y12 inhibitor switching in 1794 ACS patients undergoing PCI.

RESULTS

Switching occurred in 636 (35.5%) patients of which in the form of clopidogrel to a novel agent, novel agent to clopidogrel and between prasugrel and ticagrelor in 574 (90.4%), 34 (5.3%) and 27 (4.3%) patients, respectively. Presentation to non PCI-capable hospital, bivalirudin use, age ≥75 years (inverse predictor), and regional trends emerged as predictive factors of switching to a novel agent. At combined in-hospital and one-month follow-up, propensity matched pairs analysis showed no differences in major adverse cardiovascular (MACE) or bleeding events between switching from clopidogrel to a novel agent vs novel agent constant administration. More Bleeding Academic Research Consortium type 1, type 2 and any type events and fewer MACE were seen when switching from clopidogrel to a novel agent vs only clopidogrel administration (23.7%, 3.8%, 30.6%, 1.2% vs 8.9%, 1.2%, 12.0%, 3.8% with P < .001, P = .03, P < .001 and P = .03 respectively).

CONCLUSIONS

In a real-life experience with contemporary antiplatelet treatment in ACS patients undergoing PCI, in-hospital switching represents common clinical practice. Clinical factors and regional practice differences seem to affect this strategy's choice, while switching to a novel agent may be associated with higher risk of bleeding.

Platelet-function testing in patients undergoing neurovascular procedures: caught between a rock and a hard place

In the context of neurointerventional procedures, clopidogrel hyper-responsiveness has been associated with hemorrhage; on the other hand, clopidogrel resistance has been associated with thromboembolism. This might seem to make a compelling argument in favor of routine platelet testing. Our reading of the literature leads us to conclude that routine platelet testing in neurointerventional procedures is not, unfortunately, ready for prime time.

Pharmacodynamic effect of prasugrel 5 mg vs clopidogrel 150 mg in elderly patients with high on-clopidogrel platelet reactivity

BACKGROUND

Elderly patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) frequently exhibit high platelet reactivity (HPR) while on clopidogrel. In the elderly cohort, either prasugrel is not recommended or, if used, halving of the dose has been suggested. We aimed to test the hypothesis that in elderly patients exhibiting HPR after standard treatment with clopidogrel, prasugrel-reduced dose (5 mg) could be more effective than high-dose (150 mg) clopidogrel.

METHODS

Consecutive elderly (≥75 years old) patients with ACS undergoing PCI and loaded with clopidogrel were considered for platelet reactivity (PR) assessment at 24 hours after PCI with the VerifyNow assay (Accumetrics Inc, San Diego, CA), measured in P2Y12 reaction units (PRU). Of 63 screened patients, 30 (47.6%) were found with HPR (defined as PRU ≥230) and 27 of them participated in a prospective, randomized, single-center, single-blind, investigator-initiated, crossover study of platelet inhibition by prasugrel 5 mg/d vs clopidogrel 150 mg/d, with a 15-day treatment period.

RESULTS

The primary end point of PR at the end of the 2 study periods was lower in patients receiving low-dose prasugrel than those receiving high-dose clopidogrel (least squares estimates 190.8 [95% CI 161.5-220.1] and 240.8 [95% CI 211.0-270.6], respectively; P = .008). The secondary end point of HPR rate at the end of treatment periods was lower for prasugrel (8/24; 33.3%) compared with clopidogrel (16/24; 66.7%), P = .02.

CONCLUSIONS

In elderly patients with ACS undergoing PCI and exhibiting HPR after standard clopidogrel treatment, prasugrel 5 mg/d is significantly more efficacious than clopidogrel 150 mg/d in reducing PR and HPR rate.

Importance of potent P2Y(12) receptor blockade in acute myocardial infarction: focus on prasugrel

INTRODUCTION

Prasugrel therapy is recommended in patients with acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI).

AREAS COVERED

This article reviews the efficacy and safety profile of prasugrel, cost considerations, and its role in clinical practice based on published data. The authors searched PubMed and Ovid databases for English language clinical trial articles involving the use of prasugrel in human subjects and patients, published through June 2012. The keyword "prasugrel" was used. The review focuses on clinical trials, but other articles including Food and Drug Administration documents are also reviewed.

EXPERT OPINION

Prasugrel has a more rapid and greater pharmacodynamic (PD) effect than clopidogrel. No significant drug - drug interactions have been reported. In a large-scale randomized clinical trial, prasugrel was associated with better protection against ischemic event occurrence compared to clopidogrel, but more bleeding in ACS patients undergoing PCI. Adverse outcomes outweighed the benefit of prasugrel in certain subgroups, including patients over the age of 75, those weighing less than 60 kg, and patients with a prior history of stroke or transient ischemic attack. In subsequent PD studies, prasugrel therapy showed suboptimal platelet inhibition in selected patients. In addition, "hyper-responsiveness" to prasugrel may increase the risk of serious bleeding in high-risk patients. More detailed studies are warranted to explore antiplatelet regimens tailored to optimally limit ischemic and bleeding event occurrences. A Phase-III TRILOGY trial (NCT00699998) will indicate the clinical efficacy and safety of prasugrel in patients with non-ST-segment elevation ACS, who are medically managed without coronary revascularization.