Pharmacodynamic assessment of platelet inhibition by prasugrel vs. clopidogrel in the TRITON-TIMI 38 trial

Evaluating the pharmacokinetic and pharmacodynamic impact of different modes of ticagrelor administration

INTRODUCTION

Alternative administration modes for oral P2Y12 inhibitors, particularly ticagrelor, have emerged as a potential alternative to overcome the limitations associated with the delayed onset of action of these drugs in patients who are unable to swallow or with impaired absorption.

AREAS COVERED

This comprehensive literature review aims to provide an overview of the current state of knowledge on the pharmacokinetics and administration modes of ticagrelor, including factors that may affect its action. It also compares the pharmacokinetics of ticagrelor with that of other drugs with similar uses to provide a comprehensive understanding of the potential advantages and limitations of different modalities of P2Y12 administration. For this purpose, Embase, Medline, Web of Science Core Collection, Cochrane Central Register of Controlled Trials, Google Scholar, and ClinicalTrials.gov were searched from database inception to July 2023.

EXPERT OPINION

Among the different alternatives, crushed formulations, especially for ticagrelor, have emerged as the most promising option, showing early and robust platelet inhibition. However, important questions remain unanswered, such as the comparative clinical benefits of crushed ticagrelor versus standard administration, the cost-effectiveness of alternative modes compared to intravenous P2Y12 inhibitors such as cangrelor, and the important limitations associated with the concomitant use of opioids, who have been proven to impair even the action of crushed ticagrelor.

Abatement of potent P2Y12 antagonist-based dual antiplatelet therapy after coronary intervention: A network meta-analysis of randomized controlled trials

Introduction

Dual antiplatelet therapy (DAPT) including prasugrel or ticagrelor is recommended in patients with acute coronary syndromes (ACS) treated with coronary intervention (PCI). Acknowledging the importance of bleeding, multiple trials tested abatement schemes including uniform or guided de-escalation from the potent P2Y12 inhibitor (P2Y12-De) or P2Y12 inhibitor monotherapy (P2Y12-Mo) with heterogeneous results. We aimed to perform a systematic review and network meta-analysis of the impact of DAPT abatement strategies in patients with PCI.

Methods

Electronic databases were searched for relevant randomized clinical studies evaluating clinical outcomes of patients after PCI. The rate of adverse events was evaluated using a frequentist network metanalysis. The random-effects model was used to combine risk estimates across trials and risk ratio (RR) with 95% confidence intervals (95% CIs) served as summary statistics. The primary endpoints of interest were the rate of major cardiac adverse events (MACE, defined as the composite of cardiovascular mortality, myocardial infarction and stroke) and bleeding.

Results

Ten studies were identified randomizing 42511 patients. 6359 switched to the P2Y12-De and 13062 switched to the P2Y12-Mo. The risk of MACE, reflected a 24% reduction in the P2Y12-De and a 14% in the P2Y12-Mo in comparison with the DAPT strategy using potent P2Y12 inhibitors (RR: 0.76 [0.62, 0.94], and RR: 0.86 [0.75, 0.99], p < 0.05 both). A 35% risk reduction of major bleeding was seen with monotherapy (RR: 0.65 [0.46, 0.91],) contrasting the de-escalation trials where this effect was not significant (RR: 0.84 [0.57, 1.22]). All bleeding and minor bleeding events were reduced with both strategies. Indirect P2Y12-Mo versus P2Y12-De comparisons exhibited them as similar alternatives without significant differences.

Conclusion

Our analysis suggests that both P2Y12-De and P2Y12-Mo reduce ischemic events and bleeding among PCI-treated ACS patients. Ischemic benefit was more expressed with P2Y12-De, however, reduction of major bleeding was only significant with P2Y12-Mo strategy.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021258502, identifier CRD42021258502.

Flow cytometry for evaluating platelet immunophenotyping and function in patients with thrombocytopenia

Platelets play an essential role in primary hemostasis through bleeding and thromboembolism. Thus, the diagnosis or evaluation of impaired hereditary, acquired, and drug-related platelet dysfunction has become imperative. The assessment of the platelet function is too complex for routine platelet function study. The major methods involved in platelet function study include platelet function analyzer testing, thromboelastography, thromboelastometry, light transmission aggregometry, and flow cytometry. The current review article focuses on the methods with flow cytometry for immunophenotyping of platelet and evaluating platelet function for platelet disorders, especially in patients with thrombocytopenia. According to the consensus published by the International Society on Thrombosis and Haemostasis, for inherited and acquired platelet disorders, the two major measures by which flow cytometry determines platelet function are glycoprotein IIb/IIIa/P-selectin (CD62p) expression and percentage of leukocyte-platelet aggregates. Using flow cytometry to determine platelet function has several advantages, including good sensitivity to low platelet counts, small blood volume required, and the nonnecessity of centrifugation. However, flow cytometry has still many limitations and challenges, with standardization for routine laboratory testing also proving difficult. Although flow cytometry is available for multipurpose and sensitive study of platelet functions at the same time, the challenging analysis gradually increases and needs to be addressed before reality.

Antiplatelet agents for chronic kidney disease

BACKGROUND

Antiplatelet agents are widely used to prevent cardiovascular events. The risks and benefits of antiplatelet agents may be different in people with chronic kidney disease (CKD) for whom occlusive atherosclerotic events are less prevalent, and bleeding hazards might be increased. This is an update of a review first published in 2013.

OBJECTIVES

To evaluate the benefits and harms of antiplatelet agents in people with any form of CKD, including those with CKD not receiving renal replacement therapy, patients receiving any form of dialysis, and kidney transplant recipients.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 13 July 2021 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We selected randomised controlled trials of any antiplatelet agents versus placebo or no treatment, or direct head-to-head antiplatelet agent studies in people with CKD. Studies were included if they enrolled participants with CKD, or included people in broader at-risk populations in which data for subgroups with CKD could be disaggregated.

DATA COLLECTION AND ANALYSIS

Four authors independently extracted data from primary study reports and any available supplementary information for study population, interventions, outcomes, and risks of bias. Risk ratios (RR) and 95% confidence intervals (CI) were calculated from numbers of events and numbers of participants at risk which were extracted from each included study. The reported RRs were extracted where crude event rates were not provided. Data were pooled using the random-effects model. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included 113 studies, enrolling 51,959 participants; 90 studies (40,597 CKD participants) compared an antiplatelet agent with placebo or no treatment, and 29 studies (11,805 CKD participants) directly compared one antiplatelet agent with another. Fifty-six new studies were added to this 2021 update. Seven studies originally excluded from the 2013 review were included, although they had a follow-up lower than two months. Random sequence generation and allocation concealment were at low risk of bias in 16 and 22 studies, respectively. Sixty-four studies reported low-risk methods for blinding of participants and investigators; outcome assessment was blinded in 41 studies. Forty-one studies were at low risk of attrition bias, 50 studies were at low risk of selective reporting bias, and 57 studies were at low risk of other potential sources of bias. Compared to placebo or no treatment, antiplatelet agents probably reduces myocardial infarction (18 studies, 15,289 participants: RR 0.88, 95% CI 0.79 to 0.99, I² = 0%; moderate certainty). Antiplatelet agents has uncertain effects on fatal or nonfatal stroke (12 studies, 10.382 participants: RR 1.01, 95% CI 0.64 to 1.59, I² = 37%; very low certainty) and may have little or no effect on death from any cause (35 studies, 18,241 participants: RR 0.94, 95 % CI 0.84 to 1.06, I² = 14%; low certainty). Antiplatelet therapy probably increases major bleeding in people with CKD and those treated with haemodialysis (HD) (29 studies, 16,194 participants: RR 1.35, 95% CI 1.10 to 1.65, I² = 12%; moderate certainty). In addition, antiplatelet therapy may increase minor bleeding in people with CKD and those treated with HD (21 studies, 13,218 participants: RR 1.55, 95% CI 1.27 to 1.90, I² = 58%; low certainty). Antiplatelet treatment may reduce early dialysis vascular access thrombosis (8 studies, 1525 participants) RR 0.52, 95% CI 0.38 to 0.70; low certainty). Antiplatelet agents may reduce doubling of serum creatinine in CKD (3 studies, 217 participants: RR 0.39, 95% CI 0.17 to 0.86, I² = 8%; low certainty). The treatment effects of antiplatelet agents on stroke, cardiovascular death, kidney failure, kidney transplant graft loss, transplant rejection, creatinine clearance, proteinuria, dialysis access failure, loss of primary unassisted patency, failure to attain suitability for dialysis, need of intervention and cardiovascular hospitalisation were uncertain. Limited data were available for direct head-to-head comparisons of antiplatelet drugs, including prasugrel, ticagrelor, different doses of clopidogrel, abciximab, defibrotide, sarpogrelate and beraprost.

AUTHORS' CONCLUSIONS

Antiplatelet agents probably reduced myocardial infarction and increased major bleeding, but do not appear to reduce all-cause and cardiovascular death among people with CKD and those treated with dialysis. The treatment effects of antiplatelet agents compared with each other are uncertain.

Diurnal Variability of Platelet Aggregation in Patients with Myocardial Infarction Treated with Prasugrel and Ticagrelor

Background: Contemporary antiplatelet treatment in acute myocardial infarction (AMI) is based on one of two P2Y12 receptor inhibitors, prasugrel or ticagrelor. The aim of this study was to compare diurnal variability of platelet reactivity between patients receiving prasugrel and ticagrelor during the initial phase of maintenance treatment after AMI. Methods: It was a prospective, two-center, pharmacodynamic, observational study. Blood for platelet testing was sampled at four time points on day four after AMI (8:00, 12:00, 16:00, 20:00). Diurnal variability of platelet reactivity was expressed as a coefficient of variation (CV) of the above-mentioned measurements. Results: 73 invasively-treated patients were enrolled (ticagrelor: n = 47, prasugrel: n = 26). CV was greater in patients treated with ticagrelor compared with prasugrel according to a VASP assay (47.8 [31.6–64.6]% vs. 21.3 [12.9–25.5]%, p < 0.001), while no statistical differences were detected when the CVs of platelet aggregation according to Multiplate were compared between ticagrelor- and prasugrel-treated patients. Ticagrelor-treated patients showed more pronounced platelet inhibition than prasugrel at 16:00 and 20:00 (VASP_16:00: 20.6 ± 15.0 vs. 24.9 ± 12.8 PRI, p = 0.049; VASP_20:00: 18.6 ± 17.7 vs. 26.0 ± 11.7 PRI, p = 0.002). Conclusions: Ticagrelor shows greater diurnal variability in platelet aggregation than prasugrel during the initial maintenance phase of AMI treatment, and this is due to the continuous increase of platelet inhibition after the morning maintenance dose. Both drugs provide an adequate antiplatelet effect early after AMI. Evaluation of the clinical significance of these findings warrants further investigation.

Comparative effects of guided vs. potent P2Y12 inhibitor therapy in acute coronary syndrome: a network meta-analysis of 61 898 patients from 15 randomized trials

AIMS

Guidelines recommend the use of potent P2Y12 inhibitors over clopidogrel for the reduction of ischaemic events in patients with acute coronary syndrome (ACS). However, this comes at the expense of increased bleeding. A guided selection of P2Y12 inhibiting therapy has the potential to overcome this limitation. We aimed at evaluating the comparative safety and efficacy of guided vs. routine selection of potent P2Y12 inhibiting therapy in patients with ACS.

METHODS AND RESULTS

We performed a network meta-analysis of randomized controlled trials (RCTs) comparing different oral P2Y12 inhibitors currently recommended for the treatment of patients with ACS (clopidogrel, prasugrel, and ticagrelor). RCTs including a guided approach (i.e. platelet function or genetic testing) vs. standard selection of P2Y12 inhibitors among patients with ACS were also included. Incidence rate ratios (IRR) and associated 95% confidence intervals (CIs) were estimated. P-scores were used to estimate hierarchies of efficacy and safety. The primary efficacy endpoint was major adverse cardiovascular events (MACE) and the primary safety endpoint was all bleeding. A total of 61 898 patients from 15 RCTs were included. Clopidogrel was used as reference treatment. A guided approach was the only strategy associated with reduced MACE (IRR: 0.80, 95% CI: 0.65-0.98) without any significant trade-off in all bleeding (IRR: 1.22, 95% CI: 0.96-1.55). A guided approach and prasugrel were associated with reduced myocardial infarction. A guided approach, prasugrel, and ticagrelor were associated with reduced stent thrombosis. Ticagrelor was also associated with reduced total and cardiovascular mortality. Prasugrel was associated with increased major bleeding. Prasugrel and ticagrelor were associated with increased minor bleeding. The incidence of stroke did not differ between treatments.

CONCLUSION

In patients with an ACS, compared with routine selection of potent P2Y12 inhibiting therapy (prasugrel or ticagrelor), a guided selection of P2Y12 inhibiting therapy is associated with the most favourable balance between safety and efficacy. These findings support a broader adoption of guided approach for the selection of P2Y12 inhibiting therapy in patients with ACS.

STUDY REGISTRATION NUMBER

This study is registered in PROSPERO (CRD42021258603).

KEY QUESTION

A guided selection of P2Y12 inhibiting therapy using platelet function or genetic testing improves outcomes among patients undergoing percutaneous coronary intervention. Nevertheless, the comparative safety and efficacy of a guided versus routine selection of potent P2Y12-inhibiting therapy in acute coronary syndrome has not been explored.

KEY FINDING

In a comprehensive network meta-analysis including the totality of available evidence and using clopidogrel as treatment reference, a guided approach was the only strategy associated with reduced major adverse cardiovascular events without any significant trade-off in bleeding. Prasugrel and ticagrelor increased bleeding and only ticagrelor reduced mortality.

TAKE HOME MESSAGE

A guided selection of P2Y12-inhibiting therapy represents the strategy associated with the most favourable balance between safety and efficacy. These findings support a broader adoption of guided P2Y12 inhibiting therapy in patients with acute coronary syndrome.

Consensus recommendations on flow cytometry for the assessment of inherited and acquired disorders of platelet number and function: Communication from the ISTH SSC Subcommittee on Platelet Physiology

Flow cytometry is increasingly used in the study of platelets in inherited and acquired disorders of platelet number and function. However, wide variation exists in specific reagents, methods, and equipment used, making interpretation and comparison of results difficult. The goal of the present study was to provide expert consensus guidance on the use of flow cytometry for the evaluation of platelet disorders. A modified RAND/UCLA survey method was used to obtain a consensus among 11 experts from 10 countries across four continents, on the appropriateness of statements relating to clinical utility, pre-analytical variables, instrument and reagent standardization, methods, reporting, and quality control for platelet flow cytometry. Feedback from the initial survey revealed that uncertainty was sometimes due to lack of expertise with a particular test condition rather than unavailable or ambiguous data. To address this, the RAND method was modified to allow experts to self-identify statements for which they could not provide expert input. There was uniform agreement among experts in the areas of instrument and reagent standardization, methods, reporting, and quality control and this agreement is used to suggest best practices in these areas. However, 25.9% and 50% of statements related to pre-analytical variables and clinical utility, respectively, were rated as uncertain. Thus, while citrate is the preferred anticoagulant for many flow cytometric platelet tests, expert opinions differed on the acceptability of other anticoagulants, particularly heparin. Lack of expert consensus on the clinical utility of many flow cytometric platelet tests indicates the need for rigorous multicenter clinical outcome studies.

Crushed/chewed administration of potent P2Y12 inhibitors in ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention: Systematic review and meta-analysis

Crushed or chewed potent P2Y₁₂ inhibitors are commonly used in the hope of bridging the gap of platelet inhibition in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI). The study aimed to investigate the efficacy and safety of this alternative oral administration strategy by performing a meta-analysis of available randomized clinical trials (RCTs). PubMed, Embase, the Cochrane Library and Web of Science medical literature databases were searched for RCTs comparing crushed/chewed vs. integral administration of loading dose potent P2Y₁₂ inhibitors in patients with STEMI undergoing pPCI with no language restrictions from inception to January 20th, 2021. The primary efficacy endpoints of high on treatment platelet reactivity (HPR) and P2Y₁₂ reaction units (PRU) at 1 hour together with safety and additional clinical endpoints were evaluated by pooled odds ratio (OR) or mean differences (MD) with 95% confidence intervals (95% CI). A total of 973 patents in six RCTs were eligible for analysis, while 876 patients present baseline and procedural characteristics. HPR and PRU at 1 hour were significantly reduced in the group receiving crushed/chewed P2Y₁₂ inhibitors compared with integral tablets (OR 0.28, 95% CI 0.16 to 0.49, P < .0001; MD -60.62, 95% CI -97.06 to -24.19, P = .001, respectively). Safety endpoints of major bleeding (OR 0.54, 95% CI 0.11 to 2.73, P = .46) and any bleeding (OR 0.84, 95% CI 0.43 to 1.64, P = .61), as well as additional clinical endpoints of cardiovascular death, myocardial infarction, and stroke were not affected by the oral administration strategy. In STEMI patients undergoing pPCI, crushed or chewed administration of potent P2Y₁₂ inhibitors are associated with enhanced early platelet inhibition and appear to be safe. The clinical profile transformed from this pharmacodynamic benefit need to be determined by further researches.

Efficacy and Safety of Low-Dose Prasugrel Versus Clopidogrel in Patients with Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention: a Systematic Review and Meta-analysis

PURPOSE

To assess the efficacy and safety of low-dose prasugrel compared to clopidogrel based on the occurrence of major adverse cardiac events (MACEs) and major bleeding in patients with acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI).

METHODS

The PubMed, Embase, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov databases were systematically searched up to May 2020 to identify relevant randomized controlled trials (RCTs) and observational studies. A meta-analysis was conducted using a random effects model to estimate relative risks (RRs) with 95% confidence intervals (CIs). The primary efficacy and safety endpoints were MACE and major bleeding, respectively.

RESULTS

Three RCTs (n = 2884) and five observational studies (n = 30,117) were included. A meta-analysis of RCTs revealed no significant differences in terms of MACE (RR 0.92, 95% CI 0.74 to 1.16) or major bleeding (RR 0.97, 95% CI 0.57 to 1.65) between low-dose prasugrel and clopidogrel. A meta-analysis of observational studies revealed no significant difference in terms of MACE (RR 1.13, 95% CI 0.82 to 1.55) between the two groups, but low-dose prasugrel was associated with a significantly increased risk of major bleeding (RR 1.33, 95% CI 1.02 to 1.72).

CONCLUSIONS

We found that low-dose prasugrel was not associated with changes in MACE or major bleeding compared with clopidogrel in RCTs. However, analysis of data from observational studies revealed that low-dose prasugrel was associated with an increased risk of major bleeding compared with clopidogrel.

Pharmacodynamic Effects of Pre-Hospital Administered Crushed Prasugrel in Patients With ST-Segment Elevation Myocardial Infarction

OBJECTIVES

This study sought to compare the pharmacodynamic effects of pre-hospitally administered P2Y₁₂ inhibitor prasugrel in crushed versus integral tablet formulation in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI).

BACKGROUND

Early dual antiplatelet therapy is recommended in STEMI patients. Yet, onset of oral P2Y₁₂ inhibitor effect is delayed and varies according to formulation administered.

METHODS

The COMPARE CRUSH (Comparison of Pre-hospital Crushed Versus Uncrushed Prasugrel Tablets in Patients With STEMI Undergoing Primary Percutaneous Coronary Interventions) trial randomized patients with suspected STEMI to crushed or integral prasugrel 60-mg loading dose in the ambulance. Pharmacodynamic measurements were performed at 4 time points: before antiplatelet treatment, at the beginning and end of pPCI, and 4 h after study treatment onset. The primary endpoint was high platelet reactivity at the end of pPCI. The secondary endpoint was impact of platelet reactivity status on markers of coronary reperfusion.

RESULTS

A total of 441 patients were included. In patients with crushed prasugrel, the occurrence of high platelet reactivity at the end of pPCI was reduced by almost one-half (crushed 34.7% vs. uncrushed 61.6%; odds ratio [OR] = 0.33; 95% confidence interval [CI] = 0.22 to 0.50; p < 0.01). Platelet reactivity <150 P2Y₁₂ reactivity units at the beginning of coronary angiography correlated with improved Thrombolysis In Myocardial Infarction flow grade 3 in the infarct artery pre-pPCI (OR: 1.78; 95% CI: 1.08 to 2.94; p = 0.02) but not ST-segment resolution (OR: 0.80; 95% CI: 0.48 to 1.34; p = 0.40).

CONCLUSIONS

Oral administration of crushed compared with integral prasugrel significantly improves platelet inhibition during the acute phase in STEMI patients undergoing pPCI. However, a considerable number of patients still exhibit inadequate platelet inhibition at the end of pPCI, suggesting the need for alternative agents to bridge the gap in platelet inhibition.

Tackling the gap in platelet inhibition with oral antiplatelet agents in high-risk patients undergoing percutaneous coronary intervention

Introduction: Oral P2Y₁₂ inhibitors represent the mainstay therapy for the prevention of thrombotic complications in patients presenting with an acute coronary syndrome and/or undergoing percutaneous coronary intervention (PCI). However, the onset of antiplatelet action of the oral P2Y₁₂ inhibitors is affected by their need to be absorbed in the gastrointestinal (GI) tract before becoming systemically available.Areas covered: Following oral intake of P2Y₁₂ inhibitors, the timeframe required for GI absorption leads to a window of inadequate antiplatelet protection during which patients are at increased thrombotic risk. The onset of action of the oral P2Y₁₂ inhibitors is even further delayed in high-risk patients, underscoring the need to define strategies to bridge the gap in platelet inhibitory effects following their intake.Expert opinion: Multiple mechanisms may impair GI absorption leading to a delay in the onset of action of oral P2Y₁₂ inhibitors. Several strategies have been tested to overcome the gap in platelet inhibition in high-risk patients undergoing PCI. These include administration of crushed or chewed tablets to improve the dissolution rate and use of opioid receptor antagonists or metoclopramide to counteract impairment of gastric motility induced by opioids. However, intravenous antiplatelet therapies represent the most effective strategy to bridge such gap in platelet inhibition.

Use of the VerifyNow point of care assay to assess the pharmacodynamic effects of loading and maintenance dose regimens of prasugrel and ticagrelor

Prasugrel and ticagrelor are potent oral platelet P2Y₁₂ inhibitors and are recommended over clopidogrel in patients with acute coronary syndrome (ACS). Oral platelet P2Y₁₂ inhibitors are characterized by varying degrees of pharmacodynamic response profiles as assessed by a variety of commercially available assays. Because of its ease of use, rapid turnaround times and ability to provide results specific to P2Y₁₂ inhibitory effects, VerifyNow has emerged as one of the most commonly utilized platelet function assays. However, reference ranges with VerifyNow have been reported mainly for clopidogrel and there has not yet been any study specifically conducted to provide the expected on treatment reference ranges following administration of prasugrel and ticagrelor. This was a prospective single center investigation conducted in 120 patients with ACS who were treated with prasugrel or ticagrelor as per standard of care. Patients who underwent percutaneous coronary interventions (PCI) were treated with a loading dose of prasugrel (60 mg) or ticagrelor (180 mg), and patients who were on maintenance therapy were taking prasugrel (10 mg qd or 5 mg qd) or ticagrelor (90 mg bid). Platelet function testing was performed using the VerifyNow™ PRUTest™. The overall range of PRUTest values was lower than that observed in studies of patients treated with clopidogrel. The use of a maintenance dose regimen had a wider range of PRUTest values compared to the use of a loading dose for both prasugrel (1–179 vs. 2–128) and ticagrelor (1–196 vs. 1–177). The average PRUTest values in patients on prasugrel and ticagrelor maintenance dosing were 20% and 9% higher those observed in patients treated with a loading dose. PRUTest results following loading dose administration were very similar between drugs, but were 20% higher with prasugrel compared with ticagrelor during maintenance dosing. This study establishes expected PRUTest ranges for patients taking loading and maintenance doses of prasugrel and ticagrelor.

Clinical Trial Registrationhttp://www.clinicaltrials.gov Unique Identifier: NCT04492423, registered July 2020 retrospectively registered.

The need of a multicomponent guiding approach to personalize clopidogrel treatment

Patients bearing polymorphisms termed CYP2C19 loss of function (LoF) alleles and ABCB1-C3435T may do not properly respond to standard dosage of clopidogrel and have an increased risk of thrombosis. Moreover, co-administration of proton pump inhibitors (PPIs) and clopidogrel may attenuate the antiplatelet effect. The role of pharmacogenetics and PPIs/clopidogrel drug-drug interaction has been extensively investigated in patients with acute coronary syndrome after stent implantation (ACS/PCI), while data in patients undergoing vascular surgery are scarce. Here we have performed a systematic review to evaluate the available literature in such a clinical setting and have discussed the controversies about the use of CYP2C19 pharmacogenetics and platelet function testing to personalize clopidogrel treatment. In addition, we have made a comparison of the literature data with our findings concerning patients eligible for vascular surgery and treated with clopidogrel, in whom we used a combined management based on the CYP2C19 and ABCB1 pharmacogenetic testing with monitoring of therapeutic adherence and PPIs-clopidogrel interaction. Both our data and those produced during both observational studies and randomized clinical trials confirm the validity of pharmacogenetics to personalize clopidogrel treatment and stress the importance to make a drug monitoring considering all the known variables, potentially responsible for treatment failure. However, the American Heart Association and the European Cardiovascular Society recommend against the routine use of clopidogrel pharmacogenetic testing. An update of the international guidelines on antiplatelet therapy, incorporating the evidence related to CYP2C19 pharmacogenetics and PPIs-clopidogrel drug-drug interactions is warranted both in ACS/PCI patients and subjects undergoing vascular surgery.

Influence of intravenous fentanyl compared with morphine on ticagrelor absorption and platelet inhibition in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention: rationale and design of the PERSEUS randomized trial

AIMS

Recent evidence demonstrates that intravenous morphine significantly reduces absorption and delays onset of action of oral P2Y12 receptor inhibitors in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI). We aimed to assess the influence of intravenous fentanyl compared with morphine on pharmacokinetics and pharmacodynamics of ticagrelor and its active metabolite (AR-C124910XX) in patients undergoing pPCI for STEMI.

METHODS AND RESULTS

Single-centre, prospective, open-label, randomized controlled study that will randomly assign in a 1:1 ratio patients with STEMI undergoing pPCI to receive intravenous fentanyl or morphine following a pre-hospital 180-mg loading dose of ticagrelor (ClinicalTrials.gov Identifier: NCT02531165). Pharmacokinetic and pharmacodynamic analyses will be performed at baseline and 1, 2, 4, 6, and 12 h post-loading dose. Pharmacodynamic assessments will include P2Y12 reaction units (PRU) measured by VerifyNow P2Y12. Pharmacokinetic assessments include determination of maximal observed plasma concentrations, time for maximal plasma concentration, and area under the plasma concentration vs. time curve from time 0 to the last measurable concentration (AUC0-t) for ticagrelor and AR-C124910XX. The primary endpoint is platelet reactivity assessed by PRU at 2 h post ticagrelor loading dose.

CONCLUSION

PERSEUS will provide randomized data regarding the impact of fentanyl administration, in patients with STEMI undergoing pPCI, on platelet inhibition and ticagrelor absorption and total exposure.

Fibrin clot properties independently predict adverse clinical outcome following acute coronary syndrome: a PLATO substudy

Aims

To determine whether fibrin clot properties are associated with clinical outcomes following acute coronary syndrome (ACS).

Methods and results

Plasma samples were collected at hospital discharge from 4354 ACS patients randomized to clopidogrel or ticagrelor in the PLATelet inhibition and patient Outcomes (PLATO) trial. A validated turbidimetric assay was employed to study plasma clot lysis time and maximum turbidity (a measure of clot density). One-year rates of cardiovascular (CV) death, spontaneous myocardial infarction (MI) and PLATO-defined major bleeding events were assessed after sample collection. Hazard ratios (HRs) were estimated using Cox proportional hazards models. After adjusting for CV risk factors, each 50% increase in lysis time was associated with CV death/spontaneous MI [HR 1.17, 95% confidence interval (CI) 1.05-1.31; P < 0.01] and CV death alone (HR 1.36, 95% CI 1.17-1.59; P < 0.001). Similarly, each 50% increase in maximum turbidity was associated with increased risk of CV death (HR 1.24, 95% CI 1.03-1.50; P = 0.024). After adjustment for other prognostic biomarkers (leukocyte count, high-sensitivity C-reactive protein, high-sensitivity troponin T, cystatin C, N-terminal pro B-type natriuretic peptide, and growth differentiation factor-15), the association with CV death remained significant for lysis time (HR 1.2, 95% CI 1.01-1.42; P = 0.042) but not for maximum turbidity. These associations were consistent regardless of randomized antiplatelet treatment (all interaction P > 0.05). Neither lysis time nor maximum turbidity was associated with major bleeding events.

Conclusion

Fibrin clots that are resistant to lysis independently predict adverse outcome in ACS patients. Novel therapies targeting fibrin clot properties might be a new avenue for improving prognosis in patients with ACS.

Tailored P2Y12 inhibitor treatment in patients undergoing non-urgent PCI-the POPular Risk Score study

PURPOSE

The POPular Risk Score was developed for the selective intensification of P2Y₁₂ inhibitor treatment with prasugrel instead of clopidogrel in patients undergoing non-urgent percutaneous coronary intervention (PCI) with stent implantation. This score is based on platelet reactivity (VerifyNow P2Y₁₂ assay), CYP2C19 genotyping, and clinical risk factors. Our aim was to determine if the use of this score in clinical practice is associated with a reduction in thrombotic events without increasing bleeding events.

METHODS

In a single-center prospective cohort study, patients with a high risk score were treated with prasugrel and patients with a low risk score with clopidogrel. The risk score-guided cohort was compared with a historic cohort of clopidogrel-treated patients. The endpoint consisted of all-cause death, myocardial infarction, stroke, or stent thrombosis during 1 year of follow-up. TIMI major and minor bleeding events were also analyzed.

RESULTS

The guided cohort contained 1127 patients, 26.9% of whom were switched to prasugrel according to the POPular Risk Score. The historic cohort contained 893 patients. The incidence of the combined thrombotic endpoint was significantly lower in the guided cohort as compared with the historic cohort (8.4% versus 3.7%, p < 0.001). This strategy was safe with respect to bleeding (4.0% versus 1.3%, p < 0.001, for TIMI major or minor bleeding). Results were comparable after multivariate and propensity score matched and weighted analysis.

CONCLUSION

Selective intensification of P2Y₁₂ inhibitor treatment after non-urgent PCI based on the POPular Risk Score is associated with a reduction in thrombotic events without an increase in bleeding events.

Platelet reactivity patterns in patients treated with dual antiplatelet therapy

AIM

The aim of the present study was to investigate the patterns of platelet reactivity and discriminators of therapeutic response to dual antiplatelet therapy (DAPT) with aspirin and ticagrelor or prasugrel in patients with acute coronary syndrome (ACS).

DESIGN

In this multicentre prospective observational study, 492 patients with ACS were enrolled. Platelet aggregation was determined by multiple electrode aggregometry after stimulation with adenosine diphosphate (ADP) or arachidonic acid (AA) as agonists in the maintenance phase of treatment with prasugrel or ticagrelor.

RESULTS

Age emerged as the strongest variable influencing aspirin response status: The mean AA-induced platelet aggregation in patients <49 years of age was 49% higher than in those >49 years (13.1 U vs 8.8 U; P = 0.011). The second strongest discriminator of aspirin response was sex: Male patients had a 40% higher AA-induced platelet aggregation values than female patients (9.5 U vs 6.8 U; P = 0.026). Platelet count emerged as the only variable influencing ADP antagonists response status showing that patients with platelet count >320 g/L displayed higher ADP-induced platelet aggregation. About 12% of patients had high on-treatment platelet reactivity (HTPR) to aspirin, 3% and 4% a HTPR to prasugrel and ticagrelor, respectively, and only 2% displayed HTPR to dual antiplatelet therapy.

CONCLUSION

When potent platelet inhibitors as prasugrel and ticagrelor are administered with aspirin, HTPR to DAPT plays only a marginal role.

Efficacy and safety of alternative oral administrations of P2Y12-receptor inhibitors: Systematic review and meta-analysis

BACKGROUND

Early administration of P2Y12-receptor inhibitors is recommended in all patients with acute coronary syndrome undergoing invasive management, with the aim to achieve the fastest and most effective platelet inhibition. Several trials investigated alternative methods of P2Y12-receptor inhibitor administration (mainly chewed or crushed) aimed at ensuring faster and higher platelet inhibition. Thus, we decided to perform a systematic review and meta-analysis analyzing efficacy and safety of alternative P2Y12-receptor inhibitor administration strategies.

METHODS

Systematic research was performed on Pubmed, Cochrane Library, Biomed Central, and Web of Science databases. We included randomized or observational trials testing at least one P2Y12-receptor inhibitor alternative administration. The primary outcome of the study was the value of the platelet reactivity unit (PRU) at 1 h after drug administration, assessed by VerifyNow P2Y12 test (Accumetrics, Inc., San Diego, CA). Secondary outcomes were adverse bleeding events (safety outcome).

RESULTS AND DISCUSSION

Fourteen studies were selected for qualitative analysis. Five studies, all focused on ticagrelor, were selected for quantitative efficacy analyses. These five studies compared the administration of crushed/chewed ticagrelor 180 mg loading dose (LD) with the standard whole tablets LD. The pooled mean difference between the two administrations was -59.24 PRU (95% CI from -30.61 to -87.87 PRU) in favor of the crushed/chewed administration, corresponding to a 25% mean relative PRU reduction between alternative and standard P2Y12-receptor inhibitor administrations at 1 h after drug intake. A similar relationship was found in other studies on alternative administration of clopidogrel and prasugrel, not included in the quantitative analysis.

The Incidence of Myocardial Injury after Loading Doses of Clopidogrel versus Prasugrel in the Candidates for Percutaneous Coronary Intervention: A Randomized Controlled Trial

INTRODUCTION

Prevention of myocardial injury is an essential issue in percutaneous coronary intervention (PCI). We compared the incidence of myocardial injury after loading doses of clopidogrel versus prasugrel in the candidates for PCI.

METHODS

In this randomized-controlled clinical trial, we enrolled 88 stable angina patients, candidate for PCI. Patients received either prasugrel (60 mg orally) (n = 42) or clopidogrel (600 mg orally) (n = 46). Serum levels of creatine phosphokinase muscle-brain type, cardiac troponin I, and high sensitive C-reactive protein were measured at baseline and 6 and 12 hours postprocedural. Primary endpoint was periprocedural myocardial infarction (MI), defined as elevation of cTn values (>5 times) in patients with normal baseline values or a rise of cTn values >20% if the baseline values are elevated.

RESULTS

Based on the levels of cTnI 6 hours after PCI, 1 patient (2.4%) had MI in the prasugrel group, whereas 4 patients (8.7%) had MI in the clopidogrel group. After 12 hours, 4 patients (9.5%) had MI in the prasugrel group versus 5 patients (10.9%) in the clopidogrel arm. There was no significant difference between the groups regarding the changes in cardiac specific enzyme levels. However, serum levels of cTnI were significantly lower in patients with myocardial injury in the prasugrel arm (P < 0.001).

CONCLUSIONS

Prasugrel is an effective antiplatelet drug in preventing periprocedural MI.

Enhanced potency of prasugrel on protease-activated receptors following bivalirudin treatment for PCI as compared to clopidogrel

ACS patients undergoing percutaneous coronary intervention (PCI) when treated with bivalirudin and clopidogrel had increased frequency of early stent thrombosis. 24 patients referred for intervention with planned bivalirudin therapy, not previously treated with a P2Y₁₂ inhibitor and not receiving heparins or αIIbβ3 inhibitors were randomized to treatment with either clopidogrel (600 mg) or prasugrel (60 mg). Platelet aggregation (PA) was measured by light transmission aggregometry (LTA) of platelet-rich plasma in response to ADP, PAR1/PAR4 thrombin receptor agonists and collagen at baseline and at 1, 2, 4 and 16 h following the cessation of bivalirudin infusion. Prasugrel-mediated inhibition of PA was significantly greater than that of clopidogrel at all time points for ADP as well as PAR1. There was an unanticipated, significantly greater protection of PAR4-mediated platelet aggregation only detected with prasugrel and not observed with clopidogrel. We further examined the effect of the hyperreactive PAR4 Thr120 variant in the protease-activated receptor 4 (PAR4), single nucleotide polymorphism (SNP) rs773902 on aggregation protection. The PAR4 protective effect with prasugrel was lost in individuals carrying the PAR4 Thr120 variant, and not in Ala120 homozygote. PAR1, ADP and collagen inhibition was not significantly affected in the hyperreactive PAR4 Thr120 variant. We documented that the P2Y₁₂ ADP receptor-mediated regulation of the strength of the high-affinity conformation of αIIbβ3 as detected by PAC-1 ab, and in control of platelet adhesiveness through Rap1 GTPase protein activation. Importantly, the PAR4 Thr120 variant resulted in the increased rate and magnitude of Rap1 activation. Human platelet PAR4 mediated-activation of αIIbβ3 was phospholipase C beta (PLCβ)-dependent and unlike mouse platelet PI3K-independent. These data identify a PAR4-dependent inhibitory mechanism for the prasugrel-mediated platelet inhibition, not seen with clopidogrel that could explain the reduction in stent thrombosis documented in clinical trials with prasugrel.

Adenosine as a Marker and Mediator of Cardiovascular Homeostasis: A Translational Perspective

Adenosine, a purine nucleoside, is produced broadly and implicated in the homeostasis of many cells and tissues. It signals predominantly via 4 purinergic adenosine receptors (ADORs) - ADORA1, ADORA2A, ADORA2B and ADOosine signaling, both through design as specific ADOR agonists and antagonists and as offtarget effects of existing anti-platelet medications. Despite this, adenosine has yet to be firmly established as either a therapeutic or a prognostic tool in clinical medicine to date. Herein, we provide a bench-to-bedside review of adenosine biology, highlighting the key considerations for further translational development of this proRA3 in addition to non-ADOR mediated effects. Through these signaling mechanisms, adenosine exerts effects on numerous cell types crucial to maintaining vascular homeostasis, especially following vascular injury. Both in vitro and in vivo models have provided considerable insights into adenosine signaling and identified targets for therapeutic intervention. Numerous pharmacologic agents have been developed that modulate adenmising molecule.

Switching P2Y12 Receptor Inhibiting Therapies

Antiplatelet therapy with aspirin and a P2Y₁₂ receptor inhibitor is the cornerstone of treatment of patients with atherothrombotic disease manifestations. Switching between P2Y₁₂ inhibitors occurs commonly in clinical practice for a variety of reasons, including safety, efficacy, adherence, and economic considerations. There are concerns about the optimal approach for switching because of potential drug interactions, which may lead to ineffective platelet inhibition and thrombotic complications, or potential overdosing due to overlap in drug therapy, which might cause excessive platelet inhibition and increased bleeding. This review provides practical considerations of switching based on pharmacodynamic and clinical data available from the literature.

Current Role of Platelet Function Testing in Percutaneous Coronary Intervention and Coronary Artery Bypass Grafting

There is interindividual variability in the pharmacodynamic response to antiplatelet medications. High on-treatment platelet reactivity, reflecting a failure to achieve adequate platelet inhibition, is associated with a higher risk for thrombotic events. Low on-treatment platelet reactivity, or an enhanced response to antiplatelet medications, has been linked to a higher risk for bleeding. There is evidence for the prognostic value of platelet function testing for risk prediction. This review presents the current evidence regarding platelet function testing in patients undergoing percutaneous cardiac intervention and coronary artery bypass grafting. The possible role of platelet function testing for individualized antiplatelet treatment is highlighted.

Monitoring platelet function: what have we learned from randomized clinical trials?

Dual antiplatelet therapy, with aspirin plus a P2Y12 inhibitor agent, remains the cornerstone treatment after percutaneous coronary intervention. However, significant proportion of patients did experience recurrent ischemic events on aspirin plus clopidogrel and the concept of non-response to P2Y12 inhibitor emerged. Evaluation of platelet reactivity has known a promising era aiming to improve platelet inhibition conferred by clopidogrel. Then, the development of more potent antiplatelet agents (i.e., prasugrel and ticagrelor) shifted the concern to excessive platelet inhibition and increased risk of bleeding. Therefore, personalized antiplatelet therapy according to platelet function testing has been tested in several randomized trials for both escalation and de-escalation of antiplatelet regimen. This review aims to report the evidence from randomized trials in this field and upcoming roles for platelet function testing.

Mass Cytometry Reveals Distinct Platelet Subtypes in Healthy Subjects and Novel Alterations in Surface Glycoproteins in Glanzmann Thrombasthenia

Mass cytometry (MC) uses mass spectrometry to simultaneously detect multiple metal-conjugated antibodies on single cells, thereby enabling the detailed study of cellular function. Here, for the first time, we applied MC to the analysis of platelets. We developed a panel of 14 platelet-specific metal-tagged antibodies (targeting cluster of differentiation [CD] 9, CD29, CD31, CD36, CD41, CD42a, CD42b, CD61, CD62P, CD63, CD107a, CD154, glycoprotein [GP] VI and activated integrin αIIbβ3) and compared this panel with two fluorescence flow cytometry (FFC) panels (CD41, CD42b, and CD61; or CD42b, CD62P, and activated integrin αIIbβ3) in the evaluation of activation-dependent changes in glycoprotein expression on healthy subject and Glanzmann thrombasthenia (GT) platelets. High-dimensional analysis of surface markers detected by MC identified previously unappreciated subpopulations of platelets in healthy donors. As expected, MC and FFC revealed that GT platelets had significantly reduced CD41, CD61, and activated integrin αIIbβ3 surface expression. MC also revealed that surface expression of CD9, CD42a and CD63 were elevated, CD31, CD154 and GPVI were reduced and CD29, CD36, CD42b, CD62P and CD107a were similar on GT platelets compared to healthy donor platelets. In summary, MC revealed distinct platelet subtypes in healthy subjects and novel alterations in surface glycoproteins on GT platelets.

Consensus Document ANMCO/ANCE/ARCA/GICR-IACPR/GISE/SICOA: Long-term Antiplatelet Therapy in Patients with Coronary Artery Disease

Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor is the cornerstone of pharmacologic management of patients with acute coronary syndrome (ACS) and/or those receiving coronary stents. Long-term (>1 year) DAPT may further reduce the risk of stent thrombosis after a percutaneous coronary intervention (PCI) and may decrease the occurrence of non-stent-related ischaemic events in patients with ACS. Nevertheless, compared with aspirin alone, extended use of aspirin plus a P2Y12 receptor inhibitor may increase the risk of bleeding events that have been strongly linked to adverse outcomes including recurrent ischaemia, repeat hospitalisation and death. In the past years, multiple randomised trials have been published comparing the duration of DAPT after PCI and in ACS patients, investigating either a shorter or prolonged DAPT regimen. Although the current European Society of Cardiology guidelines provide a backup to individualised treatment, it appears to be difficult to identify the ideal patient profile which could safely reduce or prolong the DAPT duration in daily clinical practice. The aim of this consensus document is to review contemporary literature on optimal DAPT duration, and to guide clinicians in tailoring antiplatelet strategies in patients undergoing PCI or presenting with ACS.

Incidence, Predictors, and Clinical Impact of Early Prasugrel Cessation in Patients With ST-Elevation Myocardial Infarction

BACKGROUND

Early withdrawal of recommended antiplatelet treatment with clopidogrel adversely affects prognosis following percutaneous coronary interventions. Optimal antiplatelet treatment is essential following ST-segment elevation myocardial infarction (STEMI) given the increased risk of thrombotic complications. This study assessed the frequency, predictors, and clinical impact of early prasugrel cessation in patients with STEMI undergoing primary percutaneous coronary interventions.

METHODS AND RESULTS

We pooled patients with STEMI discharged on prasugrel in 2 prospective registries (Bern PCI Registry [NCT02241291] and SPUM-ACS (Inflammation and Acute Coronary Syndromes) [NCT01000701]) and 1 STEMI trial (COMFORTABLE-AMI (Comparison of Biomatrix Versus Gazelle in ST-Elevation Myocardial Infarction) [NCT00962416]). Prasugrel treatment status at 1 year was categorized as no cessation; crossover to another P2Y12-inhibitor; physician-recommended discontinuation; and disruption because of bleeding, side effects, or patient noncompliance. In time-dependent analyses, we assessed the impact of prasugrel cessation on the primary end point, a composite of cardiac death, myocardial infarction, and stroke. Of all 1830 included patients (17% women, mean age 59 years), 83% were treated with new-generation drug-eluting stents. At 1 year, any prasugrel cessation had occurred in 13.8% of patients including crossover (7.2%), discontinuation (3.7%), and disruption (2.9%). Independent predictors of any prasugrel cessation included female sex, age, and history of cerebrovascular event. The primary end point occurred in 5.2% of patients and was more frequent following disruption (hazard ratio 3.04, 95% confidence interval,1.34-6.91; P=0.008), without significant impact of crossover or discontinuation. Consistent findings were observed for all-cause death, myocardial infarction, and stent thrombosis following prasugrel disruption.

CONCLUSIONS

In this contemporary study of patients with STEMI, early prasugrel cessation was not uncommon and primarily involved change to another P2Y12-inhibitor. Disruption was the only type of early prasugrel cessation associated with statistically significant excess in ischemic risk within 1 year following primary percutaneous coronary interventions.

Myocardial reperfusion for acute myocardial infarction under an optimized antithrombotic medication: What can you expect in daily practice?

AIMS

To assess both epicardiac macrovascular as well as microvascular and tissue reperfusion following different intravenous preadmission antithrombotic strategies prior primary PCI in STEMI patients.

METHODS AND RESULTS

Consecutive STEMI patients (n = 488) undergoing pPCI received prehospitally either bivalirudin (n = 179), bivalirudin and periprocedural GPIIb/IIIa inhibitors (GPI) (n = 109), heparin (n = 99) or heparin and periprocedural GPI (n = 101). Epicardial perfusion and microvascular perfusion were assessed by angiography (TIMI flow rate and corrected TIMI frame count [cTFC]) and by ECG (ST resolution [STR]). TIMI 3 flow was restored at the end of the procedure in 85.2% of the cases; cTFC of ≤23 was obtained in 37.2% of cases and STR >70% in 42.5% of the cases. The rates of STR >70% and cTFC ≤23 were not different between the three groups. Multivariate analysis did not identify a predictive antithrombotic treatment to obtain either post-procedural TIMI 3 flow rate or a STR rate >70%. TIMI 3 flow before procedure and delay first symptoms-balloon <6 h represented a positive predictive value of STR rate >70% and the LAD as infarct related artery a negative predictive value of STR rate of >70%.

CONCLUSION

The process of myocardial reperfusion by pPCI continues to be improved with earlier reperfusion but an optimal tissular reperfusion was present in only half of the cases.

Switching from clopidogrel to prasugrel to protect early invasive treatment in acute coronary syndromes: Results of the switch over trial

BACKGROUND

Clopidogrel is used to pretreat patients with non-ST elevation acute coronary syndromes (NSTE-ACS), but prasugrel provides better platelet inhibition with improved outcome. However, switching from clopidogrel at the time of percutaneous coronary intervention (PCI) remains incompletely defined. Our aim was to compare the pharmacodynamic (PD) effects of 3 prasugrel loading doses (LDs; G1:10mg, G2: 30mg, and G3: 60mg) before PCI. A fourth group, continuing clopidogrel, served as control (G4).

METHODS

100 clopidogrel-pretreated patients were enrolled and blood collected before PCI, 30min, 1, 2, 4, 6, 24 and 48h thereafter. Platelet inhibition was measured by vasodilator-stimulated phosphoprotein phosphorylation (VASP) and Verify-Now assays. The end-points (EP) was the difference of PD effect at 4h between G3 and G4 (primary EP) with hierarchic evaluation between G2 and G1 versus G4 (secondary EP). A mixed-design ANOVA statistic was used to compare the four group scores over time.

RESULTS

Baseline characteristics were balanced across the groups. Only patients receiving 60 and 30mg prasugrel LDs showed a rapid (<1h) and significant (p<0.001) platelet inhibition up to 48h after PCI·The primary EP was met by G3 (p<0.0001), but also G2 scored different (p<0-001) from G4 at 4h after PCI. Similar findings were observed with Verify-Now. No differences in 30-day clinical outcomes were observed across groups.

CONCLUSIONS

Switching NSTE-ACS patients before PCI to prasugrel 60 or 30mg LDs determined a better and faster platelet inhibition than continuing clopidogrel, while PCI it is still underway.

Transferring from clopidogrel loading dose to prasugrel loading dose in acute coronary syndrome patients

High on-treatment platelet reactivity (HPR) has been identified as an independent risk factor for ischaemic events. The randomised, doubleblind, TRIPLET trial included a pre-defined comparison of HPR in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) following a placebo/600-mg clopidogrel loading dose (LD) immediately before a subsequent prasugrel 60-mg or 30-mg LD. Platelet reactivity was assessed using the VerifyNow® P2Y12 assay (P2Y12 Reaction Units, PRU) within 24 hours (h) following the placebo/clopidogrel LD (immediately prior to prasugrel LD), and at 2, 6, 24, 72 h following prasugrel LDs. The impact of CYP2C19 predicted metaboliser phenotype (extensive metaboliser [EM] and reduced metabolisers [RM]) on HPR status was also assessed. HPR (PRU ≥240) following the clopidogrel LD (prior to the prasugrel LD) was 58.5% in the combined clopidogrel LD groups. No significant difference was noted when stratified by time between the clopidogrel and prasugrel LDs (≤6 hs vs >6 h). At 6 h following the 2nd loading dose in the combined prasugrel LD groups, HPR was 7.1%, with 0% HPR by 72 h. There was no significant effect of CYP2C19 genotype on pharmacodynamic (PD) response following either prasugrel LD treatments at any time point, regardless of whether it was preceded by a clopidogrel 600-mg LD. In conclusion, in this study, patients with ACS intended for PCI showed a high prevalence of HPR after clopidogrel 600-mg LD regardless of metaboliser status. When prasugrel LD was added, HPR decreased substantially by 6 h, and was not seen by 72 h.

Identification of poor response to P2Y12 inhibitors in ACS patients with a new ELISA-based vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation assay

A new ELISA technique has been developed to measure the vasodilator-associated stimulated phosphoprotein (VASP) platelet reactivity index (PRI) in clopidogrel-treated patients. This technique has not been evaluated in acute coronary syndrome (ACS) patients or in prasugrel-treated patients. We assessed the accuracy of ELISA-VASP to identify high on-treatment platelet reactivity (HPR) in ACS patients in comparison with established platelet function tests. Platelet reactivity was measured in 240 ACS patients treated with clopidogrel (75 or 150 mg) or prasugrel (5 or 10 mg) using flow cytometry (FC-VASP) and the ELISA-VASP technique, light transmission aggregometry (LTA) and VerifyNow-P2Y12 assay (VN-P2Y12). When using the ELISA-VASP PRI, the rate of patients with HPR in the overall ACS population was 15.5%, including a 27% rate in clopidogrel-treated patients and a 4% rate in prasugrel-treated patients. There was a strong correlation between ELISA-VASP PRI and FC-VASP PRI (r = 0.83, r2 = 0.68 p < 0.0001) with an area under the receiver-operating characteristics (ROC) curve to identify HPR (VASP-PRI >50% with FC-VASP) of 0.94, p<0.0001. The threshold of 60% for ELISA-VASP PRI provided the best accuracy (likelihood ratio= 23.67) to identify patients with HPR when compared to FC-VASP, LTA or VN-P2Y12 assays. In conclusion, ELISA-VASP is a fast, easy-to-use and specific test to identify HPR in ACS patients on thienopyridines. A 60% threshold value displays the best accuracy to identify HPR in these patients.

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.

Decrease in high on-treatment platelet reactivity (HPR) prevalence on switching from clopidogrel to prasugrel: Insights from the switching anti-platelet (SWAP) study

The prevalence of high platelet reactivity (HPR) in patients who have switched from clopidogrel to prasugrel during maintenance phase after an acute coronary syndrome (ACS) event is unknown. Therefore, the effect of switching from clopidogrel to prasugrel on the prevalence of HPR was evaluated. This analysis from the previously reported SWAP (SWitching Anti Platelet) study assessed HPR at baseline, 2 and 24 hours, and seven days after switching from clopidogrel to prasugrel maintenance dose (MD), with or without a prasugrel loading dose (LD) using four definitions: maximum platelet aggregation (MPA) >65% (primary endpoint), MPA >50%, P2Y12 reaction units (PRU) >235, and platelet reactivity index (PRI) ≥50%. A total of 95 patients were available for analysis; 56 patients provided DNA for genetic assessments of cytochrome P450 (CYP) 2C19. There were 26 (27.4%) patients with HPR at the end of the clopidogrel run-in (defined as MPA >65%). The HPR prevalence varied by each definition and ranged from 19% (PRU >235) to 68% (PRI ≥50%). A significantly higher HPR prevalence was observed during clopidogrel versus the combined prasugrel therapy groups at seven days as measured by MPA >65% (21.2% vs. 4.5%, p>0.05), PRU >235 (18.8% vs. 0%, p=0.001), and PRI ≥50% (66.7% vs. 7.9%, p<0.0001). There was a significantly higher percentage of subjects carrying at least one reduced function allele with HPR measured by MPA >65% (p=0.02) or PRU >235 (p=0.05) than non-carriers with HPR. Switching ACS patients during maintenance clopidogrel therapy to prasugrel with or without an LD is associated with a reduced HPR prevalence and may provide an alternative strategy to treat patients with HPR, independent of CYP2C19 genotype.

Chewing versus Swallowing Ticagrelor to Accelerate Platelet Inhibition in Acute Coronary Syndrome - the CHEERS study

It was the study objective to evaluate whether chewing a 180 mg loading dose of ticagrelor versus an equal dose of traditional oral administration, enhances inhibition of platelet aggregation 1 hour (h) after administering a ticagrelor loading dose in non-ST elevation myocardial infarction (NSTEMI) patients. Dual anti-platelet therapy represents standard care for treating NSTEMI patients. Ticagrelor is a direct acting P2Y12 inhibitor and, unlike clopidogrel and prasugrel, does not require metabolic activation. Fifty NSTEMI patients were randomised to receive either a chewing loading dose of 180 mg ticagrelor or an equal standard oral dose of ticagrelor. Platelet reactivity was evaluated by VerifyNow at baseline, 1 and 4 h post-loading dose. Results are reported in P2Y12 reaction units. Patients then continued to receive standard 90 mg oral ticagrelor twice daily. Baseline characteristics did not differ between the two groups. P2Y12 reaction units in the chewing group compared with the standard group at 0, 1 and 4 h after ticagrelor loading dose were: 245 vs 239 (p=0.59), 45 vs 130 (p=0.001) and 39 vs 60 (p=0.12), respectively, corresponding to a relative inhibition of platelet aggregation of 83 % vs only 47 % at 1 h (p< 0.001), and 84 % vs 77 % (p=0.59) at 4 h. Major adverse cardiac and cardiovascular events at 30 days were low (2 %), occurring in only one patient in the standard group. In conclusion, chewing a 180 mg ticagrelor loading dose is feasible and facilitates both faster and improved early inhibition of platelet aggregation in NSTEMI patients, compared with a standard oral-loading dose.

Supplementary Material to this article is available online at www.thrombosis-online.com.

Third generation P2Y12 antagonists inhibit platelet aggregation more effectively than clopidogrel in a myocardial infarction registry

The current standard of antiplatelet therapy of patients after myocardial infarction includes the P2Y12 receptor antagonists clopidogrel, prasugrel or ticagrelor. This study aimed to compare the antiplatelet effect of clopidogrel, prasugrel and ticagrelor in patients after myocardial infarction. In a single-centre registry the antiplatelet effect of clopidogrel, prasugrel and ticagrelor was investigated by aggregometry in patients after myocardial infarction. To assess the overall capacity of platelet aggregation whole blood was induced with thrombin receptor activating peptide (TRAP; 32 μM). To specifically quantify the effect of P2Y12 antagonists, whole blood was stimulated with 6.4 μM adenosine diphophosphate (ADP). Relative ADP induced aggregation (r-ADP-agg) was defined as the ADP-TRAP ratio to reflect an individual degree of P2Y12-dependent platelet inhibition. Platelet function of 238 patients was analysed [clopidogrel (n=58), prasugrel (n=65), ticagrelor (n=115)]. The r-ADP-agg was 35 ± 14% for patients receiving clopidogrel, 28 ± 10% for patients receiving prasugrel and 26 ± 11% for patients receiving ticagrelor. The r-ADP-agg was significantly lower in patients treated with prasugrel (p=0.0024) or ticagrelor (p<0.0001) compared to clopidogrel. There was no significant difference between patients receiving prasugrel or ticagrelor (p=0.2559). In conclusion, prasugrel and ticagrelor provide a stronger platelet inhibition compared to clopidogrel in patients after myocardial infarction. No significant difference in platelet inhibition was detected between prasugrel and ticagrelor. (registry for patients after Myocardial Infarction Treated with AntiPlatelet agents; DRKS00003146).

Early determination of clopidogrel responsiveness by platelet reactivity index identifies patients at risk for cardiovascular events after myocardial infarction

While acute myocardial infarction (MI) is associated with impaired clopidogrel responsiveness, systematic evaluation is lacking due to the inability of functional aggregation-based assays to analyse clopidogrel responsiveness in the presence of glycoprotein IIb/IIIa inhibitors. Using the P2Y12-specific, non-aggregation-based platelet-reactivity-index (PRI) we assessed clopidogrel responsiveness in patients with acute MI. Clopidogrel responsiveness was determined 24 hours (h) after loading with 600 mg clopidogrel in 54 patients with acute MI admitted for coronary intervention. A PRI > 50% was considered as suboptimal inhibition. Overall response in MI patients was suboptimal with a median PRI of 58%. Diabetes, low high-density lipoprotein and pre-hospital clopidogrel loading were associated with impaired clopidogrel responsiveness. Patients loaded at first medical contact had a significantly weaker platelet inhibition by clopidogrel after 24 h (PRI 63%) compared to those loaded peri-interventionally (PRI 54%, p=0.014). Clinical outcome was assessed as a combination of cardiac death, non-fatal MI, stent thrombosis, ischaemic stroke, and urgent target vessel revascularisation after 12 months. The pre-selected cut-off of PRI ≤ 50% yielded a sensitivity of 87% at a specificity of 26%, whereas a PRI ≤ 57% determined by receiver-operating characteristics (ROC)-analysis yielded a sensitivity of 80% at a specificity of 56% (event rate: PRI ≤ 57%: 12.0%; PRI > 57%: 41.4%, p=0.0136). In conclusion, PRI detects clopidogrel responsiveness in acute MI patients requiring glycoprotein IIb/IIIa antagonism; and impaired clopidogrel responsiveness predisposes to clinical events. Pre-hospital clopidogrel loading was associated with impaired response and more adverse events challenging the concept of earliest oral clopidogrel loading in MI patients.

Eversion endarterectomy under full prasugrel treatment

The third-generation thienopyridine prasugrel has much stronger antiplatelet effect compared to other current antiplatelet inhibitors and exhibits practically zero resistance in healthy people. Prasugrel is used as a pre- and post-treatment in percutaneous coronary or neurovascular interventions with parallel aspirin regime. However, as there is a higher reported bleeding with intraluminal interventions and meticulous technique is recommended, there is nearly non-existent international experience of open surgery under full prasugrel treatment. We present, herein, a case of open carotid endarterectomy with the eversion technique in an asymptomatic patient with carotid stenosis, who was receiving dual antiplatelet therapy with aspirin and prasugrel, due to a previous insertion of two newer drug-eluting stents at the left anterior descending artery and the right coronary artery. The resistance test to prasugrel showed complete inhibition of platelet function. Open surgery was performed under continuation of prasugrel treatment and interruption of aspirin for 3 days before surgery. No perioperative and postoperative neurologic or cardiologic event occurred. No bleeding at the cervical or cerebral area was noted.

Platelet function testing and prediction of procedural bleeding risk

The essential role of platelets in haemostasis underlies the relationship between platelet function and spontaneous or procedure-related bleeding, which has important prognostic implications. Although not routinely undertaken, platelet function testing offers the potential to tailor antiplatelet therapy for individual patients. However, uncertainties remain about how well platelet function testing may predict haemostasis and guide management of bleeding risk. Studies of aspirin, P2Y12 inhibitors and other antiplatelet drugs clearly demonstrate how inhibition of platelet function increases bleeding risk. More potent antiplatelet drugs are associated with higher bleeding rates, consistent with the levels of platelet inhibition achieved by these drugs. Studies of patients treated with clopidogrel, which is associated with wide inter-individual variation in antiplatelet effect, suggest that platelet function testing may predict bleeding risk related to coronary artery bypass grafting (CABG) surgery and potentially guide the timing of surgery following discontinuation of clopidogrel. Similarly, some studies have demonstrated a relationship between clopidogrel response and bleeding in patients undergoing percutaneous coronary intervention (PCI), although other studies have not supported this. Carriage of the *17 allele of cytochrome P450 2C19, which is associated with gain of function and enhanced response to clopidogrel, seems to be associated with increased bleeding risk, although studies showing lack of apparent effect of loss-of-function alleles provide contradictory evidence. Further large studies are needed to guide best practice in the application of platelet function testing in the clinical management of patients treated with antiplatelet drugs in order to optimise individual care.

Prevalence of poor biological response to clopidogrel

The existence of poor biological response to clopidogrel has been shown in some patients. Despite the increasing number of studies, this phenomenon remains difficult to quantify. We performed a systematic review to estimate the prevalence of poor biological response to clopidogrel and investigate the factors known to modulate this. An exhaustive search was performed. Altogether 171 publications were identified, providing data for a total of 45,664 subjects. The estimated prevalence of poor biological response to clopidogrel ranged from 15.9% to 49.5% according to the platelet function assay employed. The assays most frequently used were light transmittance aggregometry (LTA), the vasodilator-stimulated phosphoprotein (VASP) assay and the Verify -now® assay. For all these assays, higher cut-off values were associated with a lower prevalence of poor biological response to clopidogrel. However, when choosing a fixed cut-off point for each assay, the prevalence of poor biological response to clopidogrel was highly variable suggesting that other factors could modulate poor biological response to clopidogrel. Finally, none of the studied factors could apparently explain the variability of poor biological response to clopidogrel. This meta-analysis shows that the prevalence of poor biological response depends on the assay employed, the cut-off value and on various unidentified additional factors.

Platelet Aggregometry Testing: Molecular Mechanisms, Techniques and Clinical Implications

Platelets play a fundamental role in normal hemostasis, while their inherited or acquired dysfunctions are involved in a variety of bleeding disorders or thrombotic events. Several laboratory methodologies or point-of-care testing methods are currently available for clinical and experimental settings. These methods describe different aspects of platelet function based on platelet aggregation, platelet adhesion, the viscoelastic properties during clot formation, the evaluation of thromboxane metabolism or certain flow cytometry techniques. Platelet aggregometry is applied in different clinical settings as monitoring response to antiplatelet therapies, the assessment of perioperative bleeding risk, the diagnosis of inherited bleeding disorders or in transfusion medicine. The rationale for platelet function-driven antiplatelet therapy was based on the result of several studies on patients undergoing percutaneous coronary intervention (PCI), where an association between high platelet reactivity despite P2Y12 inhibition and ischemic events as stent thrombosis or cardiovascular death was found. However, recent large scale randomized, controlled trials have consistently failed to demonstrate a benefit of personalised antiplatelet therapy based on platelet function testing.