A randomized comparison of high clopidogrel loading doses in patients with non-ST-segment elevation acute coronary syndromes: the ALBION (Assessment of the Best Loading Dose of Clopidogrel to Blunt Platelet Activation, Inflammation and Ongoing Necrosis) trial

High doses of clopidogrel to overcome genetic resistance: the randomized crossover CLOVIS-2 (Clopidogrel and Response Variability Investigation Study 2)

OBJECTIVES

This study sought to determine whether the pharmacokinetic (PK) and pharmacodynamic (PD) responses to high or standard clopidogrel loading doses (LDs) differ according to CYP2C19*2 allele.

BACKGROUND

CYP2C19 loss-of-function alleles are associated with reduced responsiveness to standard clopidogrel doses.

METHODS

Young post-myocardial infarction patients heterozygous (wild type [wt]/*2, n = 43) or homozygous (*2/*2, n = 8) for the CYP2C19*2 genetic variant were matched with patients not carrying the variant (wt/wt, n = 58). All patients were randomized to a 300- or 900-mg clopidogrel LD. The relative reduction in residual platelet aggregation (RR-RPA, %) and the area under the plasma concentration time curve of active metabolite from baseline to 6 h after loading (AUC(0-6)) were compared according to both LD and CYP2C19*2 carriage.

RESULTS

The 300-mg LD led to a gene-dose effect for RR-RPA (-65.7% ± 35.9% in wt/wt vs. -48.0% ± 38.4% in wt/*2 vs. -14.6% ± 32.4% in *2/*2; overall p value = 0.003, p = 0.03 for wt/wt versus wt/*2, p = 0.04 for wt/*2 versus *2/*2) with minor effect in *2/*2 carriers. After the 900-mg LD, the effect of the CYP2C19*2 variant on platelet inhibition was fully compensated in wt/*2 carriers but not in *2/*2 carriers (-83.6% ± 25.8% in wt/wt vs.-77.2% ± 26.9% in wt/*2 vs. -29.5% ± 26.8% in *2/*2; overall p value = 0.0003, p = 0.20 for wt/wt versus wt/*2, p < 0.001 for wt/*2 versus *2/*2). A similar pattern was observed for the active metabolite AUC(0-6) according to carriage of CYP2C19*2 for both LDs. There was a significant correlation between PK and PD responses irrespective of the LD.

CONCLUSIONS

Carriers of CYP2C19*2 display significantly lower responses to clopidogrel with a gene-dose effect. Clopidogrel resistance can be overcome by increasing the dose in heterozygous carriers but not in homozygous carriers. (Clopidogrel and Response Variability Investigation Study 2 [CLOVIS-2]; NCT00822666).

Platelet inhibition by adjunctive cilostazol versus high maintenance-dose clopidogrel in patients with acute myocardial infarction according to cytochrome P450 2C19 genotype

OBJECTIVES

The aim of this study was to assess the degree of platelet inhibition by adjunctive cilostazol in patients with acute myocardial infarction (AMI) according to hepatic cytochrome P450 2C19 (CYP2C19) genotype.

BACKGROUND

Although adjunctive cilostazol intensifies platelet inhibition in AMI patients, it is not established whether this regimen can be free from the effect of CYP2C19 loss-of-function variants (*2/*3).

METHODS

We randomly assigned 126 AMI patients with available CYP2C19 genotyping to receive adjunctive cilostazol (triple group; n = 64) or high maintenance-dose (MD) clopidogrel of 150 mg/day (high-MD group; n = 62). Using conventional aggregometry and VerifyNow (Accumetrics Inc., San Diego, California), platelet reactivity was measured at pre-discharge and 30-day follow-up. Primary endpoint was change in maximal platelet aggregation (ΔAgg(max)) between pre-discharge and 30-day follow-up. High on-treatment platelet reactivity (HPR) was defined as 20 μmol/l adenosine diphosphate-induced maximal platelet aggregation (Agg(max)) >59%.

RESULTS

In noncarriers, despite numerically greater inhibition by adjunctive cilostazol, changes in platelet measures and the rate of HPR did not significantly differ between the 2 groups. In carriers, ΔAgg(max) after 5 and 20 μmol/l adenosine diphosphate stimuli was significantly higher in the triple (n = 39) versus high-MD group (n = 38) (21.8 ± 13.9% vs. 9.0 ± 13.3%, p < 0.001, and 24.2 ± 17.2% vs. 7.7 ± 15.5%, p < 0.001, respectively). Likewise, changes in late platelet aggregation and P2Y12 reaction unit were consistently greater in the triple versus high-MD group. Fewer patients in the triple group met the criteria of HPR at 30-day follow-up than in the high-MD group (15.4% vs. 44.7%, p = 0.005).

CONCLUSIONS

Compared with high-MD clopidogrel, adjunctive cilostazol significantly enhances platelet inhibition and reduces the rate of HPR, especially in AMI patients with CYP2C19 loss-of-function variants. (Adjunctive Cilostazol Versus High Maintenance-Dose Clopidogrel in Acute Myocardial Infarction (AMI) Patients According to CYP2C19 Polymorphism [ACCELAMI2C19]; NCT00915733).

Clopidogrel "resistance": where are we now?

Antiplatelet therapy with aspirin and clopidogrel in PCI patients, though effective, is still associated with thrombotic complications. These are multifactorial in origin, but partially attributable to "clopidogrel resistance." However, how best to identify and manage "clopidogrel resistance" remains unclear. Targeting therapeutic changes specifically at those individuals with poor response to clopidogrel is likely to be a solution. A "one size fits all" approach to clopidogrel dosing is probably flawed. This review will explore (1) the definition and mechanisms of clopidogrel resistance, (2) assessment of clopidogrel resistance by (i) platelet function testing and (ii) genetic testing, (3) the management of "clopidogrel resistance," and (4) newer antiplatelet agents, and evolving stent technology. A pubmed literature review was performed using the keywords "clopidogrel", "resistance", "poor response", "adverse events", "platelet function tests", and "genetic tests". In looking at new agents, keywords "prasugrel", "cangrelor", "ticagrelor""Elinogrel", and "P2Y12 receptor antagonists" were used. Third, a search was performed looking at "stent design", "IVUS", "bioabsorbable stents", and "stent apposition". Whilst new P2Y12 receptor antagonists and improved stent technology may reduce thrombotic events in the future, there is still a need for clopidogrel. There is good evidence that poor response to clopidogrel is associated with adverse outcome. Platelet function tests probably provide more clinically useful data than genetic tests, but the question of how best to identify and manage variability in response to clopidogrel demands further research.

The evolution of antiplatelet therapy in cardiovascular disease

The platelet--an anucleate cell--is the bedrock of thrombosis, both physiologically and pathologically. Antagonism of the P2Y(12) receptor for ADP is one of several pathways inhibiting the activation and aggregation of platelets, thereby attenuating coronary thrombosis in response to spontaneous plaque rupture or percutaneous revascularization. The addition of clopidogrel to a background of aspirin therapy was a revolutionary change in the management of ischemic coronary syndromes. Despite this paradigm shift, clopidogrel has certain limitations, including variability in platelet inhibitory effect, which is associated with adverse thrombotic events. In the evolution of antiplatelet treatment strategies, two new P2Y(12) receptor antagonists--prasugrel and ticagrelor--have been added to the armamentarium in the past few years. Both of these drugs confer greater platelet inhibition than clopidogrel. Nevertheless, more-potent platelet inhibition comes with an increased risk of hemorrhagic complications. Cangrelor and elinogrel are novel P2Y(12) inhibitors that show potential in the periprocedural setting with their rapid onset and offset of activity. Successes in P2Y(12) inhibitory therapies have reduced use of glycoprotein IIb/IIIa inhibitors, which block the final pathway leading to platelet aggregation and thrombosis. Newer therapies aimed at various molecular factors are under clinical investigation. Pharmacodynamic platelet function assays and pharmacogenetic testing to individualize and optimize antiplatelet therapy may find their way into clinical use, although much more study is needed.

Ischaemic and bleeding complications with new, compared to standard, ADP-antagonist regimens in acute coronary syndromes: a meta-analysis of randomized trials

BACKGROUND

Platelets play a pivotal role in the pathogenesis of acute coronary syndromes (ACS) and their inhibition remains a mainstay therapy in this setting. We aimed to perform a meta-analysis of randomized trials to evaluate the benefits of new oral antiplatelet regimens to block platelet ADP-receptors compared to standard-dose clopidogrel (300 mg loading dose followed by 75 mg/daily).

METHODS

We obtained results from all randomized trials enrolling patients with ACS. Primary endpoint was mortality. Secondary endpoints were myocardial infarction and definite in-stent thrombosis. Safety endpoint was the risk of major bleeding complications. We prespecified subanalyses according to new antiplatelet drugs (prasugrel/ticagrelor), high-dose clopidogrel (600 mg) and patients undergoing percutaneous coronary intervention.

RESULTS

A total of seven randomized trials were finally included in the meta-analysis (n = 58 591). We observed a significant reduction in mortality (2.9% vs. 3.4%, OR = 0.87, 95% CI 0.79-0.95, P = 0.002), recurrent myocardial infarction (4.2% vs. 5.2%, OR = 0.80, 95% CI 0.74-0.87, P < 0.0001), definite in-stent thrombosis (0.9% vs. 1.7%, OR = 0.52, 95% CI 0.43-0.63, P < 0.0001). The benefits in mortality and reinfarction were driven by the treatment with prasugrel or ticagrelor, without a significant difference in terms of major bleeding complications as compared to standard-dose clopidogrel (5% vs. 4.7%, OR = 1.06 95% CI 0.96-1.17, P = 0.25).

CONCLUSION

This meta-analysis showed that new oral antiplatelet regimens are associated with a significant reduction in mortality, reinfarction and in-stent thrombosis in ACS patients without an overall increase of major bleeding when treated with new antiplatelet drugs.

Effect of clopidogrel pretreatment on ischemic complications of percutaneous coronary intervention among bivalirudin-treated patients (from the EVENT registry)

Although clopidogrel pretreatment benefits patients undergoing percutaneous coronary intervention (PCI) for acute coronary syndromes, these benefits are less well established among patients undergoing elective PCI--in particular, when they are treated with the direct thrombin inhibitor, bivalirudin. We used data from the multicenter Evaluation of Drug Eluting stents and ischemic Events registry to assess the association between clopidogrel pretreatment and PCI-related complications among patients undergoing elective PCI with bivalirudin as the antithrombotic regimen. The primary end point was the composite of in-hospital death or myocardial infarction. From January 2005 and December 2007, 4,681 patients underwent elective PCI at 55 United States centers, and 1,913 (41%) received bivalirudin as the planned anticoagulant. Clopidogrel pretreatment was used in 923 patients (48%). The incidence of in-hospital death or myocardial infarction was similar among patients who did and did not receive clopidogrel pretreatment (5.5% vs 5.8%, p = 0.83). This result was unchanged in propensity-adjusted analyses (adjusted odds ratio for pretreatment 0.91, 95% confidence interval 0.60 to 1.39, p = 0.66). Also, no differences were seen in the in-hospital bleeding events (1.0% vs 1.0%, p = 0.94) or 1-year ischemic complications between the 2 treatment groups (7.5% vs 8.3%, p = 0.26). In conclusion, among unselected patients undergoing elective PCI with bivalirudin as the planned anticoagulant, clopidogrel pretreatment was common but was not associated with a reduced risk of ischemic complications.

Antiplatelet therapy and vascular disease: an update

Atherosclerosis is a diffuse, systemic disorder of the large and medium-sized arterial vessels, affecting the coronary, cerebral and peripheral circulation. Chronic inflammatory processes are the central pathophysiological mechanism largely driven by lipid accumulation, and provide the substrate for occlusive thrombus formation. The clinical sequelae of acute arterial thrombosis, heart attack and stroke, are the most common causes of morbidity and mortality in the industrialized world. Such acute events are characterized by rupture or erosion of the atherosclerotic plaque leading to acute thrombosis. The atherosclerotic process and associated thrombotic complications are collectively termed atherothrombosis. The platelet is a pivotal mediator of various endothelial, immune, thrombotic and inflammatory responses and therefore a key player in the initiation and progression of atherothrombosis. A robust evidence base supports the clear clinical benefits of antiplatelet agents in the primary and secondary therapy of atherothrombotic disorders. Percutaneous coronary and peripheral interventions have an established central role in the management of atherothrombotic disease and demand a greater understanding of platelet biology. In this article, we provide a clinically orientated overview of the pathophysiology of arterial thrombosis and the evidence supporting the use of the various established antiplatelet therapies, and discuss new and future agents.

Optimizing antiplatelet therapy in acute coronary syndrome and percutaneous coronary intervention

Dual antiplatelet therapy with aspirin and clopidogrel is the standard of care for patients with acute coronary syndrome (ACS) and those undergoing percutaneous coronary intervention (PCI). It is well established that inhibition of platelet aggregation reduces the risk of recurrent thrombotic events and stent thrombosis. However, some patients show a reduced antiplatelet response to standard clopidogrel loading (300 mg) and maintenance (75 mg day(-1)) doses, which has been associated with poorer patient outcomes. Pharmacodynamic and pharmacokinetic studies show that higher-than-standard clopidogrel dosing strategies facilitate more rapid platelet inhibition of a greater intensity as a result of greater plasma concentrations of the clopidogrel active metabolite. Recently completed studies suggest that in patients with ACS undergoing PCI, higher-than-standard clopidogrel dosing regimens provide greater inhibition of platelet function and improved clinical outcomes with a small but significant increase in major bleeding. Newer, more potent antiplatelet agents such as prasugrel and ticagrelor are other alternative strategies that result in more rapid, greater inhibition of platelet function and better outcomes than standard-dose clopidogrel. Whether platelet reactivity-guided therapy or genotyping for cytochrome P450 polymorphisms is useful in managing patients needs to be further defined. Most importantly, early and effective antiplatelet therapy results in the best short- and long-term outcomes for patients with ACS or those undergoing PCI.

Early clopidogrel use in non-ST elevation acute coronary syndrome and subsequent coronary artery bypass grafting

Clopidogrel use is associated with a significant decrease in major adverse cardiac events when used in patients with non-ST elevation acute coronary syndromes (NSTE-ACS), and guidelines give a class I level of evidence A recommendation for the use of clopidogrel in these patients. The optimal timing of clopidogrel use has not been conclusively determined, but nearly all data available support early use in patients with NSTE-ACS. Despite this, clopidogrel usage is far less than expected based on current guidelines because of concern for bleeding at the time of possible subsequent coronary artery bypass grafting (CABG). Clopidogrel use has been associated with increased perioperative bleeding at the time of CABG, but data are mixed. Numerous studies have conclusively shown that this bleeding risk is confined to those patients receiving clopidogrel within 5 days of CABG. The absolute number of patients exposed to this possible bleeding risk is very small relative to the >1 million patients who present annually with NSTE-ACS and is estimated to be <0.8% of these patients. Recent data have shown that (1) holding clopidogrel for 5 days before CABG is safe in patients with NSTE-ACS and (2) clopidogrel use in patients with NSTE-ACS decreases ischemic events in patients referred for CABG compared to patients who are not given clopidogrel. These data strongly challenge the notion that clopidogrel should be withheld until it is determined if the patient will be referred for CABG.

Antiplatelet drug therapy: role of pharmacodynamic and genetic testing

Antiplatelet therapy represents the cornerstone of treatment for the short- and long-term prevention of atherothrombotic disease processes, in particular in high-risk settings such as in patients with acute coronary syndrome and those undergoing percutaneous coronary intervention. Currently, dual antiplatelet therapy with aspirin and clopidogrel represents the most commonly used treatment regimen in these settings. However, a considerable number of patients continue to experience adverse outcomes, including both bleeding and recurrent ischemic events. Numerous investigations have demonstrated that this phenomenon may be, in part, attributed to the broad variability in individual response profiles to this standard antiplatelet treatment regimen, as identified by various assays of platelet function testing. In addition, recent studies have demonstrated that genetic polymorphisms may also have an important role in determining levels of platelet inhibition and may be considered as a tool to identify patients at risk of adverse events. This article provides an overview on antiplatelet drug response variability, an update on definitions, including the role of pharmacodynamic testing, underlying mechanisms – with emphasis on recent understandings on pharmacogenetics and drug–drug interactions – and current and future perspectives on individualized antiplatelet therapy.

Modifying clopidogrel maintenance doses according to vasodilator-stimulated phosphoprotein phosphorylation index improves clinical outcome in patients with clopidogrel resistance

BACKGROUND

Despite dual antiplatelet therapy, the rate of major adverse cardiovascular events (MACE) after percutaneous coronary intervention (PCI) remains high. Ex vivo tests of clopidogrel resistance can predict MACE after PCI. The purpose of this study is to evaluate the clinical impact of adjusting phosphorylation analysis in patients with clopidogrel resistance undergoing PCI.

HYPOTHESIS

We hypothesized that VASP-guided clopidogrel maintenance doses, compared to fixed doses, improved clinical outcome.

METHODS

This monocentric, prospective, randomized study was performed on 306 patients undergoing PCI. Patients were randomized to a control group (n = 156) and to a vasodilator-stimulated phosphoprotein (VASP)-guided group (n = 150). In the VASP-guided group, patients received adjusted maintenance doses of clopidogrel to obtain platelet reactivity index (PRI) of <50% during 1 year after PCI. The primary endpoint was the rate of MACE. The secondary endpoints were major and minor bleeding.

RESULTS

All patients completed the PCI procedure and 298 patients completed follow-up. The control and VASP-guided groups had similar demographic, clinical, and angiographic characteristics. In the VASP-guided group, PRI was significantly decreased (from 72.1% ± 11.4% to 27.7% ± 8.4%; P = 0.001) in 128 patients (87.1% of all participants). During the 1-year follow-up, 14 MACEs were recorded in the VASP-guided group and 30 MACEs were recorded in the control group (9.3% vs 20.4%, respectively; P = 0.008). There was no difference in the rate of major and minor bleeding in the VASP-guided group compared with the control group (12.9% vs 16.6%; P = 0.06).

CONCLUSIONS

Modifying clopidogrel maintenance doses according to platelet reactivity monitoring decreases the rate of MACE after PCI without increasing bleeding in patients with clopidogrel resistance during 1-year follow-up.

Temporal trends and practice variations in clopidogrel loading doses in patients with non-ST-segment elevation myocardial infarction, from the National Cardiovascular Data Registry

BACKGROUND

A higher loading dose of clopidogrel achieves a more rapid and consistent degree of platelet inhibition than standard dosing, although the clinical benefit of higher doses has not been clearly established. The use of the different doses in clinical practice is not known. We evaluated the patient, procedural, and hospital characteristics associated clopidogrel loading doses given to patients with non-ST-segment elevation myocardial infarction (NSTEMI).

METHODS

The National Cardiovascular Data Registry ACTION Get With the Guidelines Registry was queried for patients with NSTEMI admitted from 2007 to 2008. Demographic, clinical, and procedural information were collected on standardized data forms. Patients were categorized according to the clopidogrel loading dose received. Temporal trends in the use of different doses were evaluated in quarterly time intervals.

RESULTS

Between January 1, 2007, and December 31, 2008, the use of a 600-mg clopidogrel loading dose increased steadily from 36.4% to 45.5%, whereas the use of 300 mg decreased slightly from 40.1% to 37.1%. Patients loaded with clopidogrel before cardiac catheterization were more likely to receive 300 mg, whereas those receiving a loading dose at the time of catheterization more often received 600 mg. The temporal increase in the use of 600 mg clopidogrel loading doses was not explained by temporal changes in periprocedural loading, use of early invasive management of patients with NSTEMI, or use of antithrombotics or glycoprotein 2b/3a inhibitors.

CONCLUSIONS

Higher loading dose clopidogrel increased between 2007 and 2008. Higher-dose clopidogrel was more frequently used in lower-risk patients undergoing an early invasive strategy and receiving periprocedural loading.

Clopidogrel loading dose and bleeding outcomes in patients undergoing urgent coronary artery bypass grafting

BACKGROUND

Coronary artery bypass grafting (CABG) performed within 5 days of clopidogrel administration is associated with increased bleeding. The impact of clopidogrel loading dose is unknown. We examined the effect of clopidogrel loading dose on bleeding outcomes in patients undergoing urgent CABG.

METHODS

Clinical outcomes were examined retrospectively for 196 consecutive patients undergoing urgent CABG within 5 days of a clopidogrel loading dose between January 2003 and June 2009. Major bleeding was defined as a fall in hemoglobin > 5 g/dL, fatal or intracranial bleeding, or cardiac tamponade.

RESULTS

One hundred forty-eight patients received 300 mg and 48 patients received ≥ 600 mg clopidogrel loading. Patients were predominantly male (78%) with a mean age of 66 ± 10 years. Mean duration from clopidogrel loading to CABG was 3.0 ± 1.5 and 3.0 ± 1.6 days for the 300 and 600 mg loading doses, respectively. Major bleeding occurred in 47% of patients receiving 300 mg and 73% of patients receiving ≥ 600 mg clopidogrel loading (P = .002). Compared with 300 mg, patients receiving ≥ 600 mg had greater 24-hour chest tube output (391 ± 251 vs 536 ± 354 mL, P = .01), stayed longer in surgical intensive care (4.3 ± 4.1 vs 5.0 ± 3.1 days, P = .0001), and trended toward greater reoperation for bleeding (5% vs 12%, P = .09). Following multivariate analysis, clopidogrel loading dose ≥ 600 mg (odds ratio 2.8, CI 1.2-6.6), preoperative hemoglobin (3.4, 2.7-5.0 per 1 g/dL increase), and female gender (2.9, 1.1-7.4) predicted major bleeding.

CONCLUSIONS

Higher clopidogrel loading doses are associated with increased bleeding when administered within 5 days of CABG. The development of shorter-acting, reversible, oral antiplatelet agents may reduce perioperative bleeding in this population.

Clinical value of antiplatelet therapy in patients with acute coronary syndromes and in percutaneous coronary intervention

Dual antiplatelet therapy with aspirin and clopidogrel is recommended in all patients who have had an acute coronary syndrome or who undergo percutaneous coronary intervention to prevent further ischemic events. Resistance or reduced responsiveness to aspirin and/or clopidogrel has been associated with adverse cardiovascular outcomes, including stent thrombosis. There have been significant advances in this field, which aim to overcome antiplatelet resistance, including the development of new antiplatelet agents. The rationale for dual antiplatelet therapy, the impact of suboptimal efficacy and the potential ways of overcoming resistance or variability in response to antiplatelet agents will be reviewed in this article.

Beyond efficacy: pharmacokinetic differences between clopidogrel, prasugrel and ticagrelor

INTRODUCTION

Clinical nonresponse to clopidogrel has been associated with variability in response. This has led to the development of other P2Y12 receptor inhibitors, such as prasugrel and ticagrelor, with different pharmacokinetic characteristics that influence their pharmacodynamics.

AREAS COVERED

Clopidogrel response variability is attributable to its complex pharmacokinetics and is vulnerable to genetic polymorphisms in genes involved in absorption, metabolism and drug-drug interactions (i.e., proton pump inhibitors). Prasugrel which has a simpler metabolism, leading to greater bioavailability, seems to be less affected by genetic or drug-drug interactions and achieves a greater antiplatelet effect. Ticagrelor is the most novel compound approved with a simpler metabolism. Both prasugrel and ticagrelor reached their antiplatelet effect faster and to a much greater extent than clopidogrel. All these differences observed in kinetics explain, to some degree, the efficacy and safety profile observed in clinical trials for these molecules associated with other antiplatelet agents (aspirin, gpIIb/IIIa inhibitors) and anticoagulants.

EXPERT OPINION

Clopidogrel is still the best standard of care. However, the pharmacokinetic advantages of both prasugrel and ticagrelor allow clinicians to center patient management by selecting the best drug for the appropriate subject.

A pharmacodynamic comparison of prasugrel vs. high-dose clopidogrel in patients with type 2 diabetes mellitus and coronary artery disease: results of the Optimizing anti-Platelet Therapy In diabetes MellitUS (OPTIMUS)-3 Trial

Aims

Patients with diabetes mellitus (DM) have increased platelet reactivity and reduced platelet response to clopidogrel compared with patients without DM. Prasugrel, a more potent antiplatelet agent, is associated with greater reductions in ischaemic events compared with clopidogrel, particularly in patients with DM. The aim of this study was to perform serial pharmacodynamic assessments of prasugrel with high-dose clopidogrel in patients with DM.

Methods and results

Optimizing anti-Platelet Therapy In diabetes MellitUS (OPTIMUS)-3 was a prospective, randomized, double-blind, crossover study in patients with type 2 DM and coronary artery disease (CAD). Patients (n= 35) were randomly assigned to either prasugrel 60 mg loading dose (LD)/10 mg maintenance dose (MD) or clopidogrel 600 mg LD/150 mg MD over two 1-week treatment periods separated by a 2-week washout period. Platelet function was assessed by VerifyNow^® P2Y12 assay, light transmission aggregometry, and vasodilator-stimulated phosphoprotein phosphorylation at 0, 1, 4, and 24 h and 7 days. Greater platelet inhibition by VerifyNow^® P2Y12 was achieved by prasugrel compared with clopidogrel at 4 h post-LD (least squares mean, 89.3 vs. 27.7%, P< 0.0001; primary endpoint). The difference in platelet inhibition between prasugrel and clopidogrel was significant from 1 h through 7 days (P < 0.0001). Similar results were obtained using all other platelet function measures. Prasugrel resulted in fewer poor responders at all time points irrespective of definition used.

Conclusion

In patients with type 2 DM and CAD, standard-dose prasugrel is associated with greater platelet inhibition and better response profiles during both the loading and maintenance periods when compared with double-dose clopidogrel.

Clinical trial identifier: www.clinicaltrials.gov—NCT00642174

Tailored antiplatelet therapy can overcome clopidogrel and aspirin resistance--the BOchum CLopidogrel and Aspirin Plan (BOCLA-Plan) to improve antiplatelet therapy

BACKGROUND

Dual antiplatelet therapy using acetylsalicylic acid (ASA, aspirin) and clopidogrel is of great importance following coronary stenting. However, the variable platelet inhibitory effectiveness compromises the antithrombotic advantages provided by dual antiplatelet therapy. The aim of this single-center prospective study was to reduce the low response incidence of dual antiplatelet therapy with ASA and clopidogrel according to a prespecified therapy algorithm.

METHODS

Platelet function testing using whole blood aggregometry (Chronolog 590) was performed 48 hours following coronary stenting (for either acute coronary syndromes or stable coronary artery disease) on 504 patients. The antiplatelet therapy included a loading dose of 600 mg clopidogrel and 500 mg ASA, followed by 75 mg clopidogrel and 100 mg ASA once daily. Clopidogrel low responders (CLR: >5 ohm; adenosine diphosphate (ADP) 5 μM) and/or ASA low responders (ALR: >0 ohm; arachidonic acid 10 μM) were treated according to a structured therapy plan: in the case of CLR, the maintenance + dose was doubled (repeated loading dose followed by 150 mg daily), and when still ineffective ticlopidine or prasugrel, if available and not contraindicated, were used. ALR was treated by increasing the dose to 300 mg in a first step or to 500 mg ASA when the first modification did not take effect sufficiently. In addition, ADP receptor antagonist 2-methylthioadenosine 5'-monophosphate triethylammonium salt (MeSAMP) testing and ASA incubation were performed to rule out either a platelet ADP-receptor defect or an ASA pharmacokinetic resistance.

RESULTS

Of the total cohort of 504 patients, we detected 30.8% clopidogrel low-responders and 19.4% aspirin low-responders. For ALR, with a dose adjustment of 300 mg ASA daily, 94.6% of ALR were effectively treated and the residual 5.4% by administration of daily dosages of 500 mg ASA. This means that after modification of the ASA maintenance dose, all initial ALRs had an adequate antiplatelet response. The results for clopidogrel revealed that 69% of the CLR were treated effectively by increasing the clopidogrel dose to 150 mg daily. When prasugrel was not available or contraindicated, 12.7% of the remaining low responders showed an adequate result after being switched to ticlopidine. Consequently, by applying the therapy algorithm, we were able to reduce the CLR prevalence by 86.6%. On including prasugrel in the therapy plan, we were finally able to eliminate thienopyridine low response. In addition, no ADP receptor defect was found in this study as a potential reason for CLR. We identified the following factors associated with both CLR and ALR status: acute coronary syndromes, positive troponin values as well as diabetes mellitus and elevated HbA1C values and a higher platelet count. Furthermore, our data revealed for CLR elevated C-reactive protein values and a high PREDICT-score (including an age >65 years, acute coronary syndrome, diabetes mellitus, renal failure, and reduced left ventricular function) as risk factors. The following factors correlated with the risk of ASA low response: patients with elevated hemoglobin, serum creatinine and C-reactive protein values. In addition, medication with nitrates reduced the risk of being CLR. As also holds true for CLR, we found the PREDICT-score to be correlated to the risk of being ALR. However, by far the strongest risk factor for CLR or ALR was the fact of dual resistance.

CONCLUSION

Following a structured therapy plan based on a "test and treat" strategy, the prevalence of clopidogrel or aspirin low response can be significantly reduced and the risk of inadequate dual antiplatelet therapy minimized.

Antiplatelet and antithrombotic treatment after primary percutaneous coronary intervention: balancing safety and efficacy

Antiplatelet therapy has been shown to significantly reduce the risk of serious vascular events in high-risk patients, including those with a prior acute ischemic event. The long-term use of antiplatelet agents is a key component of secondary prevention measures following acute coronary syndromes, including ST-segment elevation myocardial infarction. While minimizing ischemic recurrences, an intensified antiplatelet regimen also invariably leads to an increased risk for bleeding, which can in turn lead to treatment discontinuation and worse overall cardiovascular outcomes. Thus, a critical balance between efficacy and safety must be pursued in clinical practice. Selection of agents and their combination, dose optimization, and a customized approach based on genotype or assessment of on-treatment phenotype are discussed in the context of available evidence.

Clinical impact of enhanced inhibition of P2Y12-mediated platelet aggregation in patients with ST-segment elevation myocardial infarction undergoing percutaneous coronary intervention

The combination of aspirin and clopidogrel at a loading dose of 300 mg followed by a maintenance dose of 75 mg daily is a well-established antiplatelet therapy for the secondary prevention of thrombotic complications in the settings of acute coronary syndrome and/or percutaneous coronary intervention (PCI). Despite the demonstrated clinical benefits associated with this antiplatelet therapy, there is accumulating evidence that a consistent proportion of patients persist in having high levels of platelet aggregation following standard clopidogrel dose. Importantly, the high platelet reactivity after clopidogrel treatment has been associated with higher risk for cardiovascular ischemic events, including stent thrombosis. This has warranted the need for alternative oral antiplatelet regimens that achieve a higher degree of platelet inhibition. Several functional studies have shown that a higher clopidogrel loading dose (600 mg) compared with standard dose, and novel oral adenosine diphosphate platelet receptor (P2Y12) antagonists compared with clopidogrel achieve a faster onset of action, increased platelet inhibition, and a more predictable drug response. These more favorable pharmacodynamic characteristics are of particular interest in the setting of primary PCI for ST-segment elevation myocardial infarction (STEMI), in which rapid and consistent inhibition of platelet activation and aggregation is desirable for therapeutic success. The present article reviews data on the clinical impact of enhanced P2Y12 inhibition with either higher clopidogrel dosing or new oral antiplatelet agents, including prasugrel and ticagrelor, in the setting of STEMI, focusing on results in the setting of primary PCI.

Comparison of 600 versus 300-mg Clopidogrel loading dose in patients with ST-segment elevation myocardial infarction undergoing primary coronary angioplasty

The aim of the present study was to compare 600- and 300-mg clopidogrel loading doses in patients with ST-segment elevation myocardial infarctions who underwent primary percutaneous coronary intervention (PCI). Two hundred fifty-five consecutive patients presenting with ST-segment elevation myocardial infarctions who underwent primary PCI were enrolled. Patients were divided into 2 groups on the basis of the loading dose of clopidogrel received before the procedure (600 vs 300 mg). Procedural angiographic end points and 1-year major adverse cardiac events were compared between the 2 groups. Major adverse cardiac events were defined as death, nonfatal myocardial infarction, and target vessel revascularization. There were no significant differences in baseline clinical and angiographic features between the 2 groups: 157 (62%) in the clopidogrel 600 mg group and 98 (38%) in the 300 mg group. Patients receiving 600-mg loading dose of clopidogrel showed a significantly lower incidence of post-PCI myocardial blush grade 0 or 1 (odds ratio 0.64, 95% confidence interval 0.43 to 0.96, p = 0.03) and significantly less common no-reflow phenomenon (odds ratio 0.38, 95% confidence interval 0.15 to 0.98, p = 0.04) compared to those in the 300-mg group. Propensity-adjusted Cox analysis showed significantly higher survival free of major adverse cardiac events in patients receiving 600-mg loading dose of clopidogrel compared to those receiving the lower dose (hazard ratio 0.57, 95% confidence interval 0.33 to 0.98, p = 0.04). In conclusion, a 600-mg loading dose of clopidogrel is associated with improvements in procedural angiographic end points and 1-year clinical outcomes in patients with ST-segment elevation myocardial infarction who undergo primary PCI compared to a 300-mg dose.

Platelet P2Y₁₂ receptor inhibition: an update on clinical drug development

Antiplatelet therapy is the cornerstone of treatment for patients with coronary artery disease. Since adenosine diphosphate (ADP) represents one of the most important mediators of thrombosis, the inhibition of the platelet ADP receptor, in particular the P2Y₁₂ subtype, plays a pivotal role in secondary prevention of recurrent atherothrombotic events in high-risk settings. Numerous clinical trials have shown the efficacy of clopidogrel, an inhibitor of the ADP P2Y₁₂ receptor, in patients presenting with an acute coronary syndrome and undergoing percutaneous coronary intervention. However, laboratory and clinical experience with clopidogrel have led to understanding some of the limitations of this drug, the most important of which is its broad range in interindividual response variability, resulting in the development of novel ADP P2Y₁₂ receptor-inhibiting strategies. This article provides an overview of ADP P2Y₁₂ receptor-inhibiting strategies, including high clopidogrel dosing regimens and novel agents under advanced clinical development.

Double-dose versus standard-dose clopidogrel and high-dose versus low-dose aspirin in individuals undergoing percutaneous coronary intervention for acute coronary syndromes (CURRENT-OASIS 7): a randomised factorial trial

BACKGROUND

Clopidogrel and aspirin are the most commonly used antiplatelet therapies for percutaneous coronary intervention (PCI). We assessed the effect of various clopidogrel and aspirin regimens in prevention of major cardiovascular events and stent thrombosis in patients undergoing PCI.

METHODS

The CURRENT-OASIS 7 trial was undertaken in 597 centres in 39 countries. 25,086 individuals with acute coronary syndromes and intended early PCI were randomly assigned to double-dose (600 mg on day 1, 150 mg on days 2-7, then 75 mg daily) versus standard-dose (300 mg on day 1 then 75 mg daily) clopidogrel, and high-dose (300-325 mg daily) versus low-dose (75-100 mg daily) aspirin. Randomisation was done with a 24 h computerised central automated voice response system. The clopidogrel dose comparison was double-blind and the aspirin dose comparison was open label with blinded assessment of outcomes. This prespecified analysis is of the 17,263 individuals who underwent PCI. The primary outcome was cardiovascular death, myocardial infarction, or stroke at 30 days. Analyses were by intention to treat, adjusted for propensity to undergo PCI. This trial is registered with ClinicalTrials.gov, number NCT00335452.

FINDINGS

8560 patients were assigned to double-dose and 8703 to standard-dose clopidogrel (8558 and 8702 completed 30-day follow-up, respectively), and 8624 to high-dose and 8639 to low-dose aspirin (8622 and 8638 completed 30-day follow-up, respectively). Compared with the standard dose, double-dose clopidogrel reduced the rate of the primary outcome (330 events [3·9%] vs 392 events [4·5%]; adjusted hazard ratio 0·86, 95% CI 0·74-0·99, p=0·039) and definite stent thrombosis (58 [0·7%] vs 111 [1·3%]; 0·54 [0·39-0·74], p=0·0001). High-dose and low-dose aspirin did not differ for the primary outcome (356 [4·1%] vs 366 [4·2%]; 0·98, 0·84-1·13, p=0·76). Major bleeding was more common with double-dose than with standard-dose clopidogrel (139 [1·6%] vs 99 [1·1%]; 1·41, 1·09-1·83, p=0·009) and did not differ between high-dose and low-dose aspirin (128 [1·5%] vs 110 [1·3%]; 1·18, 0·92-1·53, p=0·20).

INTERPRETATION

In patients undergoing PCI for acute coronary syndromes, a 7-day double-dose clopidogrel regimen was associated with a reduction in cardiovascular events and stent thrombosis compared with the standard dose. Efficacy and safety did not differ between high-dose and low-dose aspirin. A double-dose clopidogrel regimen can be considered for all patients with acute coronary syndromes treated with an early invasive strategy and intended early PCI.

FUNDING

Sanofi-Aventis and Bristol-Myers Squibb.

Novel antiplatelet therapy

Antiplatelet therapy is a cornerstone of the management of patients with acute coronary syndromes or for those undergoing percutaneous coronary intervention. As the intricacies of platelet biology and mechanisms of thrombus formation are revealed, novel antiplatelet therapies have emerged. Bleeding risk, however, has grown in concert with more potent platelet inhibition. This article reviews platelet biology and receptors to provide a foundation for understanding of antiplatelelet therapy. It also highlights recent advances in antiplatelet therapy, with a focus on mechanisms of action, pharmacodynamic data, and the balance of thrombotic versus bleeding outcomes.

Efficacy and safety of bivalirudin in patients receiving clopidogrel therapy after diagnostic angiography for percutaneous coronary intervention in acute coronary syndromes

OBJECTIVES

This study sought to investigate if the efficacy of bivalirudin monotherapy is similar to heparin plus GP IIb/IIIa inhibition in patients with acute coronary syndromes (ACS) treated with clopidogrel following diagnostic angiography.

BACKGROUND

Prior trials have demonstrated that peri-procedural bivalirudin therapy confers similar efficacy as heparin plus GP IIb/IIIa inhibitors, while lowering the risk of bleeding complications in ACS patients undergoing percutaneous coronary interventions (PCI). However, the incidence of adverse ischemic events post-PCI appeared to be higher in patients receiving bivalirudin without adequate pretreatment with clopidogrel.

METHODS

Using the 2004/2005 Cornell Angioplasty Registry, we evaluated 980 consecutive patients undergoing urgent PCI for UA/NSTEMI who were treated with either bivalirudin or UFH plus GP IIb/IIIa inhibitor. We excluded patients who were on chronic clopidogrel therapy or received clopidogrel pretreatment prior to angiography. All patients received a clopidogrel load (≥300-mg dose) immediately before or after the PCI. Long-term all-cause mortality was obtained for 100% of patients, with a mean follow-up of 24.6 ± 7.7 months.

RESULTS

Of the 980 study patients, 461 (47.0%) were treated with bivalirudin and 519 (53.0%) patients received UFH plus GP IIb/IIIa inhibitor. DES were used in 88% of PCI; 45% of patients presented with NSTEMI. The incidence of in-hospital death (0.4% vs. 0.2%, P = 0.604), post-procedural MI (6.9% vs. 5.4%, P = 0.351), and MACE including death, stroke, emergent CABG/PCI, and MI (7.6% vs. 5.8%, P = 0.304) were similar in patients treated with bivalirudin versus UFH plus GP IIb/IIIa inhibitors, respectively. The incidence of in-hospital stent thrombosis was similar (0.7% vs. 0%, P = 0.104), while major (0.9% vs. 2.9%, P = 0.034) and minor bleeding (10.4% vs. 18.9%, P < 0.001) was reduced in the bivalirudin-treated group. By two-years of follow-up, after propensity-score adjusted multivariate Cox regression analysis, there was no significant difference in long-term mortality between the two groups (HR 1.18; 95%CI 0.64-2.19, P = 0.598).

CONCLUSIONS

In patients presenting with ACS and receiving clopidogrel treatment after angiography (before or within 30 min of PCI), peri-procedural bivalirudin monotherapy suppresses acute and long-term adverse events to a similar extent as does UFH plus GP IIb/IIIa inhibitors, while significantly lowering the risk of bleeding complications.

Residual platelet reactivity: predicting short- and long-term clinical outcome in patients undergoing percutaneous coronary revascularization

Adequate platelet inhibition is mandatory in patients undergoing percutaneous coronary intervention in order to prevent recurrent thrombotic events. Dual antiplatelet therapy with aspirin and thienopyridine (e.g., clopidogrel) is the treatment of choice in this setting, providing clear clinical benefit in most of the patients. However, a wide interindividual variability exists in the response to antiplatelet drugs and several factors may contribute to determine fluctuation in platelet reactivity, even within the individual patient. Several methodologies and devices have been developed to monitor individual response to antiplatelet treatment, assessing different pathways of platelet activation and aggregation. Studies performed with the use of these methodologies have clearly demonstrated that patients with high post-treatment residual platelet reactivity present a higher risk of ischemic events both at short (during or soon after percutaneous coronary intervention) and long term. In these patients, more aggressive antithrombotic strategies, based on the results of platelet function tests, may be beneficial in order to reduce ischemic complications after percutaneous coronary intervention.

Dose comparisons of clopidogrel and aspirin in acute coronary syndromes

BACKGROUND

Clopidogrel and aspirin are widely used for patients with acute coronary syndromes and those undergoing percutaneous coronary intervention (PCI). However, evidence-based guidelines for dosing have not been established for either agent.

METHODS

We randomly assigned, in a 2-by-2 factorial design, 25,086 patients with an acute coronary syndrome who were referred for an invasive strategy to either double-dose clopidogrel (a 600-mg loading dose on day 1, followed by 150 mg daily for 6 days and 75 mg daily thereafter) or standard-dose clopidogrel (a 300-mg loading dose and 75 mg daily thereafter) and either higher-dose aspirin (300 to 325 mg daily) or lower-dose aspirin (75 to 100 mg daily). The primary outcome was cardiovascular death, myocardial infarction, or stroke at 30 days.

RESULTS

The primary outcome occurred in 4.2% of patients assigned to double-dose clopidogrel as compared with 4.4% assigned to standard-dose clopidogrel (hazard ratio, 0.94; 95% confidence interval [CI], 0.83 to 1.06; P=0.30). Major bleeding occurred in 2.5% of patients in the double-dose group and in 2.0% in the standard-dose group (hazard ratio, 1.24; 95% CI, 1.05 to 1.46; P=0.01). Double-dose clopidogrel was associated with a significant reduction in the secondary outcome of stent thrombosis among the 17,263 patients who underwent PCI (1.6% vs. 2.3%; hazard ratio, 0.68; 95% CI, 0.55 to 0.85; P=0.001). There was no significant difference between higher-dose and lower-dose aspirin with respect to the primary outcome (4.2% vs. 4.4%; hazard ratio, 0.97; 95% CI, 0.86 to 1.09; P=0.61) or major bleeding (2.3% vs. 2.3%; hazard ratio, 0.99; 95% CI, 0.84 to 1.17; P=0.90).

CONCLUSIONS

In patients with an acute coronary syndrome who were referred for an invasive strategy, there was no significant difference between a 7-day, double-dose clopidogrel regimen and the standard-dose regimen, or between higher-dose aspirin and lower-dose aspirin, with respect to the primary outcome of cardiovascular death, myocardial infarction, or stroke. (Funded by Sanofi-Aventis and Bristol-Myers Squibb; ClinicalTrials.gov number, NCT00335452.)

Treatment patterns in patients with acute coronary syndrome undergoing percutaneous coronary intervention

BACKGROUND

The Antiplatelet Therapy Observational Registry (APTOR) is a prospective observational study of acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) in a 'real world' clinical setting. Here the authors report on the management of ACS patients in three European countries during the hospital phase and through 12-months' follow-up, including use of antiplatelet agents, co-medications and stents, as well as clinical outcomes at 12 months.

METHODS

ACS patients undergoing PCI (N = 1525) from January to August 2007 were planned to be consecutively recruited in France, Spain and the UK.

RESULTS

Index diagnosis was unstable angina/non-ST-segment elevation myocardial infarction (MI) in 62% and ST-segment elevation MI in 38%. Prior to the index ACS event, 17% were prescribed both aspirin and clopidogrel. While in-hospital clopidogrel and aspirin use was similar across countries, considerable variation was observed between countries at 12 months (clopidogrel 66-75%; aspirin 86-95%). The UK most frequently used a 300-mg clopidogrel loading dose (70%) compared with France (53%) and Spain (56%), while >300 mg was used in 21%, 34% and 16% patients, respectively. Bare metal stents only were used in 42% of subjects, drug-eluting stents (DES) only in 40%, and both in 10%, with the highest rates of DES use in Spain (70%) followed by the UK (47%) and France (31%). The composite endpoint of cardiovascular (CV) death, MI or stroke occurred in 4.7% of patients by 12 months.

CONCLUSIONS

APTOR shows marked variation in ACS management between countries in antiplatelet therapy, co-medications and stent use. Due to the observational design of the registry, statistical testing was not applied and data should be seen as hypothesis generating. These data provide a useful benchmark for comparison with current guidelines.

Clopidogrel pretreatment in ST-elevation myocardial infarction patients transferred for percutaneous coronary intervention

BACKGROUND

Pretreatment with clopidogrel reduces ischemic complications before percutaneous coronary intervention (PCI). Limited data exist regarding the effect of pretreatment for ST-segment elevation myocardial infarction (STEMI) patients undergoing primary PCI.

METHODS

Prospective data were analyzed from a regional STEMI system using rapid transfer for primary PCI in 30 community hospitals. Zone 1 community hospitals are <60 miles and Zone 2 hospitals are 60 to 210 miles away from the PCI hospital. Compared with 63 minutes in the PCI hospital, median door-to-balloon times were 94 minutes in Zone 1 and 123 minutes in Zone 2 hospitals. All patients received aspirin, unfractionated heparin, and clopidogrel 600 mg in the emergency department of the presenting hospital within 15 minutes of diagnosis.

RESULTS

From April 2003 through December 2008, 2,014 consecutive STEMI patients were pretreated with clopidogrel before PCI, with a median (25th-75th percentile) duration from pretreatment to PCI of 75 (58-93) minutes. Patients with longer pretreatment duration had significantly reduced reinfarction/reischemia at 30 days (Zone 1: 0.85%, Zone 2: 0.9%) compared with nontransferred patients (3.2%, P = .001) as well as reduced stent thrombosis (Zone 1: 0.6%, Zone 2: 0.6% vs Abbott Northwestern: 2.0%; P = .04). Similarly, pretreatment duration of >60 minutes before PCI had reduced 30-day reinfarction/reischemia (1.0% vs 2.9%, P = .003). There were no significant differences in mortality or major bleeding.

CONCLUSION

ST-segment elevation myocardial infarction patients undergoing primary PCI in a regional STEMI network who received earlier pretreatment with a 600-mg loading dose of clopidogrel had less ischemic complications without increased bleeding or mortality.