CYP2C19*2 and Other Allelic Variants Affecting Platelet Response to Clopidogrel Tested by Thrombelastography in Patients with Acute Coronary Syndrome

Background: The optimal dosing of novel oral P2Y12 receptor platelet inhibitors such as prasugrel or ticagrelor is unclear and especially challenging in East Asians. We hypothesize that half-dose prasugrel and ticagrelor may be sufficient for long-term maintenance management in Korean patients with the acute coronary syndrome (ACS) compared with conventional dosages. Design: HOPE-TAILOR (Half Dose of Prasugrel and Ticagrelor in Platelet Response after Acute Coronary Syndromes) is a prospective, randomized, open-label, blinded, endpoint (PROBE) single-center, clinical trial. A total of 100 patients with ACS undergoing drug-eluting stent implantation will be randomly assigned to prasugrel, ticagrelor, or clopidogrel, and the patients in each treatment group will receive 1-month therapy with 100 mg q.d. aspirin plus prasugrel 10 mg q.d., ticagrelor 90 mg b.i.d., or clopidogrel 75 mg q.d., followed by half-dose prasugrel 5 mg q.d. or ticagrelor 45 mg b.i.d. for maintenance treatment but without clopidogrel dose reduction. The primary endpoint will be optimal platelet reactivity 3 months after coronary intervention, defined by VerifyNow Analyzer (PRU: 85-208) and vasodilator-stimulated phosphoprotein P2Y12 flow cytometry assay (platelet reactivity indices: 16-50%). Clinical outcomes will also be assessed, including major efficacy (composite of cardiac death, nonfatal myocardial infarction, repeat revascularization, or stroke) and safety (bleeding ≥2 according to the Bleeding Academic Research Consortium). Conclusion: HOPE-TAILOR is a prospective, randomized, open-label, blinded, endpoint study to explore the efficacy and safety of novel P2Y12 receptor inhibitors administered orally at half the dose in Korean patients with ACS. The results will be available late in 2017.

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Adrenergic receptor polymorphisms and platelet reactivity after treatment with dual antiplatelet therapy with aspirin and clopidogrel in acute coronary syndrome

Thrombosis and Haemostasis ◽

10.1160/th09-06-0355 ◽

2010 ◽

Vol 103 (04) ◽

pp. 774-779 ◽

Cited By ~ 7

Author(s):

Thomas Cuisset ◽

Michalis Hamilos ◽

Leen Delrue ◽

Corinne Frere ◽

Katia Verhamme ◽

...

Keyword(s):

Acute Coronary Syndrome ◽

Platelet Aggregation ◽

Antiplatelet Therapy ◽

Adrenergic Receptor ◽

Dual Antiplatelet Therapy ◽

Platelet Reactivity ◽

Individual Variability ◽

Platelet Response ◽

Coronary Syndrome ◽

Β2 Adrenergic Receptor

SummaryPlatelet response to clopidogrel shows inter-individual variability that is partially explained by genetic polymorphisms. This variability affects clinical outcome when clopidogrel is administered in patients with acute coronary syndrome (ACS). Catecholamines, released during ACS, contribute to platelet aggregation through platelet α2A- (α2A-AR) and β2-adrenergic receptor (β2-AR) stimulation. It was the objective of this study to assess the potential influence of α2A-AR and β2-AR gene polymorphisms on platelet reactivity after dual antiplatelet therapy with aspirin and clopidogrel in ACS. We screened 641 ACS patients for 6.3/6.7 kb α2A-AR polymorphism, and for Arg16Gly and Gln27Glu β2-AR polymorphism. After 600 mg clopidogrel, we assessed ADP 10 μmol-induced platelet aggregation (ADP-Ag) and vasoactive stimulated phosphoprotein (VASP). All single nucleotide polymorphisms were in Hardy-Weinberg equilibrium. A slight though negligible association was found between 6.3 kb allele of α2A-AR with platelet reactivity ADPAg induced (beta: –2.91 [-5.68;-0.14], p=0.04). A borderline not significant reduction in PRI VASP was observed in 6.3 kb α2A-AR carriers (beta: –3.81 [-0.09;7.72], p=0.06). No significant effect on platelet parameters was observed for the other tested polymorphisms. Common α2A- and β2-adrenergic receptor polymorphisms do not show any major impact on residual platelet reactivity in non-ST-elevation ACS when a dual antiplatelet therapy with 250 mg aspirin and 600 mg clopidogrel is administered.

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Increased mean platelet volume is associated with non-responsiveness to clopidogrel

Thrombosis and Haemostasis ◽

10.1160/th13-10-0845 ◽

2014 ◽

Vol 112 (07) ◽

pp. 137-141 ◽

Cited By ~ 26

Author(s):

Elad Asher ◽

Paul Fefer ◽

Michael Shechter ◽

Roy Beigel ◽

David Varon ◽

...

Keyword(s):

Diabetes Mellitus ◽

Acute Coronary Syndrome ◽

Platelet Aggregation ◽

Mean Platelet Volume ◽

Stable Coronary Artery Disease ◽

Study Groups ◽

Individual Variability ◽

Platelet Response ◽

Platelet Volume ◽

Coronary Syndrome

SummaryPrior studies have demonstrated significant individual variability of platelet response to clopidogrel, which affects clinical outcome. In patients with stable coronary artery disease (CAD) smoking, diabetes mellitus, elevated body mass index and renal insufficiency, significantly impact response to clopidogrel. The determinants of platelet response to clopidogrel in patients with acute coronary syndrome are unknown. Adenosine diphosphate (ADP)-induced platelet aggregation (PA), hs C-reactive protein, platelet count and mean platelet volume (MPV) were determined 72 hours post clopidogrel loading in 276 consecutive acute myocardial infarction (AMI) patients. Patients with ADP-platelet aggregation ≥ 70% were considered to be clopidogrel non-responders. Eighty-four patients (30%) were clopidogrel non-responders and 192 (70%) were responders (ADP-induced PA: 81 ± 17% vs 49 ± 17%, respectively, p<0.001). Both study groups were comparable with respect to age, gender, prior cardiovascular history, prior aspirin use and risk factors for CAD, including smoking (42% for both groups) and diabetes mellitus (26% vs 22%, respectively, p=0.4). Responders and non-responders had similar angiographic characteristics, indices of infarct size, and similar hs-CRP (29 ± 34 vs 28 ± 34 mg/l, p=0.7) and creatinine (1.08 ± 0.4 mg% vs 1.07 ± 0.4, p=0.9) levels. On the contrary non-responders had significantly larger mean MPV (9 ± 1.2 fl vs 8 ± 1 fl, respectively, p=0.0018), and when patients were stratified into quartiles based on MPV, ADP-induced PA increased gradually and significantly across the quartiles of MPV (p<0.001). In conclusion, increased MPV associated with platelet activation, predicts non-responsiveness to clopidogrel among patients with acute coronary syndrome.

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