Clopidogrel responder status is uninfluenced by CYP2C19*2 in Danish patients with stroke

Background Antiplatelet therapy is a cornerstone of secondary stroke prevention, but the responsiveness to antiplatelet medication varies among patients. Clopidogrel is a pro-drug that requires hepatic transformation to reach its active metabolite. Single nucleotide polymorphisms (SNPs) in key enzymes or the target adenosine diphosphate (ADP) receptor on the platelet surface are believed to be involved in clopidogrel-mediated platelet inhibition and decreased antiplatelet effect with high-on-treatment platelet reactivity (HTPR). Objective This study investigated whether specific SNPs in key hepatic enzymes (CYP2C19*2, *3, *17, CYP3A4*1G, and NR1I2) or the ADP receptor (PR2Y12) are associated with HTPR to clopidogrel. Patients & methods This observational study included patients with ischemic stroke (IS) and transient ischemic attacks (TIAs) receiving clopidogrel at a dose of 75 mg/day. Patients were genotyped for eight different SNPs in the genes encoding CYP2C19, CYP3A4, NR1I2, and the P2Y12 receptor. Results Of the 103 patients that were included, 30.7% carried the CYP2C19*2 allele and had higher platelet reaction unit (PRU) values than non-carriers, but no patients showed HTPR. Carriers of the *17 allele had higher platelet inhibition but showed no difference in PRU values compared with non-carriers. The remaining SNPs were neither associated with PRU nor with platelet inhibition. Conclusions Patients with IS and TIAs treated with 75 mg clopidogrel/day do not have HTPR. A genetic analysis of CYP2C19*2, *3, *17, CYP3A4*1G, and NR1I2 revealed no associations with clopidogrel HTPR. CYP2C19*2 carriers and patients with HTPR in the acute phase after ischemic stroke or transient ischemic attacks exhibit higher PRU values, but not long-term treatment HTPR.

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Diurnal Variability of On-Treatment Platelet Reactivity in Clopidogrel versus Prasugrel Treated Acute Coronary Syndrome Patients: A Pre-Specified TROPICAL-ACS Sub-Study

Thrombosis and Haemostasis ◽

10.1055/s-0038-1677549 ◽

2019 ◽

Vol 119 (04) ◽

pp. 660-667 ◽

Cited By ~ 1

Author(s):

Matthias Freynhofer ◽

Ralph Hein-Rothweiler ◽

Paul Haller ◽

Daniel Aradi ◽

Döme Dézsi ◽

...

Keyword(s):

Acute Coronary Syndrome ◽

Platelet Reactivity ◽

Adenosine Diphosphate ◽

Coronary Intervention ◽

Early Morning ◽

Platelet Inhibition ◽

Control Group ◽

Diurnal Variability ◽

Coronary Syndrome ◽

Adp Receptor

AbstractLong-term evidence supports a clustering of cardiovascular events in the early morning and smaller mechanistic studies in aspirin-treated patients have shown increased platelet reactivity at the end of the dosing interval. Comparative pharmacodynamic analyses for different adenosine diphosphate (ADP) receptor inhibitors in percutaneous coronary intervention-treated acute coronary syndrome (ACS) patients are lacking and this pre-specified analysis from the randomized Testing Responsiveness To Platelet Inhibition On Chronic Antiplatelet Treatment For Acute Coronary Syndromes (TROPICAL-ACS) trial aimed for the first time at investigating diurnal variability of on-treatment platelet reactivity in clopidogrel versus prasugrel treated patients. TROPICAL-ACS randomized 2,610 ACS patients to either treatment with prasugrel (control group) or to a platelet function testing-guided de-escalation of anti-platelet treatment with a switch to clopidogrel (guided de-escalation group). This study design enabled a diurnal comparison of on-prasugrel versus on-clopidogrel treatment platelet reactivity under steady-state conditions. For 2,526 patients (97%), both the exact time of blood sampling and the ADP-induced platelet aggregation value (in units, Multiplate analyser) were available. Platelet reactivity in patients on clopidogrel (n = 1,265) was higher and subject to significant diurnal variability (p = 0.019) with a peaking of platelet reactivity in the early morning (5–10 a.m.). In prasugrel-treated patients (n = 1,261), there was no sign for diurnal variability (p = 0.174) or a peaking of platelet reactivity in the morning. The potent ADP receptor inhibitor prasugrel is not subject to diurnal variability while we observed a significant diurnal variability of on-clopidogrel platelet reactivity. The clinical impact of this observation may differ for patients with and without an adequate response to clopidogrel treatment and the issue of diurnal variability of platelet reactivity in ACS patients warrants further investigation.

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Multifactorial Background for a Low Biological Response to Antiplatelet Agents Used in Stroke Prevention

Medicina ◽

10.3390/medicina57010059 ◽

2021 ◽

Vol 57 (1) ◽

pp. 59

Author(s):

Adam Wiśniewski

Keyword(s):

Ischemic Stroke ◽

Secondary Prevention ◽

Antiplatelet Therapy ◽

Negative Impact ◽

Platelet Reactivity ◽

Antiplatelet Agent ◽

Biological Response ◽

Antiplatelet Agents ◽

Platelet Inhibition ◽

High Risk Group

Effective platelet inhibition is the main goal of the antiplatelet therapy recommended as a standard treatment in the secondary prevention of non-embolic ischemic stroke. Acetylsalicylic acid (aspirin) and clopidogrel are commonly used for this purpose worldwide. A low biological response to antiplatelet agents is a phenomenon that significantly reduces the therapeutic and protective properties of the therapy. The mechanisms leading to high on-treatment platelet reactivity are still unclear and remain multifactorial. The aim of the current review is to establish the background of resistance to antiplatelet agents commonly used in the secondary prevention of ischemic stroke and to explain the possible mechanisms. The most important factors influencing the incidence of a low biological response were demonstrated. The similarities and the differences in resistance to both drugs are emphasized, which may facilitate the selection of the appropriate antiplatelet agent in relation to specific clinical conditions and comorbidities. Despite the lack of indications for the routine assessment of platelet reactivity in stroke subjects, this should be performed in selected patients from the high-risk group. Increasing the detectability of low antiaggregant responders, in light of its negative impact on the prognosis and clinical outcomes, can contribute to a more individualized approach and modification of the antiplatelet therapy to maximize the therapeutic effect in the secondary prevention of stroke.

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Triglyceride glucose index influences platelet reactivity in acute ischemic stroke patients

BMC Neurology ◽

10.1186/s12883-021-02443-x ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Yinping Guo ◽

Jing Zhao ◽

Yi Zhang ◽

Lingshan Wu ◽

Zhiyuan Yu ◽

...

Keyword(s):

Insulin Resistance ◽

Ischemic Stroke ◽

Acute Ischemic Stroke ◽

Platelet Reactivity ◽

Multivariate Logistic Regression Analysis ◽

Platelet Inhibition ◽

Inhibition Rate ◽

Stroke Patients ◽

Tyg Index ◽

Significant Difference

Abstract Aim Insulin resistance was reported to increase the risk of ischemic stroke, which can be assessed by the triglyceride glucose (TyG) index. However, it remains unclear whether the TyG index influences the platelet reactivity during the treatment of ischemic patients. Methods Ischemic stroke patients receiving dual antiplatelet therapy (DAPT) within 48 h onset were consecutively included. The TyG index was calculated as ln (fasting triglyceride [mg/dL] × fasting glucose [mg/dL]/2). The top quartile of TyG index was defined as insulin resistance. The platelet reactivity was assessed by thromboelastography. The platelet inhibition rate induced by arachidonic acid (AA) or adenosine diphosphate (ADP) was used to confirm the high residual on-treatment platelet reactivity (HRPR) to aspirin or clopidogrel, respectively. The association between TyG index and platelet reactivity was assessed by Kruskal–Wallis test. The independent risk factors of HRPR were determined by multivariate logistic regression analysis. Results A total of 1002 patients were included and divided into 4 groups by quartiles of the TyG index (< 2.02; 2.02–2.27; 2.27–2.52; ≥2.52). The findings demonstrated that the maximum intensity of the clot increased, but the AA-induced platelet inhibition rate decreased, depending on the TyG index quartiles. No significant difference was found in the ADP-induced platelet inhibition rate among groups. The prevalence of aspirin HRPR increased depending on the TyG index quartile. Unlike the non-insulin resistance group, the insulin resistance group was independently associated with aspirin HRPR (OR = 1.689, 95% CI 1.14 to 2.51, P = 0.009). Conclusions In acute ischemic stroke patients taking DAPT, the elevation of the TyG index is associated with enhanced platelet reactivity and higher prevalence of aspirin HRPR. Insulin resistance assessed by the TyG index could be an independent risk factor for aspirin HRPR.

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In vivo effects of eltrombopag on platelet function in immune thrombocytopenia: no evidence of platelet activation

Blood ◽

10.1182/blood-2011-11-393900 ◽

2012 ◽

Vol 119 (17) ◽

pp. 4066-4072 ◽

Cited By ~ 55

Author(s):

Bethan Psaila ◽

James B. Bussel ◽

Matthew D. Linden ◽

Bracken Babula ◽

Youfu Li ◽

...

Keyword(s):

Platelet Activation ◽

Platelet Function ◽

Whole Blood ◽

Immune Thrombocytopenia ◽

Ex Vivo ◽

Platelet Reactivity ◽

Adenosine Diphosphate ◽

High Dose ◽

Platelet Surface

Abstract The effects of eltrombopag, a thrombopoietin-receptor agonist, on platelet function in immune thrombocytopenia (ITP) are not fully characterized. This study used whole blood flow cytometry to examine platelet function in 20 patients receiving eltrombopag treatment at days 0, 7, and 28. Platelet surface expression of activated GPIIb/IIIa, P-selectin, and GPIb was measured with and without low and high adenosine diphosphate (ADP) and thrombin receptor activating peptide (TRAP) concentrations. Before eltrombopag treatment with no ex vivo agonist, platelet activation was higher in ITP patients than controls. Platelet GPIb and activated GPIIb/IIIa expression without added agonist was unchanged following eltrombopag treatment, whereas a slight increase in P-selectin was observed. Expression of P-selectin and activated GPIIb/IIIa in response to high-dose ADP was lower during eltrombopag treatment than at baseline. Eltrombopag led to a slight increase in platelet reactivity to TRAP only in responders to eltrombopag but not to levels above those in controls; whole blood experiments demonstrated that this increase was probably because of higher platelet counts rather than higher platelet reactivity. In conclusion, although thrombocytopenic ITP patients have higher baseline platelet activation than controls, eltrombopag did not cause platelet activation or hyper-reactivity, irrespective of whether the platelet count increased.

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Mechanisms of platelet activation: Need for new strategies to protect against platelet-mediated atherothrombosis

Thrombosis and Haemostasis ◽

10.1160/th09-03-0192 ◽

2009 ◽

Vol 102 (08) ◽

pp. 248-257 ◽

Cited By ~ 195

Author(s):

Lisa Jennings

Keyword(s):

Antiplatelet Therapy ◽

Platelet Activation ◽

Platelet Reactivity ◽

Thrombus Formation ◽

Antiplatelet Agents ◽

Bleeding Risk ◽

Adenosine Diphosphate ◽

Adp Receptor ◽

Activation Pathways ◽

New Strategies

SummaryPlatelets are central mediators of haemostasis at sites of vascular injury, but they also mediate pathologic thrombosis. Activated platelets stimulate thrombus formation in response to rupture of an atherosclerotic plaque or endothelial cell erosion, promoting atherothrombotic disease. They also interact with endothelial cells and leukocytes to promote inflammation, which contributes to atherosclerosis. Multiple pathways contribute to platelet activation, and current oral antiplatelet therapy with aspirin and a P2Y12 adenosine diphosphate (ADP) receptor antagonist target the thromboxane A2 and ADP pathways, respectively. Both can diminish activation by other factors, but the extent of their effects depends upon the agonist, agonist strength, and platelet reactivity status. Although these agents have demonstrated significant clinical benefit, residual morbidity and mortality remain high. Neither agent is effective in inhibiting thrombin, the most potent platelet activator. This lack of comprehensive inhibition of platelet function allows continued thrombus formation and exposes patients to risk for recurrent thrombotic events. Moreover, bleeding risk is a substantial limitation of antiplatelet therapy, because these agents target platelet activation pathways critical for both protective haemostasis and pathologic thrombosis. Novel antiplatelet therapies that provide more complete inhibition of platelet activation without increasing bleeding risk could considerably decrease residual risk for ischemic events. Inhibition of the protease-activated receptor (PAR)-1 platelet activation pathway stimulated by thrombin is a novel, emerging approach to achieve more comprehensive inhibition of platelet activation when used in combination with current oral antiplatelet agents. PAR-1 inhibition is not expected to increase bleeding risk, as this pathway does not interfere with haemostasis.

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Temporal variability in the antiplatelet effects of clopidogrel and aspirin after elective drug-eluting stent implantation

Thrombosis and Haemostasis ◽

10.1160/th15-03-0257 ◽

2015 ◽

Vol 114 (11) ◽

pp. 1020-1027 ◽

Cited By ~ 9

Author(s):

Christian Stratz ◽

Stefan Leggewie ◽

Willibald Hochholzer ◽

Christian M. Valina ◽

Michael Gick ◽

...

Keyword(s):

Maintenance Therapy ◽

Temporal Variability ◽

Light Transmission ◽

Platelet Reactivity ◽

Adenosine Diphosphate ◽

Coronary Intervention ◽

Platelet Inhibition ◽

Drug Eluting Stent ◽

Elective Percutaneous Coronary Intervention ◽

Drug Eluting

SummaryGiven conflicting data on temporal variability in pharmacodynamic platelet responses to clopidogrel, we investigated platelet reactivity on clopidogrel and aspirin for up to six months after elective percutaneous coronary intervention (PCI) with drug-eluting stents. Platelet reactivity was determined in 102 patients before loading with clopidogrel and aspirin, and on maintenance therapy after PCI on day 1, at one month and six months by VerifyNow™ P2Y12 and Aspirin assays and by residual platelet aggregation (RPA) on light transmission aggregometry using adenosine diphosphate and arachidonic acid. By VerifyNow testing, median (interquartile range) P2Y12 reaction units (PRU) on clopidogrel were 166 (90–234), 195 (124–257), and 198 (141–252) on day 1, one month and six months after PCI, respectively (p=0.005 day 1 to 1 month, and p=0.86 1 month to 6 months). Using a cut-off of > 208 PRU, 35% of patients had high platelet reactivity (HPR) to clopidogrel on day 1, 43% at one month, and 46% at six months after PCI. Between day 1 and six months after PCI, 38.2% of patients changed clopidogrel responder status at least once. Other cut-offs and RPA yielded similar results. Platelet inhibition by aspirin was consistent over time with only five patients being characterised as having HPR. Considerable variation in individual on-clopidogrel platelet reactivity was present during both the subacute and the late phases of maintenance therapy after elective PCI. Hence, the utility of contemporary platelet function testing to guide antiplatelet therapy may be limited.

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Role of CYP2C19 alleles in the management of recurrent ischemic stroke

Neurology Clinical Practice ◽

10.1212/cpj.0000000000000584 ◽

2018 ◽

Vol 9 (2) ◽

pp. 140-144

Author(s):

Michael J. Lyerly ◽

Kelly Bartlett ◽

Karen C. Albright

Keyword(s):

Ischemic Stroke ◽

Stroke Prevention ◽

Drug Exposure ◽

Antiplatelet Agent ◽

Platelet Inhibition ◽

Secondary Stroke Prevention ◽

Nucleotide Polymorphisms ◽

Loss Of Function ◽

Single Nucleotide

Purpose of reviewCYP2C19 is the primary enzyme involved in the activation of clopidogrel, an antiplatelet agent used for secondary stroke prevention. An individual's CYP2C19 alleles are used to understand their CYP2C19-clopidogrel metabolizer phenotype. Single nucleotide polymorphisms of the CYP2C19 gene result in altered metabolism of this prodrug.Recent findingsThree ischemic stroke cases were treated with clopidogrel. Despite confirming adequate drug exposure, medication adherence, and ruling out drug-drug interactions, all had recurrent ischemic stroke. Each case had a CYP2C19 *2/*17 genotype, categorizing them as intermediate clopidogrel metabolizers. Even with the gain-of-function allele, the loss-of-function allele resulted in lack of prodrug activation, leading to decreased efficacy in platelet inhibition.SummaryThese cases illustrate the importance of a thoughtful approach to secondary stroke prevention and demonstrate the utility of pharmacogenomic testing in clopidogrel hyporesponders. Recognition of the importance of CYP2C19 genotyping has the potential to enable better selection of appropriate secondary prevention strategies.

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Validation of a New ELISA-Based Vasodilator-Associated Stimulated Phosphoprotein Phosphorylation Assay to Assess Platelet Reactivity Index in a Chinese Population

Clinical and Applied Thrombosis/Hemostasis ◽

10.1177/1076029616689300 ◽

2017 ◽

Vol 24 (3) ◽

pp. 452-461 ◽

Cited By ~ 1

Author(s):

Peng Ding ◽

Yujie Wei ◽

Nana Chen ◽

Huiliang Liu

Keyword(s):

Acute Coronary Syndrome ◽

Healthy Volunteers ◽

Chinese Population ◽

Platelet Reactivity ◽

Adenosine Diphosphate ◽

Coronary Intervention ◽

Platelet Inhibition ◽

Reactivity Index ◽

Enzyme Linked Immunosorbent Assay ◽

Coronary Syndrome

The level of platelet reactivity during P2Y12-adenosine diphosphate receptor antagonist is associated with ischemic and bleeding risks following percutaneous coronary intervention in acute coronary syndrome. Determining platelet reactivity inhibition may be valuable for confirming effective platelet inhibition for individual patients and identifying patients at risk of bleeding. The enzyme-linked immunosorbent assay (ELISA)-based vasodilator-stimulated phosphoprotein (VASP) assay offers unique advantages over other methods and has not been used in the Chinese population. We enrolled 10 healthy volunteers and 54 patients with acute coronary syndrome. The volunteers received no treatment, and patients were administered a loading dose of clopidogrel or ticagrelor. The platelet reactivity index (PRI) was measured using flow cytometry (FC)-VASP and ELISA-VASP at baseline and 8-hour postloading dose. Blood samples of healthy volunteers and clopidogrel- or ticagrelor-treated patients were frozen and stored for 1, 2, and 4 weeks after initial activation. All frozen samples were tested using ELISA-VASP. The PRI assessed by FC-VASP and ELISA-VASP correlated well showing a high degree of consistency in identifying high or low on-treatment platelet reactivity. No significant time-dependent changes in PRI results were observed in frozen samples stored up to 4 weeks compared to nonfrozen samples. The PRI of ticagrelor-treated patients was lower than that of clopidogrel-treated patients. The ELISA-VASP effectively assesses the PRI, and results obtained from frozen specimens are unaffected by storage and shipment prior to assay. Ticagrelor was superior to clopidogrel in decreasing the PRI.

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The Molecular Aspects of Disturbed Platelet Activation Through ADP/P2Y12 Pathway in Multiple Sclerosis

International Journal of Molecular Sciences ◽

10.3390/ijms22126572 ◽

2021 ◽

Vol 22 (12) ◽

pp. 6572

Author(s):

Angela Dziedzic ◽

Elzbieta Miller ◽

Joanna Saluk-Bijak ◽

Marta Niwald ◽

Michal Bijak

Keyword(s):

Multiple Sclerosis ◽

Platelet Activation ◽

Platelet Reactivity ◽

Adenosine Diphosphate ◽

Receptor Expression ◽

P2y12 Receptor ◽

Platelet Surface ◽

Molecular Abnormalities ◽

Increased Risk ◽

Ischemic Events

Epidemiological studies confirm a high risk of ischemic events in secondary-progressive multiple sclerosis (SP MS) patients, directly associated with an increased level of pro-thrombotic activity of platelets. Our work aimed to verify potential molecular abnormalities of the platelet P2Y12 receptor expression and functionality as a cause of an increased risk of thromboembolism observed in the course of MS. We have demonstrated an enhanced platelet reactivity in response to adenosine diphosphate (ADP) in SP MS relative to controls. We have also shown an increased mRNA expression for the P2RY12 gene in both platelets and megakaryocytes, as well as enhanced density of these receptors on the platelet surface. We postulate that one of the reasons for the elevated risk of ischemic events observed in MS may be a genetically or phenotypically reinforced expression of the platelet P2Y12 receptor. In order to analyze the effect of the PAR1 (protease activated receptor type 1) signaling pathway on the expression level of P2Y12, we also analyzed the correlation parameters between P2Y12 expression and the markers of platelet activation in MS induced by selective PAR1 agonist (thrombin receptor activating peptide-6, TRAP-6). Identifying the molecular base responsible for the enlarged pro-thrombotic activity of platelets in SP MS could contribute to the implementation of prevention and targeted treatment, reducing the development of cardiovascular disorders in the course of the disease.

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Measurement of platelet p-selectin expression by flow cytometry in patients with acute ischemic stroke

Acta Medica Martiniana ◽

10.2478/acm-2018-0002 ◽

2018 ◽

Vol 18 (1) ◽

pp. 14-20

Author(s):

K Kalmarova ◽

E Kurca ◽

V Nosal ◽

J Dluha ◽

J Ballova ◽

...

Keyword(s):

Flow Cytometry ◽

Ischemic Stroke ◽

Healthy Volunteers ◽

Antiplatelet Therapy ◽

Platelet Activation ◽

P Value ◽

Platelet Surface ◽

Antiplatelet Medication ◽

Acute Cerebral Ischemia ◽

The Difference

AbstractAims: The aim of this study was to asses the platelet activation in the acute phase of ischemic stroke and transient ischemic attack (TIA) by defining p-selectin (CD62) expression by flow cytometry in vivo – without stimulation with agonists. We also studied whether antiplatelet therapy supresses the levels of baseline p-selectin expression and verified if there is a correlation between platelet CD62 expression and the type of ischemic stroke.Methods: We determined the expression of platelet surface p-selectin using whole-blood flow cytometry within the first 48-hours after onset of cerebral symptoms in patients with atherothrombotic and lacunar ischemic stroke and in healthy volunteers. We studied the realationship between antiplatelet medication and the type of ischemic stroke to baseline p-selectin expression.Results: Patients with acute cerebral ischemia have an excess of circulating platelets that express p-selectin, compared to healthy volunteers. The difference between average p-selectin expression in the group of healthy volunteers and the group of patients with stroke was statistically significant (p-value < 0,000001). Patients with stroke without antiplatelet medication showed a higher p-selectin expression than patients with antiplatelet medication (ASA, CLP, or ASA and CLP), hovewer, the difference was not statistically significant. There is no relationship between CD62 expression and the type of stroke.Conclusions: We can conclude that p-selectin is a highly sensitive blood biomarker of increased platelet activation. Antiplatelet therapy suppresses baseline p-selectin expression only minimally, insignificantly according to our results.

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