CYP2C19 genotype-directed P2Y12 inhibitor antiplatelet therapy normalizes risk for major adverse cardiovascular events after percutaneous coronary intervention

ObjectiveTo study the use of CYP2C19 genotyping to guide P2Y₁₂ inhibitor selection to maximize efficacy, and attenuate risk in appropriate patients who underwent PCI for CAD.MethodsWe performed a retrospective analysis of 868 patients with CAD who received CYP2C19 genotyping after PCI and changed P2Y₁₂ inhibitor based on the results. Patients were divided into two groups based on clopidogrel metabolizer status. Group I: Intermediate (IM) and poor metabolizers (PM). Group II: Ultra-rapid (UM), rapid (RM) and normal metabolizers (NM). Each group was then categorized to one of two treatment arms guided by CYP2C19 genotype. Category 1: IM/PM started on clopidogrel, switched to ticagrelor or prasugrel; 2:IM/PM started on ticagrelor/prasugrel, continued these medications; 3: UM/RM/NM started on ticagrelor/prasugrel, switched to clopidogrel; 4: UM/RM/NM started on clopidogrel, continued clopidogrel. Death due to cardiac causes, bleeding events, non-fatal MI, target vessel revascularization (TVR), and MACE in all four categories were considered at 1, 6 and 12 months.ResultsWe did not observe significant difference between phenotypes for MACE at 1 (p = 0.274), 6 (p = 0.387), and 12 months (p = 0.083). Death due to cardiac causes, MI, and bleeding events were not significant at 1, 6, and 12 months. There was no significant difference in TVR at 6 (p = 0.491), and 12 months (p = 0.423) except at 1 month (p = 0.012).ConclusionCYP2C19 genotype-based intervention can be implemented effectively and reliably to guide selection of P2Y₁₂ inhibitor to optimize patient quality and safety when appropriate in post PCI patients.     

Common sequence variations in the P2Y12 and CYP3A5 genes do not explain the variability in the inhibitory effects of clopidogrel therapy

The efficacy of the platelet P2Y₁₂ receptor antagonist clopidogrel, which undergoes cytochrome-mediated metabolism to its active form, shows marked inter-individual variability. We investigated whether polymorphic variations in the P2Y₁₂ gene, which have been linked to platelet aggregation phenotypes, or the cytochrome P450 3A5 gene 6986G?>?A polymorphism, which largely determines CYP3A5 expression, influence the response to clopidogrel therapy. Fifty-four patients listed for elective percutaneous coronary intervention were studied using ADP-induced optical aggregometry, whole-blood single platelet counting (WBSPC) aggregometry, and flow-cytometric analysis of platelet P-selectin expression and platelet-monocyte conjugate formation. Platelet reactivity was measured at baseline, 4?h post clopidogrel 300?mg, and 10 and 28 days following clopidogrel 75?mg daily. A further 55 patients were studied using ADP-induced WBSPC at baseline and 4?h post clopidogrel 600?mg. Patients were genotyped for P2Y₁₂ haplotype and the CYP3A5 6986G?>?A single nucleotide polymorphism. Neither genotype was found to significantly influence the inhibition of platelet responses by either clopidogrel regimen. In conclusion, common sequence variations within the P2Y₁₂ and CYP3A5 genes do not contribute any major effect to the inter-patient variability in clopidogrel efficacy.     

Near patient anti-platelet response testing over time and gene analysis in patients admitted with acute coronary syndromes

We sought to assess the relationships between platelet reactivity at different time points, CYP2C19*2 and ABCB1 status and clinical outcomes in patients with acute coronary syndromes (ACS). Anti-platelet response to clopidogrel was studied prospectively using the VerifyNow (VN) P2Y₁₂ assay at the time of angiography and at 30 days post procedure in 151 patients admitted with ACS who underwent percutaneous coronary intervention (PCI). Troponin T levels were measured at angiography and 16–24 hour following PCI. DNA was extracted and the presence of CYP2C19*2 allele and ABCB1 polymorphisms were determined. Adverse cardiovascular and cerebral events (ACCE) were assessed at 12 months. High VN P2Y12 response at angiography was associated with a greater peri-procedural rise in troponin T, but not ACCE. However, VN P2Y₁₂ response measured at 30 days was associated with ACCE (p?=?0.017). CYP2C19*2 status was associated with higher VN P2Y12 response at angiography (p?<?0.0001) and 30 days (p?=?0.006) but not ACCE. Near-patient testing for clopidogrel response was associated with subsequent ACCE when performed 30 days following PCI, but not at angiography.     

Effect of CYP2C19 Genotype on Ischemic Outcomes During Oral P2Y12 Inhibitor Therapy: A Meta-Analysis

ObjectivesThe aim of this study was to examine the effect of CYP2C19 genotype on clinical outcomes in patients with coronary artery disease (CAD) who predominantly underwent percutaneous coronary intervention (PCI), comparing those treated with ticagrelor or prasugrel versus clopidogrel.BackgroundThe effect of CYP2C19 genotype on treatment outcomes with ticagrelor or prasugrel compared with clopidogrel is unclear.MethodsDatabases through February 19, 2020, were searched for studies reporting the effect of CYP2C19 genotype on ischemic outcomes during ticagrelor or prasugrel versus clopidogrel treatment. Study eligibility required outcomes reported for CYP2C19 genotype status and clopidogrel and alternative P2Y₁₂ inhibitors in patients with CAD with at least 50% undergoing PCI. The primary analysis consisted of randomized controlled trials (RCTs). A secondary analysis was conducted by adding non-RCTs to the primary analysis. The primary outcome was a composite of cardiovascular death, myocardial infarction, stroke, stent thrombosis, and severe recurrent ischemia. Meta-analysis was conducted to compare the 2 drug regimens and test interaction with CYP2C19 genotype.ResultsOf 1,335 studies identified, 7 RCTs were included (15,949 patients, mean age 62 years; 77% had PCI, 98% had acute coronary syndromes). Statistical heterogeneity was minimal, and risk for bias was low. Ticagrelor and prasugrel compared with clopidogrel resulted in a significant reduction in ischemic events (relative risk: 0.70; 95% confidence interval: 0.59 to 0.83) in CYP2C19 loss-of-function carriers but not in noncarriers (relative risk: 1.0; 95% confidence interval: 0.80 to 1.25). The test of interaction on the basis of CYP2C19 genotype status was statistically significant (p = 0.013), suggesting that CYP2C19 genotype modified the effect. An additional 4 observational studies were found, and adding them to the analysis provided the same conclusions (p value of the test of interaction <0.001).ConclusionsThe effect of ticagrelor or prasugrel compared with clopidogrel in reducing ischemic events in patients with CAD who predominantly undergo PCI is based primarily on the presence of CYP2C19 loss-of-function carrier status. These results support genetic testing prior to prescribing P2Y₁₂ inhibitor therapy.     

Cytochrome P450 2C19 loss-of-function polymorphism is a major determinant of clopidogrel responsiveness in healthy subjects

The capacity of clopidogrel to inhibit ADP-induced platelet aggregation shows wide intersubject variability. To determine whether frequent functional variants of genes coding for candidate cytochrome P450 (CYP) isoenzymes involved in clopidogrel metabolic activation (CYP2C19*2, CYP2B6*5, CYP1A2*1F, and CYP3A5*3 variants) influence the platelet responsiveness to clopidogrel, we conducted a prospective pharmacogenetic study in 28 healthy white male volunteers treated for 7 days with clopidogrel 75 mg/d. We observed that pharmacodynamic response to clopidogrel was significantly associated with the CYP2C19 genotype. Twenty of the subjects were wild-type CYP2C19 (*1/*1) homozygotes, while the other 8 subjects were heterozygous for the loss-of-function polymorphism CYP2C19*2 (*1/*2). Baseline platelet activity was not influenced by the CYP2C19 genotype. In contrast, platelet aggregation in the presence of 10 muM ADP decreased gradually during treatment with clopidogrel 75 mg once daily in *1/*1 subjects, reaching 48.9% +/- 14.9% on day 7 (P < .001 vs baseline), whereas it did not change in *1/*2 subjects (71.8% +/- 14.6% on day 7, P = .22 vs baseline, and P < .003 vs *1/*1 subjects). Similar results were found with VASP phosphorylation. The CYP2C19*2 loss-of-function allele is associated with a marked decrease in platelet responsiveness to clopidogrel in young healthy male volunteers and may therefore be an important genetic contributor to clopidogrel resistance in the clinical setting.     

Switching from prasugrel to clopidogrel based on Cytochrome P450 2C19 genotyping in East Asian patients stabilized after acute myocardial infarction

To evaluate the pharmacodynamic efficacy of de-escalating P2Y₁₂ inhibition from prasugrel to clopidogrel based on cytochrome P450 (CYP) 2C19 genotyping, we genotyped 50 Korean patients with AMI who underwent percutaneous coronary intervention (PCI) for CYP2C19 *2,*3, or *17 using real-time PCR. They were discharged on prasugrel 10 mg daily. A control group of 48 AMI patients who underwent PCI and were discharged on clopidogrel but did not undergo genotyping was identified retrospectively. Based on genotyping results available at 3 weeks, 12 patients found to have 2 copies of either CYP2C19 *2 or *3 loss of function alleles continued prasugrel while the remaining 38 patients switched to clopidogrel 75 mg daily. The rate of patients within the therapeutic window (TW) of on-treatment platelet reactivity (OPR), 85<P2Y₁₂ reactivity unit (PRU) ≤275, was compared in the genotype-directed cohort before (3 weeks) and after genotype-directed antiplatelet treatment (5 weeks), as well as with the control cohort at 5 weeks. In the genotype-directed group, there was an increase in the proportion of patients within the TW after genotype-directed antiplatelet treatment (48–76%, p=0.007), primarily driven by a decrease of patients with PRU <85 (52–16%, p <0.001). The proportion of patients within the TW was similar between the genotype-guided and control groups (76% vs. 72.9% p=0.726). In conclusion, individualized antiplatelet regimens based on CYP2C19 genotyping may improve likelihood of achieving a TW of OPR compared to fixed dose of prasugrel 10 mg during maintenance periods of AMI in East Asians.     

Routine CYP2C19 Genotyping to Adjust Thienopyridine Treatment After Primary PCI for STEMI: Results of the GIANT Study

ObjectivesThe aim of this study was to evaluate prospectively the clinical impact of routine transmission of CYP2C19 genotype in the management of acute ST-segment elevation myocardial infarction with primary percutaneous coronary intervention.BackgroundResponse to clopidogrel differs widely among patients, notably because of CYP2C19 genetic polymorphisms.MethodsCYP2C19 genotype (6 alleles) was determined centrally and communicated within 4.1 ± 1.9 days of primary percutaneous coronary intervention in 1,445 patients with ST-segment elevation myocardial infarction recruited at 57 centers in France. CYP2C19 metabolic status was predicted from genotype and served to adjust thienopyridine treatment. The primary endpoint was differences in 12-month outcomes (death, myocardial infarction, and stent thrombosis) between patients with the wild-type genotype or gain-of-function allele (class 1, n = 1,118) and those with loss-of-function (LOF) alleles (class 2, n = 272) who received optimized thienopyridine treatment.ResultsDetection of LOF alleles resulted in adjustment of P2Y₁₂ inhibition in 85% of patients, with significantly higher use of prasugrel or double-dose clopidogrel. The primary endpoint did not differ between class 1 and class 2 patients (3.31% vs. 3.04%, respectively; p = 0.82). In contrast, carriers of LOF alleles without treatment adjustment had significantly worse outcomes (15.6%; p < 0.05). Bleeding rates were not different between groups.ConclusionsIn a real-world setting, a complete CYPC2C19 genotype can be mostly determined in <7 days using analysis of saliva deoxyribonucleic acid collected during the in-hospital phase among patients with ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention. Genotype information led to stronger platelet inhibition treatment in the vast majority of LOF allele carriers and to similar clinical outcomes as in patients carrying the wild-type genotype or gain-of-function allele. (Genotyping Infarct Patients to Adjust and Normalize Thienopyridine Treatment [GIANT]; NCT01134380)     

Next-Generation Sequencing of CYP2C19 in Stent Thrombosis: Implications for Clopidogrel Pharmacogenomics

Purpose

Describe CYP2C19 sequencing results in the largest series of clopidogrel-treated cases with stent thrombosis (ST), the closest clinical phenotype to clopidogrel resistance. Evaluate the impact of CYP2C19 genetic variation detected by next-generation sequencing (NGS) with comprehensive annotation and functional studies.

Methods

Seventy ST cases on clopidogrel identified from the PLATO trial (n =?58) and Mayo Clinic biorepository (n =?12) were matched 1:1 with controls for age, race, sex, diabetes mellitus, presentation, and stent type. NGS was performed to cover the entire CYP2C19 gene. Assessment of exonic variants involved measuring in vitro protein expression levels. Intronic variants were evaluated for potential splicing motif variations.

Results

Poor metabolizers (n =?4) and rare CYP2C19*8, CYP2C19*15, and CYP2C19*11 alleles were identified only in ST cases. CYP2C19*17 heterozygote carriers were observed more frequently in cases (n =?29) than controls (n =?18). Functional studies of CYP2C19 exonic variants (n =?11) revealed 3 cases and only 1 control carrying a deleterious variant as determined by in vitro protein expression studies. Greater intronic variation unique to ST cases (n =?169) compared with controls (n =?84) was observed with predictions revealing 13 allele candidates that may lead to a potential disruption of splicing and a loss-of-function effect of CYP2C19 in ST cases.

Conclusion

NGS detected CYP2C19 poor metabolizers and paradoxically greater number of so-called rapid metabolizers in ST cases. Rare deleterious exonic variation occurs in 4%, and potentially disruptive intronic alleles occur in 16% of ST cases. Additional studies are required to evaluate the role of these variants in platelet aggregation and clopidogrel metabolism.

     

Underlying mechanism and specific prevention of hemolysis-induced platelet activation

Thromboembolic complications significantly impair the outcome of hemolytic disorders. We hypothesized that red cell adenosine diphosphate (ADP) release results in significant platelet activation in hemolysis and that this prothrombotic state can be prevented by inhibition of the ADP P2Y₁₂ receptor. In the current study, we therefore sought to investigate the mechanism and inhibition of hemolysis-induced platelet activation. The expression of activated integrin αIIbß3 was determined by flow cytometry, and platelet aggregation was assessed by multiple electrode platelet aggregometry. We demonstrate platelet activation and increased platelet aggregation by adding hemolytic blood (lysates) to whole blood, similarly to that achieved by the platelet agonist ADP. Enhanced platelet activation and reactivity in the presence of hemolytic blood were significantly abolished by apyrase, which catalyzes ADP degradation, and inhibited by blockade of the platelet ADP P2Y₁₂ receptor with cangrelor. Platelets from patients treated with the ADP P2Y₁₂ receptor antagonist clopidogrel showed a reduced response to lysates compared to platelets from healthy controls without antiplatelet treatment. Further, in vitro blood group ABO incompatibility induced hemolysis and led to increased platelet activation. Finally, “spontaneous” platelet aggregation seen in patients with cold agglutinin disease was completely abolished by cangrelor. In conclusion, hemolysis is associated with increased platelet activation and aggregation due to red cell derived ADP, which can be prevented by ADP receptor blockade.     

Evolving pattern of platelet P2Y12 inhibition in patients with acute coronary syndromes

Abstract

Dual antiplatelet therapy consisting of clopidogrel in addition to aspirin has previously been the standard of care for patients with acute coronary syndromes (ACS) but international guidelines have been evolving over the last 4 years with the introduction of prasugrel and ticagrelor. In October 2009, prasugrel was approved in the UK by the National Institute of Health and Clinical Excellence (NICE) for use in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI), diabetic patients with non-ST-elevation (NSTE) ACS undergoing PCI and patients with stent thrombosis while other ACS patients were to continue receiving clopidogrel. Ticagrelor was approved in October 2011 by NICE for use in patients with moderate-to-high risk NSTE ACS and STEMI undergoing primary PCI and was recommended in preference to clopidogrel in European guidelines. These recommendations were adopted in our region, constituting a population of 1.8 million. We studied the effect of changing patterns of P2Y₁₂ inhibitor usage on levels of platelet inhibition during maintenance therapy. Patients admitted to Northern General Hospital, Sheffield, with NSTE ACS or STEMI managed with primary PCI were enrolled over two periods of time: May 2010 to November 2011 (T1); and October 2012 to February 2013 (T2). Venous blood samples were obtained at 1 month after the onset of ACS. Light transmittance aggregometry (LTA) was performed and maximum aggregation response to ADP 20?μM was determined. A total of 116 patients were enrolled in T1 of whom 82 were receiving clopidogrel and 34 were receiving prasugrel. Twenty-nine patients were enrolled in T2, all of whom were receiving ticagrelor. Mean LTA results according to treatment with clopidogrel, prasugrel and ticagrelor were 57?±?18%, 41?±?20%, and 31?±?12%, respectively. Prasugrel was associated with significantly lower platelet aggregation responses than clopidogrel (p?<?0.001) and ticagrelor was associated with significantly lower platelet aggregation responses than both prasugrel (p?=?0.015) and clopidogrel (p?<?0.001). We conclude that international guidelines and NICE approval have led to increasing levels of P2Y₁₂ inhibition in ACS patients in this UK centre between May 2010 and February 2013. Ticagrelor was associated with significantly greater P2Y₁₂ inhibition than both clopidogrel and prasugrel during maintenance therapy.     

Evaluation of the INNOVANCE PFA P2Y assay and its association with CYP2C19 genotypes

The purpose of this study was to evaluate associations between INNOVANCE PFA P2Y (PFA P2Y) test results and CYP2C19 genotypes and provide baseline data for PFA P2Y testing to establish a therapeutic monitoring strategy for clopidogrel. A total of 75 new patients with acute coronary syndrome with planned percutaneous coronary intervention were enrolled between June 2012 and September 2012. All patients received clopidogrel at an initial loading dose of 600?mg followed by a 75-mg daily maintenance dose. Blood samples were obtained on the third morning after clopidogrel loading. PFA P2Y, VerifyNow P2Y12 and VASP assays were used to determine platelet inhibition due to clopidogrel, and the Verigene CYP2C19 test was used for CYP2C19 genotyping. The genotype frequency of 75 patients was as follows: CYP2C19 *1/*1 (wild type), 28 (37.3%); *1/*2, 31 (41.3%); *1/*3, 4 (5.3%); *2/*2, 5 (6.7%); *2/*3, 5 (6.7%); *1/*17, 1 (1.3%); and *2/*17, 1 (1.3%). Classified according to CYP2C19 genotypes, there were 29 (38.7%) extensive metabolizers (EM) or ultra rapid metabolizers (UM), 35 (46.7%) intermediate metabolizers (IM), and 10 (13.3%) poor metabolizers (PM). Median (interquartile range) PFA P2Y closure times (seconds) were 119 (101–260), 300 (130–300) and 300 (300–300) in the PM, IM and EM or UM groups, respectively (p?<?0.05). Median (interquartile range) VerifyNow PRUs were 294 (213–297), 215 (165–320) and 189 (118–279); and the VASP platelet reactivity index (%) was 52.7 (33.3–91.9), 59.9 (41.4–72.8) and 38.9 (26.8–62.2) in the PM, IM and EM or UM groups, respectively (p?>?0.05). Compared with non-carriers, carriers of reduced function CYP2C19 alleles tended to have higher platelet reactivity after clopidogrel treatment. The cut-off for PM versus other groups (IM and EM or UM) was ≤141 seconds (AUC 0.704, sensitivity 70%, specificity 76.6%) on the ROC curve. A statistically significant correlation between PFA P2Y (seconds) and VerifyNow (PRU) was found (ρ?=??0.47, p?<?0.0001). In conclusion, the PFA P2Y test showed a statistically significant association with CYP2C19 metabolizer phenotypes based on CYP2C19 genotyping and effectively determined the risk groups resistant to clopidogrel therapy, including PM.     

Comparison of ticagrelor and clopidogrel in the treatment of patients with coronary heart disease carrying CYP2C19 loss of function allele

BackgroundClopidogrel is a traditional P2Y12 receptor inhibitor that is widely used in clinical practice, but there are significant individual differences in its therapeutic effect. Carriers of the CYP2C19 deletion allele have a higher risk of adverse cardiovascular events than non-carriers.MethodsIn this study, 170 patients diagnosed with coronary heart disease (CHD) and on regular oral clopidogrel or ticagrelor antiplatelet therapy in the Department of Cardiology of Wuxi Second People’s Hospital from August to December 2019 were screened. Baseline patient data were collected, percutaneous coronary angiography (CAG) or coronary computed tomography angiography (CTA) results were recorded, CYP2C19 gene type was detected, and prognosis/outcome was assessed by telephone/outpatient/inpatient follow-up for 12 months.Results(I) Of the 170 patients, 0.66% were the fast metabolic type, 41.45% were the normal metabolic type, 42.76% were the intermediate metabolic type, and 15.13% were the poor metabolic type. CYP2C19*2 mutation accounted for 89.29% of all mutations, CYP2C19*3 mutation accounted for 9.82%, and CYP2C19*17 mutation accounted for only 0.89%. (II) Among the patients with CHD who regularly took clopidogrel, the risk in the intermediate metabolic group was 5.208-fold higher than that of normal metabolic group, and that of the poor metabolic group was 3.75-fold higher than that of normal metabolic group; there was no significant difference between the intermediate and poor metabolic groups. (III) Prognosis was significantly associated with regular use of ticagrelor or clopidogrel by patients in the intermediate metabolic group. There was no significant correlation between poor metabolism (PM) and normal metabolism (NM). Prognosis was significantly associated with regular use of ticagrelor or clopidogrel in patients undergoing percutaneous coronary intervention (PCI), but not in patients who did not undergo PCI.ConclusionsCYP2C19 polymorphism was associated with the prognosis of patients with CHD administered antiplatelet therapy with oral clopidogrel. The incidence of poor prognosis was significantly increased with CYP2C19*2 and/or CYP2C19*3 mutations, and patients undergoing PCI or carrying a single CYP2C19 deletion allele had a better prognosis with ticagrelor as replacement therapy.     

Inhibition of platelet aggregation by prostaglandin E1 (PGE1) in diabetic patients during therapy with clopidogrel and aspirin

Diabetes mellitus (DM) is associated with increased platelet activation and reduced platelet inhibition by clopidogrel. Prostaglandin E1 (PGE1) stimulates adenyl cyclase activity in platelets and increases cyclic AMP concentrations, which inhibit Ca²⁺release and platelet aggregation induced by P2Y1 receptor activation. PGE1 is included in the VerifyNow P2Y12 assay to suppress P2Y1 induced platelet aggregation. We hypothesized that diabetes mellitus may be associated with altered response to PGE1 in subjects treated with clopidogrel. Subjects with established coronary artery disease who were taking clopidogrel 75?mg daily and aspirin for >14 days were enrolled (n?=?96). Diabetic (n?=?34) were compared with non-diabetic subjects (n?=?62). VerifyNow P2Y12 assay and light transmittance aggregometry (LTA) were performed using ADP as agonist with and without addition of PGE1. Genomic DNA was genotyped for common cytochrome P450 (CYP) 2C19 variants using Taqman assays. Residual on-treatment platelet aggregation induced by 20?µM ADP was not significantly different between subjects with and without DM. Addition of 22?nM and 88?nM PGE1 to 20?µM ADP resulted in a significant reduction of maximal platelet aggregation (MPA). Residual LTA platelet aggregation with PGE1 and VerifyNow P2Y12 platelet reactivity were significantly higher in subjects with DM than those without DM and in carriers of CYP 2C19*2 polymorphism. We conclude that an impaired inhibitory response to PGE1 may contribute to the high platelet reactivity phenotype in subjects with DM treated with clopidogrel. Addition of PGE1 to ADP agonist platelet assays may identify subjects with blunted inhibitory response to prostaglandins and result in a higher proportion of subjects with DM being classified as non-responders.     

The active metabolite of prasugrel effectively blocks the platelet P2Y12 receptor and inhibits procoagulant and pro-inflammatory platelet responses

The aim of these studies was to investigate the extent of platelet P2Y₁₂ receptor inhibition by the thienopyridine active metabolite of prasugrel, R-138727. Blood was taken from healthy volunteers and pre-incubated with R-138727 or cangrelor (AR-C66931MX). Platelet aggregation was assessed in platelet rich plasma (PRP) and whole blood (WB). Vasodilator stimulated phosphoprotein (VASP) phosphorylation, platelet procoagulant activity (annexin V binding and microparticle formation) and calcium mobilisation were measured by flow cytometry. Platelet-leukocyte co-aggregate formation and sCD40L release, both pro-inflammatory responses of platelets, were measured by flow cytometry and ELISA, respectively. P2Y₁₂ receptor antagonism was determined using a radioligand binding assay (³³P 2-MeSADP) in resting and stimulated platelets and the effects of clopidogrel administration were also assessed. R-138727 yielded concentration-dependent inhibition of platelet aggregation, VASP phosphorylation inhibition, procoagulant activity and pro-inflammatory responses. In the presence of R-138727 or cangrelor there was increased calcium reuptake following agonist stimulation. R-138727 30 µmol/L and cangrelor 1 µmol/L completely inhibited ³³P 2-MeSADP binding, compared to partial inhibition following clopidogrel administration. Platelet activation and granule secretion did not expose an additional pool of P2Y₁₂ receptors. Prasugrel's active metabolite effectively blocks the P2Y₁₂ receptor with the highest concentrations tested yielding complete inhibition of P2Y₁₂-mediated amplification of several important platelet responses.     

Cangrelor inhibits the binding of the active metabolites of clopidogrel and prasugrel to P2Y12 receptors in vitro

Cangrelor is a rapid-acting, direct-binding, and reversible P2Y₁₂ antagonist which has been studied for use during percutaneous coronary intervention (PCI) in patients with or without pretreatment with an oral P2Y₁₂ antagonist. As cangrelor is administered intravenously, it is necessary to switch to an oral P2Y₁₂ antagonist following PCI, such as the thienopyridines clopidogrel, and prasugrel or the non-pyridine ticagrelor. Previous studies have suggested a negative pharmacodynamic interaction between cangrelor and thienopyridines. This in vitro study evaluated the receptor-level interaction between cangrelor and the active metabolite (AM) of clopidogrel or prasugrel by assessing functional P2Y₁₂ receptor number using a ³³P-2MeSADP binding assay. All P2Y₁₂ antagonists studied resulted in strong P2Y₁₂ receptor blockade (cangrelor: 93.6%; clopidogrel AM: 93.0%; prasugrel AM: 97.9%). Adding a thienopyridine AM in the presence of cangrelor strongly reduces P2Y₁₂ receptor blockade by the AM (clopidogrel AM: 7%, prasugrel AM: 3.2%). The thienopyridine AMs had limited ability to compete with cangrelor for binding to P2Y₁₂ (% P2Y₁₂ receptor blockade after co-incubation with cangrelor 1000?nmol/L: 11.7% for clopidogrel AM 3?µmol/L; 34.1% for prasugrel AM 3?µmol/L). In conclusion, in vitro cangrelor strongly inhibits the binding of clopidogrel and prasugrel AMs to the P2Y₁₂ receptor, consistent with the previous observation of a negative pharmacodynamic interaction. Care may need to be taken to not overlap exposure to thienopyridine AMs and cangrelor in order to reduce the risk of thrombotic complications following PCI.     

Poor agreement between light transmission aggregometry,Verify Now P2Y12 and vasodilatator-stimulated phosphoprotein for clopidogrel low-response assessment: A potential explanation of negative results of recent randomized trials

Abstract

Clopidogrel low response as assessed by several different biological tests correlates with poor prognosis after percutaneous coronary intervention (PCI). However, recent randomized clinical trials (RCT) testing the strategy of individual antiplatelet therapy tailoring based on one sole test have all shown negative results. Poor correlation between the different tests may explain the difficulties of patient selection and identification of “true poor responders” to clopidogrel. In this prospective study, clopidogrel response was assessed in 100 consecutive patients between 18 and 24 hours after a 600?mg clopidogrel loading dose using three different tests: light transmission aggregometry with 10?μmol ADP (LTA, results expressed as platelet aggregation percentage: PAP), Verify Now P2Y₁₂ (VN, results expressed as P2Y₁₂ reaction unit: PRU) and vasodilatator-stimulated phosphoprotein (VASP, results expressed as platelet reactivity index: PRI). Patients under chronic clopidogrel therapy were excluded. The mean PAP, PRU and PRI values were 38.6%, 176.1 PRU and 52.4%, respectively. When clopidogrel response was analyzed as continuous variable, there was a good correlation between the different tests: LTA/VN (R^2?=?0.642, p?<?0.001), LTA/VASP (R^2?=?0.409, p?<?0.001) and VN/VASP (R^2?=?0.616, p?<?0.001). However, when clopidogrel response was analyzed as pre-specified cut-off points to define patients as “poor or good responders” (according to the literature: 50% PAP for LTA, 235 PRU for VN and 50% PRI for VASP), only 47% of the patients were defined as “good” or “poor responders” by the three tests. Altogether, 33% of the patients were defined as “poor responders” by only one test, 20% by two tests and only 16% by the three tests. The correlation between the different tests is good when clopidogrel response is analyzed as continuous variable. Each individual is however rarely (less than 50%) defined as “poor or good responder” by all the three tests when pre-specified cut-off values are used. A sole test might not be sufficient to manage antiplatelet therapy in an individual patient and these results may explain the results of recent RCT showing the lack of benefit of systematic antiplatelet therapy monitoring strategy.     

Effect of cytochrome p450 polymorphisms on platelet reactivity after treatment with clopidogrel in acute coronary syndrome

Genetic polymorphisms of cytochrome P450 (CYP) isoforms may promote variability in platelet response to clopidogrel. This study was conducted to analyze, in 603 patients with non-ST elevation acute coronary syndromes, the effect of CYP3A4, CYP3A5, and CYP2C19 gene polymorphisms on clopidogrel response and post-treatment platelet reactivity assessed by adenosine diphosphate (ADP)-induced platelet aggregation, vasodilator-stimulated phosphoprotein phosphorylation index, and ADP-induced P-selectin expression. The CYP2C19*2 polymorphism was significantly associated with ADP-induced platelet aggregation, vasodilator-stimulated phosphoprotein phosphorylation index, and ADP-induced P-selectin expression in recessive (p <0.01, p <0.007, and p <0.06, respectively) and codominant (p <0.08, p <0.0001, and p <0.009, respectively) models, but the CYP3A4*1B and CYP3A5*3 polymorphisms were not. The CYP2C19*2 allele carriers exhibited the highest platelet index levels in multivariate analysis (p = 0.03). After covariate adjustment, the CYP2C19*2 allele was more frequent in clopidogrel nonresponders, defined by persistent high post-treatment platelet reactivity (ADP-induced platelet aggregation >70%; p = 0.03). In conclusion, the present data suggest that the CYPC19*2 allele influences post-treatment platelet reactivity and clopidogrel response in patients with non-ST elevation acute coronary syndromes.     

Accelerated platelet inhibition by switching from atorvastatin to a non-CYP3A4-metabolized statin in patients with high platelet reactivity (ACCEL-STATIN) study

Aims CYP3A4-metabolized statins can influence the pharmacodynamic effect of clopidogrel. We sought to assess the impact of switching to a non-CYP3A4-metabolized statin on platelet function among patients receiving clopidogrel and atorvastatin with high on-treatment platelet reactivity (HPR). Methods and results Percutaneous coronary intervention (PCI)-treated patients (n= 50) with HPR [20 μM adenosine diphosphate (ADP)-induced maximal platelet aggregation (MPA) >50%] were enrolled during chronic administration of atorvastatin (10 mg/day) and clopidogrel (75 mg/day) (≥6 months). They were randomly assigned to a 15-day therapy with either rosuvastatin 10 mg/day (n= 25) or pravastatin 20 mg/day (n= 25). Platelet function was assessed before and after switching by conventional aggregometry and the VerifyNow P2Y12 assay. Genotyping was performed for CYP2C19*2/*3, CYP3A5*3, and ABCB1 C3435T alleles. The primary endpoint was the absolute change in 20 μM ADP-induced MPA. After switching, MPAs after stimuli with 20 and 5 μM ADP were decreased by 6.6% (95% confidence interval: 3.2-10.1%; P < 0.001), and 6.3% (95% confidence interval: 2.5-10.2%; P = 0.002), respectively. Fifty-two P2Y12 reaction units fell (95% confidence interval: 35-70; P < 0.001) and the prevalence of HPR decreased (24%; P < 0.001). Pharmacodynamic effects were similar after rosuvastatin and pravastatin therapy. In addition to smoking status, the combination of calcium channel blocker usage and ABCB1 C3435T genotype significantly affected the change of 20 μM ADP-induced MPA. Conclusions Among PCI-treated patients with HPR during co-administration of clopidogrel and atorvastatin, switching to a non-CYP3A4-metabolized statin can significantly decrease platelet reactivity and the prevalence of HPR. This switching effect appears similar irrespective of the type of non-CYP3A4-metabolized statin.     

Genetic determinants of platelet response to clopidogrel

Antiplatelet agents are the mainstay treatment in the prevention and management of atherothrombotic complications. However, a substantial interpatient variability in response to clopidogrel has been reported. Furthermore, patients with coronary artery disease and lesser platelet inhibition in response to clopidogrel are at increased risk for cardiovascular events. Clopidogrel after absorption requires two-step oxidation by the hepatic cytochrome P450 to generate its active metabolite. Polymorphisms of genes encoding the cytochrome enzymes and P-glycoprotein involved in clopidogrel absorption are regarded as major determinants of the interindividual variability in the clopidogrel-induced platelet inhibition. In our review we discuss the prevalence and clinical significance of various alleles of the genes: CYP2C19 and ABCB1 in the setting of coronary artery disease. Allele CYP2C19*2 is associated with excess of ischaemic events including myocardial infarction and stent thrombosis. On the other hand, CYP2C19*17 allele poses a serious threat of bleeding. Data concerning the prognostic value of genetic variant 3435C→T of ABCB1 remain inconclusive.     

CYP 450 2C19 polymorphisms in Indian patients with coronary artery disease

Background

Dual antiplatelet therapy is the cornerstone in the management of acute coronary syndromes (ACS) and prevention of stent thrombosis (ST). Genetic polymorphisms in CYP2C19 gene involved in hepatic activation of clopidogrel leads to clopidogrel non-responsiveness and may influence clinical outcomes. These polymorphisms in CYP2C19 gene and their impact on clinical outcome in coronary artery disease (CAD) have not been studied in Indian population.

Methods

We studied 110 consecutive patients (mean age 55.7 ± 10.7 years; 90% male) taking clopidogrel with angiographically proven CAD for various genetic polymorphisms in CYP2C19 gene. Relationship between loss of function mutation and clinical presentation with recurrent ACS including ST was analyzed.

Results

Out of 110 patients, 26 (23.64%) had normal genotype, 52 (47.23%) had loss of function mutation *2 and 39 (35.45%) had a gain of function mutation *17, 7 (6.36%) patients were undefined metabolizers (*2/*17) which were excluded from analyses. Final analyses included 103 patients, with 45 (40.90%) having loss of function. Overall 51 patients had ACS, with 27 developing recurrence while on clopidogrel. The prevalence of loss of function mutation was no different between the group with recurrences and those without recurrences (55.6% vs. 50%, p = 0.7). Two patients developed ST while on clopidogrel; both had loss of function mutation.

Conclusion

CYP2C19 gene polymorphisms are common in Indian population. Loss of function mutation status did not affect the clinical outcomes. A larger study also considering P2Y12 receptor polymorphisms together with platelet activity testing, may be required to establish the role of CYP2C19 gene polymorphisms in clinical practice.