Influence of cytochrome 2C19 allelic variants on on-treatment platelet reactivity evaluated by five different platelet function tests

Background

The antiplatelet effect of clopidogrel has been linked to cytochrome P450 2C19 (CYP2C19) carrier status. The presence of loss of function and gain of function variants were found to have a gene-dose effect on clopidogrel metabolism. However, genotyping is only one aspect of predicting response to clopidogrel and several platelet function tests are available to measure platelet response.Patients and methodsWe studied the influence of CYP2C19 allelic variants on on-treatment platelet reactivity as assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the VASP assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after stenting for cardiovascular disease. Allelic variants of CYP2C19 were determined with the Infiniti® CYP450 2C19 + assay and categorized into four metabolizer states (ultrarapid, extensive, intermediate, poor).

Results

Platelet reactivity increased linearly from ultrarapid to poor metabolizers using the VerifyNow P2Y12 assay (P = 0.04), the VASP assay (P = 0.02) and the Impact-R (P = 0.04). The proportion of patients with high on-treatment residual platelet reactivity (HRPR) identified by LTA, the VerifyNow P2Y12 assay and the VASP assay increased when the metabolizer status decreased, while no such relationship could be identified for results of MEA and Impact-R. The presence of loss of function variants (*2/*2, *2-8*/wt, *2/*17) was an independent predictor of HRPR in LTA and the VASP assay while it did not reach statistical significance in the VerifyNow P2Y12 assay, MEA, and the Impact-R.

Conclusion

Depending on the type of platelet function test differences in the association of on-treatment platelet reactivity with CYP2C19 carrier status are observed.     

Impact of point-of-care testing for CYP2C19 on platelet inhibition in patients with acute coronary syndrome and early dual antiplatelet therapy in the emergency setting

Aims

Only limited data exist about the role of point of care CYP2C19 testing in the acute setting in the early phase of acute coronary syndromes (ACS). Therefore, the present study was designed to investigate the impact of CYP2C19 loss-of–function point-of-care (POC) genotyping in patients presenting with acute coronary syndromes (ACS) and treated with dual antiplatelet therapy in the emergency setting.

Methods and Results

137 subjects with ACS scheduled for percutaneous coronary intervention were consecutively enrolled. Pre- and on-treatment platelet aggregation was assessed by multiple electrode aggregometry (MEA) after stimulation with adenosine diphosphate (ADP). Patients were loaded according to current guideline adherent indications and contraindications for use of P2Y₁₂ inhibitors in ACS. POC genotyping for CYP2C19*2 was performed in the emergency room after obtaining a buccal swab using the Spartan RX CYP2C19 system and obtaining patient’s informed consent. Prasugrel and ticagrelor treated patients had significantly lower PR compared to clopidogrel-treated patients. The benefits of prasugrel and ticagrelor compared to clopidogrel treated patients in terms of platelet inhibition were more pronounced in CYP2C19*2 carriers. Non-carriers showed similar inhibition regardless of particular P2Y₁₂ inhibitor treatment. Statistical analyses adjusting for factors associated with response (e.g. smoking) revealed that CYP2C19*2 allele carrier status and loading with different type of P2Y12 receptor blockers were significant predictors of on-treatment platelet reactivity in the early phase of ACS.

Conclusion

The results of this pilot study of treatment of patients in the early phase of ACS indicate that CYP2C19*2 POC genotyping might help to identify patients at risk with poor response to clopidogrel treatment, thereby benefiting from reloading and switching to alternative P2Y₁₂ receptor inhibition.     

Genetic and non-genetic factors responsible for antiplatelet effects of clopidogrel in Japanese patients undergoing coronary stent implantation: An algorithm to predict on-clopidogrel platelet reactivity

Introduction

Antiplatelet effects of clopidogrel appear to be affected by various factors including genetic polymorphism. So far, there has been little information about the response of clopidogrel in Asians, whose prevalence of a CYP2C19 loss-of-function (LOF) allele is high.

Methods and Results

We investigated background and clinical factors affecting on-clopidogrel platelet reactivity in Japanese patients undergoing coronary stent implantation (n = 114). In univariate analysis, antiplatelet effects of clopidogrel in a steady state were associated with not only CYP2C19 genotypes but also several factors including dyslipidemia. In addition, we developed an algorithm that can estimate P2Y12 Reaction Units (PRU) in a steady state by multiple regression analysis and evaluated the adequacy of the algorithm by the Akaike Information Criterion.

Conclusions

We revealed several factors influencing on-clopidogrel platelet reactivity in Japanese patients. We also succeeded in developing an algorithm that estimates PRU in a steady state, although it is uncertain whether the algorithm can be applied to other populations.     

Response to antiplatelet therapy is independent of endogenous thrombin generation potential

Background

Thrombin is the most potent platelet activator, and achieves rapid platelet activation even in the presence of antiplatelet therapy. Since activated platelets respond stronger to additional stimuli, the extent of endogenous thrombin generation may in part be responsible for the reported response variability to aspirin and clopidogrel therapy.

Patients and methods

Thrombin generation potential was measured with a commercially available assay, and platelet reactivity was assessed with the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, light transmission aggregometry (LTA), the VerifyNow aspirin and P2Y12 assays, and multiple electrode aggregometry (MEA) in 316 patients on dual antiplatelet therapy undergoing angioplasty and stenting.

Results

Peak thrombin, the lag phase and the area under the curve of thrombin generation correlated poorly with on-treatment platelet reactivity by all test systems. High on-treatment residual platelet reactivity (HRPR) in response to arachidonic acid was seen in 33 (10.5%), 41 (13%), and 79 (25.7%) patients by LTA, the VerifyNow aspirin assay, and MEA, respectively. HRPR in response to adenosine diphosphate was seen in 150 (48.1%), 48 (15.3%), 106 (33.7%), and 118 (38.3%) patients by the VASP assay, LTA, the VerifyNow P2Y12 assay, and MEA, respectively. Peak thrombin generation did not differ between patients without and with HRPR by the VASP assay, LTA, the VerifyNow P2Y12 assay and MEA. In the VerifyNow aspirin assay, patients without HRPR had higher peak thrombin generation than patients with HRPR (p = 0.01). Finally, patients without and with high peak thrombin generation exhibited similar on-treatment platelet reactivity by all test systems, and high peak thrombin generation occurred to a similar extent in patients without and with HRPR.

Conclusion

Response to antiplatelet therapy with aspirin and clopidogrel is not associated with thrombin generation potential.     

The cytochrome 2C19*2 and *3 alleles attenuate response to clopidogrel similarly in East Asian patients undergoing elective percutaneous coronary intervention

Introduction

Carriage of CYP2C19*2 allele is associated with diminished platelet response to clopidogrel. However, the loss-of-function impact of CYP2C19*3 allele on antiplatelet effect of clopidogrel has not been definitely verified. We conducted this study to compare decreased response to clopidogrel according to carriage of CYP2C19*2 vs. *3 allele.

Materials and methods

The study included 190 consecutive Korean patients undergoing elective percutaneous coronary intervention. Light transmittance aggregometry and the VerifyNow P2Y₁₂ assay were used to assess platelet reactivity (PR) at least 12 hours after 300-mg loading of clopidogrel. The cutoff of high on-treatment PR (HPR) was defined as 5 μmol/L ADP-induced PR > 50%. CYP2C19 genotype was analyzed by the SNaPshot method.

Results

Carriers of at least one CYP2C19 variant allele were 115 patients (60.5%), and allelic frequency of CYP2C19*2 and *3 was 30.3% and 6.8%, respectively. PR and the rate of HPR increased proportionally according to the number of CYP2C19 variant allele. Carriage of CYP2C19 variant allele was an only independent predictor of HPR in multivariate analysis. When we compare the effect of allelic carriage, there were no significant differences in platelet measures and the rate of HPR between carriers of CYP2C19*2 and/or *3 allele(s) whether they were intermediate or poor metabolizers.

Conclusion

Carriage of CYP2C19*3 allele is associated with diminished antiplatelet effect of clopidogrel, which may be as potent as the loss-of-function effect of CYP2C19*2 allele.     

Sustained enhancement of residual platelet reactivity after coronary stenting in patients with myocardial infarction compared to elective patients

Introduction

Elevated platelet reactivity despite antiplatelet therapy is associated with an increased cardiovascular risk after percutaneous coronary interventions. Current guidelines recommend uniform antiplatelet maintenance regimen after percutaneous coronary interventions for patients with myocardial infarction and elective patients. We sought to demonstrate that there is a persistent enhancement of residual platelet reactivity after myocardial infarction, requiring an intensified antiplatelet maintenance therapy.

Materials and Methods

A total of 66 patients after coronary stenting for myocardial infarction (n = 36) or elective coronary stenting (n = 30) were included in this prospective, controlled study. Platelet reactivity to adenosine-5-diphosphate and arachidonic acid under treatment with clopidogrel (75 mg) and acetyl salicylic acid (100 mg) were assessed 48 hours and 30 days after coronary stenting using light transmission aggregometry and multiple electrode platelet aggregometry (Multiplate analyzer) simultaneously.

Results

Fourty-eight hours after coronary stenting all measures of residual platelet reactivity were significantly elevated in the infarction group. After a mean follow up of 37 days, residual platelet reactivity to adenosine-5-diphosphate was still consistently elevated, albeit statistically not significant. Contrarily, residual platelet reactivity to arachidonic acid significantly decreased and returned to normal by the time of follow up. Regression analyses revealed myocardial infarction, C-reactive protein and fibrinogen as predictors of enhanced platelet reactivity 48 hours after coronary stenting.

Conclusions

Patients undergoing coronary stenting for acute myocardial infarction exhibit an enhancement of residual platelet reactivity sustaining for at least 48 hours following coronary stenting. This finding provides a rationale for a continued intensified antiplatelet therapy after myocardial infarction.     

Genetic determinants of high on-treatment platelet reactivity in clopidogrel treated Chinese patients

Introduction

Cytochrome P450 (CYP), ATP-binding cassette transporters (ABCB1), and paraoxonase-1 (PON1) play crucial roles in clopidogel absorption and bioactivation. Genetic polymorphisms in these genes have been associated with the variability of the response to clopidogrel, however their contribution to high on-treatment platelet reactivity (HPR) in clopidogrel treated Chinese patients is less known.

Materials and methods

Five-hundred Chinese-Han patients treated with clopidogrel for acute coronary syndrome (ACS) were consecutively recruited from the Department of Geriatric Cardiology, General Hospital of Chinese People’s Liberation Army, from September 2010 to September 2012. We assessed the relations of CYP2C19*2 (rs4244285), CYP2C19*3 (rs4986893), CYP2C19*17 (rs12248560), PON1Q129R (rs662) and ABCB1C3435T (rs1045642) to the platelet aggregation after 5 days maintenance dose of clopidogrel administration, and the risk for HPR. The cutoff of HPR was defined as 20 μmol/L adenosine diphosphate (ADP)-induced platelet aggregation > 50%.

Results

Both CYP2C19*2 and *3 alleles were significantly associated with higher platelet aggregation after 5 days maintenance dose of clopidogrel administration (P < 0.00001and P = 0.042, respectively). The platelet aggregation in carriers of at least one CYP2C19 loss-of-function allele (*2 or *3, accounted for 58% of the study population) was obviously higher than that in non-carriers (P < 0.00001). Patients with the CYP2C19*2 allele had a higher risk of HPR than those with the CYP2C19 wild-type genotype [adjusted hazard ratio (HR), 1.56; 95% confidence interval(CI), 1.04–2.33, P = 0.03]. The carriers of at least one CYP2C19 loss-of-function allele could also predict significantly greater risk of HPR compared with non-carriers (adjusted HR1.79,95% CI: 1.33–2.4,P = 0.003). However, the carriage of CYP2C19*3 alone could not predict the risk of HPR significantly (adjusted HR, 1.5; 95% CI: 0.83–3, P = 0.16). Significant relation of CYP2C19*17, PON1Q129R and ABCB1C3435T to the platelet aggregation was not found.

Conclusion

In clopidogrel treated Chinese patients with ACS, carriers of at least one CYP2C19 loss-of-function allele could predict greater risk of HPR, with the impact mainly attributing to CYP2C19*2. Neither ABCB1 nor PON1 genotype could influence the antiplatelet response of clopidogrel in the cohort of Chinese patients.     

Paraoxonase-1 activity affects the clopidogrel response in CYP2C19 loss-of-function carriers

Background

The impact of paraoxonase-1 (PON1) activity on the response to clopidogrel may differ in patients treated with drug-eluting stents (DES) in association with CYP2C19 loss-of-function (LOF) polymorphisms.

Methods

This study included 112 Japanese patients receiving clopidogrel (75 mg/day) and aspirin (100 mg/day) who underwent optical coherence tomography (OCT) examination 9 months after DES implantation. The CYP2C19 genotype was analyzed and LOF carriers (*1/*2, *1/*3, *2/*2, *3/*3, *2/*3) were identified. At the 9-month follow-up, platelet reactivity was determined by measuring the P2Y12 reactivity unit (PRU) using a VerifyNow P2Y12 assay, PON1 activity was evaluated and intra-stent thrombus was evaluated by OCT.

Results

Of the 112 Japanese patients, 75 were LOF carriers (67.0%). The patients were divided into tertiles according to the PON1 activity (tertile 1; < 230 U/L, tertile 2; 230–283 U/L, tertile 3; > 283 U/L). In the VerifyNowP2Y12 analysis, tertile 1 had a higher PRU than tertiles 2 and 3 in LOF carriers, and there was no difference among tertiles in non-carriers. The highest incidence of intra-stent thrombus was observed in tertile 1 followed by tertiles 2 and 3 in LOF carriers, whereas there was no such difference in non-carriers. Multivariate analysis revealed that LOF carriers and PON1 activity tertile 1 were independent predictors of intra-stent thrombus in all patients. In LOF carriers, tertile 1 was the only independent predictor for intra-stent thrombus.

Conclusion

Low PON1 activity is associated with a low response to clopidogrel and a high frequency of intra-stent thrombus only in LOF carriers.     

CYP2C19*2 and other genetic variants affecting platelet response to clopidogrel in patients undergoing percutaneous coronary intervention

Introduction

Information regarding any possible additional effect of genetic variants other than CYP2C19*2 on platelet reactivity in patients undergoing percutaneous coronary intervention (PCI), while on dual antiplatelet therapy, is sparse.

Materials and Methods

Genotyping for CYP2C19*2, CYP2C19*17, CYP2C9*3, CYP2B6*5, ABCB1 and P2RY12 (c.-217 + 2739 T > C) variants was performed in 146 consecutive PCI patients receiving clopidogrel. Platelet reactivity was assessed by the Verify Now P2Y12 point-of-care assay and high on-treatment platelet reactivity (HTPR) was defined as a Platelet Reactivity Unit (PRU) ≥ 235.

Results

We identified 65(44.5%) patients with HTPR and 38(26%) carriers of at least one CYP2C19*2 allele, which had higher platelet reactivity compared to non-carriers [least square (LS) mean difference 44.5, 95%CI 15.8-77.3, p = 0.003]. In the entire study population, the presence of at least one CYP2C19*2 or P2RY12 allelic variant was independently associated with HTPR (OR = 3.02, 95%CI 1.16-7.86, p = 0.023 and OR = 3.11, 95%CI 1.03-9.39, p = 0.05 respectively). In CYP2C19*2 non-carriers, carriers of at least one CYP2B6*5 allelic variant had higher platelet reactivity compared to the remainders (LS mean difference 35.6, 95%CI 3.7-67.6, p = 0.03) and the presence of at least one CYP2B6*5 or P2RY12 allelic variant was independently associated with HTPR (OR = 3.26, 95%CI 1.08-9.86, p = 0.04 and OR = 4.27, 95%CI 1.11-16.4, p = 0.04 respectively).

Conclusions

Apart from the CYP2C19*2, other genetic variants involved in clopidogrel metabolism and action like CYP2B6*5 and P2RY12 seem to have an important association with HTPR.     

Effect of comedication with proton pump inhibitors (PPIs) on post-interventional residual platelet aggregation in patients undergoing coronary stenting treated by dual antiplatelet therapy

Introduction

Currently, there is an intense debate about whether comedication with proton pump inhibitors (PPIs) weakens the antiplatelet effect of clopidogrel in patients undergoing coronary stent implantation. Competing mechanisms on the hepatic cytochrome 2C19 level are proposed. The aim of this study was to assess the impact of PPI treatment on clopidogrel response by measuring the ex vivo platelet aggregation in patients with coronary intervention.

Methods

1425 consecutive patients with symptomatic coronary artery disease undergoing percutaneous coronary intervention were enrolled in this single centre study. PPI comedication was defined as PPI intake ≥ 1 week prior to a 600 mg clopidogrel loading dose. PPI treatment was based on physician preference. Residual platelet aggregation (RPA) was measured by optical aggregometry. To correct for potential selection bias, propensity score matching was applied.

Results

RPA was significantly higher in PPI-treated patients compared with non-PPI-users (final aggregation 34.0% vs. 29.8%, p < 0.001). Low responder defined as RPA in the upper tertile were more often found in PPI-users. After adjustment for relevant confounders, PPI treatment was independently associated with higher RPA-levels.

Discussion

We demonstrated that peri-procedural co-administration of PPIs significantly decreases the effect of clopidogrel on RPA. To assess if clopidogrel-PPI interaction results in a higher susceptibility for cardiovascular events remains subject to further investigations.     

The influence of body size on the pharmacodynamic and pharmacokinetic response to clopidogrel and prasugrel: A retrospective analysis of the FEATHER study

Introduction

Patients treated with clopidogrel who have higher body size exhibit greater platelet reactivity than patients with lower body size. In a retrospective analysis of the FEATHER trial, we examined the relationship between platelet response to thienopyridines clopidogrel 75 mg (Clop-75), prasugrel 5 mg (Pras-5), and prasugrel 10 mg (Pras-10) using 3 body size indices: body weight (BW), body mass index (BMI), and body surface area (BSA). Relationships were assessed as continuous variables and as 4 incremental body size groups.

Materials and Methods

Aspirin-treated patients with stable coronary artery disease (N = 72) and a BW range of 45-134 kg received Clop-75, Pras-5, and Pras-10 in a 3-period, blinded, cross-over study. Platelet assays included maximum platelet aggregation (MPA) to 20 μM ADP by light transmission aggregometry, VerifyNow-P2Y12 reaction units (PRU), and vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation platelet reactivity index (PRI). Exposure to active metabolites (AMs) was also assessed.

Results

Body size was a determinant of AM exposure and residual platelet reactivity regardless of type and dose of thienopyridine. BW and BSA demonstrated marginally stronger correlations with platelet reactivity; VASP-PRI demonstrated a stronger correlation with the body size than the other tests. Correlation coefficients ranged from a high of 0.64 (BW vs. PRI on Pras-5) to a low of 0.34 (BMI vs. MPA on Pras-10), but all were statistically significant (p < 0.01).

Conclusions

Using a comprehensive selection of body size indices, AM exposures, platelet function tests, and thienopyridine doses, we demonstrated a consistent inverse relationship between body size and response to clopidogrel and prasugrel.     

Factors associated with the failure of clopidogrel dose-adjustment according to platelet reactivity monitoring to optimize P2Y12-ADP receptor blockade

Introduction

Inter-individual variability in clopidogrel responsiveness is dependent on genetic polymorphisms. We aimed to investigate the impact of 3 genetic polymorphisms involved in clopidogrel metabolism on a strategy of dose-adjustment according to platelet reactivity (PR) monitoring.

Materiel and methods

This prospective multicenter study enrolled 498 ACS patients undergoing PCI. PR was measured using the Vasodilator-Stimulated Phosphoprotein index (VASP) and a cut-off value of ≥ 50% defined high on-treatment platelet reactivity (HTPR). Genetic polymorphisms of cytochrome (CYP) 2C19, Paraxonase-1 (PON1) and ABCB1 were determined by allele specific PCR. Dose-adjustment was performed using up-to 3 additional loading doses (LD) of 600 mg clopidogrel in order to obtain a VASP < 50% in patients with HTPR following the first LD.

Results

CYP 2C19 2*polymorphism (p = 0.02), but neither PON1 (p = 0.8) nor ABCB1 genotype (p = 0.9), was significantly associated with HTPR. The dose-adjustment strategy failed in 11% of patients. ABCB1 polymorphism was significantly associated with a failed dose-adjustment (FDA) (p = 0.04). No relation was found between the other genotypes and the efficacy of LD adjustment. In multivariate analysis, BMI and ABCB1 polymorphism were the only factors significantly associated with FDA (p = 0.005 and p = 0.04 respectively).

Conclusion

While CYP 2C19 2* is associated with HTPR after 600 mg of clopidogrel, ABCB1 is responsible for the failure of a strategy of loading dose-adjustment according to PR monitoring. These findings may help to define a therapeutic strategy to optimize anti-platelet therapy in ACS patients undergoing PCI.     

The Cone-and-Plate(let) analyzer is not suitable to monitor clopidogrel therapy: A comparison with the flowcytometric VASP assay and optical aggregometry

Introduction

High on-clopidogrel platelet reactivity has been associated with an increased risk for atherothrombotic events. A new player on the horizon is the IMPACT-R ADP-test using ADP pre-stimulation. We here report the results of a thorough evaluation of this new device.

Materials and methods

The IMPACT-R ADP-test was evaluated in different categories of subjects. First, normal range values were determined in healthy subjects (n = 46). Second, the effect of 600 mg of clopidogrel was evaluated with the IMPACT-R ADP-test and two other well-validated methods (flowcytometric VASP-analysis and optical aggregometry) in 21 patients. Third, a head-to-head comparison between the IMPACT-R ADP-test and optical aggregometry was performed in a large cohort of patients on dual antiplatelet therapy.

Results

The results of the IMPACT-R ADP-test were highly variable throughout healthy subjects. The administration of a high clopidogrel loading dose resulted in a small but significant increase in surface coverage but 61.9% of the patients were still identified as clopidogrel nonresponder. In contrast, optical aggregometry and VASP-analysis identified 24% and 33% of these patients as a clopidogrel nonresponder, respectively. Head-to-head comparison with optical aggregometry in 451 patients showed only a modest correlation between both methods (r ∼ 0.20, p < 0.0001).

Conclusions

The IMPACT-R ADP-test is relatively insensitive to the effects of clopidogrel and cannot substitute for methods such as flowcytometric VASP-analysis and optical aggregometry. Further studies are required to establish the clinical usefulness of IMPACT-R ADP-test to accurately predict the occurrence of major adverse cardiovascular events in patients with high on-clopidogrel platelet reactivity before it can be implemented in clinical practice.     

Determination of cut-off levels for on-clopidogrel platelet aggregation based on functional CYP2C19 gene variants in patients undergoing elective percutaneous coronary intervention

Introduction

Carriers of reduced-function CYP2C19 allele on antiplatelet therapy show diminished platelet inhibition and higher rate of clinical risk. The purpose of this study was to determine cut-off levels of VerifyNow P2Y12 system associated with effective inhibition of on-clopidogrel platelet aggregation to predict carriers of CYP2C19 reduced-function allele among patients undergoing percutaneous coronary intervention (PCI).

Materials and Methods

We enrolled 202 consecutive patients with stable coronary artery disease (CAD) undergoing PCI and treated with clopidogrel. All patients underwent CYP2C19 genotyping and measurement of residual platelet aggregation by VerifyNow system.

Results

Carriers of CYP2C19 reduced-function allele constituted 131 (65%) of 202 CAD patients. Platelet inhibition measured by P2Y12 reaction units (PRU) and %inhibition was diminished in carriers compared with noncarriers (PRU: 290.0 ± 81.2 vs 217.6 ± 82.4, p < 0.001, %inhibition: 17.9 ± 17.8 vs 35.5 ± 22.8, p < 0.001, respectively). Multiple logistic regression analysis identified PRU and %inhibition as significant predictors of carrier state [odds ratio (OR) 4.95; 95% confidence interval (95%CI): 2.49 to 9.85; p < 0.001, OR 5.55; 95%CI: 2.80 to 10.99; p < 0.001, respectively]. Receiver-operating characteristic analysis showed that PRU and %inhibition were significant predictors of carrier state [area under the curve (AUC) 0.736 (95%CI: 0.664 to 0.808; p < 0.001), AUC 0.727 (95%CI: 0.651 to 0.803; p < 0.001), respectively]. The cut-off levels of PRU and %inhibition were 256 and 26.5% for the identification of carriers.

Conclusions

Our results suggested that the cut-off levels of PRU and %inhibition to discriminate carriers of CYP2C19 reduced-function allele from noncarriers are potentially useful clinically to provide optimal clopidogrel therapy in patients with stable CAD undergoing PCI.     

Impact of CYP2C19 Polymorphism and Proton Pump Inhibitors on Platelet Reactivity to Clopidogrel and Clinical Outcomes Following Stent Implantation

Background

The response to clopidogrel, and some kind of the drug interaction are multifactorial.

Methods and Results

We enrolled 174 consecutive patients and determined CYP2C19 genotypes, measured platelet aggregation, and assessed the relationship between CYP2C19 genotype and platelet reactivity 24 hours after clopidogrel administration, and the risk of cardiovascular events over 18 months follow-up. A sub analysis examined the impact of rabeprazole, a proton pump inhibitor (PPI) less affected by CYP2C19.The CYP2C19 genotype was extensive metabolizer (EM) in 36%, intermediate metabolizer (IM) in 45%, and poor metabolizer (PM) in 19%. Platelet reactivity was significantly lower in the EM group than in the IM and PM groups (EM, IM, PM: 3560 ± 1404, 4203 ± 1302, 5084 ± 1007 AU•min, P < 0.05). The cardiovascular event rate was higher in the IM and PM groups than in the EM group (12.7% and 12.5% vs 1.6%; Hazard ratio for IM 10.6, P = 0.029; for PM 11.3, P = 0.040). No differences were seen between patients taking (N = 50) and not taking (N = 124) rabeprazole in residual platelet aggregation (4407 ± 1360 vs 4048 ± 1394, AU•min, P = 0.2782), or in cardiovascular events (10.0% vs 8.1%, HR 0.97, P = 0.97).

Conclusions

CYP2C19 genotype is associated with an increased risk of cardiovascular events following stent implantation in Japanese patients.     

A randomised study comparing the antiplatelet and antinflammatory effect of clopidogrel 150 mg/day versus 75 mg/day in patients with ST-segment elevation acute myocardial infarction and poor responsiveness to clopidogrel: Results from the DOUBLE study

Introduction

The antiplatelet effect of standard or increased clopidogrel doses in patients with ST- segment elevation acute myocardial infarction (STEMI) has never been studied. In this study we compared the antiplatelet effect of a 75 mg daily maintenance dose of clopidogrel with 150 mg in patients with STEMI undergoing primary percutaneous coronary intervention (PCI).

Materials and methods

Fifty-four patients with STEMI undergoing PCI were randomly allocated to receive either 75 mg/day clopidogrel (group 1) or 150 mg/day (group 2) for 1 month. Platelet function, measured by 5 different assays, was determined at 3 time points: 38 ± 8 hours after the procedure, 1 week and 1 month after randomization.

Results

In group 1, mean ± SD platelet reactivity index (PRI) measured with the VASP assay was 57.7 ± 15.7% and 46.9 ± 15.7% at 1 week and 1 month, respectively, compared to 38.8 ± 15.7% and 34.9 ± 12.6% in group 2 (p = 0.0001). Same results were observed for light transmittance aggregometry, whole blood aggregometry and VerifyNow, but not for thromboelastometry. In contrast to what may be expected, the 75 mg daily maintenance dose took longer than 1-week to provide the full clopidogrel antiplatelet effect. Furthermore, patients in group 2 had a nearly 50% reduction in C-reactive protein levels both at 1 week and 1 month.

Conclusion

In patients with STEMI and poor responsiveness to clopidogrel a 150 mg daily maintenance dose of clopidogrel is associated with a significant reduction of platelet aggregation and a trend towards reduced inflammation.     

Plasma and Whole Blood Clot Strength Measured by Thrombelastography in Patients Treated with Clopidogrel during Acute Coronary Syndromes

Introduction

Treatment with clopidogrel, a selective platelet P₂Y₁₂ receptor antagonist, reduces risk of recurrent ischemic events in patients with acute coronary syndrome (ACS), by limiting platelet aggregation and activation. Stable whole blood clot formation requires activation of platelets, generation of fibrin and final fibrin crosslinks. In this study we intended to compare plasma and whole blood thrombelastography (TEG) measurements in patients during ACS.

Materials and Methods

Whole blood and plasma samples from 32 patients with non-ST segment elevation myocardial infarction (NSTEMI) were collected after administration of clopidogrel. Whole blood and plasma fibrin clot strength (MA) were determined by TEG. Platelet aggregation was determined by light transmittance aggregometry (LTA) using adenosine 5'-diphosphate (ADP), thrombin receptor activation peptide (TRAP), or collagen as agonists. Fibrinogen and C-reactive protein (CRP) concentrations were measured by ELISA.

Results

Heightened plasma fibrin clot strength was associated with increased platelet reactivity stimulated by ADP (ρ = 0.536; p = 0.002), TRAP (ρ = 0.481; p = 0.007), and collagen (ρ = 0.538; p = 0.01). In contrast to plasma fibrin MA, whole blood MA did not correlate with platelet aggregation. Platelet count was the primary contributor to the difference in thrombin induced whole blood MA and plasma fibrin MA. Increasing levels of CRP were associated with increased plasma fibrin clot strength and platelet reactivity.

Conclusions

Our data suggest that inflammation is associated with increased plasma fibrin clot strength and lower platelet inhibition by clopidogrel during ACS. Platelet count is a main contributor to additional contractile force of whole blood TEG as compared to plasma TEG during treatment with clopidogrel.     

The influencing factors for clopidogrel-mediated platelet inhibition are assay-dependent

Background

Influencing factors for clopidogrel-mediated platelet inhibition have only been evaluated by one or two different test systems in the same population so far. Since previous studies revealed poor correlations between the various platelet function tests, the identification of influencing variables for clopidogrel response may vary from one test system to the next. We therefore investigated whether the influencing factors for clopidogrel-mediated platelet inhibition depend on the used assay.

Patients and methods

Adenosine diphosphate (ADP)-inducible platelet reactivity was assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after angioplasty and stenting for cardiovascular disease. By univariate and multivariate regression analyses, we evaluated the impact of age ≥ 75, gender, body mass index (BMI), diabetes, active smoking, hypertension, hyperlipidemia, C-reactive protein, platelet count, creatinine, use of calcium-channel blockers (CCBs), statins, proton pump inhibitors, beta blockers, angiotensin converting enzyme inhibitors, and angiotensin receptor blockers on clopidogrel-mediated platelet inhibition in each test system.

Results

None of the independent influencing variables was consistent through all test systems. Only by LTA and the VerifyNow P2Y12 assay, age ≥ 75 and the use of CCBs were independently associated with higher on-treatment platelet reactivity. Only by the VASP assay and MEA, on-treatment platelet reactivity increased linearly with BMI. Further, only by MEA, residual ADP-inducible platelet reactivity increased linearly with platelet count, whereas an increase in platelet count was independently associated with a decrease in ADP-inducible platelet activation by the Impact-R.

Conclusion

The influencing factors for platelet reactivity during clopidogrel therapy are assay-dependent.     

Doubling the dose of clopidogrel restores the loss of antiplatelet effect induced by esomeprazole

Introduction

Concerns have been raised about the potential adverse interaction between clopidogrel and PPIs. We studied the impact of esomeprazole and ranitidine on the antiplatelet action of clopidogrel and aspirin and sought to determine whether doubling the dose of clopidogrel could restore its efficacy.

Materials and methods

In a randomized prospective crossover study, we tested platelet reactivity to aspirin and clopidogrel (75 and 150 mg) with and without esomeprazole or ranitidine using the VerifyNow system (Accumetrics Inc, San Diego, CA, USA) in 4 stages, each lasting 7 days: T1, 160 mg aspirin and 75 mg clopidogrel; T2 : 160 mg aspirin + 75 mg clopidogrel + 20 mg esomeprazole, T3 : 160 mg aspirin + 150 mg clopidogrel + 20 mg esomeprazole and T4 : 160 mg aspirin + 75 mg clopidogrel + 150 mg ranitidine. Results are expressed in P2Y12 Reaction Units (PRU%) and Aspirin Reaction Units (ARU).

Results

In 21 patients with stable coronary artery disease, esomeprazole reduced the effect of clopidogrel with a 38.6% ± 24 loss in PRU% (p < 0.001) (absolute mean difference − 16.7 PRU% [− 21;− 12.5]), increasing 8-fold the prevalence of low responders to clopidogrel (defined as patients with PRU% below 20%). Doubling clopidogrel dosage to 150 mg restored the basal response. Ranitidine did not modify the antiplatelet effect of clopidogrel.

Conclusion

Our study demonstrates a strong negative clopidogrel/esomeprazole interaction, compensated by increasing the dose of clopidogrel to 150 mg or replacing esomeprazole with ranitidine. That could offer a simple solution to the PPI-induced clopidogrel resistance.     

Impact of CYP2C19 polymorphism on clinical outcome following coronary stenting is more important in non-diabetic than diabetic patients

Objective

The aim of this study was to examine the impact of CYP2C19 genotype on clinical outcome in coronary artery disease (CAD) patients with or without diabetes mellitus (DM).

Methods

CYP2C19 polymorphism and DM are associated with increased risk of cardiovascular events during antiplatelet therapy following stent implantation. Platelet reactivity during clopidogrel therapy and CYP2C19 polymorphism were measured in 519 CAD patients (males 70%, age 69 years) treated with stent placement. Patients were divided into two groups; DM (n = 249), and non-DM (n = 270), and clinical events were evaluated according to the carrier state, which included at least one CYP2C19 loss-of-function allele.

Results

The level of platelet reactivity and incidence of cardiovascular events were significantly different between Carriers and non-Carriers of the non-DM (platelet reactivity: 4501 +/− 1668 versus 3691 +/− 1714AUmin, P < 0.01; events, 32/178 versus 2/92, P < 0.01, respectively), however, there was no difference in clinical outcome in the DM group (events, 34/168 versus 14/81, respectively, P = 0.57). Multivariate analysis identified CYP2C19 loss-of-function allele carriage as an independent predictor of cardiovascular events in non-DM, but not in DM (non-DM, HR 7.180, 95% CI, 1.701 to 30.298, P = 0.007; DM, HR 1.374, 95% CI, 0.394 to 4.792, P = 0.618).

Conclusion

The impact of CYP2C19 polymorphism on clinical outcome seems to be more significant in non-DM compared with DM in patients with coronary stents.