Activity Of Clopidogrel Research Articles

Anti-platelet drugs, pharmacogenomics and stent thrombosis: What’s new?

Stent thrombosis is a catastrophic complication of percutaneous coronary intervention (PCI) and is associated with a mortality of 25 to 40%. The perception that stent thrombosis is very low in all patients has resulted in a lack of adherence to professional guidelines. New data to identify patients at increased risk for stent thrombosis are emerging. Clopidogrel is a prodrug and the activation of clopidogrel is dependent on CY2C19. Numerous alleles of CYP2C19 exist. The allele CYP2CP*2 has been associated with a marked decrease in platelet responsiveness to clopidogrel. Heterozygote carriers of the CYP2C19*2 have a 2.7 fold increased risk and homozygotes a 4.8 fold increased risk of stent thrombosis. Prospective randomised clinical trials will be necessary to determine the efficacy of CYP2C19 genotype directed therapy in evidence-based clinical decision making. Point-of-care platelet-function tests are becoming available and some centres are now performing such tests on their PCI patients. The most recent AHA/ACC /SCAI guidelines recommend testing for clopidogrel responsiveness in patients at high risk of subacute stent thrombosis and recommend increasing the dose of clopidogrel in non-responders.

The CYP2C19*2 and CYP2C19*17 Polymorphisms play a Vital Role in Clopidogrel Responsiveness after Percutaneous Coronary Intervention: A Pharmacogenomics Study.

Clopidogrel inhibits platelet activation and aggregation by blocking the P2Y12 receptor. Dual antiplatelet therapy with clopidogrel and aspirin is recommended treatment by current guidelines for patients undergoing percutaneous interventions. Recurrent ischaemic cardiac events after this treatment showed lack of clopidogrel responsiveness. We aimed to investigate the most noticeable variants in the genes involved in clopidogrel pharmacokinetics and pharmacodynamics. A total of 347 Turkish patients who underwent percutaneous coronary interventions with stent implantation were included in our study. Platelet reactivity (PRU) and % inhibition were measured with VerifyNow P2Y12 assay in blood samples collected from patients who took a standard dose of clopidogrel (75 mg/day) for at least 7 days. The variants in the CYP2C19, CYP3A4, CYP2B6, ABCB1, ITGB3 and PON1 genes were genotyped using the Sequenom MassARRAY system. When grouped, the patients with PRU values >208 as non-responsiveness to clopidogrel therapy; 104 (30%) patients were non-responders and 243 (70%) patients were responders. A significant association was found between the CYP2C19*2 (G636A) polymorphism and non-responsiveness to clopidogrel therapy (p < 0.001). An allele frequency of this single nucleotide polymorphism was high in non-responders; its odds ratio was 2.92 compared with G allele (p < 0.001). PRU values of CT genotypes were lower (p = 0.029) and % inhibition values of CT genotypes were higher (p = 0.008) compared with CC genotypes for the CYP2C19*17 (C806T) polymorphism. None of the other genetic variants were found to be statistically associated with non-responsiveness to clopidogrel and antiplatelet activity. Our findings suggest that the CYP2C19*2 polymorphism is associated with non-responsiveness to clopidogrel therapy and the CYP2C19*17 polymorphism enhances antiplatelet activity of clopidogrel. Depending on haplotypes of these two polymorphisms, clopidogrel-treated patients can be protected or not from stent thrombosis and ischaemic events.

Genomewide Association Study Identifies Novel Genetic Loci That Modify Antiplatelet Effects and Pharmacokinetics of Clopidogrel.

Genetic variants in the pharmacokinetic (PK) mechanism are the main underlying factors affecting the antiplatelet response to clopidogrel. Using a genomewide association study (GWAS) to identify new genetic loci that modify antiplatelet effects in Chinese patients with coronary heart disease, we identified novel variants in two transporter genes (SLC14A2 rs12456693, ATP‐binding cassette [ABC]A1 rs2487032) and in N6AMT1 (rs2254638) associated with P2Y12 reaction unit (PRU) and plasma active metabolite (H4) concentration. These new variants dramatically improved the predictability of PRU variability to 37.7%. The associations between these loci and PK parameters of clopidogrel and H4 were observed in additional patients, and its function on the activation of clopidogrel was validated in liver S9 fractions (P < 0.05). Rs2254638 was further identified to exert a marginal risk effect for major adverse cardiac events in an independent cohort. In conclusion, new genetic variants were systematically identified as risk factors for the reduced efficacy of clopidogrel treatment.

CRT-100.66 Platelet Activity in Clopidogrel Users With and Without Omeprazole: Meta-analysis of Pharmacodynamic Function

Clopidogrel is metabolized by CYP2C19 enzyme to its active metabolite and omeprazole is a strong inhibitor of this enzyme and therefore is speculated to decrease the antiplatelet activity of clopidogrel. We searched PubMed, EBSCO and Google Scholar databases to identify studies assessing platelet

THE PROTOCOL: INFLUENCE OF THE COMBINATION CARRIAGE СУР2С19*2 AND *17 ON EFFICACY OF CLOPIDOGREL

Aim. To assess the association of efficacy and safety endpoints with simultaneous carriage of polymorphic variants of the gene CYP2C19: rs4244285 (*2), and rs12248560 (*17) in treatment with clopidogrel. Material and methods. In the study, 289 patients included, from large cities of Siberia, underwent coronary stenting for acute coronary syndrome. All participants were assessed for alleles CYP2C19*2, *3, *17, and clinical outcomes were followed for 30 days (thrombotic complications, bleedings). Results. It was found that simultaneous carriage of CYP2C19*2 and CYP2C19*17 alleles is associated with the risk of serious adverse events development of thrombotic origin comparing to the absence of such polymorphism carriage (p=0,016), and with general adverse events risk related to insufficiency of clopidogrel action (р=0,046). Conclusion. According to the study results, subjects with the *2/*17 carriage should be classified to a delayed clopidogrel metabolism group, as in the group definite and probable stent thrombosis were found significantly more prevalent.

Platelet reactivity and clinical outcomes in patients using CYP3A4-metabolized statins with clopidogrel in percutaneous coronary intervention.

Statins are primarily metabolized by cytochrome P450 3A4 (CYP3A4), which reduces clopidogrel to its active metabolite. Recent studies suggest that CYP3A4-metabolized statins attenuate clopidogrel's anti-aggregatory effect on platelets. We aimed to assess the impact of concomitant CYP3A4-metabolized statin and clopidogrel use on antiplatelet activity and clinical outcomes in patients undergoing percutaneous coronary intervention (PCI). We enrolled 1187 patients from the HOST-ASSURE trial with platelet reactivity unit (PRU) values at both baseline and 1 month. Patients were assigned to the CYP3A4-metabolized statin group (group A, n=725) or non-CYP3A4-metabolized statin group (group B, n=462) according to type of statin used. Co-primary outcomes were the differences between PRU at baseline and 1 month and the composite of cardiovascular death, recurrent myocardial infarction, stent thrombosis, revascularization, and cerebrovascular accident. We found that follow-up PRU values did not change in group A and decreased significantly in group B (mean difference: -15±79, p<0.001) in both the crude and matched cohorts. Patients with a high PRU value at baseline, irrespective of statin type, had a significant reduction in mean PRU difference (group A, -62±78, p<0.001; group B, -59±69, p<0.001) in both the crude and matched cohorts. The composite of clinical events did not differ between groups in either cohort. CYP3A4-metabolized statins slightly inhibit the antiplatelet activity of clopidogrel during dual antiplatelet therapy. However, they do not inhibit clopidogrel's antiplatelet effect in patients with high platelet reactivity or increase clinical events in patients following PCI.

Omeprazole and atorvastatin reduces the ability of clopidogrel to inhibit platelet aggregation in patients undergoing percutaneous coronary intervention in a tertiary health care system: A prospective drug–drug interaction study

BackgroundClopidogrel, a prodrug is found to be less effective in inhibiting the platelet aggregation when administered along with PPI's in patients undergoing cardiac stent, ST segment elevated Myocardial infarction (STEMI) followed by percutaneous coronary intervention (PCI). Clopidogrel binds to CYP2C19, a hepatic enzyme to get converted to its active metabolite in order to achieve desired pharmacological activity. The cytochrome P450 3A4 which is partially involved in the metabolism of clopidogrel also metabolizes statins, mainly atorvastatin to the greater extent. MethodologyIn the current study patients on PPI's with dual antiplatelet therapy and patients on PPI's and statins with dual antiplatelet therapy are considered to understand the potential drug–drug interactions (pDDI) among the South Asian population. Platelet aggregation was measured in 61 patients undergoing coronary artery stent implantation treated with clopidogrel and aspirin along with PPI's and statins. ResultsIt was observed that omeprazole and atorvastatin, but not pantoprazole and rosuvastatin, inhibited the antiplatelet activity of clopidogrel. The percent platelet aggregation was 72±6 (p=0.001) and 43±23 (p=0.027) in the presence of clopidogrel with omeprazole and pantoprazole respectively. Aggregation was found to be 91±4 (p=0.001) and 12±23 (p=0.031) in the presence of clopidogrel with atorvastatin and rosuvastatin respectively. ConclusionA prominent drug–drug interaction was observed with patients on dual antiplatelet therapy along with omeprazole and atorvastatin.

CYP2C19 and CYP2D6 genotypes in Pacific peoples.

The study of pharmacogenetic variants in populations which reside in Oceania has been focused mainly on CYP2C19 and CYP2D6. Statements about the high prevalence of CYP2C19 no function genotype in 'Pacific Islanders' can be found in the literature. This review article summarizes the published information about these pharmacogenes in this geographical region and highlights the differences observed between Melanesian and Polynesian populations. It is not appropriate to combine the prevalence data of pharmacogenetic variants, particularly CYP2C19, across this region. Indeed, apocryphal assumptions about CYP2C19 no function alleles and possible effect on the therapeutic activity of clopidogrel are unhelpful and reiterate the importance of assessing the individual patient rather than relying on inappropriate ethnicity-based assumptions for drug dosing decisions.

Plasma miR-142 accounting for the missing heritability of CYP3A4/5 functionality is associated with pharmacokinetics of clopidogrel.

To investigate whether plasma miRNAs targeting CYP3A4/5 have an impact on the variance of pharmacokinetics of clopidogrel. The contribution of 13 miRNAs to the CYP3A4/5 gene expression and activity was investigated in 55 liver tissues. The association between plasma miRNAs targeting CYP3A4/5 mRNA and clopidogrel pharmacokinetics was analyzed in 31 patients with coronary heart disease who received 300 mg loading dose of clopidogrel. Among 13 miRNAs, miR-142 was accounting for 12.2% (p = 0.002) CYP3A4 mRNA variance and 9.4% (p = 0.005) CYP3A5 mRNA variance, respectively. Plasma miR-142 was negatively associated with H4 Cmax (r = -0.5269; p = 0.0040) and associated with H4 AUC0-4h (r = -0.4986; p = 0.0069) after 300 mg loading dose of clopidogrel in coronary heart disease patients. miR-142 could account for a part of missing heritability of CYP3A4/5 functionality related to clopidogrel activation.

Effect of CYP2C19*2 and *3 on clinical outcome in ischemic stroke patients treated with clopidogrel

BackgroundDespite clopidogrel has been widely applied to patients with ischemic stroke combined with aspirin, decreased metabolic activation of clopidogrel still occurs because of genetic variations in CYP2C19. MethodsThree hundred twenty-one patients completed a genetic test for CYP2C19 loss of function (LOF) alleles in hospital. Cox regression models were used to assess the relationship between CYP2C19 genotypes with the primary endpoint, which was a composite of nonfatal ischemic stroke, myocardial infarction, or vascular death. Functional outcome was measured by the modified Rankin Scale (mRS) at 3months, 6months and 12months intervals. Binary logistic regression was used to analyze the correlation between poor functional outcome and CYP2C19 LOF alleles. ResultsThe CYP2C19 LOF alleles were independently associated with the primary endpoint. There was no significant association between poor functional outcome and CYP2C19 LOF allele (*2 and *3) in overall patients. After the participants were stratified by stent treatment into two groups, the polymorphisms of CYP2C19 had significant impact on poor prognosis at 3months and 6months but not at 12months in patients without stent. No correlation was found in patients with stent. ConclusionsThe CYP2C19 LOF alleles may increase the recurrent risk of ischemic events. The polymorphisms of CYP2C19 may be predictors of poor functional outcome of patients without stent, and the effect may be weakened by time.

Significant Improvement of Metabolic Characteristics and Bioactivities of Clopidogrel and Analogs by Selective Deuteration.

In the search for prodrug analogs of clopidogrel with improved metabolic characteristics and antiplatelet bioactivity, a group of clopidogrel and vicagrel analogs selectively deuterated at the benzylic methyl ester group were synthesized, characterized, and evaluated. The compounds included clopidogrel-d3 (8), 2-oxoclopidogrel-d3 (9), vicagrel-d3 (10a), and 12 vicagrel-d3 analogs (10b–10m) with different alkyl groups in the thiophene ester moiety. The D3C-O bond length in 10a was shown by X-ray single crystal diffraction to be shorter than the H3C-O bond length in clopidogrel, consistent with the slower rate of hydrolysis of 8 than of clopidogrel in rat whole blood in vitro. A study of the ability of the compounds to inhibit ADP-induced platelet aggregation in fresh rat whole blood collected 2 h after oral dosing of rats with the compounds (7.8 μmol/kg) showed that deuteration increased the activity of clopidogrel and that increasing the size of the alkyl group in the thiophene ester moiety reduced activity. A preliminary pharmacokinetic study comparing 10a with vicagrel administered simultaneously as single oral doses (72 μmol/kg of each drug) to male Wistar rats showed 10a generated more of its active metabolite than vicagrel. These results suggest that 10a is a potentially superior antiplatelet agent with improved metabolic characteristics and bioactivity, and less dose-related toxicity.

Abstract 32: Analysis of Serum Clopidogrel Active Metabolite Concentration Identifies Novel Genetic Variants Associated With Clopidogrel Pharmacokinetics

Clopidogrel with aspirin is standard of care for the secondary prevention of ischemic events in patients with acute coronary syndromes. However, substantial inter-individual variation in clopidogrel response results in sub-optimal therapy in some patients and an increased risk of recurrent events. Up to 73% of the variation in clopidogrel efficacy is found to be heritable, and while key genetic variants such as CYP2C19 *2 have been identified, a large portion of the genetic heritability remains unaccounted for. To date, few studies have used clopidogrel active metabolite to evaluate clopidogrel pharmacogenomics. The evaluation of this biomarker may be particularly informative as it enables us to focus almost exclusively on clopidogrel pharmacokinetics and may allow new discoveries leading to a more thorough understanding of clopidogrel activation. Serum clopidogrel active metabolite concentration was measured by HPLC-MS/MS in 506 healthy, Amish participants of the Pharmacogenomics of Anti-Platelet Intervention (PAPI) Study after a 7-day 75-mg/day clopidogrel intervention. Genome-wide genotyping was performed using Affymetrix 5.0 and 6.0 arrays, and SNPs were imputed to the 1000 Genomes cosmopolitan panel. Mixed models analysis was conducted under an additive model and adjusted for age, sex, BMI, and relatedness among study participants with MMAP (http://edn.som.umaryland.edu/mmap). The most significant signal of our GWAS was the previously identified CYP2C19 / CYP2C9 locus (P= 9.2x10 -15 ), and was fully accounted for by the CYP2C19 *2 variant. In addition to this signal, novel genome-wide significant signals were identified in loci on Chr. 3 (rs187941554, P=4.7x10 -11 ), Chr. 7 (rs73407739, p=3.6x10 -8 ), and Chr. 17 (rs80343429, P=3.7x10 -8 ). In this study we conducted the first ever GWAS of serum clopidogrel active metabolite concentration. Novel associations for clopidogrel efficacy were identified, and further study is required to determine the impact of these variants on clinical care Continual analysis of clopidogrel active metabolite concentration will contribute to a better understanding of the clopidogrel metabolic pathway, and potentially lay the groundwork for improved anti-platelet treatment for CVD patients in the future.

The mechanism and risk factors of clopidogrel-induced liver injury

Context and objective: Clopidogrel (CLP) is a prodrug which is widely used as a platelet aggregation inhibitor. Hepatotoxicity is rare but a potentially serious adverse reaction that is associated with CLP. Thiophene in CLP (the thienopyridine derivative) is a group that is easily oxidated by cytochrome P450 enzymes (CYP450s) to generate reactive metabolites (RMs), it may be implicated in the mechanism of CLP-induced hepatotoxicity. CYP2C19 and CYP2B6 are important CYP450s involved in the metabolism and activation of CLP, and the aim of this study is to investigate whether the metabolites of CYP2C19 and CYP2B6 are associated with the CLP-induced liver injury. Method: Primary rat hepatocytes are applied to evaluate the hepatotoxicity of CLP. Glutathione-depleted mouse model is used to evaluate whether this toxicity of CLP is metabolized by CYP450s. We also used HepG2 cells co-incubated with recombinant CYP2B6 and CYP2C19 enzymes to further assess whether the metabolites of CYP2C19 and CYP2B6 are associated with the CLP-induced hepatocellular toxicity. Result: CLP in high dose (100 μM and 300 μM) showed cytotoxicity in primary rat hepatocytes assay. Administration of CLP with l-buthionine-S, R-sulfoxinine (BSO) for seven days enhanced the liver injury of CLP. The level of ALT, AST and TBIL in plasma increased significantly, and the histopathological results showed the obvious liver injury; Pretreatment of 1-aminobenzotriazole, a nonspecific inhibitor of CYP450s, suppressed CLP-induced hepatotoxicity; CLP showed a dose-dependent toxicity in HepG2/CYP2C19 enzyme and HepG2/CYP2B6 enzyme models. Conclusion: High activities of CYP2C19 and CYP2B6 are the risk factors for hepatocellular toxicity of CLP.

Abstract 15262: Antiplatelet Activity and Clinical Outcomes on CYP3A4-metabolized Statin in Percutaneous Coronary Intervention

Introduction: Statins primarily metabolized by cytochrome P450 3A4 (CYP3A4) reportedly reduce clopidogrel metabolism to active metabolite. Recent studies suggest that CYP 3A4-metabolized statins attenuate the anti-aggregatory effect of clopidogrel. Hypothesis: We sought to assess the antiplatelet activity of a CYP 3A4 metabolized statin and its association with clinical outcomes during dual antiplatelet therapy following percutaneous coronary intervention (PCI). Methods: Among 3,755 patients enrolled the HOST-ASSURE trial, 1,187 patients with both baseline and 1-month platelet reactivity unit (PRU) values assessed by VerifyNow P2Y12 assay were assigned to the CYP 3A4-metabolized statin group (n=725) or non-CYP 3A4-metabolized statin group (n=462) according to type of statins used. The co-primary outcome were the differences between baseline and 1-month follow-up of PRU value and the composite of cardiovascular death, recurrent MI, including stent thrombosis, any revascularization and cerebrovascular accident (CVA) during the follow-up period. We compared the outcomes between groups both in the propensity adjusted and matched cohorts. Results: Mean difference of PRU values was not significant in the CYP 3A4-metabolized statin group (mean difference: -4±84, p=0.367) and was significant in the non-CYP 3A4-metabolized statin group (mean difference: -12±69, p=0.006) both in the propensity score adjusted and matched cohorts. Patients with high PRU value at baseline, irrespective of the type of used statins, were associated with a significant reduction in mean difference of PRU values both in the propensity score adjusted (mean difference: -53.35, p&lt;0.001) and matched cohort (mean difference: -41.57, p&lt;0.001). The composite of clinical events did not differ between groups both in the propensity score adjusted (hazard ratio [HR] 0.962, 95% confidence interval [CI] 0.621-1.489, p=0.861) and matched (HR 0.902, 95% CI 0.554-1.468, p=0.678) cohorts. Conclusions: This study showed that a CYP 3A4-metabolized statin slightly reduces antiplatelet activity of clopidogrel during dual antiplatelet therapy but did not increase clinical events in patients following PCI.

Correlation between the CYP2C19 phenotype status and the results of three different platelet function tests in cardiovascular disease patients receiving antiplatelet therapy: an emphasis on newly introduced platelet function analyzer-200 P2Y test.

BackgroundAn association has been reported between CYP2C19 polymorphism and the altered antiplatelet activity of clopidogrel. We investigated this association using the newly introduced platelet function analyzer (PFA)-200 (INNOVANCE PFA-200 System; Siemens Healthcare, Germany) P2Y test.MethodsPolymorphisms of CYP2C19*2, *3, *17 and the degree of inhibition of platelet function were determined in 83 patients. Three different platelet function tests were used to evaluate the degree of platelet inhibition and to check the association with genotype.ResultsThe post-procedure PFA-200 values of extensive metabolizers (EM) patients (285.3±38.8) were higher than those of intermediate metabolizers (IM) and poor metabolizers (PM) patients (227.7±98.3 and 133.7±99.2, respectively; P=0.024). Light transmittance aggregometry (LTA) and the VerifyNow system showed that the post-procedure values for EM patients were lower than those of IM and PM patients (LTA: 24.4±15.7, 34.1±17.6, and 42.2±16.9, respectively, P<0.001; VerifyNow: 133.2±60.5, 171.5±42.6, and 218.7±59.3, respectively, P<0.001). The high residual platelet reactivity (HPR) rates were significantly different among the EM, IM, and PM groups using PFA-200 (PM:IM:EM=82.4:40.6:11.8, P<0.001).ConclusionsApproximately, 59.0% of Korean patients with cardiovascular disease receiving clopidogrel had CYP2C19 loss-of-function genotypes classified as IM or PM, and the frequency was similar to the data from Asian people. The PFA-200, LTA, and VerifyNow platelet function tests revealed evidence of a significant association between the efficacy of clopidogrel and CYP2C19 genotypes.

Association between CYP2C19 Polymorphisms and Outcomes in Cerebral Endovascular Therapy.

Differing responses to clopidogrel following endovascular treatment of cerebrovascular diseases may increase the risk of vascular complications. CYP2C19 gene polymorphisms influence clopidogrel activity. We aimed to study the clinical impact of CYP2C19 gene polymorphisms in patients undergoing endovascular treatment. This was a prospective, longitudinal, observational study. Information on demographics and cerebrovascular status was collected as baseline. Clopidogrel response was tested by the VerifyNow P2Y12 assay. CYP2C19 genotyping was undertaken by polymerase chain reaction-restriction fragment length polymorphism. Three-month follow-up data included vascular complications, mortality, and modified Rankin Scale score. Associations were investigated among CYP2C19 genotypes, clopidogrel responsiveness, and clinical outcomes. One hundred and eight participants were included. Median age was 56 years (interquartile range, 48.8-65.0 years), and 35 (32.4%) were male. Forty-four participants were classified into group 1 (homozygous CYP2C19*1/*1); 31, into group 2 (25 with CYP2C19*1/*2, two with CYP2C19*1/*3, three with CYP2C19*3/*3, one with CYP2C19*2/*3); 28, into group 3 (24 with CYP2C19*1/*17, four with CYP2C19*17/*17); and 5, into group 4 (CYP2C19*2/*17). A significantly higher proportion of participants in group 3 experienced ischemic events (9 of 28, 32.1%) compared with group 1 (5 of 44, 11.4%; P = .04; odds ratio, 3.7; 95% confidence interval, 1.1-12.6). There was no significant difference in clopidogrel response among the 4 genotype groups. Individuals with CYP2C19*17 may have increased risk of ischemic events following endovascular treatment, independent of clopidogrel responsiveness. Larger studies are required to confirm the influence of CYP2C19*17 on clinical outcomes and to understand the mechanisms for increased ischemic events.

Cytochrome P450 CYP 2C19*2 Associated with Adverse 1-Year Cardiovascular Events in Patients with Acute Coronary Syndrome.

BackgroundThe cytochrome P450 (CYP450) 2C19 681 genotypes affect the antiplatelet activity of clopidogrel. We investigated the correlation of CYP 2C19 681G > A mutation with clopidogrel resistance (CR). Additionally, we studied the effect of CR on clinical prognosis of patients with acute coronary syndrome (ACS).MethodsOne hundred ten ACS patients undergoing percutaneous coronary intervention, who were followed-up for 1 year, were included in the study. The patients were co-administered aspirin 100 mg/d and clopidogrel 75mg/d following a loading dose of 300 mg. CR was assessed on the basis of polymorphism observed in the CYP2C19 subgroup.ResultsPatients in GG genotype group exhibited greater inhibition of platelet aggregation than patients in GA and AA genotype groups (16.2 ± 10.1%; 10.2 ± 9.9%; 8.0 ± 5.9%, respectively, p < 0.01). CYP2C19 681GG genotype group was associated with lower CR than CYP2C19 681A allele (GA + AA) group (9/59 vs. (12+5)/51; p = 0.009). Over a follow-up of 12 months, the incidence of recurrent angina, acute myocardial infarction, and intra-stent thrombosis in CYP2C19 681 GG carriers was significantly lower than that in CYP2C19 681A allele (GA + AA) group (2/59 vs. 8/51, 1/59 vs. 6/51, 0 vs. 4/51, respectively, p < 0.05).ConclusionCYP 2C19*2 is associated with reduced clopidogrel antiplatelet activity and might be an important marker for poor prognosis of ACS.

Effect of grapefruit juice on the bioactivation of prasugrel.

The P2Y12 inhibitor prasugrel is a prodrug, which is activated after its initial hydrolysis partly by cytochrome P450 (CYP) 3A4. Grapefruit juice, a strong inactivator of intestinal CYP3A4, greatly reduces the activation and antiplatelet effects of clopidogrel. The aim of this study was to investigate the effects of grapefruit juice on prasugrel. In a randomized crossover study, seven healthy volunteers ingested 200 ml of grapefruit juice or water three times daily for 4 days. On day 3, they ingested a single 10 mg dose of prasugrel with an additional 200 ml of grapefruit juice or water. Plasma concentrations of prasugrel metabolites and the antiplatelet effect were measured. Grapefruit juice increased the geometric mean area under the plasma concentration-time curve (AUC(0-∞)) of the primary, inactive metabolite of prasugrel to 164% of the control value (95% confidence interval 122-220%, P = 0.008), without a significant effect on its peak plasma concentration (C(max)). The C(max) and AUC(0-∞) of the secondary, active metabolite were decreased to 51% (95% confidence interval 32-84%, P = 0.017) and 74% of the control value (95% confidence interval 60-91%, P = 0.014) by grapefruit juice (P < 0.05). The average platelet inhibition, assessed with the VerifyNow® method at 0-24 h after prasugrel intake, was 5 percentage points (95% confidence interval 1-10 percentage points) lower in the grapefruit juice phase than in the water phase (P = 0.034). Grapefruit juice reduces the bioactivation of prasugrel, but this has only a limited effect on the antiplatelet effect of prasugrel.

Paraoxonase-1 Deficiency does not Influence Clopidogrel Antiplatelet Function in Mice

Abstract Background: Clopidogrel is an antiplatelet agent used in the treatment of vascular diseases. It requires in vivo bio activation linked to the cytochrome P450. Several studies reported that paraoxonase-1 (PON1) was a crucial enzyme in clopidogrel activation, and that patients carrying a variant of the PON1192 gene polymorphism have a high risk of thrombosis. However, these reports were not confirmed by subsequent results. The present study was aimed at investigating whether PON1 deficiency affects the biological action of clopidogrel in mice. Methods: PON1-deficient mice (n = 50) and wild type animals (n = 50) received different treatments for 3 days: a) clopidogrel, b) aspirin, c) cilostazol, d) clopidogrel + aspirin, and e) clopidogrel + aspirin + cilostazol. Blood was collected for the Platelet Function Analysis (PFA-100). Results: The different anticoagulant treatments resulted in higher aggregation times in all the mice, compared to the internal PFA control; demonstrating the anti-platelet effect of these compounds. We did not observe any significant alterations on the PFA assay in PON1-deficient mice, relative to wild type animals. Conclusion: PON1 deficiency does not influence the antiplatelet action of clopidogrel in mice, and supports the proposition that this enzyme is not involved in clopidogrel bio activation.

Carboxylesterase 1-mediated drug-drug interactions between clopidogrel and simvastatin.

Patients with coronary artery disease often receive concurrent treatment with clopidogrel and a hydroxymethylglutaryl (HMG)-CoA reductase inhibitor medication. Accordingly, potential drug-drug interactions associated with the concomitant use of these agents present an area of concern. Both CYP enzymes and carboxylesterase 1 (CES1) are involved in the metabolism of clopidogrel, while CES1 is believed to be the enzyme responsible for the activation of simvastatin. Some in vitro studies have suggested that simvastatin could attenuate clopidogrel activation via inhibiting CYP3A activity. However, these findings have not found support in several recently published clinical investigations. The present study addresses these inconsistencies by exploring the potential role of CES1 in the metabolism of clopidogrel and simvastatin. Our in vitro human liver s9 fraction incubation study demonstrated that simvastatin significantly enhanced the formation of the intermediate metabolite 2-oxo-clopidogrel, and inhibited the CES1-mediated hydrolysis of clopidogrel, 2-oxo-clopidogrel, and the active metabolite. However, the production of the active metabolite remained unchanged. Conversely, clopidogrel was not found to influence the CES1 mediated hydrolysis (activation) of simvastatin. Moreover, we provided evidence that CES1 is not an efficient enzyme for catalyzing simvastatin activation. In summary, the inhibitory effect of simvastatin on the hydrolysis of clopidogrel and its principal metabolites may have offset the influence of simvastatin-mediated inhibition of CYP3A, and permitted the unaltered formation of the clopidogrel active metabolite. These data help explain the conflicting accounts in previous reports regarding clopidogrel and simvastatin interactions by taking into consideration CES1; they suggest that the interactions are unlikely to significantly influence clinical outcomes.