Relation of genetic polymorphisms in the cytochrome P450 gene with clopidogrel resistance after drug-eluting stent implantation in Koreans

Rare variants discovery by extensive whole-genome sequencing of the Han Chinese population in Taiwan: Applications to cardiovascular medicine

Introduction

A population-specific genomic reference is important for research and clinical practice, yet it remains unavailable for Han Chinese (HC) in Taiwan.

Objectives

We report the first whole genome sequencing (WGS) database of HC (1000 Taiwanese genome (1KTW-WGS)) and demonstrate several applications to cardiovascular medicine.

Methods

Whole genomes of 997 HC were sequenced to at least 30X depth. A total of 20,117 relatively healthy HC individuals were genotyped using a customized Axiom GWAS array. We performed a genome-wide genotype imputation technique using IMPUTE2.

Results

We identified 26.7 million single-nucleotide variants (SNVs) and 4.2 million insertions-deletions. Of the SNVs, 16.1% were novel relative to dbSNP (build 152), and 34.2% were novel relative to gnomAD. A total of 18,450 healthy HC individuals were genotyped using a customized Genome-Wide Association Study (GWAS) array. We identified hypertension-associated variants and developed a hypertension prediction model based on the correlation between the WGS data and GWAS data (combined clinical and genetic models, AUC 0.887), and also identified 3 novel hyperlipidemia-associated variants. Each individual carried an average of 16.42 (SD = 3.72) disease-causing variants. Additionally, we established an online SCN5A (an important cardiac gene) database that can be used to explore racial differences. Finally, pharmacogenetics studies identified HC population-specific SNVs in genes (CYP2C9 and VKORC1) involved in drug metabolism and blood clotting.

Conclusion

This research demonstrates the benefits of constructing a population-specific genomic reference database for precision medicine.

The Role of Genetic Polymorphism and Other Factors on Clopidogrel Resistance (CR) in an Asian Population with Coronary Heart Disease (CHD)

Clopidogrel is a widely-used antiplatelet drug. It is important for the treatment and prevention of coronary heart disease. Clopidogrel can effectively reduce platelet activity and therefore reduce stent thrombosis. However, some patients still have ischemic events despite taking the clopidogrel due to the alteration in clopidogrel metabolism attributable to various genetic and non-genetic factors. This review aims to summarise the mechanisms and causes of clopidogrel resistance (CR) and potential strategies to overcome it. This review summarised the possible effects of genetic polymorphism on CR among the Asian population, especially CYP2C19 *2 / *3 / *17, where the prevalence rate among Asians was 23.00%, 4.61%, 15.18%, respectively. The review also studied the effects of other factors and appropriate strategies used to overcome CR. Generally, CR among the Asian population was estimated at 17.2-81.6%. Therefore, our overview provides valuable insight into the causes of RC. In conclusion, understanding the prevalence of drug metabolism-related genetic polymorphism, especially CYP2C19 alleles, will enhance clinical understanding of racial differences in drug reactions, contributing to the development of personalised medicine in Asia.

The impact of cytochrome 450 and Paraoxonase polymorphisms on clopidogrel resistance and major adverse cardiac events in coronary heart disease patients after percutaneous coronary intervention

Background

Clopidogrel is an inactive prodrug, it catalyzed into its active form by Cytochrome 450 and Paraoxonase-1(PON-1). polymorphisms of genes encoding these enzymes will affect the efficacy of Clopidogrel. The main objective of our study was to investigate the association of CYP2C19*2, CYP2C19*3 and PON-1Q192R polymorphisms with Clopidogrel resistance and major adverse cardiac events in Jin Hua district in the middle of Zhe Jiang Province in China.

Methods

One hundred sixty coronary heart disease patients with percutaneous coronary intervention, who were followed-up for 1 year, were enrolled in our study. These patients were co-administered aspirin 100 mg/d and clopidogrel 75 mg/d following a loading dose of 300 mg. The ADP-induced platelet aggregation rate was measured by Platelet aggregator. Genotypes of CYP2C19*2, CYP2C19*3, PON-1Q192R were determined using Sanger sequencing in all patients. Various clinical data were collected.

Results

The frequencies of CYP2C19*2, CYP2C19*3 and PON-1Q192R homozygous mutant genotypes were significantly lower in non-responders than those in responders. After for all variables, CYP2C19*2, CYP2C19*3 and PON-1Q192R independently increased the risk of clopidogrel resistance with adjusted ORs 46.65(95% CI,1.77–25.04; p = 0.005); 22.74(95% CI, 3.11–166.27; p = 0.002); 5.69 (95% CI,1.06–30.47; p = 0.042). Over a follow-up of 12 months, the incidence of major adverse cardiac events (MACE) in CYP2C19*1/*2, *1/*3, *2/*2, *2/*3 was significantly higher than no mutant genotype (18/40vs.2/63,3/9vs.2/63, 11/6vs.2/63, 7/1vs2/63, respectively). There was no significant correlation between PON-1Q192R mutant allele and MACE.

Conclusion

Our study was first time to report on CYP2C19 and PON-1 polymorphisms in Jin Hua population in the middle of Zhe Jiang province in China. The carriage of CYP2C19*2 or *3 mutant allele significantly reduced the platelet response to clopidogrel and increase the MACE. The carriage of PON-1 mutant allele also significantly reduced the platelet response to clopidogrel, but would not increase the major adverse cardiac events after 1 year follow-up.

Trial registration

ChiCTR, ChiCTR1800018316. Registered 11 September 2018 – prospective registered, http://www.chictr.org.cn/edit.aspx?pid=30927&htm=4.

Investigating the Effect of Demographics, Clinical Characteristics, and Polymorphism of MDR-1, CYP1A2, CYP3A4, and CYP3A5 on Clopidogrel Resistance

Clopidogrel is an antiplatelet agent that is indicated for cardiovascular emergencies and procedures. The drug, however, is subject to response variability leading to therapy resistance. In this research, we explored the demographic, clinical, and genetic factors associated with clopidogrel resistance. Data analysis among our 280 subjects receiving clopidogrel showed some risk factors that are significantly associated with clopidogrel resistance compared with responders. Those were: female sex (P = 0.021), advanced age (P = 0.011), obesity (P = 0.002), and higher body mass index (P = 0.008) and higher platelets count (P = 0.002). However, known polymorphisms of MDR-1, CYP1A2, CYP3A4, and CYP3A5 were not associated with treatment resistance when compared to responders to clopidogrel therapy. Knowledge about such risk factors might provide recommendation in the future about starting doses or monitoring recommendations.

Pharmacogenomic considerations for antiplatelet agents: the era of precision medicine in stroke prevention and neurointerventional practice

Antiplatelet drugs are widely utilized in the setting of primary stroke prevention, secondary stroke prevention, and neuroendovascular device-related stroke prevention. These medications are effective in general, although significant variability in drug activity exists between patients. Although this variation may be related in part to a multitude of factors, a growing body of evidence suggests that individual genotypes are a main contributor. The PharmGKB database was mined to prioritize genetic variants with potential clinical relevance for response to aspirin, clopidogrel, prasugrel, and ticagrelor. Although variants were reported for all drugs, the highest level of evidence was found in cytochrome P450 (CYP450) genotype variation related to clopidogrel response. Individual genetic influences have an impact on the pharmacodynamics of antiplatelet agents. Current clinical practice for stroke prevention is primarily empiric or guided by functional assays; however, there now exists a third potential pathway to base treatment decisions: genotype-guided treatment.

Association among genetic variants in the vitamin D pathway and circulating 25-hydroxyvitamin D levels in Korean adults: results from the Korea National Health and Nutrition Examination Survey 2011-2012

Vitamin D deficiency affects >60% of the Korean population. Recent reports in Caucasian, African American, and Chinese populations indicate an association between vitamin D status and related single nucleotide polymorphisms (SNPs), but specific associations differ among study populations. We investigated the relationship between five SNPs involved in the vitamin D metabolic pathway (DHCR7 rs12785878, GC rs2282679, CYP2R1 rs12794714, CYP2R1 rs10741657, and CYP24A1 rs6013897) and serum 25-hydroxyvitamin D [25(OH)D] status in Koreans using the Korea National Health and Nutrition Examination Survey, a nationwide database. Whether the association was modified by demographic and lifestyle factors, including sex, body mass index (BMI), smoking status, drinking status, physical activity, and sun exposure, were also investigated. The results showed the serum level of 25(OH)D was associated with rs12785878, rs2282679, and rs12794714 genotypes, but not with rs10741657 or rs6013897. The genetic risk score (GRS) calculated by summing the number of alleles of these 5 SNPs was associated with low circulating levels of 25(OH)D. However, the negative association between 25(OH)D and GRS was modified by obesity and sun exposure. Specifically, negative associations between 25(OH)D and GRS were present in adults with lower BMI (<25 kg/m²) and longer sun exposure time (≥2 h/day). In conclusion, common variants of vitamin D-related SNPs are associated with vitamin D status in Koreans, and this genetic effect was masked when BMI ≥25 kg/m² or sun exposure <2 h/day. Additionally, seasonal variation must be considered in future studies among Koreans.

Clopidogrel-associated genetic variants on inhibition of platelet activity and clinical outcome for acute coronary syndrome patients

Acute coronary syndrome (ACS) has become a vital disease with high mortality worldwide. A combined antiplatelet therapy (aspirin and a P2Y₁₂ antagonist) is commonly used to prevent re-infarction in ACS patients who have undergone percutaneous coronary intervention (PCI). Clopidogrel, a P2Y₁₂ antagonist, plays an important role in the inhibition of platelet aggregation (IPA). However, it is a pro-drug requiring biotransformation by cytochrome P450 (CYP450). The aim of this study is to unravel the effect of clopidogrel-associated genetic variants on inhibition of platelet activity and clinical outcomes in ACS patients. In our study, a total of 196 patients with metabolic gene polymorphism of clopidogrel were enrolled, and their antiplatelet effect as well as their cardiovascular events were collected. Approximately 2 mL of venous blood samples were used for genotype detection and another 4 mL were collected for platelet reactivity with thrombelastography. The primary clinical end-point was defined as a combination of cardiovascular mortality and revascularization for targeted vascular lesion. Based on the results of IPA, the prevalence of high on-treatment platelet reactivity (HPR) was 17.3% and the majority of patients (82.7%) obtained normal on-treatment platelet reactivity (NPR). The HPR group had significantly higher body mass index (BMI) and lower arachidonic acid (AA) induced IPA (P < 0.05). Therapy including Glycoprotein (GP) IIb/IIIa antagonist increased IPA (P < 0.05). ADP-induced IPA effect was lower with the presence of CYP2C19*2, *3 and paraoxonase (PON)1 Q192R loss-of-function (LOF) alleles, respectively (P < 0.05). Multivariate logistic regression analysis demonstrated that aspirin resistance (AA-induced IPA < 50%) had a greater risk of the occurrence of major adverse cardiovascular events (MACE) (OR = 3.817; 95% CI: 1.672-8.700; P = 0.002). CYP2C19*2 LOF alleles were associated with high risk of MACE in 1-year post PCI operations (OR = 2.571; 95% CI: 1.143-5.780; P = 0.030). For the ACS patients, the presence of CYP2C19*2 and PON1 Q192R LOF alleles were the major drivers of HPR.

CYP2C19 genotype and adverse cardiovascular outcomes after stent implantation in clopidogrel-treated Asian populations: A systematic review and meta-analysis

The effect of CYP2C19 gene polymorphism on clinical outcomes of patients with coronary artery disease (CAD) treated with clopidogrel remains controversial. Ethnicity has been proposed to influence clopidogrel response following stent implantation in CAD patients with different CYP2C19 genotypes. Furthermore, Asian populations are reported to have a relatively greater prevalence of CYP2C19 loss-of-function (LOF) alleles. We aimed to evaluate the impact of CYP2C19 gene polymorphism on clinical outcomes in Asian populations who underwent percutaneous coronary interventions (PCI) and received clopidogrel therapy. We conducted a comprehensive search in PubMed, EMBASE, and Cochrane Library from their inceptions to January 20, 2017. Studies that reported clopidogrel therapy information, clinically relevant outcomes (adverse cardiovascular events, stent thrombosis and bleeding), and CYP2C19 genotypes among Asian populations were included. The primary endpoint was major adverse cardiovascular events (MACE), defined as a composite of cardiovascular death and myocardial infarction. The safety endpoint was any kind of bleeding. We retrieved 20 studies of 15056 patients reporting 1301 cardiovascular events. The primary analysis showed at least one CYP2C19 LOF allele (*2 and/or *3) carriers were at an increased risk of MACE compared with non-carriers (10.58% vs. 6.07%, OR: 1.99, 95% CI: 1.64 to 2.42, p < .001). Stent thrombosis (ST) was also more frequent in LOF allele carriers (2.22% vs. 0.44%, OR: 4.77, 95% CI: 2.84 to 8.01, p < .001). Inversely, the risk of bleeding was lower in LOF allele carriers (OR: 0.66, 95% CI: 0.46 to 0.96, p < .001). Subgroup analysis was performed to assess differences by high (600 mg) or routine (300 mg) loading dose of clopidogrel and by different nationalities. The risk of MACE in LOF allele carriers remained significantly higher even in high loading dose group (high loading dose: OR 1.72, 95% CI: 1.37 to 2.16, and routine loading dose: OR 2.22, 95% CI: 1.68 to 2.94, p for subgroup heterogeneity = 0.16). Subgroup analysis between three nationalities of China, Korea, and Japan demonstrated that the risk of MACE among Chinese LOF allele carriers was the greatest (OR: 2.28; 95% CI:1.91 to 2.73). In conclusion, among Asian populations with CAD undergoing stent implantation, CYP2C19 LOF allele carriers are at greater risk of adverse cardiovascular events and lower risk of bleeding compared with non-carriers. Genetic testing may be helpful for clinicians to personalize antiplatelet therapy especially in Asian population.

Genetic variability in response to clopidogrel therapy and its clinical implications

This article concentrates on individual genetic differences responsible for variations of action of clopidogrel, which have been found to be partially responsible for increased cardiovascular events in patients with coronary artery disease under dual antiplatelet therapy. According to these results, genotyping for the relevant gene polymorphisms, especially for the CYP2C19 loss-of-function alleles, has been discussed to be an effective method of individualising and optimising clopidogrel treatment. However, due to the facts that 1) there are no prospective studies demonstrating a clinical benefit of personalising antiplatelet therapy based on genotyping; 2) CYP2C19 polymorphisms account for only approximately 12% of variability in clopidogrel platelet response; 3) the positive predictive value of CYP2C19 loss-of-function polymorphisms for cardiovascular events in patients with acute coronary syndrome undergoing percutaneous coronary intervention is only approximately 12% – 20%; 4) it is likely that other clinical factors and risk constellations might be of greater clinical importance; and 5) it is unknown whether a specific genetic polymorphism is capable of influencing outcome for the individual patient; genetic profiling cannot be recommended for routine use at present but will remain of considerable scientific interest.

Prevalence of poor biological response to clopidogrel

The existence of poor biological response to clopidogrel has been shown in some patients. Despite the increasing number of studies, this phenomenon remains difficult to quantify. We performed a systematic review to estimate the prevalence of poor biological response to clopidogrel and investigate the factors known to modulate this. An exhaustive search was performed. Altogether 171 publications were identified, providing data for a total of 45,664 subjects. The estimated prevalence of poor biological response to clopidogrel ranged from 15.9% to 49.5% according to the platelet function assay employed. The assays most frequently used were light transmittance aggregometry (LTA), the vasodilator-stimulated phosphoprotein (VASP) assay and the Verify -now® assay. For all these assays, higher cut-off values were associated with a lower prevalence of poor biological response to clopidogrel. However, when choosing a fixed cut-off point for each assay, the prevalence of poor biological response to clopidogrel was highly variable suggesting that other factors could modulate poor biological response to clopidogrel. Finally, none of the studied factors could apparently explain the variability of poor biological response to clopidogrel. This meta-analysis shows that the prevalence of poor biological response depends on the assay employed, the cut-off value and on various unidentified additional factors.

A Novel Multiplex HRM Assay to Detect Clopidogrel Resistance

Clopidogrel is an antiplatelet medicine used to prevent blood clots in patients who have had a heart attack, stroke, or other symptoms. Variability in the clinical response to clopidogrel treatment has been attributed to genetic factors. In particular, five SNPs of rs4244285, rs4986893, rs12248560, rs662 and rs1045642 have been associated with resistance to clopidogrel therapy in Chinese population. This work involves the development of a multiplex high-resolution melting (HRM) assay to genotype all five of these loci in 2 tubes. Amplicons corresponding to distinct SNPs in a common tube were designed with the aid of uMelt prediction software to have different melting temperatures Tm by addition of a GC-rich tail to the 5' end of the certain primers. Two kinds of commercial methods, Digital Fluorescence Molecular Hybridization (DFMH) and Sanger sequencing, were used as a control. Three hundred sixteen DFMH pretested samples from consecutive acute coronary syndrome patients were used for a blinded study of multiplex HRM. The sensitivity of HRM was 100% and the specificity was 99.93% reflecting detection of variants other than the known resistance SNPs. Multiplex HRM is an effective closed-tube, highly accurate, fast, and inexpensive method for genotyping the 5 clopidogrel resistance associated SNPs.

Clinical Pharmacogenetic Testing and Application: Laboratory Medicine Clinical Practice Guidelines

Pharmacogenetic testing for clinical applications is steadily increasing. Correct and adequate use of pharmacogenetic tests is important to reduce unnecessary medical costs and adverse patient outcomes. This document contains recommended pharmacogenetic testing guidelines for clinical application, interpretation, and result reporting through a literature review and evidence-based expert opinions for the clinical pharmacogenetic testing covered by public medical insurance in Korea. This document aims to improve the utility of pharmacogenetic testing in routine clinical settings.

No Effect of SLCO1B1 and CYP3A4/5 Polymorphisms on the Pharmacokinetics and Pharmacodynamics of Ticagrelor in Healthy Chinese Male Subjects

Ticagrelor is a direct-acting P2Y12 receptor antagonist. It is rapidly absorbed and partly metabolized to the active metabolite AR-C124910XX by CYP3A4 and CYP3A5. Three genetic loci (SLCO1B1, CYP3A4, and UGT2B7) were reported to affect ticagrelor pharmacokinetics. This study aimed to investigate the possible effects of SLCO1B1 and CYP3A4/5 genetic polymorphisms on the pharmacokinetics and pharmacodynamics of ticagrelor in healthy Chinese male volunteers. Eighteen healthy male volunteers who participated in pharmacogenetics study of ticagrelor were genotyped for SLCO1B1 rs113681054, SLCO1B1*5 (rs4149056), CYP3A4*1G (rs2242480), and CYP3A5*3 (rs776746). All subjects received a single 180 mg loading dose of ticagrelor and then series blood samples were collected from 0 to 48 h. Plasma concentrations of ticagrelor and AR-C124910XX were determined by the high performance liquid chromatography-tandem mass spectrometry method. Inhibition in platelet aggregation (IPA) was assessed and the area under the time-effect curve (AUEC) for the IPA was calculated as pharmacodynamic parameters. No significant difference in ticagrelor pharmacokinetics among genotypes of the two genes was observed. The AUEC did not differ significantly among genotypes of candidate single nucleotide polymorphisms (SNPs). Our data suggest that common genetic variants in SLCO1B1 and CYP3A4/5 may have no effect on the pharmacokinetics and pharmacodynamics of ticagrelor in healthy Chinese volunteers.

Impact of CYP2C19 Variants on Clinical Efficacy of Clopidogrel and 1-Year Clinical Outcomes in Coronary Heart Patients Undergoing Percutaneous Coronary Intervention

The impact of pharmacogenetic variants of cytochrome P450 2C19 (CYP2C19) on clopidogrel-mediated effects on platelet inhibition, inflammatory response and endothelial function, as well as risk of major adverse cardiovascular events (MACE), in coronary heart patients undergoing percutaneous coronary intervention (PCI) was investigated. To this end, we assessed the residual platelet aggregation rate (RPA), maximal aggregation rate (MAR) and plasma levels of sCD40L, sP-selectin, MMP-9, sVCAM-1 and sE-selectin after 24 h of PCI in 559 patients treated with clopidogrel and followed up for 1 year for evidence of MACE. CYP2C19^*2 and ^*3 variants were identified using a clopidogrel-sensitive gene detection kit. Our results showed higher RPA and MAR as well as increased sE-selectin, sCD40L, sP-selectin, MMP-9, and sVCAM-1 levels in CYP2C19 intermediate metabolizer (IM, CYP2C19^*1/^*2, or ^*1/^*3), poor metabolizer (PM, CYP2C19^*2/^*2, ^*2/^*3, or ^*3/^*3) and combined IM+PM groups, relative to those in extensive metabolizers (EM, CYP2C19^*1/^*1). In total, 519 patients completed 1 year of follow-up, among which 69 (13.3%) experienced MACE. The risk of MACE in CYP2C19 IM+PM patients was 2.664 times higher than that in CYP2C19 EM patients (OR = 2.664 (1.397–5.193), P = 0.004). The data suggest that CYP2C19^*2 and ^*3 variants modulate the drug efficacy of clopidogrel in coronary heart patients undergoing PCI and further enhance the risk of MACE. Accordingly, CYP2C19 pharmacogenetic profiling may be beneficial for coronary heart patients undergoing PCI to predict the efficacy of treatment with clopidogrel. We propose that IM and PM patients should benefit from treatment with higher clopidogrel doses to improve efficacy and reduce the incidence of MACE.

Association between CYP3A5 polymorphisms and the risk of adverse events in patients undergoing clopidogrel therapy: Meta-analysis

INTRODUCTION

We wished to explore the relationship between CYP3A5 polymorphisms and adverse events in patients undergoing clopidogrel therapy.

METHODS

A Boolean search of the PubMed, EMbase, OVID and Cochrane Library databases was conducted in April 2016. The primary outcome was major adverse cardiovascular events (MACE). The secondary outcome was bleeding events and resistance to the effects of clopidogrel. The CYP3A5 polymorphism was classified into three types: wild-type (AA), heterozygote (AG) and homozygous mutant (GG). We estimated pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) using the Mantel-Haenszel model.

RESULTS

Twelve studies involving 8284 patients were eligible for our meta-analysis. CYP3A5 polymorphisms had no obvious influence on MACE (AA+AG vs. GG: OR=1.032, 95% CI=0.583-1.824, p=0.915; AA vs. AG+GG: 1.415, 0.393-5.094, 0.595). There was no significant relationship between CYP3A5 polymorphisms and bleeding (GG vs. AA+AG: OR=0.798, 95% CI=0.370-1.721, p=0.565) or clopidogrel resistance (AA+AG vs. GG: 1.009, 0.685-1.488, 0.963; AA vs. AG+GG, 0.618, 0.368-1.039, 0.069).

CONCLUSION

No significant correlation was found between CYP3A5 polymorphisms and adverse events due to clopidogrel therapy.

Differential impact of selective serotonin reuptake inhibitors on platelet response to clopidogrel: a randomized, double-blind, crossover trial

STUDY OBJECTIVE

To assess the effect of two selective serotonin reuptake inhibitors (SSRIs), fluvoxamine and citalopram, that markedly differ in their level of cytochrome P450 (CYP) 2C19 inhibition, on the laboratory response to clopidogrel, a prodrug requiring metabolism by the CYP system, and especially CYP2C19, to produce its active form.

DESIGN

Randomized, double-blind, crossover trial.

SETTING

Clinical research unit of an academic medical center.

SUBJECTS

Fifteen healthy male volunteers.

INTERVENTION

All subjects received clopidogrel as a 300-mg loading dose on day 1, followed by 75 mg/day on days 2 and 3. Platelet function was tested at baseline and then after clopidogrel treatment on day 3. After a washout period of 2 weeks, subjects were randomly assigned in a double-blind manner to receive either citalopram 20 mg/day or fluvoxamine 100 mg/day for 7 days. On day 5, platelet function was tested while receiving the SSRI treatment alone; then, a 300-mg clopidogrel loading dose was administered, followed by clopidogrel 75 mg/day on days 6 and 7. Platelet function was then reassessed on day 7 while receiving the combination of the SSRI and clopidogrel. The treatment protocol was then repeated after a washout period of 2 weeks in all subjects with the other SSRI.

MEASUREMENTS AND MAIN RESULTS

The antiplatelet effects of fluvoxamine and citalopram and their interactions with clopidogrel were assessed. The response to these three drugs was assessed by light transmittance aggregometry and vasodilator-stimulated phosphoprotein phosphorylation, reporting P2Y12 receptor reactivity. Both fluvoxamine and citalopram tended to reduce adenosine diphosphate-induced aggregation: 80.8 ± 3.4% at baseline, 67.3 ± 6.3% while receiving citalopram, and 65.8 ± 6.4% while receiving fluvoxamine. All subjects had a good laboratory response to clopidogrel, with a mean aggregation of 23.5 ± 3.2% and a mean platelet reactivity index of 47.7 ± 3.9% (p<0.001 compared with baseline for both methods). Laboratory response to clopidogrel was significantly attenuated in the presence of fluvoxamine compared with the response in the presence of citalopram as tested both by aggregometry (32.3 ± 4.2% vs 23.4 ± 3%, p=0.04) and by vasodilator-stimulated phosphoprotein phosphorylation (52.7 ± 5.1% vs 35.9 ± 4.2%, p=0.02).

CONCLUSION

Fluvoxamine attenuated the laboratory response to clopidogrel, possibly through inhibition of CYP2C19, whereas citalopram did not affect this response. These potential drug interactions should be taken into consideration in the selection of the appropriate antidepressant agent for patients who are treated with clopidogrel.

The role of clinical parameters and of CYP2C19 G681 and CYP4F2 G1347A polymorphisms on platelet reactivity during dual antiplatelet therapy

Dual antiplatelet therapy with aspirin and clopidogrel is used to lower the risk of arterial thrombosis. However, this strategy is not always successful owing to high interindividual variability in response to antiplatelet therapy. To evaluate an impact of CYP2C19 G681A and CYP4F2 G1347A polymorphisms and clinical factors on dual antiplatelet effect of clopidogrel and aspirin. Totally 89 patients who continued dual aspirin and clopidogrel antiplatelet therapy for at least of 14 days were included into the further study. Test for platelet aggregation was performed according to the classical Born method. Genotyping of CYP2C19*2 and CYP2C19*3 and CYP4F2*3 was done by using commercial probes from Applied Biosystems (UK). Patient age, weight and body weight index did not correlate significantly with platelet aggregation level both induced by ADP and epinephrine (P > 0.05). Serum concentration of creatinine, diabetes, angiotensin II receptor blockers, B-blockers, statin or omeprazole use had no significant effect on platelet aggregation. The users of angiotensin-converting enzyme inhibitors had lower platelet aggregation levels with epinephrine vs. nonusers: 28.80 ± 13.25 vs. 51.15 ± 23.50, P < 0.03, respectively. Platelet aggregation with ADP was higher in CYP2C19*1*2 genotype carriers than in CYP2C19*1*1 carriers (P = 0.01). Platelet aggregation with epinephrine was higher in CYP4F2 GA genotype carriers than in GG (P = 0.04) or AA (P = 0.01) carriers. Our study confirms that CYP2C19 G681A genotype has an impact on antiplatelet effect of clopidogrel. The novelty is that the platelet aggregation after induction with epinephrine is influenced by CYP4F2 G1347A genotype.

[Antithrombotic treatment in patients with stable coronary artery disease. Which drugs and for how long?]

Stable chronic coronary artery disease (SCAD) encompasses several groups of patients including those with stable angina pectoris or other symptoms thought to be linked to CAD as well as patients with known prior acute coronary syndrome or prior coronary interventions, who have become asymptomatic with treatment and need regular follow-up. Patients with SCAD have an elevated risk for subsequent ischemic events and significantly benefit not only from lipid-lowering therapy with statins but also in particular from long-term antithrombotic treatment. These patients therefore need lifelong antithrombotic treatment with 100 mg acetylsalicylic acid (ASA) daily whereby clopidogrel 75 mg daily is indicated as an alternative in cases of aspirin intolerance. As chronic CAD may present with very different developmental phases spanning from chronic stable phases to acute coronary syndromes, antithrombotic treatment in SCAD patients needs continuous evaluation and adaptation. In addition, new concomitant diseases, such as atrial fibrillation may necessitate further adaptation of antithrombotic therapy. The current overview focuses on the description of the long-term antithrombotic treatment of SCAD as well as on the need for adaptation in the setting of elective percutaneous coronary interventions (PCI).

Influence of Different β-Blockers on Platelet Aggregation in Patients With Coronary Artery Disease on Dual Antiplatelet Therapy

INTRODUCTION

The use of β-blockers in the treatment of patients with coronary heart disease is associated with a decrease in the frequency of angina pectoris and mortality of patients. Due to the severity of the disease and previous cardiovascular interventions, many patients with coronary artery disease (CAD) use dual antiplatelet therapy to achieve greater inhibition of platelet aggregation. The influence of β-blockers on platelet aggregation in patients using antiplatelet therapy is not well understood.

OBJECTIVE

To examine the effect of different β-blockers on platelet aggregation in patients on dual antiplatelet therapy.

METHODOLOGY

The study included 331 patients who were treated at the Department of Cardiology, Clinical Center Kragujevac during 2011. Patients were divided into 4 groups depending on the type of β-blockers that were used (bisoprolol, nebivolol, metoprolol, and carvedilol). Platelet aggregation was measured using the multiplate analyzer and expressed through the value of adenosine diphosphate (ADP) test (to assess the effect of clopidogrel), ASPI test (to assess the effect of acetyl salicylic acid), TRAP test (to assess baseline platelet aggregation), and the ratio of ADP/TRAP and ASPI/TRAP ASPI/TRAP (ASPI - aranchidonic acid induced aggregation, TRAP - thrombin receptor activating peptide) representing the degree of inhibition of platelet aggregation compared to the basal value. In consideration were taken the representation of demographic, clinical characteristics, laboratory parameters, and cardiovascular medications between the groups.

RESULTS

Patients who used nebivolol had a significantly lower value of the ratio of ADP/TRAP (0.39 ± 0.30) compared to patients who used bisoprolol (0.48 ± 0.26; P = .038), and trend toward the lower values of ADP test (328.0 ± 197.3 vs 403.7 ± 213.2; P = .059), while there was no statistically significant difference in values of other laboratory parameters of platelet function between other groups.

CONCLUSION

Patients with CAD on dual antiplatelet therapy who used nebivolol had significantly lower levels of residual ADP-induced platelet aggregation compared to baseline than patients who used bisoprolol.

The relationship between on-clopidogrel platelet reactivity, genotype, and post-percutaneous coronary intervention outcomes in Chinese patients

BACKGROUND

High on-clopidogrel platelet reactivity reflects a poor response to clopidogrel and is associated with ischemic events, which has been attributed to several factors such as demographic, clinical characteristics and a polymorphism of CYP2C19. Some new platelet assays monitoring on-clopidogrel platelet reactivity are currently available in China, but their relevance to the CYP2C19 genotype and post-percutaneous coronary intervention outcomes remain to be elucidated.

METHODS

Patients were prospectively included if they had a successful percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) and received clopidogrel and aspirin. CYP2C19 loss-of function genotype, adenosine diphosphate (ADP)-induced maximum platelet aggregation rate (MPA ADP) measured by light transmittance aggregometry, ADP-induced platelet-fibrin clot strength (MA ADP) measured by thrombelastography, platelet reactivity index (PRI) measured by vasodilator-stimulated phosphoprotein phosphorylation (VASP), and the occurrence of 6-month major adverse cardiovascular events (MACE) were assessed in 178 patients.

RESULTS

High on-treatment platelet reactivity prevalence defined by MPA ADP > 46.0%, MA ADP > 47 mm and PRI > 50.0% was 27.0%, 24.2%, and 61.2%, respectively. ADP-specific assays (VASP PRI) differed according to CYP2C19 genotype, with a significant gene-dose effect (PMs > IMs > EMs, p < 0.05). Multivariate analysis showed MPA ADP > 46.0% and MA ADP > 47 mm to be independent predictors of MACE at 6 months.

CONCLUSIONS

CYP2C19 loss-of function genotypes with the *2 and/or *3 allele are highly prevalent in the Chinese population and are associated with higher residual platelet reactivity. High on-treatment platelet reactivity defined by MPA ADP or MA ADP predicts an increased risk of MACE for ACS patients undergoing PCI.

Challenges and solutions in medically managed ACS in the Asia-Pacific region: expert recommendations from the Asia-Pacific ACS Medical Management Working Group

Acute coronary syndromes (ACS) remain a leading cause of mortality and morbidity in the Asia-Pacific (APAC) region. International guidelines advocate invasive procedures in all but low-risk ACS patients; however, a high proportion of ACS patients in the APAC region receive solely medical management due to a combination of unique geographical, socioeconomic, and population-specific barriers. The APAC ACS Medical Management Working Group recently convened to discuss the ACS medical management landscape in the APAC region. Local and international ACS guidelines and the global and APAC clinical evidence-base for medical management of ACS were reviewed. Challenges in the provision of optimal care for these patients were identified and broadly categorized into issues related to (1) accessibility/systems of care, (2) risk stratification, (3) education, (4) optimization of pharmacotherapy, and (5) cost/affordability. While ACS guidelines clearly represent a valuable standard of care, the group concluded that these challenges can be best met by establishing cardiac networks and individual hospital models/clinical pathways taking into account local risk factors (including socioeconomic status), affordability and availability of pharmacotherapies/invasive facilities, and the nature of local healthcare systems. Potential solutions central to the optimization of ACS medical management in the APAC region are outlined with specific recommendations.

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.

Association between genetic polymorphisms of cytochrome P450 2C19 and the risk of cerebral ischemic stroke in Chinese

Background

Cytochrome P450 (CYP) 2C19 is a very important drug metabolizing enzyme. Although the single nucleotide polymorphisms (SNPs) of CYP2C19 G681A and G636A have been suggested that they may increase the incidence of cardiovascular events, the relationship between SNPs in CYP2C19 and cerebral ischemic stroke (CIS) are unclear. The aim of this study was to investigate the correlation between the distribution of G681A and G636A polymorphisms in CYP2C19 gene and the risk of CIS in Chinese.

Methods

The peripheral blood DNA was extracted from 299 patients with CIS and 295 healthy controls. The genotyping was conducted using the polymerase chain reaction-restriction fragment length polymorphism. The sampled sequencing was applied to verify the correctness of genotyping results. Both the genotype and allele distributions were compared in patients with CIS and healthy controls.

Results

The frequencies of CYP2C19 681AA (11.7% vs. 2.7%; P = 0.000), 636AA (4.0% vs. 0.7%; P = 0.007), 636AG (7.0% vs. 2.2%; P = 0.038) genotype, CYP2C19 681A (30.9% vs. 20.8%; P = 0.000) and 636A (13.0% vs. 5.8%; P = 0.000) allele in the CIS group are significantly higher than those in the controls. The frequencies of CYP2C19 681AA (16.7% vs. 8.6%; P = 0.036), CYP2C19 636AA (7.0% vs. 2.2%; P = 0.038) genotype, CYP2C19 681A (36.4% vs. 27.6%; P = 0.023) and CYP2C19 636A (17.5% vs.10.3%; P = 0.010) allele in the recurrent stroke group are significantly higher than those in the first onset group. Multivariate logistic regression analysis of risk factors for cerebral ischemic stroke and recurrent stroke respectively suggests that the CYP2C19 681AA genotype may be an independent risk factor for CIS (OR = 6.179, 95% CI: 2.285 ~ 16.708; P = 0.000) and recurrent stroke (OR = 2.305, 95% CI: 1.121 ~ 4.743; P = 0.023).

Conclusions

The AA genotype and A allele of CYP2C19 G681A may be related to the occurrence and recurrence of cerebral ischemic stroke.

Gene polymorphism of cytochrome P450 2C19*2 and clopidogrel resistance reflected by platelet function assays: a meta-analysis

BACKGROUND

The relationship between CYP2C19*2 gene polymorphism and clopidogrel resistance reflected by platelet function assays has been studied extensively in the past several years, while no clear conclusion can be drawn from the previous studies. To explore a more precise estimation of the relationship, a meta-analysis was conducted in the present study.

METHODS

The relevant studies were identified by searching PubMed, EMBASE, the Web of Science, Cochrane Collaboration Database, Chinese National Knowledge Infrastructure (CNKI), Wanfang Database, and China Biological Medicine (CBM) up to February, 2014. The meta-analysis was performed by the STATA 11.

RESULTS

Eight studies with a total of 2,331 subjects, including 1,066 patients with clopidogrel resistance and 1,265 patients without clopidogrel resistance were included. The pooled analysis showed that CYP2C19*2 gene polymorphism was probably associated with clopidogrel resistance (OR (95% CI): GA vs. GG: 2.10 (1.74-2.53); AA vs. GG: 3.05 (2.10-4.45); dominant model: 2.22 (1.85-2.65); recessive model: 2.33 (1.62-3.36)). No statistically significant difference was found in the analysis of the three subgroups. The statistical stability and reliability was also demonstrated by the sensitivity analysis and publication bias outcomes.

CONCLUSION

The meta-analysis suggests that CYP2C19*2 gene polymorphism may be associated with clopidogrel resistance.

Benefits and harms of extending the duration of dual antiplatelet therapy after percutaneous coronary intervention with drug-eluting stents: a meta-analysis

BACKGROUND

The optimal duration of dual antiplatelet therapy (DAPT) after percutaneous coronary intervention (PCI) is unclear.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials evaluating risk of adverse events in participants receiving different durations of DAPT following insertion of drug-eluting stents.

RESULTS

Five trials were included, but only four had data suitable for meta-analysis (n = 8,231 participants). No significant increase in the composite endpoint of death and nonfatal myocardial infarction was observed with earlier cessation of DAPT in any instance when compared to longer durations of DAPT (RR 0.64 95% CI 0.25-1.63 for 3 versus 12 months, RR 1.09 95% CI 0.84-1.41 for 6 versus 12 months and, RR 0.64 95% CI 0.35-1.16 for 12 versus 24 months). Pooled results showed a significantly lower risk of major bleeding (RR 0.48 95% CI 0.25-0.93) and total bleeding (RR 0.30 95% CI 0.16-0.54) for shorter compared to longer duration of DAPT. Subgroup analysis based on age, prior diabetes, and prior ACS failed to show any group where longer durations were consistently better than shorter ones.

CONCLUSIONS

There are no cardiovascular or mortality benefits associated with extended duration of DAPT, but the risk of major bleeding was significantly lower with shorter lengths of therapy.

Effect of P2Y1 and P2Y12 genetic polymorphisms on the ADP-induced platelet aggregation in a Korean population

BACKGROUND

P2Y1 and P2Y12 receptors are expressed in platelet membranes and are involved in ADP-induced platelet aggregation. Genetic polymorphisms of P2Y1 and P2Y12 play a major role in the variation of ADP-induced platelet aggregation and in response in antiplatelet therapy.

OBJECTIVE

To evaluate the allele frequencies of P2Y1 and P2Y12 genetic polymorphisms in a Korean population and to assess their role in ADP (5 μmol/L)-induced maximal platelet aggregation.

METHODS

P2Y1 (c.1622A>G) and P2Y12 (i-139C>T, i-744T>C, i-ins801, c.52G>T, c.34C>T) polymorphisms were analyzed in 158 Korean healthy participants using pyrosequencing methods. Their ADP-induced maximal platelet aggregation was assessed by the turbidometric method.

RESULTS

The observed allele frequencies of P2Y1 and P2Y12 were as follows: 0.3101 for P2Y1 c.1622A>G; 0.1804 for P2Y12 i-139C>T, 0.1804 for i-744T>C, 0.1804 for i-801insA, 0.1266 for P2Y12 c.52G>T, and 0.2658 for P2Y12 c.34C>T. ADP-induced maximal platelet aggregation was not influenced by the P2Y1 c.1622A>G polymorphism and was also not affected by three intronic P2Y12 polymorphisms and the P2Y12 c.34C>T polymorphism. However, the P2Y12 c.52G>T polymorphism caused a substantial difference in ADP-induced maximal platelet aggregation (62.75% for c.52GG, 66.27% for c.52GT, and 80.60% for c.52TT; P=0.0092).

CONCLUSIONS

The P2Y1 and P2Y12 genes were very polymorphic in a Korean population. Three intronic P2Y12 polymorphisms (i-139C>T, i-744T>C, i-801insA) were in complete linkage disequilibrium but not with the c.52C>T polymorphism in this population. Maximal platelet aggregation in response to ADP is associated with the c.52C>T polymorphism but not with the three intronic polymorphisms or the P2Y1 c.1622A>T polymorphism.

Effects of CYP2C19 variant alleles on postclopidogrel platelet reactivity and clinical outcomes in an actual clinical setting in China

Whether the current pharmacogenetic knowledge of clopidogrel could be translated into Chinese clinical practice is yet to be defined. To address this issue, we assessed the relation of single nucleotide polymorphisms within genes modulating clopidogrel absorption (ABCB1), metabolic activation (CYP2B6, CYP2D6, CYP3A4, CYP2C9, and CYP2C19), and biologic activity (P2RY12) to the response of clopidogrel as measured by ex-vivo platelet reactivity and ischemic events during half a year of follow-up. Only CYP2C19*2 and *3, of the investigated polymorphisms, were associated with postclopidogrel platelet aggregation and the presence of high platelet reactivity. Moreover, the effect of the CYP2C19*2 versus the *3 allele on platelet reactivity did not differ. Although the carriage of one or two CYP2C19 loss-of-function alleles, irrespective of the CYP2C19*2 or *3 allele, increased the propensity for high platelet reactivity, only the two loss-of-function allele carriage was associated with clinical outcome in the first 6 months.

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<0.00001 and 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.

Platelet inhibitory effect of clopidogrel in patients treated with omeprazole, pantoprazole, and famotidine: a prospective, randomized, crossover study

BACKGROUND

Concerns about an inhibitory effect of proton pump inhibitors (PPIs) on clopidogrel metabolism have been raised. Because the pharmacological effect of clopidogrel is dependent on genetically determined activity of the hepatic cytochrome P450 isoenzymes system, it is important to examine the interaction between different PPIs and high on-treatment platelet reactivity (HPR) after controlling for genetic variability. The aim of the study was to assess the effect of 2 PPIs and a histamine-2 (H2) receptor-blocker on platelet reactivity in a crossover trial where each patient was alternately treated with each drug.

HYPOTHESIS

Omeprazole reduces HPR more than other PPI or H2 blockers.

METHODS

Patients treated with aspirin and clopidogrel for at least 1 month were assigned to 3 consecutive 1-month treatment periods during which they were treated with each of the 3 study medications twice daily: omeprazole 20 mg, famotidine 40 mg, and pantoprazole 20 mg. At the end of each treatment phase, platelet function was evaluated with the Verify Now system using 2 cutoff values (>208 P2Y12 reaction units [PRUs] and >230 PRUs) for the definition of HPR.

RESULTS

Patients with HPR were older than those without HPR (62 ± 10 vs 55 ± 8 years, respectively, P = 0.03). HPR was more prevalent during omeprazole therapy compared to famotidine or pantoprazole (48%, 33%, and 31%, respectively, for the 208 PRU cutoff, P= 0.04; and 37%, 17%, and 23%, respectively, for the 230 PRU cutoff, P= 0.003).

CONCLUSIONS

After eliminating the effects of interindividual variability in clopidogrel metabolism, omeprazole therapy was associated with substantially more HPR than famotidine or pantoprazole.

The discovery and development of prasugrel

INTRODUCTION

Prasugrel (CS-747, LY640315) is a third-generation thienopyridine, which gained approval by the FDA in 2009 for its use in patients with acute coronary syndrome undergoing percutaneous coronary intervention.

AREAS COVERED

This article focuses on the preclinical profile of prasugrel. Using published preclinical and clinical studies, the authors summarize the pharmacokinetics, pharmacodynamics, and pharmacogenomics of prasugrel and their distinguishing features in efficacy and safety.

EXPERT OPINION

Prasugrel has a more rapid, more potent antiplatelet effect with less interindividual response variability when compared to clopidogrel. Those therapeutic advantages are attributed to features of its chemical structure that favor the metabolic conversion of prasugrel to its active metabolite. However, the increased risk of bleeding has been associated with a greater antiplatelet effect and dosing profile; this is especially the case in those patients who are at a higher risk of bleeding complications. It is therefore important for an optimal dosing strategy of prasugrel to be identified to provide a formulation that has the best balance for efficacy and safety.

P2Y12 Receptor Inhibitors in Acute Coronary Syndromes: What Is New on the Horizon?

Dual antiplatelet therapy with aspirin and a P2Y₁₂ receptor inhibitor represents the cornerstone therapy for patients with acute coronary syndromes or undergoing percutaneous interventions, leading to a reduction of subsequent ischemic events. Variable response to clopidogrel has received close attention, and pharmacokinetic, pharmacodynamic, and pharmacogenomic factors have been identified as culprits. This led to the introduction of newer, potentially safer, and more effective antiplatelet agents (prasugrel and ticagrelor). Additionally, several point-of-care assays of platelet function have been developed in recent years to rapidly screen individuals on antiplatelet therapy. While the routine use of platelet function testing is uncertain and not currently recommended, it may be useful in instances when the degree of platelet inhibition may be uncertain such as high-risk patients undergoing percutaneous coronary intervention or when there may be a suspected pharmacodynamic interaction with other drugs. The current paper focuses on the P2Y₁₂ receptor inhibitors and their pharmacogenetics and indications in patients with acute coronary syndromes or receiving percutaneous coronary interventions as well as the applicability of platelet function testing in this clinical context.

Dual antiplatelet therapy clopidogrel with low-dose cilostazol intensifies platelet inhibition in patients with ischemic stroke

OBJECTIVE

We previously reported that the antiplatelet action is intensified with combined use of clopidogrel and cilostazol in ischemic stroke patients using the VerifyNow P2Y12 Assay. In this study, the relationship between the cilostazol dose and the platelet function achieved with combination therapy was investigated.

METHODS

The subjects included 231 patients with noncardiogenic ischemic stroke treated at our hospital (18 patients treated with a combination of clopidogrel (75 mg) and cilostazol (100 mg), 52 patients treated with a combination of clopidogrel (75 mg) and cilostazol (200 mg), 126 patients treated with clopidogrel (75 mg) alone and 35 patients treated with cilostazol (200 mg) alone). The platelet function achieved with 20 μM of adenosine diphosphate was measured using the VerifyNow P2Y12 Assay. Clopidogrel resistance was defined as P2Y12 Reaction Units (PRU) >230 and/or % inhibition <20%. Results The PRU was >230 in 32 patients (25.4%) receiving clopidogrel alone, one patient (5.6%) receiving combination therapy with cilostazol (100 mg) and one patient (1.9%) receiving combination therapy with cilostazol (200 mg). The rate of PRU >230 was significantly lower in both of the cilostazol combination groups than in the clopidogrel alone group. The percent inhibition was <20% in 41 patients (32.5%) receiving clopidogrel alone, one patient (5.6%) receiving a combination with cilostazol (100 mg) and one patient (1.9%) receiving a combination with cilostazol (200 mg). The rate of % inhibition <20% was significantly lower in both of the cilostazol combination groups than in the clopidogrel alone group.

CONCLUSION

Clopidogrel resistance was clearly decreased with combination clopidogrel (75 mg) and low-dose (100 mg) cilostazol therapy. The use of combination therapy with clopidogrel and low-dose cilostazol may be one means of overcoming clopidogrel resistance.

Association of CYP2C19*2 and *3 genetic variants with essential hypertension in Koreans

PURPOSE

The cytochrome P450 2C19 (CYP2C19) metabolizes arachidonic acid to produce epoxyicosanoid acids, which are involved in vascular tone and regulation of blood pressure. Recent findings suggest that CYP2C19 gene might be considered as a novel candidate gene for treatment of cardiovascular disease. The aim of the present study was to evaluate the association between two variants, CYP2C19* 2 (681G>A) and CYP2C19*3 (636G>A) and the development of essential hypertension (EH) in Koreans.

MATERIALS AND METHODS

We carried out an association study in a total of 1190 individuals (527 hypertensive subjects and 663 unrelated healthy controls). The CYP2C19 polymorphisms were genotyped using the SNaPShot™ assay.

RESULTS

The distribution of alleles and genotypes of CYP2C19* 3 showed significant difference between hypertensive patients and normal controls (p=0.011 and p=0.013, respectively). Logistic regression analysis indicated that the CYP2C19*3 (636A) allele carriers were significantly associated with EH [odds ratio, 0.691; 95% confidence interval (CI), 0.512-0.932, p=0.016], in comparison to wild type homozygotes (CYP2C19*1/*1). Neither genotype nor allele distribution of CYP2C19*2 polymorphism showed significant differences between hypertensive and control groups (p>0.05).

CONCLUSION

Our present findings strengthen the evidence of an association between CYP2C19 gene polymorphism and EH prevalence. In particular, the CYP2C19*3 defective allele may contribute to reduced risk for the development of EH.

Clinical outcomes of high on-treatment platelet reactivity in Koreans receiving elective percutaneous coronary intervention (from results of the CROSS VERIFY study)

Platelet reactivity after clopidogrel therapy varies among patients. Whether clopidogrel response variability can predict clinical outcomes has not been verified in Asians. A prospective cohort was analyzed to evaluate clinical impact of clopidogrel response variability in patients who underwent elective percutaneous coronary intervention (PCI). A total of 809 consecutive patients receiving clopidogrel after elective PCI were followed for 1 year. On-treatment platelet reactivity (OPR) after clopidogrel therapy was measured with a point-of-care test, the VerifyNow P2Y12 assay. The primary end point was the composite of cardiac death and nonfatal myocardial infarction (MI) at 1 year. In this exclusively Korean cohort, the median OPR was 236 P2Y12 reactivity units. Using the definition of OPR ≥235 P2Y12 reactivity units as high OPR (HOPR), 50.3% of the cohort showed HOPR. The group with HOPR had significantly higher rates of cardiac death and spontaneous MI (2.5% vs 0.5%, p = 0.022) than the group without HOPR. Multivariate-adjusted analysis showed that HOPR was an independent predictor of the composite of cardiac death and nonfatal MI. The difference in major adverse cardiac events between the groups with and without HOPR was more profound in those without major cardiovascular disease, such as hypertension, diabetes mellitus, or dyslipidemia. In conclusion, HOPR to clopidogrel was significantly associated with cardiac death and spontaneous MI after elective PCI, suggesting that clopidogrel response variability may be a significant risk factor of hard end points in Koreans.

Effect of CYP2C19*2 and *3 loss-of-function alleles on platelet reactivity and adverse clinical events in East Asian acute myocardial infarction survivors treated with clopidogrel and aspirin

BACKGROUND

As compared with whites, East Asians more often carry the cytochrome P450 (CYP) 2C19 loss-of-function (LOF) allele with the CYP2C19*3 variant. The influence of the CYP2C19 LOF alleles (*2 and *3) on clopidogrel response and clinical outcomes in East Asians with acute myocardial infarction (AMI) has not been reported. We sought to evaluate the effect of the CYP2C19 variants on clopidogrel pharmacodynamics and long-term prognosis in these patients.

METHODS AND RESULTS

Patients who survived an AMI (n=266) were enrolled in a single-center registry. Predischarge platelet reactivity was assessed with light transmittance aggregometry and the VerifyNow P2Y12 assay; the CYP2C19*2, *3, *17 and ABCB1 3435C>T variants were determined. The primary clinical end point was the composite of cardiovascular death, nonfatal MI, and ischemic stroke. The median exposure to clopidogrel was 21 months (interquartile range, 13-29). The ABCB1 3435C>T was not related to clopidogrel response or cardiovascular events. Carriage of the CYP2C19 LOF variant allele was relatively high (60.9%, n=162; *2/*17=2, *3/*17=1, *1/*2=96, *1/*3=29, *2/*2=20, and *2/*3=14). Platelet reactivity increased proportionally according to the number of the CYP2C19 LOF alleles. In a multivariate regression analysis, the risk of high on-treatment platelet reactivity (HPR) increased depending on the number of CYP2C19 LOF allele [1 LOF allele; odds ratio (OR), 1.8; 95% confidence interval (CI), 0.8 to 4.2, P=0.152; and 2 LOF alleles; OR, 2.8; 95% CI, 1.2 to 6.5; P=0.016]; platelet reactivity and the rate of HPR did not differ between the CYP2C19*2 versus *3 allele carriage. In addition, cardiovascular event occurrence increased according to the number of the CYP2C19 LOF allele; compared with noncarriers, carriers of 1 [hazard ratio (HR), 3.1; 95% CI, 0.8 to 11.6; P=0.089] and 2 CYP2C19 LOF allele(s) (HR, 10.1; 95% CI, 1.8-58.8; P=0.008) were associated with clinical end point. The clinical impact of the CYP2C19*2 versus *3 allele carriage also did not differ.

CONCLUSIONS

Among East Asian patients who survived an AMI, the CYP2C19 LOF allele carriage appears to affect clopidogrel pharmacodynamics and cardiovascular events according to the number of the CYP2C19 LOF allele; the influence of the CYP2C19*2 and *3 alleles on clopidogrel response and long-term outcomes does not differ.

Cytochrome P450 2C19 polymorphism is associated with reduced clopidogrel response in cerebrovascular disease

PURPOSE

Clopidogrel is a prodrug that requires transformation into an active metabolite by cytochrome P450 (CYP) in the liver in order to irreversibly inhibit the P2Y12 adenosine diphosphate platelet receptor. CYP2C19 polymorphism has been reported to correlate with reduced antiplatelet activity of clopidogrel in coronary artery disease. We assessed the association between CYP2C19 polymorphism and clopidogrel resistance in patients with cerebrovascular disease.

MATERIALS AND METHODS

We retrospectively gathered data from patients who experienced cerebrovascular disease, received clopidogrel, and were tested for clopidogrel resistance and CYP2C19 polymorphism. Clopidogrel resistance was tested by the VerifyNow P2Y12 system, and the CYP2C19 polymorphism was tested by the Seeplex CYP2C19 ACE Genotyping system. Clopidogrel resistance was expressed in P2Y12 reaction units (PRU) and percent inhibition. High PRU and low percent inhibition suggests clopidogrel resistance. CYP2C19 polymorphisms were expressed as extensive, intermediate, and poor metabolizers. Clopidogrel resistance was assessed according to the subgroup of CYP2C19 polymorphism.

RESULTS

A total of 166 patients were evaluated. The PRU values of extensive CYP2C19 metabolizers (195.0±84.9) were significantly lower than those of intermediate and poor metabolizers (237.9±88.0, 302.2±58.9). The percent inhibition of extensive metabolizers (44.6±21.8) was significantly higher than that of intermediate and poor metabolizers (30.5±21.5, 14.0±13.4).

CONCLUSION

Intermediate and poor metabolizing CYP2C19 polymorphism is associated with reduced clopidogrel antiplatelet activity in patients with cerebrovascular disease. The clinical implications of this finding require further investigation.

Clinical, pharmacokinetic, and pharmacogenetic determinants of clopidogrel resistance in Korean patients with acute coronary syndrome

BACKGROUND

Clopidogrel has been widely used to prevent recurrent ischemia in patients with acute coronary syndrome (ACS). However, inter-individual variability in response to clopidogrel has been a problem in the clinical setting. The aim of the present study was to investigate the frequency of clopidogrel resistance and to determine the clinical, pharmacokinetic, and pharmacogenetic factors for clopidogrel resistance in Korean patients with ACS.

METHODS

Clinical information, such as the underlying diseases and concurrent medications, of 114 patients with ACS who received clopidogrel therapy was studied. The degree of inhibition of platelets was assessed using the VerifyNow assay (Accumetrics, USA). The patients who showed less than 20% inhibition of platelets were defined as non-responders to clopidogrel treatment. Steady state plasma concentrations of clopidogrel were measured using HPLC/tandem mass spectrometry. CYP2C19 genotyping was also performed.

RESULTS

A wide inter-individual variability was observed in platelet inhibition (0-76%); 56 patients (49%) showed less than 20% inhibition. There were no differences between the patients' history of diabetes mellitus and concurrent medications as well as the plasma concentrations of clopidogrel of the responders and non-responders. CYP2C19 variants, including CYP2C19*2 and CYP2C19*3, were more commonly observed in the non-responders than in the responders (P value < 0.0001).

CONCLUSIONS

The response to clopidogrel was highly variable in Korean patients with ACS. The results of the present study confirmed that the genetic polymorphism of CYP2C19 could be important in clopidogrel response. However, further studies are required to investigate other likely factors involved in clopidogrel resistance.

Genetic polymorphisms and the impact of a higher clopidogrel dose regimen on active metabolite exposure and antiplatelet response in healthy subjects

A double-blind crossover study was conducted in four CYP2C19 genotype-defined metabolizer groups to assess whether increase in clopidogrel dosing can overcome reduced pharmacodynamic response in CYP2C19 poor metabolizers (PMs). Ten healthy subjects in each of four metabolizer groups were randomized to a clopidogrel regimen of a 300-mg loading dose (LD) and a 75-mg/day maintenance dose (MD) for 4 days followed by 600-mg LD and 150 mg/day MD, or vice versa. The exposure levels of clopidogrel's active metabolite H4 (clopi-H4) in PMs were 71% lower on the 75-mg/day regimen and 64% lower on the 150-mg/day regimen than the corresponding exposure levels in extensive metabolizers (EMs). In PMs, the maximal platelet aggregation (MPA) induced by adenosine diphosphate (ADP) 5 µmol/l was 10.5% lower on the 75-mg/day regimen and 7.9% lower on the 150-mg/day regimen than the corresponding values in EMs. PMs who were on the clopidogrel regimen of 600-mg LD/150 mg/day MD showed clopi-H4 exposure and MPA levels similar to those in EMs who were on the regimen of 300-mg LD/75 mg/day MD. In a pooled analysis evaluating CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP3A5, CYP2D6, ABCB1, and P2RY12 polymorphisms (N = 396 healthy subjects), only CYP2C19 had a significant impact on antiplatelet response. In healthy CYP2C19 PMs, a clopidogrel regimen of 600-mg LD/150 mg/day MD largely overcomes diminished clopi-H4 exposure and antiplatelet response, as assessed by MPA levels.