Besides CYP2C19*2, the variant allele CYP2C9*3 is associated with higher on-clopidogrel platelet reactivity in patients on dual antiplatelet therapy undergoing elective coronary stent implantation

Pharmacogenetic considerations in therapy with novel antiplatelet and anticoagulant agents

Antiplatelets and anticoagulants are extensively used in cardiovascular medicine for the prevention and treatment of thrombosis in the venous and arterial circulations. Wide inter-individual variability has been observed in response to antiplatelets and anticoagulants, which triggered researchers to investigate the genetic basis of this variability. Data from extensive pharmacogenetic studies pointed to strong evidence of association between polymorphisms in candidate genes and the pharmacokinetics and pharmacodynamic action and clinical response of the antiplatelets clopidogrel and the anticoagulant warfarin. In this review, we conducted an extensive search on Medline for the time period of 2009-2023. We also searched the PharmGKB website for levels of evidence of variant-drug combinations and for drug labels and clinical guidelines. We focus on the pharmacogenetics of novel antiplatelets and anticoagulants while excluding acetylsalicylic acid, warfarin and heparins, and discuss the current knowledge with emphasis on the level of evidence.

CYP2C9 Polymorphisms and the Risk of Cardiovascular Events in Patients Treated with Clopidogrel: Combined Data from the POPular Genetics and POPular AGE Trials

BACKGROUND

The cytochrome P450 (CYP) 2C9 enzyme plays a role in the metabolization of clopidogrel. Carriage of a CYP2C9 loss-of-function (LoF) allele has been associated with attenuated pharmacokinetics, leading to a diminished pharmacodynamic response and increased risk for developing stent thrombosis in patients treated with clopidogrel.

METHODS

In this study, we aimed to determine the effect of the CYP2C9*2 and *3 LoF alleles on thrombotic events. Therefore, a post hoc analysis was performed in 878 patients with available CYP2C9 genotype status included in the POPular Genetics and POPular Age trials, which enrolled patients with ST-elevation myocardial infarction and non-ST-elevation myocardial infarction, respectively. The primary thrombotic outcome was a composite of cardiovascular death, myocardial infarction or stroke.

RESULTS

A total of 526 (60%) patients were CYP2C9 LoF allele noncarriers and 352 (40%) were CYP2C9 LoF allele (*2 or *3) carriers. After correction for differences in baseline characteristics, there were no significant differences between CYP2C9 LoF allele carriers and noncarriers for the combined thrombotic outcome (6.3% vs. 5.9%, hazard ratio 1.16 [0.67-2.0], p = 0.60), or the individual thrombotic outcomes. Moreover, no differences were seen in the event rates for clinically relevant bleeding (Bleeding Academic Research Consortium [BARC] 2-5 bleeding) as well as major bleeding (BARC 3 or 5 bleeding).

CONCLUSIONS

Carriers of a CYP2C9 *2 or *3 LoF allele presenting with acute coronary syndrome and treated with clopidogrel did not have an increased risk for thrombotic events compared with noncarriers. Given the limited number of poor metabolizers, no firm conclusions could be drawn with regard to the thrombotic risk for patients carrying two CYP2C9 LoF alleles.

The efficacy of clopidogrel in preventing recurrent cardiovascular events among Arab population carrying different CYP2C19 mutations: systematic review and meta-analysis

Background

The prevalence and the role of CYP2C19 gene mutations concerning recurrent Cardiovascular Events (CVEs) among patients treated with clopidogrel is still controversial especially among Arab people. Therefore, this review aimed to determine the frequency of CYP2C19 polymorphic alleles among the Arab population and to investigate the efficacy of clopidogrel as an antiplatelet drug among those carrying different variants of this gene.

Methodology

Two authors independently searched in PubMed, Google Scholar, and EMBASE databases at any year for studies related to the role of CYP2C19 gene on the prognosis of patients with CVEs treated with clopidogrel. The review included Arab people who were genotyped to determine the frequency of CYP2C19 genotypes and alleles (the qualitative part). Concerning the quantitative part (meta-analysis), only patients who previously had CVEs and using clopidogrel as secondary prophylaxis had been included. The Newcastle Ottawa Scale for non-randomizes Studies was utilized to consider the risk of bias among included studies. We analyzed the data using odds ratio at 95% confidence interval and the quality of evidence of each outcome measure was judged using GRADE approach.

Results

The current study revealed that 4% of Arabs reported in the included studies are homozygous, and 25% are heterozygous for the CYP2C19*2 allele. While 3% and 18.5% of them are homozygous and heterozygous of CYP2C19*17 alleles, respectively. A significant increased risk of recurrent CVEs by about threefold was associated with CYP2C19*2 or CYP2C19*3 allele carriers (OR = 3.32, CI = 1.94–5.67, and OR = 3.53, CI = 1.17–10.63, respectively). However, no significant increased risk among carriers of CYP2C19*17 mutation (OR = 0.80, (CI = 0.44–1.44) was documented.

Conclusion

The present study revealed that Arabs carrying CYP2C19*2 and CYP2C19*3 alleles could be at increased risk of decreasing the antiplatelet efficacy of clopidogrel and an alternative drug should be prescribed for those patients to avoid recurrent CVEs. However, few available studies were included in the quantitative part of the analysis and further studies with large sample size are recommended to confirm our results.

Genotyping genetic variants of CYP2C19 for precision antiplatelet dosing: state of the art and future perspectives

INTRODUCTION

Clopidogrel is the only antiplatelet agent whose activity is significantly affected by CYP2C19 polymorphism.

AREAS COVERED

This review has summarized the available evidence on the clinically significant association between CYP2C19 polymorphism and clopidogrel-based therapy; reviewed the current recommendations for clinical use of CYP2C19 genotype test results in patients on clopidogrel treatment; and discussed possible pitfalls of routine application, and future perspectives of antiplatelets pharmacogenetics.

EXPERT OPINION

The available body of evidence, reflected in several meta-analyses and high-quality clinical practice guidelines, shows that the presence of CYP2C19 LOF alleles, especially CYP2C19*2, correlates with impaired activation of clopidogrel and variable platelet inhibition, followed by minimal or no antiplatelet effect, and higher risk of treatment failure. In combination with other known risk factors, CYP2C19 genetic testing could be very valuable in predicting low clopidogrel efficacy. At the same time, it could be very successful in selecting patients who will most probably benefit from the clopidogrel-based therapy, thus decreasing the pool of those who might need more expensive and otherwise riskier antiplatelet alternatives.

Sex Differences in Clopidogrel Effects Among Young Patients With Acute Coronary Syndrome: A Role for Genetics?

Background

Poorer health outcomes experienced by young women with acute coronary syndrome may be related to sex differences in the safety and efficacy of antiplatelet agents, such as clopidogrel. Polymorphisms in drug metabolism enzyme (cytochrome P450 [CYP] family) genes are independent factors for the variability in response to clopidogrel. However, a sex-specific impact of genetics to explain worse clinical outcomes in women has not been explored extensively. Therefore, our objective was to determine whether an interaction of sex with CYP variants occurs among users of clopidogrel, and if so, its impact on 1-year adverse clinical outcomes.

Methods

We used data from a combined cohort of 2272 patients (median age 49 years; 56% female) hospitalized for acute coronary syndrome. We examined interactions between sex and CYP variants among clopidogrel users at admission and discharge to assess associations with 1-year readmission due to cardiac events.

Results

The case-only analysis of 177 participants on clopidogrel at the time of presentation showed that the risk of an atherothrombotic event was greater in female carriers of the CYP2C9∗3 loss-of-function allele (odds ratio = 3.77, 95% confidence interval = 1.54-9.24). The results of the multivariable logistic regression model for users of clopidogrel at discharge (n = 1733) indicated that women had significantly higher risk of atherothrombotic readmissions at 1 year (odds ratio = 1.55, 95% confidence interval = 1.16-2.07), compared to the risk for men, but the loss-of-function alleles, either individually or through a genetic risk score, were not associated with 1-year readmissions.

Conclusion

This study highlights the need for an improved understanding of the role of sex-by-gene interactions in causing sex differences in drug metabolism.

Polymorphisms of genes related to phase II metabolism and resistance to clopidogrel

Clopidogrel is an antiplatelet drug commonly used to prevent coagulation. This review aimed to investigate the effect of polymorphisms of G6PD, GCLC, GCLM, GSS, GST, GSR, HK and GLRX genes on clopidogrel during phase II metabolism through exploring previous studies. The results revealed that low glutathione plasma levels caused by several alleles related to these genes could affect the bioactivation process of the clopidogrel prodrug, making it unable to inhibit platelet aggregation perfectly and thus leading to severe consequences in patients with a high risk of blood coagulation. However, the study recommends platelet reactivity tests to predict clopidogrel efficacy rather than studying gene mutations, as most of these mutations are rare and other nongenetic factors could affect the drug's efficacy.

Biomarkers for Antiplatelet Therapies in Acute Ischemic Stroke: A Clinical Review

Stroke is one of the world's leading causes of disability and death. Antiplatelet agents are administered to acute ischemic stroke patients as secondary prevention. Clopidogrel involves biotransformation by cytochrome P450 (CYP) enzymes into an active metabolite, and single nucleotide polymorphisms (SNPs) can influence the efficacy of this biotransformation. Despite the therapeutic advantages of aspirin, there is significant inter-individual heterogeneity in response to this antiplatelet drug. In this clinical review, the recent advances in the biomarkers of antiplatelet agents in acute ischemic stroke are discussed. The studies reviewed herein highlight the clinical relevance of antiplatelet resistance, pharmacotherapy of antiplatelet agents predicting drug response, strategies for identifying aspirin resistance, pharmacogenetic variants of antiplatelet agents, miRNAs, and extracellular vesicles (EVs) as biomarkers toward the personalized approach in the management of acute ischemic stroke. The precise pathways contributing to antiplatelet resistance are not very well known but are presumably multi-factorial. It is essential to understand the clinical relevance of clopidogrel and aspirin-related single nucleotide polymorphism (SNPs) as potential predictive and prognostic biomarkers. Prasugrel is a next-generation antiplatelet agent that prevents ADP-platelet activation by binding irreversibly to P2Y12 receptor. There are sporadic reports of prasugrel resistance and polymorphisms in the Platelet endothelial aggregation receptor-1 (PEAR1) that may contribute to a change in the pharmacodynamics response. Ticagrelor, a direct-acting P2Y12-receptor antagonist, is easily absorbed and partly metabolized to major AR-C124910XX metabolite (ARC). Ticagrelor's primary active metabolite, ARC124910XX (ARC), is formed via the most abundant hepatic cytochrome P450 (CYP) enzyme, CYP3A4, and CYP3A5. The integration of specific biomarkers, genotype as well as phenotype-related data in antiplatelet therapy stratification in patients with acute ischemic stroke will be of great clinical significance and could be used as a guiding tool for more effective, personalized therapy.

Polymorphisms of genes related to phase-I metabolic enzymes affecting the clinical efficacy and safety of clopidogrel treatment

Introduction: Clopidogrel is an antiplatelet medication described as a prodrug, which cannot exert the antiplatelet effect until being biotransformed to the active metabolite. It is commonly used to reduce the risk of blood coagulation in patients diagnosed with acute coronary syndrome, or ischemic stroke.Area covered: We reviewed published articles in PubMed and Google Scholar that focused on the mutations of CYP2C19, CYP3A4, CYP2C9, CYP2B6, and CYP1A2 genes related to clopidogrel clinical efficacy and safety.Expert opinion: Based on current pharmacogenetic studies, patients carrying CYP2C19*2, CYP2C19*3, CYP2C9*3, and CYP2B6*5 alleles may not respond to clopidogrel due to poor platelet inhibition efficacy revealed among them. In contrast, carriers of CYP2C19*17, CYP3A4*1G, and CYP1A2*1C alleles showed a more significant antiplatelet effect in clopidogrel users and expected to have a protective role as a genetic factor against cardiovascular events. Genotyping for either CYP2C19, CYP3A4, CYP2C9, CYP2B6, or CYP1A2 variants is not recommended when considering clopidogrel treatment for patients, as some trials showed specific non-genetic factors (e.g. age and diabetes) that could affect clopidogrel responsiveness. Instead, platelets inhibition tests could be used as predictors of the clinical efficacy of clopidogrel treatment. Other P2Y12 receptor inhibitors should be considered as alternative medications.

A Pharmacogenetic Study of CYP2C19 in Acute Coronary Syndrome Patients of Colombian Origin Reveals New Polymorphisms Potentially Related to Clopidogrel Therapy

Clopidogrel, an oral platelet P2Y₁₂ receptor blocker, is used in the treatment of acute coronary syndrome. Interindividual variability in treatment response and the occurrence of adverse effects has been attributed to genetic variants in CYP2C19. The analysis of relevant pharmacogenes in ethnically heterogeneous and poorly studied populations contributes to the implementation of personalized medicine. We analyzed the coding and regulatory regions of CYP2C19 in 166 patients with acute coronary syndrome (ACS) treated with clopidogrel. The allele frequencies of CYP2C19 alleles *1, *2, *4, *17, *27 and *33 alleles were 86.1%, 7.2%, 0.3%, 10.2%, 0.3% and 0.3%, respectively. A new potentially pathogenic mutation (p.L15H) and five intronic variants with potential splicing effects were detected. In 14.4% of the patients, a new haplotype in strong linkage disequilibrium was identified. The clinical outcome indicated that 13.5% of the patients presented adverse drugs reactions with a predominance of bleeding while 25% of these patients were carriers of at least one polymorphic allele. We propose that new regulatory single-nucleotide variants (SNVs) might potentially influence the response to clopidogrel in Colombian individuals.

Genetic polymorphisms of high platelet reactivity in Chinese patients with coronary heart disease under clopidogrel therapy

BACKGROUND

The variability in the clinical response to clopidogrel treatment has been attributed to genetic factors, but the specific genes and other risk factors remain unclear.

OBJECTIVE

To investigate the incidence of high on-treatment platelet reactivity in coronary heart disease patients following clopidogrel therapy by analyzing the correlation between genetic polymorphisms and high on-treatment platelet reactivity.

SETTING

This study was conducted in the Chinese People's Liberation Army (PLA) general hospital.

METHOD

578 patients with coronary heart disease undergoing percutaneous transluminal coronary intervention treatment were enrolled. They received dual antiplatelet therapy with aspirin (300 mg) plus clopidogrel (300 mg) over 24 h, or aspirin (100 mg/day) and clopidogrel (75 mg/day) over 3 days. Patients were divided into two groups according to the adenosine diphosphate inhibition rate. The follow-up lasted at least 12 months and adverse endpoint events were recorded.

MAIN OUTCOME MEASURE

The single nucleotide polymorphisms were detected by MassArray genotyping system.

RESULTS

The incidence of HTPR was 15.74% in total, being higher in females than in males (24.29% vs. 13.01%, P < 0.01). Diabetes mellitus, homocysteine and high sensitivity C-reactive protein (hs-CRP) levels were significantly higher in the HTPR group than those in the non-HTPR group (P < 0.05). Polymorphisms of rs1057910 (OR 2.90, P = 0.003), rs2246709 (OR 0.69, P = 0.039), and rs776746 (OR 0.66, P = 0.034) were associated with the incidence of high on-treatment platelet reactivity. Female patients were prone to polymorphisms of rs1057910 (OR 3.24, P = 0.004) and rs776746 (OR 0.57, P = 0.025). Compared to non-high on-treatment platelet reactivity group, no differences in high reactivity group were observed with coexisting single nucleotide polymorphisms (14.6% vs. 14.8%, P > 0.05). The adverse endpoint events were significantly higher in the high on-treatment platelet reactivity group than in the non-treatment reactivity group. The survival analysis showed that high on-treatment platelet reactivity was significantly associated with the risk of the endpoint events (P = 0.0219).

CONCLUSION

Gender (female), diabetes mellitus, high levels of homocysteine and hs-CRP were risk factors for high on-treatment platelet reactivity, and high reactivity was a strong predictor for adverse endpoint events in the coronary heart disease patients. The polymorphism of rs1057910 was a risk factor of high on-treatment platelet reactivity while rs2246709 and rs776746 polymorphisms were protective factors, and coexisting single nucleotide polymorphisms didn't increase the incidence of high on-treatment platelet reactivity.

MGB Block ARMS Real-Time PCR for Diagnosis of CYP2C19 Mutation in a Chinese Population

Background:

CYP2C19 is an important genetic factor modulating clopidogrel dose requirement.

Objective:

Therefore, a simple and economic genotyping method for predicting the clopidogrel dose of patients would be useful in clinical applications.

Methods:

In this study, the MGB blocker ARMS real-time PCR contained two forward primers, two MGB blockers and a common reverse primer have been used for CYP2C19*2, *3 and *17 substitutions.

Results:

Results showed that heterozygotes and homozygotes of CYP2C19*2, *3 and *17 could be distinguished by the MGB blocker ARMS real-time PCR successfully. In the Chinese population, patients with allele frequencies of CYP2C19*2, *3, and *17 are 18.43%, 3.03% and 0.76%, respectively.

Conclusion:

This study indicates that the MGB blocker ARMS real-time PCR will be a simple, economical method for the rapid detection of SNPs in CYP2C19.

Influence of CYP450 Enzymes, CES1, PON1, ABCB1, and P2RY12 Polymorphisms on Clopidogrel Response in Patients Subjected to a Percutaneous Neurointervention

PURPOSE

Clopidogrel is a thienopyridine prodrug that inhibits platelet aggregation. It is prescribed to prevent atherothrombotic and thromboembolic events in patients receiving a stent implant in carotid, vertebral, or cranial arteries. The influence of cytochrome P-450 (CYP) 2C19 on the response to clopidogrel has been widely studied; however, the effect of other genes involved in clopidogrel absorption and metabolism has not been established in this cohort of patients.

METHODS

This observational retrospective study assessed the antiplatelet response and the prevalence of hemorrhagic or ischemic events after percutaneous neurointervention in clopidogrel-treated patients, related to 35 polymorphisms in the genes encoding the clopidogrel-metabolizing enzymes (CYP2C19, CYP1A2, CYP2B6, CYP2C9, CYP2C9, CYP3A4, CYP3A5, carboxylesterase-1 [CES1], and paraoxonase-1 [PON1]), P-glycoprotein transporter (ABCB1), and platelet receptor P2Y₁₂. Polymorphisms were analyzed by quantitative real-time polymerase chain reaction and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. Antiplatelet response was documented with the VerifyNow system (Accriva, San Diego, California).

FINDINGS

We confirmed that CYP2C19 is the most important enzyme involved in clopidogrel response. The carriage of the CYP2C19*2 allele was strongly associated with hyporesponse to clopidogrel, while the CYP2C19*17 allele was a protective factor for the development of ischemic events (odds ratio = 0.149; P = 0.002) but a risk factor for bleeding (odds ratio = 3.60; P = 0.038). Patients carrying ABCB1 mutated alleles showed lower aggregation values, suggesting that clopidogrel absorption is influenced by P-glycoprotein. In fact, the percentage of responders was significantly higher in the group carrying the mutated haplotype compared to the wild type (80.8% vs 43.3%; P = 0.009). Patients with the CES1 G143E C/T genotype showed a considerably lower, aggregation value versus wild-type patients, although the difference was not significant likely due to the small sample size (59.0 [21.2] vs 165.2 [86.0] PRU; P = 0.084), which suggests an increased active metabolite formation. No relationship was found between polymorphisms in other CYP genes, PON1, or P2RY12 and response to clopidogrel in patients subjected to neurointervention procedures.

IMPLICATIONS

Therapeutic guidelines recommend that CYP2C19 intermediate and poor metabolizers with acute coronary syndromes undergoing percutaneous coronary intervention receive an alternative antiplatelet therapy; however, genotype-guided therapy is not a standard recommendation for neurovascular conditions. This is the first study to carry out a joint analysis of CYP2C19 and other genes involved in clopidogrel treatment in patients receiving percutaneous neurointervention. Our findings support routine genotyping in clopidogrel-treated patients. Moreover, we encourage considering an alternative antiplatelet therapy in CYP2C19 intermediate, poor and ultrarapid metabolizers. Additionally, ABCB1 polymorphisms could be considered for a better pharmacogenetic approach.

Genetic Determinants of P2Y12 Inhibitors and Clinical Implications

There is significant interpatient variability in clopidogrel effectiveness, which is due in part to cytochrome P450 (CYP) 2C19 genotype. Approximately 30% of individuals carry CYP2C19 loss-of-function alleles, which have been consistently shown to reduce clopidogrel effectiveness after an acute coronary syndrome and percutaneous coronary intervention. Guidelines recommend consideration of prasugrel or ticagrelor in these patients. A clinical trial examining outcomes with CYP2C19 genotype-guided antiplatelet therapy is ongoing. In the meantime, based on the evidence available to date, several institutions have started clinically implementing CYP2C19 genotyping to assist with antiplatelet selection after percutaneous coronary intervention.

The ABCB1, CYP2C19, CYP3A5 and CYP4F2 genetic polymorphisms and platelet reactivity in the early phases of acute coronary syndromes

Background

The aim was to study seven polymorphic markers of genes encoding proteins involved in the absorption, metabolism and pharmacokinetics of clopidogrel among patients with an acute coronary syndrome (ACS), who have undergone percutaneous coronary intervention (PCI).

Methods

Eighty-one ACS and PCI patients older than 18 years and treated with dual antiplatelet therapy were enrolled in the study. Platelet function testing and ABCB1, CYP2C19, CYP3A5 and CYP4F2 genotyping were performed. The predictive role of categorical variables, such as genotypes (carriers and non-carriers of polymorphism), on platelet reactivity (platelet reactivity units [PRU] platelet inhibition [PI]) was assessed by logistic regression (for categorical outcomes) and linear regression (for continuous outcomes) analysis. A p-value<0.05 was considered significant. The allele frequencies were estimated by gene counting, and Hardy-Weinberg equilibrium was tested using the chi-square test.

Results

Regarding clopidogrel response, 62 patients (76.5%) were clopidogrel responders and 19 were non-responders (23.5%). Mean PRU value and the percentage of platelet inhibition were 170.0±50.9 PRU and 28.6±19.9%, respectively. The effects of the CYP2C19*2 polymorphisms on PRU (166.0±50.8 vs. 190.7±48.2, p<0.038) and PI (30.6±20.0 vs. 18.1±16.3, p<0.013) were observed, and the rates of high platelet reactivity (HPR) were lower in CYP2C19*1/*1 than those in CYP2C19*1/*2+CYP2C19*2/*2 (16.2% vs. 53.8% p<0.0067). In comparison, no significant difference in PRU value and PI was observed at <5 days between the rest of polymorphisms (p>0.05). Based on the logistic regression analysis, CYP2C19*2 (OR: 4.365, CI: 1.25–17.67, p=0.022) was an independent predictor of HPR at <5 days, as was the stent diameter (OR: 0.219, CI: 0.002–0.229, p=0.049). The remaining polymorphisms had no influence.

Conclusions

The reactivity of the on-clopidogrel platelet in the early phase of ACS is influenced primarily by the CYP2C19 polymorphisms. We believe that the findings of the present study could supply additional evidence regarding the clinical appropriateness of the CYP2C19 genetic testing for designing suitable antiplatelet therapy in the early phase of ACS.

Influence of CYP2C19 Phenotype on the Effect of Clopidogrel in Patients Undergoing a Percutaneous Neurointervention Procedure

This observational retrospective study assessed the antiplatelet response and clinical events after clopidogrel treatment in patients who underwent percutaneous neurointervention, related to CYP2C19 metabolizer status (normal (NM), intermediate/poor (IM-PM), and ultrarapid (UM); inferred from *2, *3, and *17 allele determination). From 123 patients, IM-PM had a higher aggregation value (201.1 vs. 137.6 NM, 149.4 UM, P < 0.05) and lower response rate (37.5% vs. 69.8% NM, 61.1% UM), along with higher treatment change rate (25% vs. 5.7% NM, 10.5% UM). The highest ischemic events incidence occurred in NM (11.3% vs. 6.3% IM, 10.5% UM) and hemorrhagic events in UM (13.2% vs. 0% IM and 3.8% NM). No differences were found regarding ischemic event onset time, while hemorrhagic event frequency in UM was higher with shorter onset time (P = 0.047). CYP2C19 no-function and increased function alleles defined the clopidogrel response. UM patients had increased bleeding risk. Therapeutic recommendations should include dose reduction or treatment change in UM.

Role of genetic testing in patients undergoing percutaneous coronary intervention

INTRODUCTION

Variability in individual response profiles to antiplatelet therapy, in particular clopidogrel, is a well-established phenomenon. Genetic variations of the cytochrome P450 (CYP) 2C19 enzyme, a key determinant in clopidogrel metabolism, have been associated with clopidogrel response profiles. Moreover, the presence of a CYP2C19 loss-of-function allele is associated with an increased risk of atherothrombotic events among clopidogrel-treated patients undergoing percutaneous coronary interventions (PCI), prompting studies evaluating the use of genetic tests to identify patients who may be potential candidates for alternative platelet P2Y12 receptor inhibiting therapies (prasugrel or ticagrelor). Areas covered: The present manuscript provides an overview of genetic factors associated with response profiles to platelet P2Y12 receptor inhibitors and their clinical implications, as well as the most recent developments and future considerations on the role of genetic testing in patients undergoing PCI. Expert commentary: The availability of more user-friendly genetic tests has contributed towards the development of many ongoing clinical trials and personalized medicine programs for patients undergoing PCI. Results of pilot investigations have shown promising results, which however need to be confirmed in larger-scale studies to support the routine use of genetic testing as a strategy to personalize antiplatelet therapy and improve clinical outcomes.

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.

CYP2C19⁎2 Polymorphism in Chilean Patients with In-Stent Restenosis Development and Controls

Clopidogrel is an antiplatelet drug especially used in patients undergoing percutaneous coronary interventions (PCI). Polymorphisms within CYP2C19 can result in important interindividual variations regarding therapeutic efficacy. Therefore, we aimed to evaluate the impact of the CYP2C19^⁎2 variant (rs4244285) on in-stent restenosis occurrence in Chilean patients who underwent PCI and received clopidogrel. A total of 77 cases with stenosis >50% in the angioplasty site (62.75 ± 9.8 years, 80.5% males) and 86 controls (65.45 ± 9.8 years, 72.1% males) were studied. The polymorphism was genotyped using TaqMan® Drug Metabolism Genotyping Assays. Overall, CYP2C19^⁎2 allele frequency was 8.3%. Diabetes, chronic lesions, and bare metal stents (BMS) were observed more often in cases than in controls (p = 0.05, p = 0.04, and p = 0.02, resp.). Genotypic frequencies did not differ significantly between the groups (p = 0.15). Nonetheless, the mutated allele was observed in a greater proportion in patients without in-stent restenosis (p = 0.055). There was no significant association between the rs4244285 variant and the occurrence of in-stent restenosis after PCI (OR = 0.44; 95% CI: 0.19 to 1.04; p = 0.06). In summary, no association was identified between the CYP2C19^⁎2 variant and the development of coronary in-stent restenosis.

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.

Genotyping of six clopidogrel-metabolizing enzyme polymorphisms has a minor role in the assessment of platelet reactivity in patients with acute coronary syndrome

OBJECTIVE

To evaluate the contribution of six polymorphisms to the platelet reactivity in patients with acute coronary syndrome (ACS) treated with clopidogrel.

METHODS

Cross-sectional study of 278 consecutive patients with ACS. Detailed clinical information for each patient was collected and genotypes (CYP2C9*2, CYP2C9*3, CYP2C19*2, CYP2C19*17, CYP3A4*1B, and PON1-Q192R) were evaluated with TaqMan® and KASPar® assays. Platelet reactivity was measured with VerifyNow®.

RESULTS

Mean age of patients was 66±11 years and 182 (65.5%) patients presented ACS without ST-segment elevation. A total of 206 (74.1%) patients presented poor response to clopidogrel (PRC). CYP2C19*2 polymorphism (p=0.038) was associated with PRC in the univariate setting. In the multiple logistic regression analysis, the risk factors for PRC were the presence of CYP3A4*1B allele (odds ratio [OR] 4.03; 95% confidence interval [CI] 1.01-16.34), age (OR 1.43; 95% CI 1.03-2.00), and body mass index (OR 4.05; 95% CI 1.21-13.43), whereas elevated hemoglobin was a protective factor. Discrimination of PRC through the model that included the six polymorphisms added modest information to the model based on clinical variables (C statistic difference 3.9%).

CONCLUSION

CYP3A4*1B allele may be an independent determinant of PRC in patients with ACS, although the variability in response to clopidogrel explained by the six polymorphisms is poor when compared to clinical variables.

Potential Usefulness of Clopidogrel Pharmacogenetics in Cerebral Endovascular Procedures and Carotid Artery Stenting

BACKGROUND

Previous reports have shown inadequate response to dual antiplatelet therapy (DAPT) with aspirin and clopidogrel in 5-30% of patients undergoing percutaneous coronary interventions (PCI), due mostly to clopidogrel resistance. This prevalence increases up to 66% in patients undergoing neurointerventional procedures. However, clinical significance of CYP2C19 genotypes in neurointerventional procedures or carotid artery stenting (CAS) is unknown.

OBJECTIVE

The purpose of this review is to update our current knowledge and understanding of the pharmacogenetic basis for poor clopidogrel responsiveness in patients undergoing CAS and endovascular interventions as well as to explore usefulness of genotyping to reduce the rate of procedure-related thrombosis that results in ischemic complications.

METHOD

A literature search for pharmacogenetic studies in cerebral endovascular interventions and CAS was conducted on three databases using a list of the most relevant pharmacogenetic biomarkers.

RESULTS

The review included 7 papers involving 3 genetic polymorphisms on CYP2C19 and 442 subjects. Patients harboring at least one loss-of-function CYP2C19 polymorphism (e.g., CYP2C19*2 and *3) are at an increased risk of thromboembolic complications such as stent thrombosis following neurointerventional procedures. Notably, patients who carry the gain-of-function CYP2C19*17 allele may have increased risk of ischemic events following endovascular treatment, independent of clopidogrel responsiveness.

CONCLUSION

Studies assessing the influence of CYP2C19 polymorphisms on high on-treatment platelet reactivity in CAS and cerebrovascular disease patients are still limited and need further validation in large multicenter studies. This review covers an important topic in the field of antiplatelet therapy for cerebral endovascular procedures and CAS.

The pharmacogenetic control of antiplatelet response: candidate genes and CYP2C19

INTRODUCTION

Aspirin, clopidogrel, prasugrel and ticagrelor are antiplatelet agents for the prevention of ischemic events in patients with acute coronary syndromes (ACS), percutaneous coronary intervention (PCI) and other indications. Variability in response is observed to different degrees with these agents, which can translate to increased risks for adverse cardiovascular events. As such, potential pharmacogenetic determinants of antiplatelet pharmacokinetics, pharmacodynamics and clinical outcomes have been actively studied.

AREAS COVERED

This article provides an overview of the available antiplatelet pharmacogenetics literature. Evidence supporting the significance of candidate genes and their potential influence on antiplatelet response and clinical outcomes are summarized and evaluated. Additional focus is directed at CYP2C19 and clopidogrel response, including the availability of clinical testing and genotype-directed antiplatelet therapy.

EXPERT OPINION

The reported aspirin response candidate genes have not been adequately replicated and few candidate genes have thus far been implicated in prasugrel or ticagrelor response. However, abundant data support the clinical validity of CYP2C19 and clopidogrel response variability among ACS/PCI patients. Although limited prospective trial data are available to support the utility of routine CYP2C19 testing, the increased risks for reduced clopidogrel efficacy among ACS/PCI patients that carry CYP2C19 loss-of-function alleles should be considered when genotype results are available.

Clinical implications of neuropharmacogenetics

INTRODUCTION

Pharmacogenetics aims to identify the underlying genetic factors participating in the variability of drug response. Indeed, genetic variability at the DNA or RNA levels can directly or indirectly modify the pharmacokinetic or the pharmacodynamic parameters of a drug. The ultimate aim of pharmacogenetics is to move towards a personalised medicine by predicting responders and non-responders, adjusting the dose of the treatment, and identifying individuals at risk of adverse drug effects.

METHODS

A literature research was performed in which we reviewed all pharmacogenetic studies in neurological disorders including neurodegenerative diseases, multiple sclerosis, stroke and epilepsy.

RESULTS

Several pharmacogenetic studies have been performed in neurology, bringing insights into the inter-individual drug response variability and in the pathophysiology of neurological diseases. The principal implications of these studies for the management of patients in clinical practice are discussed.

CONCLUSION/DISCUSSION

Although several genetic factors have been identified in the modification of drug response in neurological disorders, most of them have a marginal predictive effect at the single gene level, suggesting mutagenic interactions as well as other factors related to drug interaction and disease subtypes. Most pharmacogenetic studies deserve further replication in independent populations and, ideally, in pharmacogenetic clinical trials to demonstrate their relevance in clinical practice.

Pharmacogenomics of oral antiplatelet drugs

Pharmacogenomics has been implicated in the response variability of antiplatelet drugs in coronary artery disease (CAD), particularly for aspirin and clopidogrel. A large number of studies and several meta-analyses have been published on this topic, but until recently, there have been no clear conclusions and no definite guidelines on the clinical use of pharmacogenetic testing before prescribing antiplatelet drugs for CAD. In this review, the available evidence is summarized. The most consistent results are on clopidogrel, where CYP2C19 loss-of-function alleles are associated with stent thrombosis events. We recommend to genotype for CYP2C19 loss-of-function alleles in patients with CAD who are to undergo percutaneous coronary intervention and stenting, and to adjust the antiplatelet treatment based on the genotyping results.

Pharmacokinetic drug interactions with clopidogrel: updated review and risk management in combination therapy

Background

Coprescribing of clopidogrel and other drugs is common. Available reviews have addressed the drug–drug interactions (DDIs) when clopidogrel is as an object drug, or focused on combination use of clopidogrel and a special class of drugs. Clinicians may still be ignorant of those DDIs when clopidogrel is a precipitant drug, the factors determining the degree of DDIs, and corresponding risk management.

Methods

A literature search was performed using PubMed, MEDLINE, Web of Science, and the Cochrane Library to analyze the pharmacokinetic DDIs of clopidogrel and new P2Y₁₂ receptor inhibitors.

Results

Clopidogrel affects the pharmacokinetics of cerivastatin, repaglinide, ferulic acid, sibutramine, efavirenz, and omeprazole. Low efficacy of clopidogrel is anticipated in the presence of omeprazole, esomeprazole, morphine, grapefruit juice, scutellarin, fluoxetine, azole antifungals, calcium channel blockers, sulfonylureas, and ritonavir. Augmented antiplatelet effects are anticipated when clopidogrel is coprescribed with aspirin, curcumin, cyclosporin, St John’s wort, rifampicin, and angiotensin-converting enzyme inhibitors. The factors determining the degree of DDIs with clopidogrel include genetic status (eg, cytochrome P540 [CYP]2B6*6, CYP2C19 polymorphism, CYP3A5*3, CYP3A4*1G, and CYP1A2-163C.A), species differences, and dose strength. The DDI risk does not exhibit a class effect, eg, the effects of clopidogrel on cerivastatin versus other statins, the effects of proton pump inhibitors on clopidogrel (omeprazole, esomeprazole versus pantoprazole, rabeprazole), the effects of rifampicin on clopidogrel versus ticagrelor and prasugrel, and the effects of calcium channel blockers on clopidogrel (amlodipine versus P-glycoprotein-inhibiting calcium channel blockers). The mechanism of the DDIs with clopidogrel involves modulating CYP enzymes (eg, CYP2B6, CYP2C8, CYP2C19, and CYP3A4), paraoxonase-1, hepatic carboxylesterase 1, P-glycoprotein, and organic anion transporter family member 1B1.

Conclusion

Effective and safe clopidogrel combination therapy can be achieved by increasing the awareness of potential changes in efficacy and toxicity, rationally selecting alternatives, tailoring drug therapy based on genotype, checking the appropriateness of physician orders, and performing therapeutic monitoring.

Personalized antiplatelet and anticoagulation therapy: applications and significance of pharmacogenomics

In recent years, substantial effort has been made to better understand the influence of genetic factors on the efficacy and safety of numerous medications. These investigations suggest that the use of pharmacogenetic data to inform physician decision-making has great potential to enhance patient care by reducing on-treatment clinical events, adverse drug reactions, and health care-related costs. In fact, integration of such information into the clinical setting may be particularly applicable for antiplatelet and anticoagulation therapeutics, given the increasing body of evidence implicating genetic variation in variable drug response. In this review, we summarize currently available pharmacogenetic information for the most commonly used antiplatelet (ie, clopidogrel and aspirin) and anticoagulation (ie, warfarin) medications. Furthermore, we highlight the currently known role of genetic variability in response to next-generation antiplatelet (prasugrel and ticagrelor) and anticoagulant (dabigatran) agents. While compelling evidence suggests that genetic variants are important determinants of antiplatelet and anticoagulation therapy response, significant barriers to clinical implementation of pharmacogenetic testing exist and are described herein. In addition, we briefly discuss development of new diagnostic targets and therapeutic strategies as well as implications for enhanced patient care. In conclusion, pharmacogenetic testing can provide important information to assist clinicians with prescribing the most personalized and effective antiplatelet and anticoagulation therapy. However, several factors may limit its usefulness and should be considered.

Genetic polymorphisms of CYP2C19 2 and ABCB1 C3435T affect the pharmacokinetic and pharmacodynamic responses to clopidogrel in 401 patients with acute coronary syndrome

BACKGROUNDS AND OBJECTIVES

Clopidogrel, an inhibitor of platelet ADP P2Y12 receptors, plays an important role in the prevention of stent thrombosis. However, some patients do not attain adequate antiplatelet effects. Studies have shown that the genetic variation in CYP2C19*2 is associated with an impaired response to clopidogrel. This study was designed to investigate the genetic variants of 21 genes involving in the absorption, metabolism, and pharmacodynamics of clopidogrel. The effects of these genes on the plasma level of clopidogrel and its metabolites (active clopi-H4 and inactive CLPM) and platelet reactivity were also studied.

METHODS AND RESULTS

401 acute coronary syndrome (ACS) patients received either a 300 mg loading dose following 75 mg maintenance dose daily or a 75mg maintenance dose daily of clopidogrel. The inhibition of platelets was assessed using light transmittance aggregometry. Plasma concentrations of clopidogrel as well as its active (clopi-H4) and inactive (CLPM) metabolites were measured using HPLC-MS-MS method. Among 21 genes, the carriers of CYP2C19*2 were associated with lower exposure to its active (clopi-H4) and inactive (CLPM) metabolites (both P<0.05 vs. non-carriers) and thus decreased platelet inhibition (P<0.05 vs. non-carriers). Notably, the carriers of ABCB1 C3435T were associated with lower levels of plasma clopidogrel and its active (clopi-H4) and inactive (CLPM) metabolites (all P<0.05 vs. non-carriers) which also correlated with subsequently decreased platelet inhibition (P<0.05 vs. non-carriers). There were no obvious effects of other studied genes on clopidogrel.

CONCLUSIONS

CYP2C19*2 is a determinant for the formation of the active metabolite of clopidogrel and its antiplatelet effects. Meanwhile, ABCB1 C3435T plays an important role in intestinal absorption of clopidogrel which further affects the exposure to the active metabolite of clopidogrel and platelet aggregation.

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.

Individualization of drug therapy in older people

Older people are high consumers of prescription drugs and are at increasing risk of polypharmacy and adverse reactions. Pharmacokinetic and pharmacodynamic modifications due to age and co-morbidities are an important consideration, but pharmacological background evidence to guide safe and effective therapeutic approaches are often inadequate since the older population is under-represented in clinical trials. We review the pharmacokinetic and pharmacodynamic changes that are characteristic in old age and consider evidence regarding potentially safer prescription and monitoring of drugs commonly used in older patients. We also introduce the possible role of pharmacogenomics and therapeutic drug monitoring as tools to guide the individualization of drug therapy.

[Cardiovascular pharmacogenomics]

Cardiovascular disease remains a major cause of morbidity and mortality worldwide. Current medical practice takes into account information based on population studies and benefits observed in large populations or cohorts. However, individual patients present great differences in both toxicity and clinical efficacy that can be explained by variations in adherence, unknown drug to drug interactions and genetic variability. The latter seems to explain from 20% up to 95% of patient to patient variability. Treating patients with cardiovascular disorders faces the clinician with the challenge to include genomic analysis into daily practice. There are several examples within cardiovascular disease of treatments that can vary in toxicity or clinical usefulness based on genetic changes. One of the main factors affecting the efficacy of Clopidogrel is the phenotype associated with polymorphisms in the gene CYP 2C9. Furthermore, regarding oral anticoagulants, changes in CYP2C9 and VKORC1 play an important role in changing the clinical response to anticoagulation. When analyzing statin treatment, one of their main toxicities (myopathy) can be predicted by the SLCO1B1 polymorphism. The potential for prediction of toxicity and clinical efficacy from the use of genetic analysis warrants further studies aiming towards its inclusion in daily clinical practice.

Pharmacogenomics and cardiovascular disease

Variability in drug responsiveness is a sine qua non of modern therapeutics, and the contribution of genomic variation is increasingly recognized. Investigating the genomic basis for variable responses to cardiovascular therapies has been a model for pharmacogenomics in general and has established critical pathways and specific loci modulating therapeutic responses to commonly used drugs such as clopidogrel, warfarin, and statins. In addition, genomic approaches have defined mechanisms and genetic variants underlying important toxicities with these and other drugs. These findings have not only resulted in changes to the product labels but also have led to development of initial clinical guidelines that consider how to facilitate incorporating genetic information to the bedside. This review summarizes the state of knowledge in cardiovascular pharmacogenomics and considers how variants described to date might be deployed in clinical decision making.

Pharmacogenomics of anti-platelet and anti-coagulation therapy

Arterial thrombosis is a major component of vascular disease, especially myocardial infarction (MI) and stroke. Current anti-thrombotic therapies such as warfarin and clopidogrel are effective in inhibiting cardiovascular events; however, there is great inter-individual variability in response to these medications. In recent years, it has been recognized that genetic factors play a significant role in drug response, and, subsequently, common variants in genes responsible for metabolism and drug action have been identified. These discoveries along with new diagnostic targets and therapeutic strategies hold promise for more effective individualized anti-coagulation and anti-platelet therapy.

Pharmacogenomics in cardiovascular disease: focus on aspirin and ADP receptor antagonists

Antiplatelet agents like aspirin and adenosine diphosphate receptor antagonists are effective in reducing recurrent ischemic events. Considerable inter-individual variability in the platelet inhibition obtained with these drugs has initiated a search for explanatory mechanisms and ways to improve treatment. In recent years, numerous genetic polymorphisms have been linked with reduced platelet inhibition and lack of clinical efficacy of antiplatelet drugs, particularly clopidogrel and aspirin. Consequently, attempts to adjust antiplatelet treatment according to genotype have been made, but the clinical benefit has been modest in studies performed so far. The progress in genome science over the last decade and the declining cost of sequencing technologies hold the promise of enabling genetically tailored antiplatelet therapy. However, more evidence is needed to clarify which polymorphisms may serve as targets to improve treatment. The present review outlines the panel of polymorphisms affecting the benefit of aspirin and adenosine diphosphate receptor antagonists, including novel and ongoing studies evaluating whether genotyping may be beneficial in tailoring antiplatelet therapy.

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 variation of platelet function and pharmacology: an update of current knowledge

Platelets are critically involved in atherosclerosis and acute thrombosis. The platelet phenotype shows a wide variability documented by the inherited difference of platelet reactivity, platelet volume and count and function of platelet surface receptors. Several candidate genes have been put into focus and investigated for their functional and prognostic role in healthy individuals and patients with cardiovascular (CV) disease treated with antiplatelet agents. In addition to genetic variation, other clinical, disease-related and demographic factors are important so-called non-genetic factors. Due to the small effect sizes of single nucleotide polymorphisms (SNP) in candidate genes and due to the low allele frequencies of functional relevant candidate SNPs, the identification of genetic risk factors with high predictive values generally depends on the sample size of study cohorts. In the post-genome era new array and bioinformatic technologies facilitate high throughput genome-wide association studies (GWAS) for the identification of novel candidate genes in large cardiovascular cohorts. One of the crucial aspects of platelet genomic studies is the precise definition of a specific clinical phenotype (e.g. stent thrombosis) as this will impact importantly the findings of genomic studies like GWAS. Here, we provide an update on genetic variation of platelet receptors and drug metabolising enzymes under specific consideration of data derived by GWAS. The potential impact of this information and the role in personalised therapeutic concepts will be discussed.

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.

Genetic polymorphisms and drug interactions leading to clopidogrel resistance: why the Asian population requires special attention

Ischemic heart disease and stroke are the two leading causes of death worldwide. Antiplatelet therapy plays the most significant role in the management of these cardiovascular and cerebrovascular occlusive events to prevent recurrent ischemic attack. Clopidogrel, an antiplatelet drug, is widely prescribed either alone or in combination with aspirin as dual antiplatelet therapy for the prevention of vascular occlusive events. The antiplatelet response to clopidogrel varies widely. Hyporesponders and nonresponders are likely to have adverse cardiovascular events during follow-up. Some drugs, such as proton pump inhibitors (omeprazole), calcium channel blockers, selective serotonin reuptake inhibitors (nefazadone), coumarin derivatives (phenprocoumon), benzodiazepines, sulfonylurea, erythromycin, and itraconazole, decrease the antiplatelet effect of clopidogrel when administered concomitantly. Decreased response to clopidogrel is common among Asians due to genetic polymorphisms associated with clopidogrel resistance, and it is nearly 70% in some of the Asian communities. It is necessary to study Asian populations, because there are a large number of Asians throughout the world due to increased migration. Current guidelines do not make genetic testing or platelet response testing mandatory prior to clopidogrel prescription. Therefore, it is important for clinicians treating Asian patients to keep in mind the interindividual variability in response to clopidogrel when prescribing the drug.

Genetic determinants of response to cardiovascular drugs

PURPOSE OF REVIEW

To survey genetic variation contributing to variable responsiveness and toxicity to important cardiovascular drugs and highlight recent developments in the field of cardiovascular pharmacogenomics and personalized medicine.

RECENT FINDINGS

Previously recognized pharmacogenomic associations with drug efficacy have been further validated (e.g. with clopidogrel and warfarin) and shown to influence clinically important outcomes. The clinical significance of variants modulating toxicity (e.g. SLCO1B1 with simvastatin) has also been confirmed. The genetic contribution to variable efficacy and toxicity of other important classes of cardiovascular drugs, such as beta-blockers, is becoming increasingly recognized. Prospective trials testing whether the use of genomic information improves clinical care are underway. Guidance based on the most well-established pharmacogenomic findings has appeared in prescribing labeling and is in the early stages of being implemented into routine clinical care.

SUMMARY

Clinically validated gene variants that modulate responsiveness to cardiovascular drugs continue to be discovered and validated. Early steps are underway to translate these discoveries into clinical care.