Reduced Clopidogrel Metabolism in a Multiethnic Population: Prevalence and Rates of Recurrent Cerebrovascular Events

Impact of CYP2C19 Genotype on Efficacy and Safety of Clopidogrel-based Antiplatelet Therapy in Stroke or Transient Ischemic Attack Patients: An Updated Systematic Review and Meta-analysis of Non-East Asian Studies

PURPOSE

Inconclusive and limited results have been reported on the clinical utility of CYP2C19 genotyping in stroke/TIA patients of non-East Asian ancestries. We herein performed an updated systematic review and meta-analysis to quantitatively estimate the association of CYP2C19 loss-of function (LOF) status with efficacy and safety of clopidogrel-based antiplatelet therapy in non-East Asian patients affected by stroke or TIA.

METHODS

A comprehensive search was performed up to July 2023 using PubMed, Web of Knowledge, and Cochrane Library databases. The clinical outcomes investigated were stroke, composite vascular events and bleeding. Pooled estimates were calculated as risk ratios (RR) with 95% CI using the Mantel- Haenszel random-effects model. The quality of evidence was assessed using the GRADEpro tool.

RESULTS

A total number of 1673 stroke/TIA patients from 8 non-East Asian studies, published between 2014 and 2022, were included in the systematic review. Clopidogrel-treated carriers of CYP2C19 LOF alleles were found at increased risk of stroke compared to non-carriers (RR: 1.68, 95%CI: 1.04-2.71, P = 0.03). However, no significant association was observed with the risk of composite vascular events (RR: 1.15, 95%CI: 0.58-2.28, P = 0.69) or bleeding (RR: 0.84, 95%CI: 0.38-1.86, P = 0.67). Similarly, European ancestry patients carrying CYP2C19 LOF alleles displayed a higher risk of stroke (RR: 2.69 (1.11-6.51, P = 0.03), but not of composite vascular events or bleeding.

CONCLUSION

The present updated meta-analysis provides moderate quality evidence of association between CYP2C19 LOF alleles and an increased risk of stroke in non-East Asian patients with stroke/TIA after receiving clopidogrel therapy. Further large pharmacogenetic studies are still warranted to corroborate these findings.

Impact of CYP2C19 Genotype Status on Clinical Outcomes in Patients with Symptomatic Coronary Artery Disease, Stroke, and Peripheral Arterial Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Clopidogrel is widely used for the secondary prevention of atherothrombotic events in patients with coronary artery disease (CAD), ischemic stroke, and peripheral arterial disease (PAD). CYP2C19 plays a pivotal role in the conversion of clopidogrel to its active metabolite. Clopidogrel-treated carriers of a CYP2C19 loss-of-function allele (LOF) may have a higher risk of new atherothrombotic events. Previous studies on genotype-guided treatment were mainly performed in CAD and showed mixed results.

PURPOSE

To simultaneously investigate the impact of CYP2C19 genotype status on the rate of atherothrombotic events in the most common types of atherosclerotic disease (CAD, stroke, PAD).

METHODS

A comprehensive search in Pubmed, EMBASE, and MEDLINE from their inception to July 23rd 2023 was performed. Randomized controlled trials (RCTs) comparing genotype-guided and standard antithrombotic treatment, and cohort studies and post hoc analyses of RCTs concerning the association between CYP2C19 genotype status and clinical outcomes in clopidogrel-treated patients were included. The primary efficacy endpoint was major adverse cardiovascular events (MACE) and the safety end point major bleeding. Secondary endpoints were myocardial infarction, stent thrombosis, and ischemic stroke.

RESULTS

Forty-four studies were identified: 11 studies on CAD, 29 studies on stroke, and 4 studies on PAD. In CAD, genotype-guided therapy significantly reduced the risk of MACE [risk ratio (RR) 0.60, 95% confidence interval (CI) 0.43-0.83], myocardial infarction (RR 0.53, 95% CI 0.42-0.68), and stent thrombosis (RR 0.64, 95% CI 0.43-0.94), compared with standard antithrombotic treatment. The rate of major bleeding did not differ significantly (RR 0.93, 95% CI 0.70-1.23). Most RCTs were performed in patients after percutaneous coronary intervention (9/11). In stroke, LOF carriers had a significantly higher risk of MACE (RR 1.61, 95% CI 1.25-2.08) and recurrent ischemic stroke (RR 1.89, 95% CI 1.48-2.40) compared with non-carriers. No significant differences were found in major bleeding (RR 0.90, 95% CI 0.43-1.89). In the 6955 patients with symptomatic PAD treated with clopidogrel in the EUCLID trial, no differences in MACE or major bleeding were found between LOF carriers and non-carriers. In three smaller studies on patients with PAD treated with clopidogrel after endovascular therapy, CYP2C19 genotype status was significantly associated with atherothrombotic events.

CONCLUSIONS

Genotype-guided treatment significantly decreased the rate of atherothrombotic events in patients with CAD, especially after PCI. In patients with history of stroke, LOF carriers treated with clopidogrel had a higher risk of MACE and recurrent stroke. The available evidence in PAD with regard to major adverse limb events is too limited to draw meaningful conclusions.

REGISTRATION

PROSPERO identifier no. CRD42020220284.

Clinical and cost-effectiveness of clopidogrel resistance genotype testing after ischaemic stroke or transient ischaemic attack: a systematic review and economic model

Background

Stroke or transient ischaemic attack patients are at increased risk of secondary vascular events. Antiplatelet medications, most commonly clopidogrel, are prescribed to reduce this risk. Factors including CYP2C19 genetic variants can hinder clopidogrel metabolism. Laboratory-based or point-of-care tests can detect these variants, enabling targeted treatment.

Objective

To assess the effectiveness of genetic testing to identify clopidogrel resistance in people with ischaemic stroke or transient ischaemic attack. Specific objectives: Do people tested for clopidogrel resistance, and treated accordingly, have a reduced risk of secondary vascular events? Do people with loss-of-function alleles associated with clopidogrel resistance have a reduced risk of secondary vascular events if treated with alternative interventions compared to clopidogrel? Do people with loss-of-function alleles associated with clopidogrel resistance have an increased risk of secondary vascular events when treated with clopidogrel? What is the accuracy of point-of-care tests for detecting variants associated with clopidogrel resistance? What is the technical performance and cost of CYP2C19 genetic tests? Is genetic testing for clopidogrel resistance cost-effective compared with no testing?

Design

Systematic review and economic model.

Results

Objective 1: Two studies assessed secondary vascular events in patients tested for loss-of-function alleles and treated accordingly. They found a reduced risk, but confidence intervals were wide (hazard ratio 0.50, 95% confidence interval 0.09 to 2.74 and hazard ratio 0.53, 95% confidence interval 0.24 to 1.18). Objective 2: Seven randomised controlled trials compared clopidogrel with alternative treatment in people with genetic variants. Ticagrelor was associated with a lower risk of secondary vascular events than clopidogrel (summary hazard ratio 0.76, 95% confidence interval 0.65 to 0.90; two studies). Objective 3: Twenty-five studies compared outcomes in people with and without genetic variants treated with clopidogrel. People with genetic variants were at an increased risk of secondary vascular events (hazard ratio 1.72, 95% confidence interval 1.43 to 2.08; 18 studies). There was no difference in bleeding risk (hazard ratio 0.98, 95% confidence interval 0.68 to 1.40; five studies). Objective 4: Eleven studies evaluated Genomadix Cube accuracy; no studies evaluated Genedrive. Summary sensitivity and specificity against laboratory reference standards were both 100% (95% confidence interval 94% to 100% and 99% to 100%). Objective 5: Seventeen studies evaluated technical performance of point-of-care tests. Test failure rate ranged from 0.4% to 19% for Genomadix Cube. A survey of 8/10 genomic laboratory hubs revealed variation in preferred technologies for testing, and cost per test ranging from £15 to £250. Most laboratories expected test failure rate to be < 1%. Additional resources could enhance testing capacity and expedite turnaround times. Objective 6: Laboratory and point-of-care CYP2C19 testing strategies were cost-saving and increase quality-adjusted life-years compared with no testing. Both strategies gave similar costs, quality-adjusted life-years and expected net monetary benefit.

Conclusions

Our results suggest that CYP2C19 testing followed by tailored treatment is likely to be effective and cost-effective in both populations.

Future work

Accuracy and technical performance of Genedrive. Test failure rate of Genomadix Cube in a National Health Service setting. Value of testing additional loss-of-function alleles. Appropriateness of treatment dichotomy based on loss-of-function alleles.

Limitations

Lack of data on Genedrive. No randomised 'test-and-treat' studies of dipyramidole plus aspirin.

Study registration

This study is registered as PROSPERO CRD42022357661.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Evidence Synthesis programme (NIHR award ref: NIHR135620) and is published in full in Health Technology Assessment; Vol. 28, No. 57. See the NIHR Funding and Awards website for further award information.

CYP2C19 Genetic Testing for Oral P2Y12 Inhibitor Therapy: A Scientific Statement From the American Heart Association

There is significant variability in the efficacy and safety of oral P2Y12 inhibitors, which are used to prevent ischemic outcomes in common diseases such as coronary and peripheral arterial disease and stroke. Clopidogrel, a prodrug, is the most used oral P2Y12 inhibitor and is activated primarily after being metabolized by a highly polymorphic hepatic cytochrome CYP2C219 enzyme. Loss-of-function genetic variants in CYP2C219 are common, can result in decreased active metabolite levels and increased on-treatment platelet aggregation, and are associated with increased ischemic events on clopidogrel therapy. Such patients can be identified by CYP2C19 genetic testing and can be treated with alternative therapy. Conversely, universal use of potent oral P2Y12 inhibitors such as ticagrelor or prasugrel, which are not dependent on CYP2C19 for activation, has been recommended but can result in increased bleeding. Recent clinical trials and meta-analyses have demonstrated that a precision medicine approach in which loss-of-function carriers are prescribed ticagrelor or prasugrel and noncarriers are prescribed clopidogrel results in reducing ischemic events without increasing bleeding risk. The evidence to date supports CYP2C19 genetic testing before oral P2Y12 inhibitors are prescribed in patients with acute coronary syndromes or percutaneous coronary intervention. Clinical implementation of such genetic testing will depend on among multiple factors: rapid availability of results or adoption of the concept of performing preemptive genetic testing, provision of easy-to-understand results with therapeutic recommendations, and seamless integration in the electronic health record.

The association of CYP2C19 LoF alleles with adverse clinical outcomes in stroke patients taking clopidogrel: An updated meta-analysis

The aggregated risk of recurrent stroke in stroke/transient ischemic attack (TIA) patients carrying CYP2C19 LoF alleles who take clopidogrel has not been investigated recently, and the available research is limited. This study aimed to perform an updated meta-analysis to assess the association between CYP2C19 LoF alleles and the risk of recurrent stroke in patients taking clopidogrel. Databases were searched for the literature on eligible studies. The end points were recurrent stroke, composite vascular events, and bleeding events. Odds ratios (ORs) were calculated using RevMan software, where p < 0.05 was considered statistically significant. Patients carrying CYP2C19 LoF alleles who were treated with clopidogrel had a significantly increased risk of recurrent ischemic stroke compared with non-carriers (OR 2.18, 96% CI 1.80-2.63; p < 0.00001). The risk of recurrent stroke was only significantly different in Asian patients (OR 2.29, 96% CI 1.88-2.80; p < 0.00001) but not in patients of other ethnicities; however, there were a limited number of studies in other ethnic groups. Both observational studies (OR 2.83, 96% CI 2.20-3.65; p < 0.00001) and RCTs (OR 1.48, 96% CI 1.10-1.98; p = 0.009) found associations with a significantly increased risk of recurrent ischemic stroke. Asian stroke patients or TIA patients carrying CYP2C19 LoF alleles and taking clopidogrel were at a significantly higher risk of recurrent ischemic stroke than non-carriers. Significantly increased risk of recurrent ischemic stroke was found in both observational studies and RCTs.

The Frequency of CYP2C19 Loss-of-Function Variants in Patients with Non-Cardioembolic Ischemic Stroke or Transient Ischemic Attack in the Dutch Population

INTRODUCTION

The CYP2C19 enzyme converts clopidogrel into an active metabolite. Carriers of CYP2C19 loss-of-function (LOF) variants with a history of ischemic stroke or transient ischemic attack (TIA) using clopidogrel may have a higher risk of recurrent stroke. To study the implications of genetic CYP2C19 heterogeneity in treatment of cerebral ischemia, knowledge about the prevalence of CYP2C19 LOF variants within the population is important. We investigated the frequency of CYP2C19 LOF variants in patients with non-cardioembolic ischemic stroke or TIA in the Dutch population.

METHODS

We performed a single-center observational study with a cross-sectional design in a Dutch thrombectomy-capable stroke center. We included all patients presenting with non-cardioembolic ischemic stroke or TIA. We determined the frequency of CYP2C19 LOF variants in the full cohort. Additionally, we compared the frequency of CYP2C19 LOF variants in two subgroups: patients with first-ever non-cardioembolic ischemic stroke or TIA versus patients with recurrent ischemic stroke or TIA using clopidogrel because of a history of ischemic stroke or TIA.

RESULTS

We enrolled 410 patients between January 1, 2021, and July 1, 2021. 109 (26.6%) patients were carriers of CYP2C19 LOF variants. We found no difference in the frequency of CYP2C19 LOF variants between patients with first-ever ischemic stroke or TIA versus patients with recurrent ischemic stroke or TIA using clopidogrel (25.9 vs. 31.9%, respectively, p = 0.31).

DISCUSSION AND CONCLUSION

About a quarter of patients with non-cardioembolic ischemic stroke or TIA in the Dutch population carry a CYP2C19 LOF variant. This is lower than estimates found in studies with Asian populations but similar to estimates found among Caucasian patients in other parts of the world.

The role of CYP2C19 genotyping to guide antiplatelet therapy following ischemic stroke or transient ischemic attack

Introduction

Clopidogrel is an antiplatelet agent recommended for secondary prevention of ischemic stroke (IS) and transient ischemic attack (TIA). Conversion of clopidogrel to its active metabolite by hepatic cytochrome P450-2C19 (CYP2C19) is essential for the inhibition of the P2Y12 receptor and subsequent platelet aggregation to prevent thrombotic events. CYP2C19 is highly polymorphic, with over 30 loss of function (LoF) alleles. This review considers whether there is sufficient data to support genotype guided antiplatelet therapy after stroke.

Areas covered

A systematic literature review retrieved articles, which describe the interaction between CYP2C19 genotype and clinical outcomes following IS or TIA when treated with clopidogrel. The review documents efforts to identify optimal antiplatelet regimens and explores the value genotype guided antiplatelet therapy. The work outlines the contemporary understanding of clopidogrel metabolism and appraises evidence linking CYP2C19 LoF variants with attenuated platelet inhibition and poorer outcomes.

Expert opinion

There is good evidence that CYP2C19 LoF allele carriers of Han-Chinese ancestry have increased risk for further vascular events following TIA or IS when treated with clopidogrel. The evidence base is less certain in other populations. The expansion of pharmacogenetics into routine clinical practice will facilitate further research and help tailor other aspects of secondary prevention.

Risk of stroke in CYP2C19 LoF polymorphism carrier coronary artery disease patients undergoing clopidogrel therapy: An ethnicity-based updated meta-analysis

BACKGROUND

Antiplatelet agent clopidogrel has been widely used for stroke management for many years, although resistance to clopidogrel may increase the chance of stroke recurrence. CYP2C19 loss-of-function (LoF) polymorphism is assumed to be responsible for the poor metabolism of clopidogrel that ultimately turns to resistance. Previous publications could not provide firm evidence due to highly conflicting and heterogeneous outcomes.

AIM

To get clear evidence from an updated meta-analysis on CYP2C19 LoF polymorphism association with stroke risk in clopidogrel treated patients, this study has been performed.

METHODS

We conducted a meta-analysis with 72 selected studies from authentic databases, including 40,035 coronary artery disease patients treated with clopidogrel.

RESULTS

This analysis showed that the worldwide carrier of one or more CYP2C19 LoF alleles had a significantly higher risk of stroke and composite events than the non-LoF carriers (RR=1.78, 95% CI=1.52-2.07, p<0.00001 and RR=1.39, 95% CI=1.26-1.54, p<0.00001, respectively). Besides, subgroup analysis showed that Asian CYP2C19 LoF carriers had a significantly increased risk of stroke (RR=1.91, 95% CI=1.60-2.28, p<0.00001) while the risk of composite events was significantly higher in all ethnic populations (Asian: RR=1.58, 95% CI=1.32-1.89, p<0.00001; Caucasian: RR=1.27, 95% CI=1.08-1.50, p=0.003; Hispanic and others: RR=1.21, 95% CI=1.09-1.34, p=0.0003).

CONCLUSION

Our meta-analysis confirmed that the presence of CYP2C19 LoF alleles increases the risk of stroke and composite events recurrence in the worldwide population, especially in Asians undergoing clopidogrel treatment. Alternative antiplatelet therapy should be investigated thoroughly for the intermediate and poor metabolizers.

Personalized antiplatelet therapy based on clopidogrel/aspirin resistance tests in acute ischemic stroke and transient ischemic attack: Study protocol of a multi-center, single-blinded and randomized controlled trial

BACKGROUND

Clopidogrel and aspirin are key intervention for acute ischemic stroke (AIS) and transient ischemic attack (TIA). However, with increased clinical application, many patients have shown clopidogrel resistance (CR) and/or aspirin resistance (AR) that affect antiplatelet therapy on AIS/TIA. At present, there is no research reported on personalized antiplatelet therapy guidelines for patients with CR and/or AR. Our study aims to assess the effect of personalized antiplatelet therapy based on CYP2C19 genotype and urine 11-dhTxB2 tests in patients with AIS or TIA.

METHODS

This is a multi-center randomized controlled trial. Eligible patients with AIS/TIA from 14 comprehensive hospitals in Jiangxi province will be recruited after obtaining informed consent. Participants will be randomly divided into the intervention group and the control group at a ratio of 1:1. personalized antiplatelet therapy based on the CYP2C19 genotype/urine11-dhTxB2 tests will be given to the intervention group. Demographics, disease history, laboratory investigations, therapys, physiological tests, imaging reports and other clinical features will be collected. Clinical outcomes including stroke recurrence, Modified Rankin Scale (mRS) score, bleeding events and all-cause mortality will be assessed at the 1st, 3rd, 6th, and 12th-month post-discharge.

DISCUSSION

Our study will conduct free antiplatelet resistance tests and personalized antiplatelet therapy for AIS/TIA patients with CR/AR, ultimately evaluating personalized therapy effectiveness through one-year follow-up. The research results will help to assess the impact of personalized antiplatelet therapy on the prognosis of stroke, thus providing reference for precise clinical treatment.

Does CYP2C19 polymorphisms affect neurological deterioration in stroke/TIA patients?: A systematic review and meta-analysis of prospective cohort studies

BACKGROUND

The association between cytochrome P450 2C19 (CYP2C19) polymorphisms and neurological deterioration in stroke or transient ischemic attack (TIA) patients is not completely understood. Hence, we performed a systematic review and meta-analysis of prospective cohort studies to quantify this association.

METHODS

PubMed, Cochrane Library, Excerpta Medica Database, China National Knowledge Infrastructure and WanFang databases were searched for studies published up to April 2019. Prospective cohort studies that reported an association between CYP2C19 polymorphisms and neurological deterioration in stroke/TIA patients were included. Data on risk ratio (RR) and 95% confidence intervals (CI) were extracted and pooled by the authors. Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were followed.

RESULTS

Twelve eligible studies were included. Twelve studies reported CYP2C19∗2, ∗3 loss-of-function alleles and 5 studies reported CYP2C19∗17 gain-of-function allele. Compared to non-carriers, carriers of CYP2C19∗2, ∗3 loss-of-function alleles had a significantly higher risk of neurological deterioration (RR, 1.63; 95%CI, 1.32-2.02). Conversely, carriers of CYP2C19∗17 gain-of-function allele had a significantly lower risk of neurological deterioration (RR, 0.520; 95%CI, 0.393-0.689) compared to non-carriers.

CONCLUSIONS

This meta-analysis demonstrated that the carriers of CYP2C19∗2, ∗3 loss-of-function alleles have an increased risk of neurological deterioration compared to non-carriers in stroke or TIA patients. Additionally, CYP2C19∗17 gain-of-function allele can reduce the risk of neurological deterioration.

The correlation between recurrent risk and CYP2C19 gene polymorphisms in patients with ischemic stroke treated with clopidogrel for prevention

BACKGROUND

To explore the correlation between recurrent risk and CYP2C19 gene polymorphisms in patients with ischemic stroke (IS) treated with clopidogrel for prevention.

METHODS

A total of 289 patients with IS treated with clopidogrel regularly were enrolled in this study, and stroke recurrence of all patients were recorded by follow-up. The correlation between CYP2C19 gene polymorphism and stroke recurrence in patients taking clopidogrel regularly was analyzed.

RESULTS

After a mean follow-up period of 6 months, there were 289 patients who took clopidogrel regularly, and 41 of which occurred recurrent stroke. Patients of poor metabolizer and intermediate metabolizer had higher risk of recurrent stroke comparing with patients of extensive metabolize, and the odds ratios were 2.88 (95% confidence interval [CI] 1.31-6.33, P = .068) and 3.00 (95% CI 1.09-8.22, P = .027), respectively. The recurrence risk of *2 (G681A)A allele carriers was 3.30 times that of G allele carriers (P = .0065). The recurrence rate of stroke in patients carrying heterozygous and homozygous *2 allele mutant was 1.96 times (P = .071) and 3.30 times (P = .012) that of patients with wild-type genes. Multifactor logistic regression analysis result indicated carrying loss of function (LOF) allele was an independent risk factor of stroke recurrence.

CONCLUSION

For patients with IS treated with clopidogrel regularly for secondary prevention, poor metabolizer, and intermediate metabolizer patients had higher risk of recurrent stroke comparing with extensive metabolize ones. Carrying CYP2C19 LOF allele is an independent risk factor of stroke recurrence in patients with IS.

Cytochrome P450: genotype to phenotype

The cytochromes P450 comprise a family of enzymes that are responsible for around three-quarters of all drug metabolism reactions that occur in human populations. Many isoforms of cytochrome P450 exist but most reactions are undertaken by CYP2C9, CYP2C19, CYP2D6 and CYP3A4. This brief review focusses on the first three isozymes which exhibit polymorphism of phenotype.If there is a wide variation in drug metabolising capacity within the population, this may precipitate clinical consequences and influence the drug treatment of patients. Such problems range from a lack of efficacy to unanticipated toxicity. In order to minimise untoward events and "personalise" a patient's treatment, efforts have been made to discover an individual's drug metabolism status. This requires knowledge of the subject's phenotype at the time of clinical treatment. Since such testing is difficult, time-consuming and costly, the simpler approach of genotyping has been advocated.However, the correlation between genotype and phenotype is not good, with values of up to 50% misprediction being reported. Genotype-assisted forecasts cannot therefore be used with confidence to replace actual phenotype measurements. Obfuscating factors discussed include gene splicing, single nucleotide polymorphisms, epigenetics and microRNA, transcription regulation and multiple gene copies.

Association of CYP2C19 Polymorphisms With Clopidogrel Reactivity and Clinical Outcomes in Chronic Ischemic Stroke

BACKGROUND

CYP2C19variants are associated with the antiplatelet effects of clopidogrel against recurrent cardiovascular events. However, it remains unknown whether the elapsed time from stroke onset affects the relationship between the genetic variants and such events. To address this, we conducted a prospective cohort study to determine the effect ofCYP2C19variants on clinical outcomes in the chronic phase.

METHODS AND RESULTS

In total, 518 Japanese non-acute stroke patients treated with clopidogrel were registered at 14 institutions. Patients were classified into 3 clopidogrel-metabolizing groups according toCYP2C19genotype: extensive metabolizer (EM:*1/*1), intermediate metabolizer (IM:*1/*2or*1/*3), and poor metabolizer (PM:*2/*2,*2/*3, or*3/*3). Antiplatelet effects of clopidogrel were assessed by adenosine diphosphate (ADP)-induced platelet aggregation and vasodilator-stimulated phosphoprotein (VASP) phosphorylation. The endpoint was composite cerebrocardiovascular events (CVEs). In 501 successfully followed-up patients, the median time from index stroke to enrollment was 181 days. There were 28 cardiovascular and 2 major bleeding events. There were no significant differences in the rates of cardiovascular events among the groups.

CONCLUSIONS

Despite associations betweenCYP2C19variants and on-clopidogrel platelet reactivity, there was no significant difference in rates of CVEs in the chronic stroke phase among the 3 clopidogrel-metabolizing groups ofCYP2C19variants.

Genetic Polymorphisms and Clopidogrel Efficacy for Acute Ischemic Stroke or Transient Ischemic Attack

Background:

The association of genetic polymorphisms and clopidogrel efficacy in patients with ischemic stroke or transient ischemic attack (TIA) remains controversial. We performed a systematic review and meta-analysis to assess the association between genetic polymorphisms, especially CYP2C19 genotype, and clopidogrel efficacy for ischemic stroke or TIA.

Methods:

We conducted a comprehensive search of PubMed and EMBASE from their inceptions to June 24, 2016. Studies that reported clopidogrel-treated patients with stroke or TIA and with information on genetic polymorphisms were included. The end points were stroke, composite vascular events, and any bleeding.

Results:

Among 15 studies of 4762 patients with stroke or TIA treated with clopidogrel, carriers of CYP2C19 loss-of-function alleles (*2, *3, and *8) were at increased risk of stroke in comparison with noncarriers (12.0% versus 5.8%; risk ratio, 1.92, 95% confidence interval, 1.57–2.35; P <0.001). Composite vascular events were also more frequent in carriers of CYP2C19 loss-of-function alleles than in noncarriers (13.7% versus 9.4%; risk ratio, 1.51, 95% confidence interval, 1.10–2.06; P =0.01), whereas bleeding rates were similar (2.4% versus 3.1%; risk ratio, 0.89, 95% confidence interval, 0.58–1.35; P =0.59). There was no evidence of statistical heterogeneity among the included studies for stroke, but there was for composite vascular events. Genetic variants other than CYP2C19 were not associated with clinical outcomes, with the exception that significant associations of PON1 , P2Y12 , and COX-1 with outcomes were observed in 1 study.

Conclusions:

Carriers of CYP2C19 loss-of-function alleles are at greater risk of stroke and composite vascular events than noncarriers among patients with ischemic stroke or TIA treated with clopidogrel.

Expression of miRNA-26a in platelets is associated with clopidogrel resistance following coronary stenting

The present study aimed to evaluate the association between platelet microRNA (miRNA)-26a expression and clopidogrel resistance in patients who underwent coronary stenting. Between September 2013 and August 2014, 43 patients with coronary heart disease underwent percutaneous coronary intervention at Heibei General Hospital (Shijiazhuang, China). In the same period, 20 healthy volunteers without any history of cardiovascular disease were enrolled in the present study as the control group. Flow cytometry was used to measure the phosphorylation levels of vasodilator-stimulated phosphoprotein (VASP), and to calculate the platelet reactivity index (PRI). Low response to clopidogrel was defined as PRI ≥50% on day 7 following clopidogrel administration. Western blotting was used to measure protein expression of VASP and reverse transcription-quantitative polymerase chain reaction analysis was performed to determine the expression levels of mRNA and miRNAs. Bioinformatics tools were employed to predict that miR-26a, miR-199 and miR-23a may target VASP mRNA. The results of the present study demonstrated that the activity of platelets in patients with low or high clopidogrel response was increased, as compared with healthy subjects. No differences in platelet VASP protein expression levels were detected between patients with high clopidogrel response and healthy subjects; whereas VASP protein expression was elevated in patients with low clopidogrel response. Furthermore VASP gene transcription was maintained at low levels in healthy subjects and patients with high clopidogrel response, whereas patients with low clopidogrel response exhibited increased VASP mRNA expression levels. Platelet expression of miRNA-26a, but not miRNA-199 or miRNA-23a, was associated with high platelet reactivity. Serum miRNA-26a, miRNA-199 and miRNA-23a were not demonstrated to be involved in clopidogrel resistance. Therefore, the present study demonstrated that platelet miRNA-26a has an important role in clopidogrel resistance. Combined miRNA and VASP PRI tests may aid the early diagnosis and prediction of clopidogrel resistance.

Protocol for the comparison of triflusal and clopidogrel in secondary prevention of stroke based on cytochrome P450 2C19 genotyping (MASETRO study): A multicenter, randomized, open-label, parallel-group trial

RATIONALE AND AIM

The antiplatelet effect of clopidogrel is reportedly influenced by cytochrome P450 2C19 (CYP2C19) polymorphisms. However, there is no data concerning the relationship between stroke recurrence and CYP2C19 polymorphisms in patients treated with clopidogrel for secondary prevention of ischemic stroke. Triflusal may be an alternative therapy for clopidogrel in patients with poor genotype. The Comparison of Triflusal and Clopidogrel Effects in Secondary Prevention of Stroke Based on Cytochrome P450 2C19 Genotyping (MAESTRO) study will investigate the effect of antiplatelet agents based on CYP2C19 polymorphisms in secondary prevention of ischemic stroke.

SAMPLE SIZE AND DESIGN

Assuming that 55% of patients belong to the poor genotype group, the required sample size is 1080 patients with at least 24 months of follow-up. This study is designed as a prospective, multicenter, randomized, parallel-group, open-label, and blind genotype trial. Patients who experience their first non-cardiogenic ischemic stroke within 30 days prior to screening are eligible. Patients received 300 mg triflusal twice a day or 75 mg clopidogrel once daily during the trial. The study is registered with ClinicalTrials.gov (NCT01174693).

STUDY OUTCOME

The primary outcome is recurrent ischemic stroke or hemorrhagic stroke. Secondary outcomes consist of composite major vascular events including stroke, myocardial infarction, coronary revascularization, or vascular death.

DISCUSSION

Personalized medicine may be essential for patients according to individual drug metabolism abilities. MAESTRO is the first prospective study designed to evaluate the effect of CYP2C19 polymorphism in secondary stroke prevention and will resolve several questions regarding preventive antiplatelet agents for recurrent stroke.

CYP2C19 metabolizer status and clopidogrel efficacy in the Secondary Prevention of Small Subcortical Strokes (SPS3) study

Background

The role of the CYP2C19 genotype on clopidogrel efficacy has been studied widely, with data suggesting reduced clopidogrel efficacy in loss-of-function variant carriers taking clopidogrel after percutaneous coronary intervention; however, data are limited regarding the association between CYP2C19 genetic variants and outcomes in stroke patients. We investigated whether CYP2C19 metabolizer status affects the risk of recurrent stroke or major bleeding in subcortical stroke patients taking dual antiplatelet therapy with aspirin and clopidogrel.

Methods and Results

CYP2C19*2 and CYP2C19*17 were genotyped in 522 patients treated with dual antiplatelet therapy from the Secondary Prevention of Small Subcortical Strokes (SPS3) study. CYP2C19 metabolizer status was inferred from genotype, and associations with the risk of recurrent stroke and major bleeding were assessed in the overall cohort and by race/ethnic group with logistic regression modeling. In the overall cohort, there were no differences in outcomes by CYP2C19 metabolizer status (recurrent stroke, odds ratio 1.81 [95% CI 0.76 to 4.30]; major bleeding, odds ratio 0.67 [95% CI 0.22 to 2.03]). In white participants, those with CYP2C19 intermediate or poor metabolizer status had higher odds of recurrent stroke (odds ratio 5.19 [95% CI 1.08 to 24.90]) than those with extensive or ultrarapid metabolizer status, but there was no evidence of difference in major bleeding.

Conclusions

There were significant differences in recurrent stroke by CYP2C19 genotype-inferred metabolizer status in white subcortical stroke patients receiving dual antiplatelet therapy with aspirin and clopidogrel, consistent with cardiovascular studies on CYP2C19 and clopidogrel; however, the bleeding risk that led to early termination of the antiplatelet arm of the SPS3 trial does not appear to be explained by CYP2C19 genotype. This study was relatively underpowered; therefore, these findings should be interpreted with caution and warrant replication.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00059306.

Effects of CYP2C19 and P2Y12 Gene Polymorphisms on Clinical Results of Patients Using Clopidogrel after Acute Ischemic Cerebrovascular Disease

The CY2C19 and P2Y12 gene polymorphisms are responsible for resistance to clopidogrel, known as drug unresponsiveness. In this study we researched the effect of gene polymorphism on clinical results of patients who began clopidogrel therapy after acute ischemic cerebrovascular disease.

The study included 51 patients. The patient group included patients who had begun prophylactic clopidogrel due to acute ischemic cerebrovascular disease in the last 2 years. All patients were monitored by the Neurology Outpatient Clinic at Çanakkale Onsekiz Mart Üniversity Research Hospital, Çanakkale, Turkey, and only those monitored for at least 1 year were included in the study.

When the *1, *2 and *3 alleles of the CYP2C19 gene polymorphism were evaluated, two patients were homozygotes for *2/*2, 13 patients were heterozygous for *1/*2 and 36 patients were homozygotes for the wild type *1/*1. No patient had the *3 allele. Three heterozygous patients, one for *2/*2 and two for *1/*2, stopped clopidogrel therapy due to repeated strokes and began taking warfarin. When evaluating P2Y12 52 (G>T) and 34 (C>T) polymorphisms, all alleles were of the wild type.

The CYP2C19 and P2Y12 gene polymorphisms may cause recurring strokes linked to insufficient response to treatment of ischemic cerebrovascular disease. In our patient group, three patients suffered repeated strokes and these patients had the CYP2C19*2 gene polymorphism. As a result, before medication use, genetic testing is important for human life, quality of life and economic burden.

CYP2C19 genotype and early ischemic lesion recurrence in stroke patients treated with clopidogrel

BACKGROUND

Early recurrent ischemic lesions detected on diffusion-weighted imaging (DWI) have been proposed as a surrogate marker for clinical recurrence. We hypothesized that cytochrome P450 2C19 (CYP2C19) genotype influences the incidence of early recurrence on DWI in acute stroke patients treated with clopidogrel.

METHODS

We enrolled 76 Korean patients with acute ischemic stroke due to large artery atherosclerosis who were treated with clopidogrel. Early ischemic lesion recurrence was defined as new lesions separate from the index lesion. We compared the rates of early ischemic lesion recurrence on DWI based on the CYP2C19 genotypes.

RESULTS

Early recurrence on DWI was observed in 36 patients (47.4%). A total of 76 patients were classified into 3 phenotypic groups: extensive metabolizers (EMs; n = 27, 35.5%), intermediate metabolizers (IMs; n = 36, 47.4%), and poor metabolizers (PMs; n = 13, 17.1%). Early recurrence on DWI was more common in PMs (84.6%), followed by IMs (50.0%), and EMs (25.9%; P < .001). PMs had a significantly higher recurrence rate than EMs (P < .001). In multivariate analysis, CYP2C19 genotypes were independently associated with early DWI recurrence (for PMs: odds ratio, 19.3; 95% confidence interval, 3.15-117.56).

CONCLUSIONS

CYP2C19 genotypes are significantly associated with early lesion recurrence in Korean acute stroke patients treated with clopidogrel.

Personalized medicine: importance of clinical interpretative skills for real-world patient care

Sequencing of the human genome led to great hopes and expectations for a 'genomics revolution' where disease diagnosis as well as therapies would be based on an individual's genetic makeup. Although significant progress has been made, a number of challenging hurdles must be overcome prior to the broader adoption and implementation of pharmacogenomics and personalized medicine as a part of standard patient care. One aspect of pharmacogenomics-based personalized medicine that has not garnered as much attention, a key focus of this perspective, is the importance of interpreting pharmacogenomic test results in a patient-specific clinical context, and expert physicians and other allied health care providers with the requisite expertise in clinical pharmacology and genomics who are able to provide such services.