Determinants to optimize response to clopidogrel in acute coronary syndrome

The effects of polymorphisms in CYP2C19, ATP-binding cassette transporter B1, and paraoxonase-1 on clopidogrel treatment of Uygur patients following percutaneous coronary intervention

BACKGROUND

Acute coronary syndrome (ACS) carries a high mortality in Uygur populations. Percutaneous coronary intervention (PCI) is a safe treatment for patients with ACS. Clopidogrel reduces the risk for recurrent cardiovascular events after PCI; however, its activity is influenced by cytochrome P450 (CYP450), ATP-binding cassette transporter B1 (ABCB1), and paraoxonase-1 (PON1).

OBJECTIVES

To assess the effects of genetic polymorphisms CYP2C19*2, *3, *17, ABCB1 C3435T, and PON1 Q192R along with clinical and demographic factors on variations in responses in Uygur patients following PCI.

METHODS

We enrolled 281 patients with PCI who were treated with clopidogrel and aspirin for at least 12 months and recorded major adverse cardiovascular events (MACE) or bleeding within 1 year. Approximately, 2 mL of peripheral venous blood samples were used for genotype detection. Binary logistic regression with likelihood ratio forward stepwise analysis and redundancy analysis were carried out to identify factors associated with MACE. We analyzed risk factors including age, body mass index, smoking, hypertension, dyslipidemia, gender, alcohol consumption, diabetes mellitus, carriers of ABCB1 C3435T T allele, carriers of PON1 Q192R A allele, metabolizer phenotype of CYP2C19, number of targeted vessels, and number of stents.

RESULTS

The CYP2C19 IMs (OR 3.546, 95% CI 1.972-6.375, P = 0.001), CYP2C19 PMs (OR 7.038, 95% CI 1.658-29.880, P = 0.008), and number of targeted vessels (OR 2.033, 95% CI 1.078-3.648, P = 0.026) were significantly associated with MACE.

CONCLUSION

The CYP2C19 IMs, PMs, and the number of targeted vessels are essential factors associated with MACE risk in dual clopidogrel-treated Uygur population with ACS following PCI. These data provide valuable insights into the genetic polymorphisms affecting clopidogrel response among minority groups in China.

Pharmacogenetics of CYP2C19 genetic polymorphism on clopidogrel response in patients with ischemic stroke from Saudi Arabia

OBJECTIVE

To elucidate the degree of genetic polymorphisms CYP2C19 (CYP2C19*2, CYP2C19*3) of key drug metabolizing enzymes on the antiplatelet effect of clopidogrel response in patients with acute ischemic stroke from Saudi Arabia.

METHODS

A case-control study carried out at Neurology Clinics at Asser Central Hospital, Abha, Kingdom of Saudi Arabia from October 2015 to January 2016 and included 25 stroke patients responding to clopidogrel therapy and 25 stroke patients non responding to clopidogrel monotherapy. After obtaining their informed consent, the blood samples were collected and genotyped for CYP2C19 polymorphisms by the polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP Method). Allele frequencies were derived from genotypic data and platelet aggregation was measured using multiple electrode aggregometry on the multiplate analyser. Chi Square tests, p-values, odds ratio (OR) and corresponding confidence intervals were calculated for each polymorphism.

RESULTS

The CYP2C19*2 (681G>A) and CYP2C19*3 (636 G>A) polymorphism were seen to be in Hardy-Weinberg equilibrium and showed significant allelic and genotypic association between responders and non-responders to clopidogrel (p<0.01). The CYP2C19*2: allelic chi-square=21.49, p=0.000036, OR=5.52 (2.42-12.83); Genotypic Chi-square=10.27, p=0.001, OR=7.88 (1.78-9.73). The CYP2C19*3: Allelic chi-square=11.66, p=0.0006, OR=3.45 (1.57-7.70); genotypic chi-square=4.37, p=0.036, OR=3.69 (0.90-5.81). The variant allele (homozygous and homozygous Mutant) showed significant influence on platelet inhibition and the antiplatelet effect of clopidogrel in ischemic stroke.

CONCLUSION

Our findings provide certain evidence on the genetic effect of CYP2C19 on clopidogrel responsiveness in stroke patients from Saudi Arabia.

Pharmacogenetics in the Treatment of Cardiovascular Diseases and Its Current Progress Regarding Implementation in the Clinical Routine

There is a special interest in the implementation of pharmacogenetics in clinical practice, although there are some barriers that are preventing this integration. A large part of these pharmacogenetic tests are focused on drugs used in oncology and psychiatry fields and for antiviral drugs. However, the scientific evidence is also high for other drugs used in other medical areas, for example, in cardiology. In this article, we discuss the evidence and guidelines currently available on pharmacogenetics for clopidogrel, warfarin, acenocoumarol, and simvastatin and its implementation in daily clinical practice.

Do CYP2C19 and ABCB1 gene polymorphisms and low CYP3A4 isoenzyme activity have an impact on stent implantation complications in acute coronary syndrome patients?

AIM

The aim of this study was to determine the impact of CYP2C19 and ABCB1 gene polymorphisms and CYP3A4 isoenzyme activity on stent implantation complications among patients with an acute coronary syndrome (ACS) who underwent percutaneous coronary intervention (PCI).

PATIENTS AND METHODS

Seventy-six patients (median age 63, range 37-91 years) with an ACS who underwent PCI were screened for CYP2C19 and ABCB1 gene polymorphisms with real-time polymerase chain reaction: CYP2C19*2, CYP2C19*17, and ABCB1 3435. CYP3A4 isoenzyme activity was determined by urine cortisol and 6-beta-hydroxycortisol levels. Stent implantation complications such as stent thrombosis (n=2) and restenosis (n=1) were observed among drug-eluting stent recipients.

RESULTS

Low mean 6-beta-hydroxycortisol/cortisol ratio is indicative of impaired CYP3A4 activity and was associated with higher risk of thrombosis (b coefficient=0.022, SE 0.009, p=0.021 in the linear regression model). The increase in the length of the implanted stent was associated with higher risk of restenosis (b coefficient=0.006, SE=0.002, p=0.001 in the linear regression model). The presence of the CYP2C19*2 polymorphism did not affect the incidence of stent thrombosis (b coefficient=-1.626, SE=1.449, p=0.262 in the logistic regression model), nor did the CYP2C19*17 (b coefficient=-0.907, SE=1.438, p=0.528 in the logistic regression model) and ABCB1 3435 polymorphisms (b coefficient=1.270, SE=1.442, p=0.378 in the logistic regression model).

CONCLUSION

We did not find evidence that the presence of CYP2C19*2, CYP2C19*17, and ABCB1 3435 polymorphisms may jeopardize the safety of stent implantation in patients with an ACS. Patients with low CYP3A4 isoenzyme activity may have increased risk of stent thrombosis.

Genetic polymorphisms influence on the response to clopidogrel in peripheral artery disease patients following percutaneous transluminal angioplasty

AIM

To study the association of ABCB1 and CYP2C19 polymorphisms and the clopidogrel response in Spanish peripheral artery disease patients following percutaneous transluminal angioplasty (PTA) and to perform a meta-analysis.

MATERIALS & METHODS

72 patients were recruited and 122 patients included in the meta-analysis. We evaluated the effect of ABCB1 3435 C>T, CYP2C19*2 and CYP2C19*3 and primary end point (restenosis/occlusion of the treated lesions) during 12 months after PTA.

RESULTS

CYP2C19*2 and/or ABCB1 TT patients were associated with primary end point (OR: 5.00; 95% CI: 1.75-14.27). The meta-analysis confirmed the association of CYP2C19*2 and new atherothrombotic ischemic events (OR: 5.40; 95% CI: 2.30-12.70).

CONCLUSION

The CYP2C19 and ABCB1 polymorphisms could be genetic markers of cardiovascular events in peripheral artery disease patients following PTA treated with clopidogrel.

Single nucleotide polymorphism of CYP3A5*3 contributes to clopidogrel resistance in coronary artery disease patients among Tamilian population

Clopidogrel is an antiplatelet drug. It is used for the treatment as well as for the prophylaxis of coronary artery disease. Clopidogrel resistance is an emerging problem in clinical settings. The aim of the present study was to evaluate the effect of CYP3A5*3 genetic polymorphism on clopidogrel resistance. One hundred and forty-seven patients from outpatient Department of Cardiology on 75 mg/day of clopidogrel as maintenance dose were recruited from April 2010 to July 2011. All subjects gave written informed consent to participate in the study. DNA extraction was performed using phenol chloroform extraction procedure and genotyping by standard Taqman based RT-PCR method. Platelet aggregation was done at the end of 7th and 14th day by using chronolog lumi Aggregometer which is expressed as impedance in ohms. Impedance values of >5 ohms at the end of 6 min were considered as clopidogrel resistance. Subjects (N = 147) were analysed for CYP3A5*3 polymorphism, of which 49 (33%) were found to be clopidogrel resistant. Homomutants of CYP3A5*3 gene had 2.78 (0.97-7.98; p < 0.05) fold risk and heteromutants had 2.4 (0.93-6.46; p < 0.05) fold risk of developing clopidogrel resistance. Carriers of defective allele G of CYP3A5*3 had higher propensity to cause clopidogrel resistance with an odds ratio of 1.63. Variant alleles and genotypes of CYP3A5*3 polymorphism contributed significantly to clopidogrel resistance with a higher odds ratio. Thus, pharmacogenomics paves way for the emergence of stratified medicine in clopidogrel therapy and personalised pharmacotherapy in ischaemic heart disease.

Genetic polymorphisms of CYP2C19 influences the response to clopidogrel in ischemic heart disease patients in the South Indian Tamilian population

BACKGROUND

The antiplatelet activity of clopidogrel is variable among patients suffering from ischemic heart disease. Variation in the cytochrome P450 2C19 (CYP2C19) gene coding for the CYP2C19 enzyme is one of the major determinants of this variable response to clopidogrel. The activity of the CYP2C19 enzyme, which plays a role in the conversion of the prodrug clopidogrel to its active metabolite, is genetically influenced by polymorphisms in its gene. The aim of our study was to evaluate the association of CYP2C19 polymorphisms and the antiplatelet effect of clopidogrel in the South Indian Tamilian population.

MATERIALS AND METHODS

Genotyping and platelet aggregation results of 149 ischemic heart disease patients on clopidogrel maintenance therapy (75 mg daily dose) were analyzed in this study. CYP2C19 polymorphisms were genotyped by the PCR-restriction fragment length polymorphism method. We measured residual platelet activities in these patients on clopidogrel therapy in terms of impedance (expressed as ohms). The study subjects were divided into two metabolizer phenotype groups [group 1: poor/intermediate metabolizers (PM/IM); group 2: extensive/ultra-rapid metabolizers (EM/URM)] based on CYP2C19 genotype, and the residual platelet activities were compared. Higher values of impedance denote increased residual platelet activity.

RESULTS

Poor/intermediate metabolizers had significantly higher impedance values than EM/URM [(median; range) 4.0; 0-13 vs. 2.0; 0-11, respectively; p = 0.04]. These higher impedance values denote higher residual platelet activities among the carriers of loss-of-function alleles (CYP2C19*2,*3) than among non-carriers. However, residual platelet activities were lower among the carriers of the gain-of-function allele (CYP2C19*17) than among non-carriers, although this difference was not significant.

CONCLUSION

Patients with CYP2C19 (*2 or *3) genetic polymorphisms had higher residual platelet activities and were associated with a reduced antiplatelet response to clopidogrel. As the South Indian Tamilian population is characterized with higher frequencies of these genetic polymorphisms, our findings mandate further studies aimed at initiating genome-based personalized antiplatelet therapy.

Pharmacogenetics of clopidogrel: comparison between a standard and a rapid genetic testing

AIMS

CYP2C19 variant alleles are independent predictors of clopidogrel response variability and occurrence of major adverse cardiovascular events in high-risk vascular patients on clopidogrel therapy. Increasing evidence suggests a combination of platelet function testing with CYP2C19 genetic testing may be more effective in identifying high-risk individuals for alternative antiplatelet therapeutic strategies. A crucial point in evaluating the use of these polymorphisms in clinical practice, besides test accuracy, is the cost of the genetic test and rapid availability of the results. One hundred acute coronary syndrome patients were genotyped for CYP2C19*2,*3,*4,*5, and *17 polymorphisms with two platforms: Verigene(®) and the TaqMan(®) system.

RESULTS

Genotyping results obtained by the classical TaqMan approach and the rapid Verigene approach showed a 100% concordance for all the five polymorphisms investigated. The Verigene system had shorter turnaround time with respect to TaqMan. The cost of reagents for TaqMan genotyping was lower than that for the Verigene system, but the effective manual staff involvement and the relative cost resulted in higher cost for TaqMan than for Verigene.

CONCLUSIONS

The Verigene system demonstrated good performance in terms of turnaround time and cost for the evaluation of the clopidogrel poor metabolizer status, giving genetic information in suitable time (206 min) for a therapeutic strategy decision.

Animal models in an age of personalized medicine

Personalized medicine is based on intraspecies differences. It is axiomatic that small differences in genetic make-up can result in dramatic differences in response to drugs or disease. To express this in more general terms: in any given complex system, small changes in initial conditions can result in dramatically different outcomes. Despite human variability and intraspecies variation in other species, nonhuman species are still the primary model for ascertaining data for humans. We call this practice into question and conclude that human-based research should be the primary means for obtaining data about human diseases and responses to drugs.

Reduced-function CYP2C19 genotype and risk of adverse clinical outcomes among patients treated with clopidogrel predominantly for PCI: a meta-analysis

CONTENT

Clopidogrel, one of the most commonly prescribed medications, is a prodrug requiring CYP450 biotransformation. Data suggest its pharmacologic effect varies based on CYP2C19 genotype, but there is uncertainty regarding the clinical risk imparted by specific genotypes.

OBJECTIVE

To define the risk of major adverse cardiovascular outcomes among carriers of 1 (≈ 26% prevalence in whites) and carriers of 2 (≈ 2% prevalence in whites) reduced-function CYP2C19 genetic variants in patients treated with clopidogrel.

DATA SOURCES AND STUDY SELECTION

A literature search was conducted (January 2000-August 2010) in MEDLINE, Cochrane Database of Systematic Reviews, and EMBASE. Genetic studies were included in which clopidogrel was initiated in predominantly invasively managed patients in a manner consistent with the current guideline recommendations and in which clinical outcomes were ascertained.

DATA EXTRACTION

Investigators from 9 studies evaluating CYP2C19 genotype and clinical outcomes in patients treated with clopidogrel contributed the relevant hazard ratios (HRs) and 95% confidence intervals (CIs) for specific cardiovascular outcomes by genotype.

RESULTS

Among 9685 patients (91.3% who underwent percutaneous coronary intervention and 54.5% who had an acute coronary syndrome), 863 experienced the composite end point of cardiovascular death, myocardial infarction, or stroke; and 84 patients had stent thrombosis among the 5894 evaluated for such. Overall, 71.5% were noncarriers, 26.3% had 1 reduced-function CYP2C19 allele, and 2.2% had 2 reduced-function CYP2C19 alleles. A significantly increased risk of the composite end point was evident in both carriers of 1 (HR, 1.55; 95% CI, 1.11-2.17; P = .01) and 2 (HR, 1.76; 95% CI, 1.24-2.50; P = .002) reduced-function CYP2C19 alleles, as compared with noncarriers. Similarly, there was a significantly increased risk of stent thrombosis in both carriers of 1 (HR, 2.67; 95% CI, 1.69-4.22; P < .0001) and 2 (HR, 3.97; 95% CI, 1.75-9.02; P = .001) CYP2C19 reduced-function alleles, as compared with noncarriers.

CONCLUSION

Among patients treated with clopidogrel for percutaneous coronary intervention, carriage of even 1 reduced-function CYP2C19 allele appears to be associated with a significantly increased risk of major adverse cardiovascular events, particularly stent thrombosis.