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

Prevalence of CYP2C19*2 and CYP2C19*3 Allelic Variants and Clopidogrel Use in Patients with Cardiovascular Disease in Trinidad & Tobago

INTRODUCTION

Trinidad & Tobago has the highest prevalence of cardiovascular disease (CVD) in the Caribbean and clopidogrel is a ubiquitously used treatment. Yet, the extent of genetically mediated clopidogrel resistance is unknown. To determine this, we investigated whether the association between CYP2C19*2 and CYP2C19*3 genetic variants and clopidogrel resistance holds, and calculated the frequencies of these in the Trinidadian CVD population.

METHODS

Demographic data, clinical data, and a saliva sample were collected under informed consent from 22 patients with CVD on dual anti-platelet therapy whose biochemical resistance to clopidogrel is known, and a further 162 patients accessing the main public CVD clinic in Trinidad and who are either currently being treated or are likely to be treated with clopidogrel. A polymerase chain reaction (PCR) and restriction enzyme digestion procedure was used to genotype each patient for the CYP2C19*2 and CYP2C19*3 allelic variants. Genotype was compared to known clopidogrel resistance in the 22 patients, and to disease status and clopidogrel usage in the larger cohort.

RESULTS

CYP2C19*2 genotype was concordant with clopidogrel resistance. CYP2C19*2 was detected in 61.1% (99/162) of patients and CYP2C19*3 was undetected. Clopidogrel was the most prescribed antiplatelet therapy (42%). A total of 120 people presented with coronary artery disease (CAD) and 52.5% of these (n = 63/120) are currently prescribed clopidogrel. 63.5% (40/63) of patients with CAD who are prescribed clopidogrel carry the CYP2C19*2 allele; ten homozygous and 30 heterozygous. Indian patients comprised 65% of the cohort and were four times more likely to carry the CYP2C19*2 allele than African patients.

CONCLUSIONS

A large proportion of Trinidadian patients with CVD who are prescribed or may be prescribed clopidogrel carry genetic variants associated with clopidogrel resistance. These results emphasize the clinical need for further investigation into whether CYP2C19*2 genotype should guide clopidogrel use for the cardiovascular disease population in Trinidad & Tobago. A slide deck is available for this article.

A HANC Risk Stratification Score for Antiplatelet Therapy Optimization with Low-Dose Prasugrel in Taiwanese Acute Coronary Syndrome Patients from the Switch Study

BACKGROUND

A significant proportion of acute coronary syndrome (ACS) patients experience high on-treatment platelet reactivity (HPR) on clopidogrel-based dual antiplatelet therapy (DAPT) after percutaneous coronary intervention (PCI).

OBJECTIVES

This study assessed key independent risk factors associated with significant HPR risk on clopidogrel, but not prasugrel, in the Switch Study cohort of 200 Taiwanese ACS patients who switched from clopidogrel to low-dose prasugrel for maintenance DAPT after PCI.

METHODS

Univariate analysis and stepwise multivariate logistic regression analysis were conducted to identify key independent risk factors for HPR on clopidogrel, but not prasugrel.

RESULTS

A HANC [H: low hemoglobin (< 13 g/dL for men and < 12 g/dL for women); A: age ≥ 65 years; N: non-ST elevation myocardial infarction; C: chronic kidney disease as defined by estimated glomerular filtration rate < 60 mL/min] risk stratification score was developed, and demonstrated optimal sensitivity and specificity at a cutoff score of ≥ 2. The HANC score compared favorably against the recently validated ABCD score in the full Switch Study cohort (n = 200), and the ABCD-GENE score in a genotyped cohort (n = 102).

CONCLUSIONS

The HANC score may serve to alert clinicians to patients at potentially higher HPR risk on clopidogrel, but not prasugrel. Further research to validate this score and assess its correlation with clinical outcomes is warranted.

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

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

A comparison of three platelet function tests in ischemic stroke patients with antiplatelet therapy

Predicting the effectiveness of antiplatelet drugs is critical to precision antiplatelet therapy. However, there is a lack of an acceptable method, although there are a variety of methods for detecting platelet function. In this study, we compared three major platelet function tests to assess their performance and found better methods for platelet function evaluation after aspirin or clopidogrel treatment in ischemic stroke patients by comparative study. A total of 249 ischemic stroke patients were enrolled who were treated with aspirin or clopidogrel or both. Three platelet function tests including light transmittance aggregometry (LTA), thromboelastography (TEG), platelet function analyzer (PFA) were performed as well as CYP2C19 genotype determination. Correlation analyses and kappa statistics were used. All three methods were effective in evaluating aspirin function. However, only LTA and TEG had good correlation and consistency (r = -0.37, kappa = 0.634). TEG-ADP was the least sensitive for clopidogrel, as the platelet inhibition ratio did not differ between the clopidogrel-user group and the control (P = 0.074), while LTA and PFA were sensitive (P ＜ 0.001). Correlations between platelet assays were poor for clopidogrel (the absolute value of r range from 0.13 to 0.35) and so was the agreement (Kappa from 0.232 to 0.314). LTA and PFA have a good correlation with CYP2C19 genotyping (P = 0.034 and 0.014). In conclusion, all three tests were able to evaluate aspirin effect, LTA-AA and TEG-AA had a good correlation. TEG perform badly for clopidogrel effect detection. The fair-to-modest agreement among assays indicated further study was indispensable.

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.

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

BACKGROUND

An association has been reported between CYP2C19 polymorphism and the altered antiplatelet activity of clopidogrel. We investigated this association using the newly introduced platelet function analyzer (PFA)-200 (INNOVANCE PFA-200 System; Siemens Healthcare, Germany) P2Y test.

METHODS

Polymorphisms of CYP2C19*2, *3, *17 and the degree of inhibition of platelet function were determined in 83 patients. Three different platelet function tests were used to evaluate the degree of platelet inhibition and to check the association with genotype.

RESULTS

The post-procedure PFA-200 values of extensive metabolizers (EM) patients (285.3±38.8) were higher than those of intermediate metabolizers (IM) and poor metabolizers (PM) patients (227.7±98.3 and 133.7±99.2, respectively; P=0.024). Light transmittance aggregometry (LTA) and the VerifyNow system showed that the post-procedure values for EM patients were lower than those of IM and PM patients (LTA: 24.4±15.7, 34.1±17.6, and 42.2±16.9, respectively, P<0.001; VerifyNow: 133.2±60.5, 171.5±42.6, and 218.7±59.3, respectively, P<0.001). The high residual platelet reactivity (HPR) rates were significantly different among the EM, IM, and PM groups using PFA-200 (PM:IM:EM=82.4:40.6:11.8, P<0.001).

CONCLUSIONS

Approximately, 59.0% of Korean patients with cardiovascular disease receiving clopidogrel had CYP2C19 loss-of-function genotypes classified as IM or PM, and the frequency was similar to the data from Asian people. The PFA-200, LTA, and VerifyNow platelet function tests revealed evidence of a significant association between the efficacy of clopidogrel and CYP2C19 genotypes.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Enhanced solubility and intestinal absorption of candesartan cilexetil solid dispersions using everted rat intestinal sacs

OBJECTIVE

Candesartan cilexetil (CAN) is a poor aqueous soluble compound and a P-glycoprotein (P-gp) efflux pump substrate. These key factors are responsible for its incomplete intestinal absorption.

METHODS

In this study, we investigated to enhance the absorption of CAN by improving its solubility and inhibiting intestinal P-gp activity. A phase solubility method was used to evaluate the aqueous solubility of CAN in PVP K30 (0.2-2%). Gibbs free energy [Formula: see text] values were all negative. Solubility was enhanced by the freeze drying technique. The in vitro dissolution was evaluated using the USP paddle method. The interaction between drug and carrier was evaluated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Differential scanning calorimetry (DSC) studies. Naringin was selected as P-gp inhibitor. Absorption studies were performed using the everted gut sac model from rat jejunum. The drug analysis was performed by HPLC.

RESULTS

FTIR spectra revealed no interaction between drug and PVP K30. From XRD and DSC data, CAN was in the amorphous form, which explains the cumulative release of drug from its prepared systems. We noticed an enhancement of CAN absorption by improving its solubility and inhibiting the P-gp activity. The significant results (p < 0.05) were obtained for freeze dried solid dispersions in the presence of P-gp inhibitor than without naringin (15 mg/kg) with an absorption enhancement of 8-fold.

CONCLUSION

Naringin, a natural flavonoid, has no undesirable side effects. Therefore, it could be employed as an excipient in the form of solid dispersions to increase CAN intestinal absorption and its oral bioavailability.

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.