Clopidogrel Pharmacogenetics and Its Clinical Implications

The Prevalence of CYP2C19 Polymorphism in Patients with Symptomatic Intracranial Atherosclerosis

INTRODUCTION

Clopidogrel and aspirin were proved to have benefit in symptomatic intracranial stenosis. CYP2C19 polymorphism (CYP2C19*1, CYP2C19*2, CYP2C19*3, and CYP2C19*17 alleles) affects efficacy of clopidogrel. Epidemiologic study of CYP2C19 polymorphism has been conducted in Thai population. There was no data showed the frequency of allelic variants of CYP2C19 in Thai symptomatic intracranial stenosis patients. The aim of this study was to determine the prevalence of CYP2C19 polymorphism in symptomatic intracranial stenosis patients.

METHODS

The study group included 100 Thai symptomatic intracranial stenosis patients. Genotyping of CYP2C19 alleles (CYP2C19*1, CYP2C19*2, CYP2C19*3, and CYP2C19*17 alleles) was carried out by real-time polymerase chain reaction (rt-PCR) technique.

RESULTS

The allele frequency of CYP2C19*1, CYP2C19*2, CYP2C19*3, and CYP2C19*17 were 70.5%, 26%, 2.5%, and 1%, respectively. The result showed that 53% of symptomatic intracranial stenosis patients are normal metabolizers, while intermediate and poor metabolizer were 36 and 10 percent, respectively.

CONCLUSION

Almost one-half of Thai symptomatic intracranial stenosis patients were intermediate or poor metabolizers. Usage of combination of aspirin and clopidogrel might not be effective in this group of patients.

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.

Evaluation of Tolerability, Pharmacokinetics and Pharmacodynamics of Vicagrel, a Novel P2Y12 Antagonist, in Healthy Chinese Volunteers

Background: Vicagrel is a novel anti-platelet drug and hydrolyzed to the same intermediate as clopidogrel via esterase, instead of CYP2C19. Here we report the first clinical trial on the tolerability, pharmacokinetics and pharmacodynamics of different doses of vicagrel, and comparison with clopidogrel in healthy Chinese volunteers. Methods: This study was conducted in two parts. Study I was a dose-escalating (5-15 mg) study. For each dose, 15 participants were randomized into three groups (total n = 45); nine participants were given vicagrel, three were given clopidogrel, and three were given a placebo. Study II was conducted to assess interactions between vicagrel and aspirin in 15 healthy participants. The plasma concentrations of the metabolites of vicagrel and clopidogrel were determined using a LC-MS/MS method. Platelet aggregation was assessed using the VerifyNow-P2Y12 assay. Results: Vicagrel (5-15 mg per day) dosing for 10 days or addition of aspirin was well tolerated in healthy volunteers. The exposure of the active metabolite increased proportionally across the dose range and was higher (~10-fold) than clopidogrel. The levels of IPA dosing 75 mg clopidogrel were between the responses of 5 mg and 10 mg vicagrel. After a single loading dose of vicagrel (30 mg) and a once-daily maintenance dose (7.5 mg) for 8 days, the maximum inhibition of platelet aggregation was similar to that seen with the combined use of vicagrel and aspirin (100 mg/day). Conclusion: Oral vicagrel demonstrated a favorable safety profile and excellent anti-platelet activity, which could be a promising P2Y12 antagonist as anti-platelet drug and can be further developed in phase II/III studies, and marketing for the unmet medical needs of cardiovascular diseases. The study was registered at http://www.chictr.org.cn (ChiCTR-IIR-16009260).

Cardiovascular pharmacogenetics: a promise for genomically-guided therapy and personalized medicine

Cardiovascular disease (CVD) is the leading cause of death worldwide. The basic causes of CVD are not fully understood yet. Substantial evidence suggests that genetic predisposition plays a vital role in the physiopathology of this complex disease. Hence, identification of genetic contributors to CVD will likely add diagnostic accuracy and better prediction of an individual's risk. With high-throughput genetics and genomics technology and newer genome-wide study approaches, a number of genetic variations across the human genome were uncovered. Evidence suggests that genetic defects could influence CVD development and inter-individual responses to widely used cardiovascular drugs like clopidogrel, aspirin, warfarin, and statins, and therefore, they may be integrated into clinical practice. If clinically validated, better understanding of these genetic variations may provide new opportunities for personalized diagnostic, pharmacogenetic-based drug selection and best treatment in personalized medicine. However, numerous gaps remain unsolved due to the lack of underlying pathological mechanisms for how genetic predisposition could contribute to CVD. This review provides an overview of the extraordinary scientific progress in our understanding of genetic and genomic basis of CVD as well as the development of relevant genetic biomarkers for this disease. Some of the actual limitations to the promise of these markers and their translation for the benefit of patients will be discussed.

Influence of genetic variations on levels of inflammatory markers of healthy subjects at baseline and one week after clopidogrel therapy; results of a preliminary study

We aimed to assess the association between the most common polymorphisms of cytochrome P450 (CYP) epoxygenases on the plasma levels of inflammatory markers in a population of healthy subjects. We also sought to determine whether CYP2C19*2 polymorphism is associated with the anti-inflammatory response to clopidogrel. In a population of 49 healthy young males, the baseline plasma levels of inflammatory markers including C-reactive protein, haptoglobin, orosomucoid acid, CD-40 were compared in carriers vs. non-carriers of the most frequent CYP epoxygenase polymorphisms: CYP2C9*2, CYP2C9*3, CYP2C19*2, CYP2C8*2 and CYP2J2*7. Also, the variation of inflammatory markers from baseline to 7 days after administration of 75 mg per day of clopidogrel were compared in carriers vs. non-carriers of CYP2C19* allele and also in responders vs. hypo-responders to clopidogrel, determined by platelet reactivity tests. There was no significant association between epoxygenase polymorphisms and the baseline levels of inflammatory markers. Likewise, CYP2C19* allele was not associated with anti-inflammatory response to clopidogrel. Our findings did not support the notion that the genetic variations of CYP epoxygenases are associated with the level of inflammatory markers. Moreover, our results did not support the hypothesis that CYP2C19*2 polymorphism is associated with the variability in response to the anti-inflammatory properties of clopidogrel.