ABCB1 C3435T and CYP2C19*2 polymorphisms in a Palestinian and Turkish population: A pharmacogenetic perspective to clopidogrel

The Effect of CYP2C19 and Nongenetic Factors on Clopidogrel Responsiveness in the MENA Region: A Systematic Review

Clopidogrel is the cornerstone antiplatelet used in the treatment and prevention of thrombotic events. Some studies examined the effect of CYP2C19 polymorphism and nongenetic factors on clopidogrel response in the Middle East and North Africa (MENA) region. However, the consistency among these studies is yet unknown. This study aims to estimate the prevalence of CYP2C19 genetic variants in MENA region and to evaluate the effect of these variants as well as the nongenetic factors on clopidogrel responsiveness. A systematic literature search was performed to identify relevant articles. Only observational studies were included. A total of 20 studies in 8 different populations were included. The CYP2C19*2 variant is the most prevalent loss-of-function (LOF) allele in the MENA region (1.7%-35%). The frequency of CYP2C19*17 ranged from 5.3% to 26.9%. Of the 9 studies, 6 found an association between carriers of at least 1 LOF allele and clopidogrel resistance. Older age, high body mass index, females, and the use of calcium channel blockers were associated with clopidogrel resistance as well. Association between the CYP2C19*2 allele and clopidogrel resistance is common among MENA populations. Future studies should focus on having larger sample sizes to detect other minor variant alleles and their effect on bleeding and cardiovascular outcomes.

The clinical effects of CYP2C19 *2 allele frequency on Palestinian patients receiving clopidogrel after percutaneous coronary intervention

BackgroundCYP2C19 loss-of-function polymorphic alleles (*2 and *3) have been documented to impair clopidogrel metabolism, and represent a risk factor for major adverse cardiac events. CYP2C19 polymorphism exhibits marked ethnic heterogeneity. Objective To determine the prevalence of CYP2C19 *2 and *3 alleles in a cohort of Palestinian patients managed with percutaneous coronary intervention and dual antiplatelet therapy, and to determine their role in causing major adverse cardiac events. Setting The blood samples were collected at the European Gaza Hospital, and the molecular techniques performed at the molecular genetics laboratory of the Islamic university of Gaza. Method The frequency of CYP2C19 *2 and *3 alleles was determined in 110 patients managed with percutaneous coronary intervention and clopidogrel. Genotyping was performed by PCR-RFLP. Personal and clinical data was obtained from patient record and 6-month follow-up for major adverse cardiac events. Main outcome measureCYP2C19 genotype, personal and clinical data and incidence of major adverse cardiac events. Results The frequency of CYP2C19 *1, *2 and *3 alleles was 82.3%, 15.5% and 2.3% respectively. Genotyping analysis showed that, 67.3% were homozygotes for CYP2C19 *1, 27.3% were *1/*2, 2.7% with *1/*3 genotype, 1.8% were *2/*3 and 0.9% were *2/*2. These frequencies were consistent with those of Caucasian populations. According to this study the poor metabolizers phenotype frequency was 2.7%, which is in the same range reported in Caucasians (2-5%) and lower than Oriental populations 13-23%. A strong significant relation was found between major adverse cardiac events and carrying the variant allele CYP2C19 *2 (P = 0.001). On the other hand, there was no significant relation between major adverse cardiac events and carrying the variant allele CYP2C19 *3 (P = 0.324). Conclusion The CYP2C19 *2 allele is relatively common in our population, and its associated reduced metabolic activity deserves attention as it leads to an increased incidence of major adverse cardiac events in the follow-up of patients receiving clopidogrel.

Population-scale genomics-Enabling precision public health

The current excitement for affordable genomics technologies and national precision medicine initiatives marks a turning point in worldwide healthcare practices. The last decade of global population sequencing efforts has defined the enormous extent of genetic variation in the human population resulting in insights into differential disease burden and response to therapy within and between populations. Population-scale pharmacogenomics helps to provide insights into the choice of optimal therapies and an opportunity to estimate, predict and minimize adverse events. Such an approach can potentially empower countries to formulate national selection and dosing policies for therapeutic agents thereby promoting public health with precision. We review the breadth and depth of worldwide population-scale sequencing efforts and its implications for the implementation of clinical pharmacogenetics toward making precision medicine a reality.

Analysis of the CYP2C19 genotype associated with bleeding in Serbian STEMI patients who have undergone primary PCI and treatment with clopidogrel

PURPOSE

Bleeding is one of the possible adverse events during clopidogrel therapy. The CYP2C19 gene is the most significant genetic factor which influences response to clopidogrel treatment. We aimed to examine the contribution of the CYP2C19 gene to bleeding occurrence during clopidogrel therapy in Serbian patients with ST segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

METHODS

This case-control study included 53 patients who experienced bleeding and 55 patients without bleeding. Bleeding events were defined and classified using the Bleeding Academic Research Consortium (BARC) criteria. All patients were prescribed daily doses of clopidogrel during the 1-year follow-up after PCI. The CYP2C19*17 (c.-806C>T, rs12248560), rs11568732 (c.-889T>G, CYP2C19*20), CYP2C19*2 (c.681G>A; rs4244285) and CYP2C19*3 (c.636G>A; rs4986893) variants were analysed in all 108 patients. Additionally, sequencing of all nine exons, 5'UTR and 3'UTR in the rs11568732 carriers was performed.

RESULTS

Association between bleeding (BARC type ≥ 2) and the CYP2C19*17 variant was not observed [odds ratio (OR), 0.53; 95% confidence interval (CI), 0.2-1.1; p = 0.107). The rs11568732 variant showed significant association with bleeding (OR, 3.7; 95% CI, 1.12-12.44; p = 0.025). Also, we found that the rs11568732 variant appears independently of haplotype CYP2C19*3B, which is contrary to the previous findings.

CONCLUSIONS

Our results indicate the absence of CYP2C19*17 influence and turn the attention to the potential significance of the rs11568732 variant in terms of adverse effects of clopidogrel. However, it is necessary to conduct an independent conformation study in order to verify this finding. Also, an analysis of the functional implication of the rs11568732 variant is necessary in order to confirm the significance of this variant, both in relation to its influence on gene expression and in relation to its medical significance.

Harnessing Knowledge on Very Important Pharmacogenes CYP2C9 and CYP2C19 Variation for Precision Medicine in Resource-Limited Global Conflict Zones

Pharmacogenomics harnesses the utility of a patient's genome (n = 1) in decisions on which therapeutic drugs and in what amounts should be administered. Often, patients with shared ancestry present with comparable genetic profiles that predict drug response. However, populations are not static, thus, often, population mobility through migration, especially enmasse as is seen for refugees, changes the pharmacogenetic profiles of resultant populations and therefore observed responses to commonly used therapeutic drugs. For example, in the aftermath of the Syrian civil war since 2011, millions have fled their homes to neighboring countries in the Middle East. The growing permanence of refugees and mass migrations is a call to shift our focus in the life sciences community from old models of pharmaceutical innovation. These seismic social changes demand faster decisions for "population-to-population bridging," whereby novel drugs developed in or for particular regions/countries can meet with rational regulatory decisions/approval in world regions impacted by migrant/refugee populations whose profiles are dynamic, such as in the Eastern Mediterranean region at present. Thus, it is important to characterize and report on the prevalence of pharmacogenes that affect commonly used medications and predict if population changes may call for attention to particular differences that may impact health of patients. Thus, we report here on four single-nucleotide polymorphism (SNP) variations in CYP2C9 and CYP2C19 genes among Mersin-Turkish healthy volunteers in the Mersin Province in the Eastern Mediterranean region that is currently hosting a vast number of migrant populations from Syria. Both CYP2C9 and CYP2C19 are very important pharmacogene molecular targets. We compare and report here on the observed SNP genetic variation in our sample with data on 12 world populations from dbSNP and discuss the feasibility of forecasting the pharmacokinetics of drugs utilized by migrant communities in Mersin and the Eastern Mediterranean region. This study can serve as a catalyst to invest in research in Syrian populations currently living in the Eastern Mediterranean. The findings have salience for rapid and rational regulatory decision-making for worldwide precision medicine and, specifically, "pharmacogenovigilance-guided bridging of pharmacokinetics" across world populations in the current era of planetary scale migration.

Genetic Polymorphisms of Cytochrome P450 Enzymes and Transport Proteins in a Russian Population and Three Ethnic Groups of Dagestan

AIM

The objective of this study was to investigate the prevalence of polymorphic markers of the CYP2C19, CYP2C9, CYP2D6, SLCO1B1, and ABCB1 genes among the three ethnic groups in Dagestan and compare it with the carrier frequency of these markers among the Russian population living in Moscow.

METHODS

The study involved 186 healthy, unrelated, and chronic medication-free volunteers (53 males and 133 females) of the three ethnic groups in the Dagestan Republic: 46 Laks, 90 Avars, and 50 Dargins. Genotyping was performed using real-time polymerase chain reaction-based methods. The allelic prevalences of the three Dagestan peoples were compared with ethnic Russians from the Moscow region.

RESULTS

Statistically significant differences for the following gene polymorphisms: CYP2C19*17, CYP2C9*3, ABCB1 (C3435T), SLCO1B1*5 were found between the Russian population and the three ethnic groups of the Dagestan republic.

CONCLUSION

The data obtained from this study will help with prioritization genotyping in the region.

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.

Genomewide Association Study Identifies Novel Genetic Loci That Modify Antiplatelet Effects and Pharmacokinetics of Clopidogrel

Genetic variants in the pharmacokinetic (PK) mechanism are the main underlying factors affecting the antiplatelet response to clopidogrel. Using a genomewide association study (GWAS) to identify new genetic loci that modify antiplatelet effects in Chinese patients with coronary heart disease, we identified novel variants in two transporter genes (SLC14A2 rs12456693, ATP‐binding cassette [ABC]A1 rs2487032) and in N6AMT1 (rs2254638) associated with P2Y12 reaction unit (PRU) and plasma active metabolite (H4) concentration. These new variants dramatically improved the predictability of PRU variability to 37.7%. The associations between these loci and PK parameters of clopidogrel and H4 were observed in additional patients, and its function on the activation of clopidogrel was validated in liver S9 fractions (P < 0.05). Rs2254638 was further identified to exert a marginal risk effect for major adverse cardiac events in an independent cohort. In conclusion, new genetic variants were systematically identified as risk factors for the reduced efficacy of clopidogrel treatment.