Frequency of cytochrome P450 CYP2C9 variants in a Turkish population and functional relevance for phenytoin

Fibrinogen-Aα THR312ALA Polymorphism is Associated to Chronic Thromboembolic Pulmonary Hypertension in Turkey

BACKGROUND

Chronic thromboembolic pulmonary hypertension is a condition that occurs after mechanical obstruction of the pulmonary arteries by thrombus. Since the frequency and demographics of chronic thromboembolic pulmonary hypertension differ between countries, it is thought that genetic factors may play a role in its development. The aim of this study is to reveal the status of VKORC1, CYP2C9*3, CYP2C9*7, and fibrinogen-Aα THR312ALA gene polymorphisms in chronic thromboembolic pulmonary hypertension patients in Turkey.

METHODS

In this prospective cross-sectional study, a total of 46 chronic thromboembolic pulmonary hypertension patients and 106 healthy volunteers were included. Polymerase chain reaction-restriction fragment length polymorphism method was used to determine candidate gene polymorphisms for chronic thromboembolic pulmonary hypertension. The general population parameters of each locus were calculated, and the relationship between dominant, codominant, and recessive genotype models and chronic thromboembolic pulmonary hypertension was analyzed.

RESULTS

For the fibrinogen-Aα gene, those with the THR/THR genotype were found to have a 13.51 (95% CI: 2.688-33.333) times less susceptibility rate to the disease than those with the ALA/THR genotype, the susceptibility of THR/ALA genotype to the disease was 5.026 (95% CI: 1.774-14.242) times more than those with ALA/ALA genotype. There was no difference between patient groups for VKORC1, CYP2C9*3 genes (P >.05). Since the CYP2C9*7 patient group was monomorphic for the ILE allele, the patient/control odds ratio and 95% CI could not be calculated.

CONCLUSION

This study shows that there is an association between the fibrinogen-Aα gene ALA polymorphism at the amino acid position of 312 and the development of chronic thromboembolic pulmonary hypertension, but not between the CYP2C9 and VKORC1 gene polymorphisms.

Variations in the Frequencies of Polymorphisms in the CYP450s Genes in Eight Major Ethnicities of Iran: A Review of the Human Data

Genetic polymorphisms in cytochrome P450 genes can cause variation in metabolism. Thus, single nucleotide variants significantly impact drug pharmacokinetics, toxicity factors, and efficacy and safety of medicines. The distribution of CYP450 alleles varies drastically across ethnicities, with significant implications for personalized medicine and the healthcare system. We combined whole-genome and exome sequencing data to provide a review of CYP450 allele polymorphisms with clinical importance. Data were collected from 800 unrelated Iranians (100 subjects from 8 major ethnicities of Iran), more than 32,000 unrelated Europeans (other than Caucasian), and four Middle Eastern countries. We analyzed the frequencies and similarities of 17 CYP450 frequent alleles related to nine important CYP450 isoenzymes and homozygous and heterozygous genotypes based on these alleles in eight major Iranian ethnics by integrating these data with population-specific linkage information and compared these datasets with mentioned populations.

Genetic abnormality of cytochrome-P2C9*3 allele predisposes to epilepsy and phenytoin-induced adverse drug reactions: genotyping findings of cytochrome-alleles in the North Indian population

Background

This research aims to study the association of genetic polymorphism in genes coding for CYP2C9 and CYP2C19 in phenytoin-induced dose-related toxicity and to assess if the presence of allele CYP2C9*3 plays a role in phenytoin-induced idiosyncratic adverse effects. Current observational case control study included 142 patients with phenytoin-induced adverse drug reactions (ADRs) and 100 controls. All these patients underwent genotyping to determine the type of CYP2C9 allele [CYP2C9*1, CYP2C9*2 or CYP2C9*3) and CYP2C19 allele (CYP2C19*1, CYP2C19*2 or CYP2C19*3] by real-time polymerase chain reaction (RT-PCR) using Applied Biosystems (ABI) 7500 Real-Time PCR System (USA).

Results

Presence of homozygous status for allele CYP2C9*3 was associated with significantly higher risk of phenytoin-induced dose-dependent ADRs, dose-independent ADRs, gum hyperplasia, and skin rash. Presence of heterozygous status for allele CYP2C9*3 was associated with significantly higher risk of phyenytoin-induced dose-dependent ADRs and dose-independent ADRs. Presence of either heterozygous or homozygous status for CYP2C9*2 and CYP2C19*2 did not have any bearing on dose-related side effects. None of the patients showed CYP2C19*3 allele.

Conclusion

Variant alleles of CYP2C9*3 are significantly overexpressed among patients with phenytoin-induced ADRs, thereby suggesting the role for CYP2C9 genotype testing to predict risk of phenytoin-related ADRs.

CYP2C9 gen polimorfizmlerinin losartan kullanan hipertansif hastalarda tedavi yanıtı üzerine etkisi

Amaç: Bu çalışmada, anti-hipertansif olarak losartan kullanan hastalarda CYP2C9 polimorfizmlerinin tedavi yanıtı üzerine etkileri incelenmiştir. Yöntemler: Araştırmaya yeni tanı almış, evre 1 esansiyel hipertansiyonu olan 74 hasta dahil edildi. Bu hastalara tedavi öncesi ve losartan başlandıktan altı hafta sonra kan basıncı ölçümleri yapılarak elde edilen kan basıncı düşüşleri kaydedildi. Hastalardan ilk tanı sırasında alınmış olan kan örneklerinden DNA izolasyonu yapılarak CYP2C9 *2 ve *3 polimorfik alelleri için genetik analizler yapıldı. Polimorfik alelleri taşıyan bireyler ile yabanıl tip (wild-type) genotip taşıyıcılarının anti-hipertansif tedavi yanıtları karşılaştırıldı. Bulgular: CYP2C9*1*2 genotipine sahip hastalar, yabanıl tip genotipe sahip hastalar ile kıyaslandığında diyastolik kan basıncı için gruplar arasında istatistiksel açıdan anlamlı fark saptanmazken, sistolik kan basıncındaki düşüşün yabanıl tip genotipe sahip hastalarda daha belirgin olma eğiliminde olduğu görüldü. CYP2C9*1*3 genotipi ise tedavi sonuçlarında anlamlı bir değişikliğe neden olmadı. Sonuç: Bulgularımız, CYP2C9*1*2 polimorfizminin hipertansif hastaların losartan ile tedavisinde sistolik kan basıncı yanıtını etkileyebileceğini düşündürmektedir. Öte yandan, CYP2C9*1*3 genotipinin sistolik veya diyastolik kan basıncı yanıtlarıyla ilişkisi gösterilememiştir. Anahtar kelimeler: Hipertansiyon, losartan, CYP2C9, genetik polimorfizm, farmakogenetik

Pharmacogenetics of the cytochromes P450: Selected pharmacological and toxicological aspects

With the availability of detailed genomic data on all 57 human cytochrome P450 genes, it is clear that there is substantial variability in gene product activity with functionally significant polymorphisms reported across almost all isoforms. This article is concerned mainly with 13 P450 isoforms of particular relevance to xenobiotic metabolism. After brief review of the extent of polymorphism in each, the relevance of selected P450 isoforms to both adverse drug reaction and disease susceptibility is considered in detail. Bleeding due to warfarin and other coumarin anticoagulants is considered as an example of a type A reaction with idiosyncratic adverse drug reactions affecting the liver and skin as type B. It is clear that CYP2C9 variants contribute significantly to warfarin dose requirement and also risk of bleeding, with a minor contribution from CYP4F2. In the case of idiosyncratic adverse drug reactions, CYP2B6 variants appear relevant to both liver and skin reactions to several drugs with CYP2C9 variants also relevant to phenytoin-related skin rash. The relevance of P450 genotype to disease susceptibility is also considered but detailed genetic studies now suggest that CYP2A6 is the only P450 relevant to risk of lung cancer with alleles associated with low or absent activity clearly protective against disease. Other cytochrome P450 genotypes are generally not predictors for risk of cancer or other complex disease development.

Genetic Determinants in HLA and Cytochrome P450 Genes in the Risk of Aromatic Antiepileptic-Induced Severe Cutaneous Adverse Reactions

Adverse drug reaction (ADR) is a pressing health problem, and one of the main reasons for treatment failure with antiepileptic drugs. This has become apparent in the event of severe cutaneous adverse reactions (SCARs), which can be life-threatening. In this review, four hypotheses were identified to describe how the immune system is triggered in the development of SCARs, which predominantly involve the human leukocyte antigen (HLA) proteins. Several genetic variations in HLA genes have been shown to be strongly associated with the susceptibility to developing SCARs when prescribed carbamazepine or phenytoin. These genetic variations were also shown to be prevalent in certain populations. Apart from the HLA genes, other genes proposed to affect the risk of SCARs are genes encoding for CYP450 drug-metabolising enzymes, which are involved in the pharmacokinetics of offending drugs. Genetic variants in CYP2C9 and CYPC19 enzymes were also suggested to modulate the risk of SCARs in some populations. This review summarizes the literature on the manifestation and aetiology of antiepileptic-induced SCARs, updates on pharmacogenetic markers associated with this reaction and the implementation of pre-emptive testing as a preventive strategy for SCARs.

Genomic Risk Factors Driving Immune-Mediated Delayed Drug Hypersensitivity Reactions

Adverse drug reactions (ADRs) remain associated with significant mortality. Delayed hypersensitivity reactions (DHRs) that occur greater than 6 h following drug administration are T-cell mediated with many severe DHRs now associated with human leukocyte antigen (HLA) risk alleles, opening pathways for clinical prediction and prevention. However, incomplete negative predictive value (NPV), low positive predictive value (PPV), and a large number needed to test (NNT) to prevent one case have practically prevented large-scale and cost-effective screening implementation. Additional factors outside of HLA contributing to risk of severe T-cell-mediated DHRs include variation in drug metabolism, T-cell receptor (TCR) specificity, and, most recently, HLA-presented immunopeptidome-processing efficiencies via endoplasmic reticulum aminopeptidase (ERAP). Active research continues toward identification of other highly polymorphic factors likely to impose risk. These include those previously associated with T-cell-mediated HLA-associated infectious or auto-immune disease such as Killer cell immunoglobulin-like receptors (KIR), epistatically linked with HLA class I to regulate NK- and T-cell-mediated cytotoxic degranulation, and co-inhibitory signaling pathways for which therapeutic blockade in cancer immunotherapy is now associated with an increased incidence of DHRs. As such, the field now recognizes that susceptibility is not simply a static product of genetics but that individuals may experience dynamic risk, skewed toward immune activation through therapeutic interventions and epigenetic modifications driven by ecological exposures. This review provides an updated overview of current and proposed genetic factors thought to predispose risk for severe T-cell-mediated DHRs.

Metabolizer phenotype prediction in different Peruvian ethnic groups through CYP2C9 polymorphisms

OBJECTIVES

The CYP2C9 gene have three common alleles, CYP2C9*1, CYP2C9*2 and CYP2C9*3, associated with different homozygous (*1/*1, *2/*2 and *3/*3) and heterozygous (*1/*2 and *1/*3) genotypes, which in turn are related to extensive (gEM), intermediate (gIM) and poor (gPM) metabolizers. Likewise, the inter-ethnic variability was intimately associated with different drug metabolism. Therefore, the aim of the present study was predict the metabolizer phenotypes in different Peruvian ethnic groups from lowland (<2,500 m) and highland (>2,500 m).

METHODS

TaqMan genotyping assays were performed in a group of 174 healthy unrelated Peruvian individuals.

RESULTS

In this study, the allelic comparison between the three eco-regions showed that the CYP2C9*1 was the most common in Andean (96.32%); the *2 was the most frequent in Coast (7.45%, p<0.05). Regarding the *3 was the most common in Amazonian (6.25%, p<0.05). In a corroborative manner, the gEM was the most common in Andean (94.74%), the gIM in Coast (17.02%) and gPM in Amazonian (6.25%) populations.

CONCLUSIONS

Our study provides a valuable source of information about to metabolizer phenotype drugs in different Peruvian ethnic groups. In this way, it could be established suitable genetic-dosage medicaments for various common diseases in these heterogenetic populations.

Pharmacogenetics of tamoxifen therapy in Asian populations: from genetic polymorphism to clinical outcomes

BACKGROUND

Compared with western countries, Asian breast cancer patients have unique pathological and biological characteristics. Most of them are premenopausal women with HR positive. Tamoxifen as the first-line drug for premenopausal women with HR+ is involved in multiple enzymes and transporters during metabolizing and transporting process. Variants that cause decreased or inactive gene products leading to abnormal responses in tamoxifen therapy have well been studied in western countries, whereas such information is much less reported in Asian populations.

OBJECTIVE

In order to elucidate the relationship between genetic variants and tamoxifen-induced individual drug reactions in different Asian populations and further identify genotypes/phenotypes with potential therapeutic significance.

METHODS

We reviewed the frequencies of genetic variants in major enzymes and transporter genes involved in the metabolism and transport of tamoxifen across Asian populations as well as significant correlations between genotypes/metabolic phenotypes and metabolites concentrations or BC clinical outcomes.

RESULTS

Significant inter-ethnic differences in allele frequencies was found among Asian populations, such as CYP2D6*4, *10, *41, CYP2C9*2, ABCB1 C3435T and SLCO1B1*5, and CYP2D6*10/*10 is the most common genotype correlated with adverse clinical outcomes. Moreover, we summarized the barriers and controversies of implementing pharmacogenetics in tamoxifen therapy and concluded that more population-specific pharmacogenetic studies are needed in the future.

CONCLUSION

This review revealed more systematic pharmacogenomics of genes involved in the metabolism and transport besides CYP2D6, are required to optimize the genotyping strategies and guide the personalized tamoxifen therapy in Asian populations.

Variations in the frequencies of polymorphisms in the CYP2C9 gene in six major ethnicities of Pakistan

Genetic variation in cytochrome P450 (CYP) 2C9 is known to cause significant inter-individual differences in drug response and adverse effects. The frequencies of CYP2C9*2 and CYP2C9*3, both of which are responsible for the low activity of the enzyme, are not known in the Pakistani population. Therefore, we screened various ethnic groups residing in Pakistan for these polymorphisms. A total of 467 healthy human volunteers were recruited from six major ethnicities of Pakistan after written informed consent. Our results indicate that about 20% of the Pakistani population has a genotype containing at least one low activity allele. Ethnic Punjabi and Pathan populations had the highest frequencies of wild type genotypes while Urdu, Seraiki, and Sindhi populations showed higher rates of both low activity genotypes. The Baloch population showed the highest rates of low activity genotypes with less than 50% of the samples showing wild type genotypes, suggesting that more than half of the Baloch population possesses low activity genotypes. The frequencies found in various ethnic groups in Pakistan were comparable with ethnicities in the South Asian region except for the Baloch population. These results suggest that pharmacogenetics screening for low activity genotypes may be a helpful tool for clinicians while prescribing medications metabolized by CYP2C9.

The Effect of CYP2C9 Genotype Variants in Type 2 Diabetes on the Pharmacological Effectiveness of Sulfonylureas, Diabetic Retinopathy, and Nephropathy

Aim

Type 2 diabetes (T2D), as a major cause of morbidity and mortality, is predicted to have a prevalence of 629 million by 2045. As diabetic patients show considerable inter-individual variation in response to antidiabetic treatment, this study aimed to investigate the gene polymorphism of cytochrome P450 as well as the effectiveness and safety of glibenclamide and gliclazide for different genotypes of CYP2C9. Besides, the chronic side effects of T2D including retinal microvasculature complications or retinopathy and renal dysfunction due to nephropathy in different genotypes were considered.

Patients and Methods

The participants including 80 T2D patients treated with glibenclamide or gliclazide were recruited from university hospitals of Ahvaz Jundishpur University of Medical Sciences, Ahvaz, in the southwest of Iran. Blood samples were collected from the patients at 2.5h after the morning dose of glibenclamide and 12h after the last dose of gliclazide. Genotyping from the extracted DNA was, then, performed using PCR-RFLP. The plasma level of glibenclamide and gliclazide was, in turn, measured by the reverse-phase high-pressure liquid chromatography.

Results

The results showed that the wild-type allele, i.e., CYP2C9*1, occurred in the highest frequency (0.8), while the frequency rates of the mutant allele, i.e., CYP2C9*2 and CYP2C9*3, were 0.15 and 0.05, respectively. Moreover, no significant association was found between any of the genotypes as well as the clinical and biochemical characteristics of the patients. The findings also showed that the plasma level of sulfonylureas (i.e., glibenclamide and gliclazide) was the highest in the patients with the CYP2C9*3 allele. It was also found that 75.9% of the patients with variant genotypes had experienced hypoglycemia events. Furthermore, in the absence of wild type allele, a significant increase was observed in retinopathy (p=0.039) and nephropathy (p=0.05).

Conclusion

The findings can provide guidelines for the optimal management of the treatment protocols with sulfonylurea intended to control the T2D complications.

Pharmacogenomic considerations for medications in the perioperative setting

Several high-profile examples of adverse outcomes from medications used in the perioperative setting are well known (e.g., malignant hyperthermia, prolonged apnea, respiratory depression, inadequate analgesia), leading to an increased understanding of genetic susceptibilities underlying these risks. Pharmacogenomic information is increasingly being utilized in certain areas of medicine. Despite this, routine preoperative genetic screening to inform medication risk is not yet standard practice. In this review, we assess the current readiness of pharmacogenomic information for clinical consideration for several common perioperative medications, including description of key pharmacogenes, pharmacokinetic implications and potential clinical outcomes. The goal is to highlight medications for which emerging or considerable pharmacogenomic information exists and identify areas for future potential research.

Interpretation of the effect of CYP2C9, VKORC1 and CYP4F2 variants on warfarin dosing adjustment in Turkey

It was aimed to underline the importance and explain the meaning of genetic testing in warfarin dosing and investigate and evaluate the contributions of the CYP2C9, VKORC1, and CYP4F2 variants in a Turkish population. Two hundred patients were genotyped for CYP2C9 (rs1799853, rs1057910 and rs56165452), VKORC1 (rs9934438, rs8050894, rs9923231, rs7294 and rs2359612) and CYP4F2 (rs2108622), yet, only 127 patients were found suitable for further evaluation in terms of their personal response to warfarin due to long term usage and available INR and dose usage information. The DNA sequences were determined by the ABI PRISM 3100 Genetic Analyzer to 3130xl System (Applied Biosystems, Foster City, California). Warfarin dose application suggestions by warfaringdosing.org, FDA and MayoClinic were followed. Dose requirements in the Turkish population were found higher than the suggested doses by warfarindosing.org. The multivariate logistic regression analysis reveals the utilization of VCORC1 genetic evaluation is valuable in warfarin dosing (low and moderate vs. high) in this study (p < 0.001). The present study provides findings for clinicians to adapt the genetic data to the daily practice. We observed that the VKORC1 variant showed a more potent impact in warfarin dosing in this study.

Targeted metabolomic analysis of plasma metabolites in patients with coronary heart disease in southern China

Coronary heart disease (CHD), one of the leading causes of death in the world, is a complex metabolic disorder due to genetic and environmental interactions. The potential mechanisms and diagnostic biomarkers for different types of coronary heart disease remain unclear. Metabolomics is increasingly considered to be a promising technology with the potential to identify metabolomic features in an attempt to distinguish the different stages of CHD.We aimed to investigate serum metabolite profiling between CHD patients and normal coronary artery (NCA) subjects and identify metabolic biomarkers associated with CHD progression in an ethnic Hakka population in southern China.Using a novel targeted metabolomics approach, we explored the metabolic characteristics of CHD patients. Blood samples from 302 patients with CHD and 59 NCA subjects were collected that analyses using targeted liquid-chromatography coupled with tandem mass spectrometry (LC-MS).A total of 361 blood samples were determined using targeted LC-MS. Plasma concentrations for trimetlylamine oxide (TMAO), choline, creatinine, and carnitine were significantly higher in patients with CHD compared to the NCA cohort. Further, we observed that the concentration of the 4 metabolites were higher than that of the NCA group in any group of CHD, which including acute myocardial infarction (AMI), unstable angina (UA), and stable angina (SA). In addition, the diagnostic model was constructed based on the metabolites identified and the ROC curve of the NCA subjects and CHD patients were performed. For choline and creatinine, the AUCs ranged from 0.720 to 0.733. For TMAO and carnitine, the AUCs ranged from 0.568 to 0.600.In conclusion, the current study illustrates the distribution of 4 metabolites between CHD patients and NCA subjects. Metabolomics analysis may yield novel predictive biomarkers that will potentially provide value for clinical diagnosis of CHD.

FREQUENCIES OF POLYMORPHISMS IN THE CYTOCHROME’S P450 GENES OF WARFARIN TRANSFORMATION IN A EUROPEAN POPULATION OF EASTERN SIBERIA

Background. Genotypes of the cytochrome p450 isoform (CYP2C9 and CYP4F2) determine warfarin dose requirements. Frequencies of risk alleles and genotypes of CYP2C9 and CYP4F2 gene vary in different races and ethnic groups.

Aim. This study analyzed the frequencies of *2, *3 alleles of CYP2C9 gene and the 1347 C>T allele of CYP4F2 gene in the Caucasians of Eastern Siberia, and compare with other populations.

Materials and methods. Participants were 147 patients (Caucasians): 67 (45.58 %) man and 80 (54.42 %) women), taking warfarin for the prevention of thrombosis with a mean age of 64.74 ± 14.29 years. There were patients with atrial fibrillation – 77 (52.38 %) persons, coronary artery disease – 10 (6.80 %), pulmonary embolism – 5 (3.40 %), 15 (10.20 %) patients after implantation of an mechanical heart valve, etc. The subjects were genotyped for CYP2C9 (*1,*2,*3), and CYP4F2 (1347 C>T) by real-time polymerase chain reaction (RT-PCR) using “Pharmacogenetics Warfarin” reagent kits (DNA technology, Russia).

Results. 69.4 % of Caucasians of Eastern Siberia (Russians), have two functional alleles (*1/*1) of CYP2C9 (they’re extensive/normal metabolizers), the number of intermediate metabolizers (*1/*2, *1/*3) was 29.8 % and 0.68 % of slow metabolizers (*3/*3). Homozygous carriers of two non-functional alleles *2 and *3 (*2/*2, *2/*3) were absent. Carriers of one coumarin-resistant Т-allele of CYP4F2 were 57 (38.7 %) respondents, two coumarin-resistant alleles – 10 (6.8 %) respondents.

Conclusions. Frequencies of polymorphisms in the Cytochrome’s p450 genes of warfarin transformation in a European population of Eastern Siberia have no differences with other European populations of the world

Polymorphic analysis of CYP2C9 gene in Vietnamese population

Genetic variations in CYP2C9 are associated to inter-individual variability of drugs metabolism and response. The only report has been done previously mainly focusing on the common variant alleles of CYP2C9 in Vietnamese Kinh subjects. However, little is known about the complete spectrum of this gene polymorphism in different ethnic groups of Vietnam. We sequenced the promoter region and all exons of CYP2C9 in 100 healthy unrelated Vietnamese Kinh subjects. Additionally, common CYP2C9 variants, *2 and *3, were also analyzed by RFLP-PCR in extra 194 Kinh subjects and 279 of other four ethnic groups in Vietnam. The results of these common variants observed from five ethnic groups were compared with other populations in the world. Seven previously reported alleles and two genotypes were determined in Kinh subjects. The percentage of CYP2C9*1 and CYP2C9*3 alleles are 96.5 and 3.5%, respectively. We found one novel non-synonymous variant in exon 7 leading to amino acid change at 363 position from proline to histidine. Functional analysis by SIFT and Polyphen-2 indicated that this mutation is intolerant and probably damaging. Prevalence of CYP2C9*2 observed in Vietnamese population was significantly lower compared with that of other populations in the South and West of Asia as well as in Europe. This study provides information of genetic distribution pattern of CYP2C9 in Vietnamese, which would be useful for optimizing drug therapies in Vietnam.

The role of ethnicity on pregnancy outcomes in women with epilepsy: The need for specific research

The role of ethnicity on pregnancy outcomes of women with epilepsy (WWE) has received little research attention but is important to guide management. The aim of this review is to identify and describe current knowledge of ethnicity for WWE giving birth. Literature searches were performed with the following terms: ethnic/race combined with epilepsy/seizure, antiepileptic drugs (AED), and/or pregnancy, and combined them with congenital malformation, birth outcome, or pregnancy complication, with English language restriction in PubMed, EMBASE, and Web of Science. Both primary studies and review articles were included. Ethnicity disparities exist in specific congenital malformations, pregnancy complications, and birth outcomes among the general population. There is also ethnicity-related diversity of AED disposition. Information on ethnicity is rarely considered in studies about pregnant WWE. The association between ethnicity and pregnancy outcomes of WWE remains to be elucidated. The lack of data relating to ethnicity in pregnancy studies among WWE needs addressing. Knowledge of potential effects of ethnicity on pregnancy outcomes in WWE will help inform better clinical care around the world.

CYP2C9 polymorphisms in epilepsy: influence on phenytoin treatment

Phenytoin (PHT) is an antiepileptic drug widely used in the treatment of focal epilepsy and status epilepticus, and effective in controlling focal seizures with and without tonic-clonic generalization and status epilepticus. The metabolization of PHT is carried out by two oxidative cytochrome P450 enzymes CYP2C9 and CYP2C19; 90% of this metabolization is done by CYP2C9 and the remaining 10% by CYP2C19. Genetic polymorphism of CYP2C9 may reduce the metabolism of PHT by 25-50% in patients with variants *2 and *3 compared to those with wild-type variant *1. The frequency distribution of CYP2C9 polymorphism alleles in patients with epilepsy around the world ranges from 4.5 to 13.6%, being less frequent in African-Americans and Asians. PHT has a narrow therapeutic range and a nonlinear pharmacokinetic profile; hence, its poor metabolization has significant clinical implications as it causes more frequent and more serious adverse effects requiring discontinuation of treatment, even if it had been effective. There is evidence that polymorphisms of CYP2C9 and the use of PHT are associated with an increase in the frequency of some side effects, such as cerebellar atrophy, gingival hypertrophy or acute cutaneous reactions. The presence of HLA-B*15:02 and CYP2C9 *2 or *3 in the same patient increases the risk of Stevens-Johnson syndrome and toxic epidermal necrolysis; hence, PHT should not be prescribed in these patients. In patients with CYP2C9 *1/*2 or *1/*3 alleles (intermediate metabolizers), the usual PHT maintenance dose (5-10 mg/kg/day) must be reduced by 25%, and in those with CYP2C9 *2/*2, *2/*3 or *3/*3 alleles (poor metabolizers), the dose must be reduced by 50%. It is controversial whether CYP2C9 genotyping should be done before starting PHT treatment. In this paper, we aim to review the influence of CYP2C9 polymorphism on the metabolization of PHT and the clinical implications of poor metabolization in the treatment of epilepsies.

Pharmacogenomics of CYP2C9: Functional and Clinical Considerations

CYP2C9 is the most abundant CYP2C subfamily enzyme in human liver and the most important contributor from this subfamily to drug metabolism. Polymorphisms resulting in decreased enzyme activity are common in the CYP2C9 gene and this, combined with narrow therapeutic indices for several key drug substrates, results in some important issues relating to drug safety and efficacy. CYP2C9 substrate selectivity is detailed and, based on crystal structures for the enzyme, we describe how CYP2C9 catalyzes these reactions. Factors relevant to clinical response to CYP2C9 substrates including inhibition, induction and genetic polymorphism are discussed in detail. In particular, we consider the issue of ethnic variation in pattern and frequency of genetic polymorphisms and clinical implications. Warfarin is the most well studied CYP2C9 substrate; recent work on use of dosing algorithms that include CYP2C9 genotype to improve patient safety during initiation of warfarin dosing are reviewed and prospects for their clinical implementation considered. Finally, we discuss a novel approach to cataloging the functional capabilities of rare 'variants of uncertain significance', which are increasingly detected as more exome and genome sequencing of diverse populations is conducted.

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.

Impact of Genetic Polymorphisms on Phenytoin Pharmacokinetics and Clinical Outcomes in the Middle East and North Africa Region

BACKGROUND

Genetic polymorphisms are known to influence outcomes with phenytoin yet effects in the Middle East and North Africa region are poorly understood.

OBJECTIVES

The objective of this systematic review was to evaluate the impact of genetic polymorphisms on phenytoin pharmacokinetics and clinical outcomes in populations originating from the Middle East and North Africa region, and to characterize genotypic and allelic frequencies within the region for genetic polymorphisms assessed.

METHODS

MEDLINE (1946-3 May, 2017), EMBASE (1974-3 May, 2017), Pharmacogenomics Knowledge Base, and Public Health Genomics Knowledge Base online databases were searched. Studies were included if genotyping and analyses of phenytoin pharmacokinetics were performed in patients of the Middle East and North Africa region. Study quality was assessed using a National Institutes of Health assessment tool. A secondary search identified studies reporting genotypic and allelic frequencies of assessed genetic polymorphisms within the Middle East and North Africa region.

RESULTS

Five studies met the inclusion criteria. CYP2C9, CYP2C19, and multidrug resistance protein 1 C3435T variants were evaluated. While CYP2C9*2 and *3 variants significantly reduced phenytoin metabolism, the impacts of CYP2C19*2 and *3 variants were unclear. The multidrug resistance protein 1 CC genotype was associated with drug-resistant epilepsy, but reported impacts on phenytoin pharmacokinetics were conflicting. Appreciable variability in minor allele frequencies existed both between and within countries of the Middle East and North Africa region.

CONCLUSIONS

CYP2C9 decrease-of-function alleles altered phenytoin pharmacokinetics in patients originating from the Middle East and North Africa region. The impacts of CYP2C19 and multidrug resistance protein 1 C3435T variants on phenytoin pharmacokinetic and clinical outcomes are unclear and require further investigation. Future research should focus on the clinical outcomes associated with phenytoin therapy. PROSPERO 2017: CRD42017057850.

In vitro metabolism of exemestane by hepatic cytochrome P450s: impact of nonsynonymous polymorphisms on formation of the active metabolite 17β-dihydroexemestane

Exemestane (EXE) is an endocrine therapy commonly used by postmenopausal women with hormone‐responsive breast cancer due to its potency in inhibiting aromatase‐catalyzed estrogen synthesis. Preliminary in vitro studies sought to identify phase I EXE metabolites and hepatic cytochrome P450s (CYP450s) that participate in EXE biotransformation. Phase I metabolites were identified by incubating EXE with HEK293‐overexpressed CYP450s. CYP450s 1A2, 2C8, 2C9, 2C19, 2D6, 3A4, and 3A5 produce 17β‐dihydroexemestane (17β‐DHE), an active major metabolite, as well as two inactive metabolites. 17β‐DHE formation in pooled human liver microsomes subjected to isoform‐specific CYP450 inhibition was also monitored using tandem mass spectrometry. 17β‐DHE production in human liver microsomes was unaffected by isoform‐specific inhibition of CYP450s 2A6, 2B6, and 2E1 but decreased 12–39% following inhibition of drug‐metabolizing enzymes from CYP450 subfamilies 1A, 2C, 2D, and 3A. These results suggest that redundancy exists in the EXE metabolic pathway with multiple hepatic CYP450s catalyzing 17β‐DHE formation in vitro. To further expand the knowledge of phase I EXE metabolism, the impact of CYP450 genetic variation on 17β‐DHE formation was assessed via enzyme kinetic parameters. Affinity for EXE substrate and enzyme catalytic velocity were calculated for hepatic wild‐type CYP450s and their common nonsynonymous variants by monitoring the reduction of EXE to 17β‐DHE. Several functional polymorphisms in xenobiotic‐metabolizing CYP450s 1A2, 2C8, 2C9, and 2D6 resulted in deviant enzymatic activity relative to wild‐type enzyme. Thus, it is possible that functional polymorphisms in EXE‐metabolizing CYP450s contribute to inter‐individual variability in patient outcomes by mediating overall exposure to the drug and its active metabolite, 17β‐DHE.

A prospective study to assess the association between genotype, phenotype and Prakriti in individuals on phenytoin monotherapy

Background

Genetic polymorphisms in drug metabolizing enzymes (DMEs) impart distinct drug metabolizing capacity and a unique phenotype to an individual. Phenytoin has large inter-individual variability in metabolism due to polymorphisms in CYP2C9 and CYP2C19. As per Ayurveda, Prakriti imparts a unique phenotype to an individual.

Objective

To assess whether Prakriti can substitute phenotyping [therapeutic drug monitoring (TDM)] and genotyping in individualizing therapy with phenytoin in epilepsy patients.

Methods and materials

This was a cross-sectional study conducted over a period of three years. Prakriti was assessed using standardized and validated software. Polymorphisms in CYP2C9 and CYP2C19 were assessed using Polymerase Chain Reaction (PCR)-Restriction fragment length polymorphism (PCR-RFLP). Plasma concentrations of phenytoin (phenotype) were determined using reverse phase-high performance liquid chromatography (RF-HPLC).

Results

Total 351 patients were enrolled for the study. Kapha vata (KV) (39%) was the predominantly observed Prakriti followed by vata kapha (VK) (20.8%) and vata pitta (VP) (8.83%) among the patients. The CYP2C9 and CYP2C19 genotype distributions were in accordance with Hardy–Weinberg equilibrium. There was no association between Prakriti and genotypes and Prakriti and phenotype (p > 0.05 each). Patients with CYP2C9 *1/*3 genotype were thrice more likely to have toxic plasma concentrations of phenytoin as compared to those with wild-type genotype (*1/*1) (Adjusted odds ratio – 3.36; 95% C.I. 1.61, 7.01). However, no such association was observed between polymorphisms of CYP2C19 and phenotype.

Conclusions

We did not find any association between Prakriti and either phenotype or genotypes suggesting that Prakriti assessment would be of limited utility in individualizing phenytoin therapy in epilepsy patients.

The allele frequency of CYP2C9 and VKORC1 in the Southern Khorasan population

The genetic factors are determinants in required dosage changes of warfarin among which are polymorphisms of CYP2C9 and VKORC1 genes. The present study aimed to determine the allele and genotype frequency of CYP2C9 and VKORC1 genes in Birjand population. This study was conducted on 120 individuals who referred to Imam Reza and Vali-Asr hospitals for PT/INR test. After extracting the genomic DNA, the considered sequences were amplified by PCR, and restriction fragment length polymorphism analysis was done by AvaII and KpnI enzymes to determine allele polymorphisms. Moreover, related sequences of VKORC1, after amplification, were sequenced for determining the genotype. Allelic and genotypic frequencies as well as Hardy-Weinberg equilibrium, observed heterozygosity, expected heterozygosity, and polymorphism information content were calculated by PowerMarker V 3.25 software. Amongst 120 individuals in this study with the mean age of 58.12 ± 12.7 years, 80.8%, 9.1%, and 10% exhibited the alleles of 1, 2, and 3 CYP2C9 gene, respectively. The genotype frequencies of 1/1, 1/2, 2/2, 3/1, 3/2, and 3/3 of this gene were found to be 64.1, 15.8, 0, 17.5, 2.5, and 0 %, respectively. In -1639 G>A region, VKORC1 had normal homozygote genotype (GG) and in 1173 C>T region, heterozygote (CT) with the frequency of 48.7% and 45.9% had the most prevalence. Compared with other populations, there is a considerable difference between the allele frequency of CYP2C9 and VKORC1 genetic variance. Since 35.8% of the selected populations carry an abnormal allele causing sensitivity to warfarin, the specialists at medical centers must be informed about the genotypes of patients before prescribing warfarin.

CYP2C9 Genotypes Modify Benzodiazepine-Related Fall Risk: Original Results From Three Studies With Meta-Analysis

OBJECTIVE

To investigate whether the CYP2C9*2 and *3 variants modify benzodiazepine-related fall risk.

DESIGN

Three prospective studies; the Rotterdam Study, B-PROOF, and LASA.

SETTING

Community-dwelling individuals living in or near five Dutch cities.

PARTICIPANTS

There were 11,485 participants aged ≥55 years.

MEASUREMENTS

Fall incidents were recorded prospectively. Benzodiazepine use was determined using pharmacy dispensing records or interviews. Cox proportional hazard models adjusted for age and sex were applied to determine the association between benzodiazepine use and fall risk stratified for CYP2C9 genotype and comparing benzodiazepine users to nonusers. The results of the three studies were combined applying meta-analysis. Within benzodiazepine users, the association between genotypes and fall risk was also assessed.

RESULTS

Three thousand seven hundred five participants (32%) encountered a fall during 91,996 follow-up years, and 4% to 15% (depending on the study population) used benzodiazepines. CYP2C9 variants had frequencies of 13% for the *2 allele and 6% for the *3 allele. Compared to nonusers, current benzodiazepine use was associated with an 18% to 36% increased fall risk across studies with a combined hazard ratio (HR) = 1.26 (95% confidence interval [CI], 1.13; 1.40). CYP2C9*2 or *3 allele variants modified benzodiazepine-related fall risk. Compared to nonusers, those carrying a CYP2C9*2 or *3 allele and using benzodiazepines had a 45% increased fall risk (HR, 1.45 95% CI, 1.21; 1.73), whereas CYP2C9*1 homozygotes using benzodiazepines had no increased fall risk (HR, 1.14; 95% CI, 0.90; 1.45). Within benzodiazepine users, having a CYP2C9*2 or *3 allele was associated with an increased fall risk (HR, 1.35; 95% CI, 1.06; 1.72). Additionally, we observed an allele dose effect; heterozygous allele carriers had a fall risk of (HR = 1.30; 95% CI, 1.05; 1.61), and homozygous allele carriers of (HR = 1.91 95% CI, 1.23; 2.96).

CONCLUSIONS

CYP2C9*2 and *3 allele variants modify benzodiazepine-related fall risk. Those using benzodiazepines and having reduced CYP2C9 enzyme activity based on their genotype are at increased fall risk. In clinical practice, genotyping might be considered for elderly patients with an indication for benzodiazepine use. However, because the exact role of CYP2C9 in benzodiazepine metabolism is still unclear, additional research is warranted.

Pharmacogenomics of Drug Metabolizing Enzymes and Transporters: Relevance to Precision Medicine

The interindividual genetic variations in drug metabolizing enzymes and transporters influence the efficacy and toxicity of numerous drugs. As a fundamental element in precision medicine, pharmacogenomics, the study of responses of individuals to medication based on their genomic information, enables the evaluation of some specific genetic variants responsible for an individual’s particular drug response. In this article, we review the contributions of genetic polymorphisms to major individual variations in drug pharmacotherapy, focusing specifically on the pharmacogenomics of phase-I drug metabolizing enzymes and transporters. Substantial frequency differences in key variants of drug metabolizing enzymes and transporters, as well as their possible functional consequences, have also been discussed across geographic regions. The current effort illustrates the common presence of variability in drug responses among individuals and across all geographic regions. This information will aid health-care professionals in prescribing the most appropriate treatment aimed at achieving the best possible beneficial outcomes while avoiding unwanted effects for a particular patient.

CYP2C9 variants as a risk modifier of NSAID-related gastrointestinal bleeding: a case-control study

The aim of this study was to assess whether the CYP2C9*2 and/or *3 variants might modify the risk for NSAID-related upper gastrointestinal bleeding (UGIB) in NSAID users.

Pharmacogenomic Effect of Cytochrome P450 2C9 Polymorphisms in Different Populations

Presently, warfarin sodium or coumadin is the therapeutic drug of choice for maintenance anticoagualtion therapy. One of several factors underlying the variability in warfarin dose response in the patients receiving this oral anticoagulant is a genetic predisposition, especially the CYP2C9 polymorphisms. The pharmacogenomic effect of CYP2C9 polymorphisms is assessed in different racial populations. A retrospective review was performed with an electronic search engine on this topic to get the data for further meta-analysis. A significant correlation between population ethnicity and gene frequencies was detected in this study. A significant low frequency of CYP2C9 variants among the Asian can be demonstrated. The clinical correlation between CYP2C9 polymorphism and warfarin metabolism was also assessed. Four available case-control reports were selected for this meta-analysis. CYP2C9 variants are strongly associated with low-dose warfarin requirement. In summary, the CYP2C9 variants strongly affect the warfarin dose requirement. This phenomenon is ethnically dependent. Due to the high variant frequency among whites in the West, the investigation for CYP2C9 might be useful for this population, not the Asians, whose variant frequency is very low.

Influence of VKORC1 and CYP2C9 Polymorphisms on Daily Acenocoumarol Dose Requirement in South Indian Patients With Mechanical Heart Valves

Background and Aim:

Chronic rheumatic heart disease (RHD) patients who undergo valve replacement with mechanical valves require lifelong anticoagulation. Acenocoumarol, a vitamin K antagonist has a narrow therapeutic range and wide inter-individual variability. Our aim was to investigate the influence of polymorphisms of VKORC1 and CYP2C9 genes on the mean daily dose requirement of acenocoumarol.

Methods:

205 chronic RHD patients, with mechanical heart valves and on acenocoumarol therapy, were recruited. Genotyping for VKORC1 (−1639G>A and 1173C>T) and CYP2C9 (*2 & *3 alleles) polymorphisms was done by PCR-RFLP. There was complete linkage disequilibrium between VKORC1 polymorphisms (r2 = 0.98, D′ = 1.0, LOD = 74.02). VKORC1 genotype distribution for GG/CC, GA/CT, and AA/TT were 57.6%, 36.1%, and 6.3%, respectively. CYP2C9 genotype distribution for *1/*1, *1/*3, *1/*2, *2/*2, and *2/*3 were 78.5%, 14.1%, 6.3%, 0.5%, and 0.5%, respectively. Patients with a wild type of both VKORC1 (−1639GG and 1173CC) and CYP2C9 gene variants required higher acenocoumarol dose compared to those with mutant genotype ( P = 0.023 and P = 0.008 respectively). On combined genotype analysis, patients having a combination of wild type of VKORC1 with wild type of CYP2C9 (44.4%) required higher daily dose compared to patients bearing heterozygous VKORC1 (−1639GA & 1173CT) with wild type of CYP2C9 (30.2%, P = 0.008).

Conclusion:

Presence of a mutant allele of VKORC1 (−1639A & 1173T) and CYP2C9 genes increased the odds of requiring a lower mean dosage of acenocoumarol. Studying the combination of genotypes in RHD patients could predict acenocoumarol dose requirement more accurately.

Evaluation of cytochrome P450 2C9 activity in normal, healthy, adult Western Indian population by both phenotyping and genotyping

Objectives:

Cytochrome P450 2C9 (CYP2C9) is a member of cytochrome P450 (CYP) family that accounts for nearly 18% of the total CYP protein content in the human liver microsomes and catalyzes almost 15–20% of the drugs. Considering the paucity of data on the polymorphisms of CYP2C9 in Western Indian population, the present study was conducted to evaluate the prevalence of CYP2C9 polymorphisms (*1, *2 and *3) and correlate it with the activity using flurbiprofen (FLB) as a probe drug.

Materials and Methods:

A 100 mg FLB capsule was administered to 298 healthy adult participants. Venous blood samples were analyzed at 2 h postdose for the estimation of FLB and 4-hydroxy FLB. Metabolic ratio (MR) was calculated to determine the extent of poor metabolizer (PM) and rapid metabolizer status using probit plot. Genotyping of CYP2C9 polymorphism was performed using polymerase chain reaction-restriction fragment length polymorphism technique.

Results:

Of the total 298 participants, phenotype was assessable in 288 and genotype was performed in 289 participants. The median (range) MR of the study population was 6.6 (1.65–66.05). Five participants were found to be PMs by phenotype. Of the total 289 participants, 209 (72.3%) (66.7, 77.2) had CYP2C9*1/*1, 25 (8.7%) (5.8, 12.7) with CYP2C9*1/*2, 55 (19%) (14.8, 24.1) had CYP2C9*1/*3, 3 (1%) (0.3, 3.3) had CYP2C9*2/*3 genotype. A significant association between phenotype and genotype was observed.

Conclusion:

To conclude, the present study found significant association of CYP2C9 activity by both phenotype and genotype and these findings have to be corroborated in different kinds of patients.

Distribution of polymorphisms in the CYP2C9 gene and CYP2C19/CYP2C9 haplotypes among Venezuelan populations

BACKGROUND

Polymorphisms with decreased enzyme activity of their gene products have been reported in region CYP2C with population variations in haplotype structure.

AIM

To estimate the allelic and genotypic frequencies of variants CYP2C9*2 and CYP2C9*3 and of CYP2C9/CYP2C19 haplotypes in Venezuelan populations.

SUBJECTS AND METHODS

Six hundred and thirty-four individuals from nine admixed populations (AP) and the Warao indigenous group were studied. Allelic frequencies, linkage disequilibrium and genetic distances for haplotypes were calculated and compared within Venezuela and with data available in the literature.

RESULTS

Heterogeneity in the distribution of CYP2C9 alleles and CYP2C9/CYP2C19 haplotypes among the AP and the Warao was observed. The joint frequency of haplotypes, with at least one non-functional variant, shows values in AP between 21-41%, while in Warao it reaches 5%. The haplotype that includes the Asian and rare Latin America CYP2C19*3 allele was detected in most AP and in Warao. Pairwise Fst values showed that the Warao was an outlier compared with the AP, while these are closer to European-derived populations. No significant correlation was found between haplotype frequencies and admixture.

CONCLUSIONS

These results support the need to understand the distribution of genomic biomarkers related to the metabolism of drugs, for planning national public health strategies.

Frequencies of CYP2C9 polymorphisms in North Indian population and their association with drug levels in children on phenytoin monotherapy

Background

Phenytoin, mainly metabolized by cytochrome P450 enzyme system, has a narrow therapeutic index and may have adverse effects due to inter-individual variation in the dose requirement and genetic polymorphisms. This cross-sectional study was done to study the prevalence of cytochrome P450 CYP2C9 polymorphisms in Indian epileptic children and to see the effect of polymorphisms on serum levels in epileptic children on phenytoin monotherapy.

Methods

We studied 89 epileptic children of North Indian population, randomly selected, to see the genotypic and allelic frequency of CYP2C9 and its association with drug levels on phenytoin monotherapy. Analysis was done using STATA 9 Software. The results were analyzed as prevalence at 95 % C.I. (Confidence Interval). The difference in mean phenytoin serum levels between wild and mutant alleles was tested using Student`s T test for independent samples. P value less than 0.05 was considered statistically significant.

Results

CYP2C9*1, *2 & *3 allelic frequencies were 85.4, 4.5 and 10.1 % respectively. CYP2C9*3 allelic group showed significantly higher serum phenytoin levels compared to the wild variants (P = 0.009). There was no statistically significant difference in the dose received (P = 0.12) and side effects of CYP2C9*2 and CYP2C9*3 genotypes (P = 0.442 and 0.597 respectively) when compared with wild variant.

Conclusion

CYP2C9*3 is more common than *2 in the present study. All the polymorphisms demonstrated in our study were heterozygous with no homozygosity. Serum phenytoin levels are higher in polymorphic groups (*3) which suggest their poor metabolizing nature. Genotyping may help to avoid toxicity and concentration-dependent adverse effects.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-016-0603-0) contains supplementary material, which is available to authorized users.

Analysis of CYP2C9 polymorphisms (*2 and *3) in warfarin therapy patients in Pakistan. Association of CYP2C9 polymorphisms (*2 and*3) with warfarin dose, age, PT and INR

Warfarin is a widely used anticoagulant characterized by having a narrow therapeutic index and exhibiting a wide range of inter-individual and inter-ethnic variation. Single nucleotide polymorphisms in hepatic VKORC1 and CYP2C9 genes causes decreased and increased metabolism of warfarin respectively. The objective of this study was to evaluate the allele frequency of CYP2C9 polymorphic variants *2 and *3 and the association of these allelic variants with PT/INR and daily/weekly dose of warfarin. Seventy-four patients with heart valve replacement were selected. Patients taking low warfarin dose (4.90-17.50 mg weekly) for at least last 3 months and had a stable INR in the range of 2-3 were included in this study. CYP2C9 polymorphism was analyzed by polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) technique. Among 74 patients, 9 (12.1 %) showed to have *2 allele, whereas 11 (14.1 %) had *3 allele. Genotype frequencies of wild and variant alleles were, 54.1, 17.6, 21.6 and 6.8 % for *1/*1, *1/*2, *1/*3 and *2/*3 respectively. None of the patient was homozygous for *2 and *3. Statistical analysis showed that low warfarin dose (weekly) is significantly associated with *1/*2 and *1/*3 genotypes (p value ≥ 0.001), whereas PT/INR showed no significant association with the any genotypes of CYP2C9. Our study suggest that polymorphic variants of CYP2C9 (*2 and *3) might influence warfarin dose requirements and associated with the low dose of warfarin in patients.

The effect of CYP2C9 and VKORC1 genetic polymorphisms on warfarin dose requirements in a pediatric population

OBJECTIVE

The aim was to investigate the frequency of genetic polymorphisms of cytochrome P4502C9 (CYP2C9) and vitamin K epoxide reductase complex subunit1 (VKORC1) and determine the effect of these polymorphisms on warfarin dose requirements in pediatric patients.

METHODS

Fifty-eight pediatric patients with cardiac disease, thrombophilia, or other conditions, taking a stable warfarin dose, aged 0.2-18 years, and with international normalized ratio (INR) between 2 and 3 and 149 healthy children as a control group were included in this prospective, observational study. Patients receiving drugs that interact with warfarin, having chronic liver or renal disease, obesity, or thyroid dysfunctions were excluded. Polymerase chain reaction (real time and restriction fragment length polymorphism) was used to analyze the CYP2C9*2, CYP2C9*3, and VKORC1 polymorphisms. The ideal warfarin dose was calculated according to the patient's age, height, and the presence of CYP2C9*2, CYP2C9*3, and VKORC1 genetic polymorphisms. The mean daily administered doses and ideal doses were compared. Analysis of variance, Student's t-test, logistic regression analysis, and Pearson's correlation analysis were used for statistical analyses.

RESULTS

The frequency of the CYP2C9 and VKORC1 genetic polymorphisms was determined as CYP2C9*1/*1 (54.6%), *1/*2 (16.4%), *1/*3 (24.2%), *2/*3 (2.9%), *3/*3 (1.9%), wild-type VKORC1 (26.6%), heterozygote alleles (52.7%), and mutant alleles (20.8%). Patients with allelic variants were found to require lower warfarin doses, and a 64.5% correlation was found between the calculated ideal doses and the administered warfarin doses.

CONCLUSION

Considering CYP2C9 and VKORC1 genetic polymorphisms prior to commencing warfarin treatment will make it easier to reach target INRs and reduce the rate of complications.

Cytochrome P450 2C9 (CYP2C9) polymorphisms in Chinese Li population

BACKGROUND

The frequencies of Cytochrome P450 2C9 (CYP2C9) genotypes were various between populations. The aim of this study was to investigate the frequencies of the major variants of the CYP2C9 in Chinese Li minority populations.

METHODS

The promoter, exons and surrounding introns, and 3'-untranslated region of the CYP2C9 gene was detected by DNA sequencing to investigate in 100 unrelated healthy Chinese Li subjects. The protein function prediction was used the online tools: Sorting Intolerant From Tolerant (SIFT) and Phenotyping Version 2 (PolyPhen-2). The comparison of CYP2C9 allele frequencies in different populations were analyzed by Chi-square (χ(2)) test. Linkage disequilibrium (LD) analysis was performed using Haploview software.

RESULTS

We identified 17 different CYP2C9 single nucleotide polymorphisms (SNPs) in the Li population, including two missense mutations (3549 G > A and 42614 A > C) and two silent mutations (3514 T > Cand 50298A > T). The protein function prediction revealed the two missense mutations result in protein damaging. In addition, we detected the allele frequencies of CYP2C9*1, CYP2C9*3 and CYP2C9*42 were 98%, 1%, and 1%, respectively. Finally, we compared three major allelic frequency (CYP2C9*1, CYP2C9*2, and CYP2C9*3) between Li and other populations. We found that our results were similar to East Asians and Africans.

Genetic polymorphism analysis of the drug-metabolizing enzyme CYP2C9 in a Chinese Tibetan population

OBJECTIVES

The enzymatic activity of CYP2C9 results in broad inter-individual variability in response to certain pharmacotherapies. The present study aimed to screen Tibetan volunteers for CYP2C9 genetic polymorphisms. Previous research has focused on Han Chinese patients, while little is known about the genetic variation of CYP2C9 in Tibetan populations.

METHODS

We used DNA sequencing to investigate the promoter, exons and surrounding introns, and 3'-untranslated region of the CYP2C9 gene in 96 unrelated healthy Tibetan individuals.

RESULTS

We identified 26 different CYP2C9 polymorphisms in the Tibetan population, including two novel variants detected in exon 9 (50193G>A and 50197G>C). In addition, we determined the allele frequencies of CYP2C9*1 and *3 were 93.75% and 5.73%, respectively. The rare CYP2C9*55 allele was also found in 0.52% of the study population.

CONCLUSIONS

Our results provide information on CYP2C9 polymorphisms in Tibetan individuals, which may help to optimize pharmacotherapy effectiveness by providing personalized medicine to this ethnic group.

The effect of genetic polymorphisms of cytochrome P450 CYP2C9, CYP2C19, and CYP2D6 on drug-resistant epilepsy in Turkish children

BACKGROUND AND OBJECTIVE

Despite the availability of several antiepileptic drugs, drug resistance remains one of the major challenges in epilepsy therapy. Genetic factors are known to play a significant role in the prognosis and treatment of epilepsy. The aim of this study was to determine the frequencies of alleles for CYP2C9, CYP2C19, and CYP2D6 genes in Turkish children with epilepsy, and to investigate the relationship between the genetic polymorphism of these genes with multiple drug resistance in epilepsy patients.

METHODS

We genotyped 132 epileptic patients (60 drug resistant and 72 drug responsive) and 55 healthy controls for six single nucleotide polymorphisms (SNPs) in CYP2C9, CYP2C19, and CYP2D6. Genotype, allele, and haplotype frequencies were compared between groups.

RESULTS

The frequencies of CYP2C9*3/*3 genotype and CYP2C9*3 allele, and the haplotype CCGG (CYP2C9*2 C>T, CYP2C9*3 A>C, and CYP2C19*2 G>A, CYP2C19* G>A) were significantly higher in drug-resistant versus -responsive patients.

CONCLUSION

Our results demonstrated the important role of the CYP2C9*3 allelic variant in preventing epilepsy patients from developing drug resistance. These data suggest that CYP2C9, CYP2C19, and CYP2D6 SNPs and haplotypes may affect the response to antiepileptic drugs.

Drug-induced gingival overgrowth: the genetic dimension

Background:

Currently, the etiology of drug-induced gingival overgrowth is not entirely understood but is clearly multifactorial. Phenytoin, one of the common drugs implicated in gingival enlargement, is metabolized mainly by cytochrome P450 (CYP)2C9 and partly by CYP2C19. The CYP2C9 and CYP2C19 genes are polymorphically expressed and most of the variants result in decreased metabolism of the respective substrates.

Aims:

The present study was undertaken to investigate the influence of the CYP2C9*2 and *3 variant genotypes on phenytoin hydroxylation in subjects diagnosed with epilepsy from South India, thus establishing the genetic polymorphisms leading to its defective hydroxylation process.

Materials and Methods:

Fifteen epileptic subjects, age 9 to 60 years were included in the study. Among the study subjects, 8 were males and 7 were females. Genomic DNA was extracted from patients’ blood using Phenol-chloroform method and genotyping was done for CYP2C9 using customized TaqMan genotyping assays on a real time thermocycler, by allelic discrimination method. The genetic polymorphisms *1, *2 and *3 on CYP2C9 were selected based on their function and respective allele frequencies in Asian subcontinent among the Asian populations.

Results:

CYP2C9*1*2 and CYP2C9*3/*3 were identified with equal frequency in the study population. There were seven subjects with CYP2C9*1/*2 genotype (heterozygous mutant), one subject with CYP2C9*1/*1 (wild type) and seven study subjects with CYP2C9*3/*3 (homozygous mutant).

Conclusion:

The results obtained in the present study will be helpful in the medical prescription purposes of phenytoin, and a more personalized patient approach with its administration can be advocated.

The effect of polymorphic metabolism enzymes on serum phenytoin level

Phenytoin has a widespread use in epilepsy treatment and is mainly metabolized by hepatic cytochrome P450 enzymes (CYP). We have investigated CYP2C9*2, CYP2C9*3, CYP2C19*2 and CYP2C19*3 allelic variants in a Turkish population of patients on phenytoin therapy. Patients on phenytoin therapy (n = 102) for the prevention of epileptic seizures were included. Polymorphic alleles were analyzed by restriction fragment length polymorphism method. Serum concentrations of phenytoin were measured by fluorescence polarization immune assay method. The most frequent genotype was detected for CYP2C9 wild-type alleles (78.43 %), whereas CYP2C19*2/*2 (5.88 %) was the least frequent genotype group. According to the classification made with both enzyme polymorphisms, CYP2C9*1/*1-CYP2C19*1/*1 (G1: 41.17 %) genotype group was the most frequent whereas CYP2C9*1/*2-CYP2C19*1/*3 (G7: 0.98 %) was the least frequent one. The highest mean phenytoin level (27.95 ± 1.85 µg/ml) was detected in the G8 genotype group (CYP2C9*1/*3-CYP2C19*2/*3) and the G1 genotype group showed the lowest mean phenytoin level (7.43 ± 0.73 µg/ml). The mean serum concentration of phenytoin of the polymorphic patients with epilepsy was higher than that for the wild-type alleles both in the monotherapy and polytherapy patients. These results show the importance of the genetic polymorphism analysis of the main metabolizing enzyme groups of phenytoin for the dose adjustment.

Clinical pharmacogenetics implementation consortium guidelines for CYP2C9 and HLA-B genotypes and phenytoin dosing

Phenytoin is a widely used antiepileptic drug with a narrow therapeutic index and large interpatient variability, partly due to genetic variations in the gene encoding cytochrome P450 (CYP)2C9 (CYP2C9). Furthermore, the variant allele HLA-B*15:02, encoding human leukocyte antigen, is associated with an increased risk of Stevens-Johnson syndrome and toxic epidermal necrolysis in response to phenytoin treatment. We summarize evidence from the published literature supporting these associations and provide recommendations for the use of phenytoin based on CYP2C9 and/or HLA-B genotype (also available on PharmGKB: http://www.pharmgkb.org). The purpose of this guideline is to provide information for the interpretation of HLA-B and/or CYP2C9 genotype tests so that the results can guide dosing and/or use of phenytoin. Detailed guidelines for the use of phenytoin as well as analyses of cost-effectiveness are out of scope. Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines are periodically updated at http://www.pharmgkb.org.