Genetic determinants of acenocoumarol and warfarin maintenance dose requirements in Slavic population: a potential role of CYP4F2 and GGCX polymorphisms

PharmVar GeneFocus: CYP4F2

The Pharmacogene Variation Consortium (PharmVar) serves as a global repository providing star (*) allele nomenclature for the polymorphic human CYP4F2 gene. CYP4F2 genetic variation impacts the metabolism of vitamin K, which is associated with warfarin dose requirements, and the metabolism of drugs, such as imatinib or fingolimod, and certain endogenous compounds including vitamin E and eicosanoids. This GeneFocus provides a comprehensive overview and summary of CYP4F2 genetic variation including the characterization of 14 novel star alleles, CYP4F2*4 through *17. A description of how haplotype information cataloged by PharmVar is utilized by the Pharmacogenomics Knowledgebase (PharmGKB) and the Clinical Pharmacogenetics Implementation Consortium (CPIC) is also provided.

Genetic polymorphisms of pharmacogenomic VIP variants in the Lahu population from Yunnan Province

BACKGROUND

Pharmacogenomics has been widely used to study the very important pharmacogenetic (VIP) variants among populations, but information on pharmacogenomics in the Lahu population is limited. The purpose of this study was to determine the differences in the distribution of VIP variants between the Lahu and the other 26 populations.

METHODS

We genotyped 55 VIP variants of 27 genes in the Lahu population from the PharmGKB database. χ² test was used to compare the genotype and allele frequencies between the Lahu and the other 26 populations from the 1000 Genomes Project.

RESULTS

The genotype and allele frequencies of single nucleotide polymorphisms (SNPs) on rs20417 (PTGS2), rs776746 (CYP3A5), rs2115819 (ALOX5), and rs3093105 (CYP4F2) were considerably different in the Lahu population compared with those in the other 26 populations. Besides, based on the PharmGKB database, we identified several VIP variants that may alter the drug metabolism of aspirin (PTGS2), tacrolimus (CYP3A5), montelukast (ALOX5), and vitamin E (CYP4F2).

CONCLUSION

The results show that there are significant differences in the genotype frequency distribution between the Lahu and the other 26 populations. Our study supplements the pharmacogenomics information of the Lahu population and provides a theoretical basis for individualized medicine in Lahu.

Genetic variation of pharmacogenomic VIP variants in the Chinese Li population: an updated research

Previous studies have shown that the frequency of very important pharmacogenomic (VIP) genes varies in different populations which leads to the diversities in drug efficacy, safety, and the risk associated with adverse drug reactions (ADRs). The purpose of this study was to identify the distribution differences of VIP variants between the Li population and the other 13 populations. Based on the Pharmacogenomics Knowledgebase database (PhamGKB), we successfully genotyped 52 VIP variants within 27 genes in 200 unrelated Li population. χ² test was used to evaluate the significant differences of genotype and allele frequencies between the Li and the other 13 populations from 1000 Genomes Project. Our study showed that the genotype frequencies of single nucleotide polymorphisms (SNPs) on KCNH2, ACE, CYP4F2, and CYP2E1 were considerably different between Li and the other 13 populations, especially in rs1805123 (KCNH2), rs4291 (ACE), rs3093105 (CYP4F2), and rs6413432 (CYP2E1) loci. Meanwhile, we found several VIP variants that might alter the drug metabolism of cisplatin-cyclophosphamide (CYP2E1), vitamin E (CYP4F2), asthma amlodipine, chlorthalidone, and lisinopril (ACE) through PharmGKB. We also identified other variants which were associated with adverse effects in isoniazid and rifampicin (CYP2E1; hepatotoxicity). The four loci rs1805123 (KCNH2), rs4291 (ACE), rs3093105 (CYP4F2), and rs6413432 (CYP2E1) provided a reliable basis for the prediction of the efficacy of certain drugs. The study complemented the existed pharmacogenomics information, which could provide theoretical basis for predicting the efficacy of certain drugs in the Li population.

A Pharmacogenetically Guided Acenocoumarol Dosing Algorithm for Chilean Patients: A Discovery Cohort Study

Background

Vitamin K antagonists (VKA) are used as prophylaxis for thromboembolic events in patients with cardiovascular diseases. The most common VKA are warfarin and acenocoumarol. These drugs have a narrow therapeutic margin and high inter-individual response variability due to clinical and pharmacogenetic variables.

Objective

The authors aim to develop an algorithm comprised of clinical and genetic factors to explain the variability in the therapeutic dose of acenocoumarol among Chilean patients

Methodology

DNA was obtained from 304 patients as a discovery cohort with an international normalized ratio (INR) range of 2.0–3.0. The non-genetic (demographic and clinical) variables were also recorded. Genotype analyses were performed using real-time PCR for VKORC1 (rs9923231), VKORC1 (rs7294), GGCx (rs11676382), CYP4F2 (rs2108622), ABCB1 (rs1045642), CYP2C9*2 (rs1799853), ApoE (rs429358), and CYP2C9*3 (rs1057910).

Results

The clinical variables that significantly influenced the weekly therapeutic dose of VKA were age, sex, body mass index (BMI), and initial INR, collectively accounting for 19% of the variability, and the genetic variables with a significant impact were VKORC1 (rs9923231), CYP2C9*2 (rs1799853), and CYP2C9*3 (rs1057910), explaining for another 37% of the variability.

Conclusion

We developed an algorithm that explains 49.99% of the variability in therapeutic VKA dosage in the Chilean population studied. Factors that significantly affected the dosage included VKORC1, CYP2C9*2, and CYP2C9*3 polymorphisms, as well as age, sex, BMI, and initial INR.

Deciphering DMET genetic data: comprehensive assessment of Northwestern Han, Tibetan, Uyghur populations and their comparison to eleven 1000 genome populations

We investigated the allele frequencies of drug absorption, distribution, metabolism and elimination (ADME)-related drug-metabolizing enzymes and transporters (DMET) genes in the Northwestern Han, Tibetan and Uyghur populations and compared the related genes in these three populations with those in eleven 1000 Genome populations. We examined 1936 single nucleotide polymorphisms of 225 DMET genes involved in ADME processes and found 732, 679 and 804 sites were polymorphic in Han, Tibetan and Uyghur. Tibetan differed from Han in only four sites (p < .05), whereas Uyghur differed from Han and Tibetan in 24 and 21 sites, respectively (p < .05). The distributions of 1058 genotyping data of 245 individuals from Han, Tibetan and Uyghur were compared with 1207 other individuals from the eleven 1000 Genomes populations. The top four populations in Han that exhibited the smallest pairwise Fst values were CHB, Tibetan, CHD and JPT; those in Tibetan were Han, CHB, Uyghur and CHD; and those in Uyghur were Han, Tibetan, GIH and CEU. MEGA results revealed that CHB, CHD, JPT, Han, Tibetan and Uyghur were grouped in cluster 1. GIH, MEX, CEU and TSI were grouped in cluster 2. MKK, ASW, LWK and YRI were grouped in cluster 3.

Genetic causes of resistance to vitamin K antagonists in Polish patients: a novel p.Ile123Met mutation in VKORC1 gene

: Mutations in the genes encoding vitamin K epoxide reductase complex subunit 1 (VKORC1) and cytochrome P450 2C9 (CYP2C9) largely contribute to the inter-individual variations in vitamin K antagonists (VKAs) dose requirements. Up to 50% of the dosage variability can be explained by genetic polymorphisms in these genes. We sought to identify the mutations responsible for VKA resistance in a series of Polish patients. Of the 607 patients treated with VKA, 35 (6%) individuals with the VKA resistance defined as a daily dose of acenocoumarol more than 8 mg (n = 15, 43%) or warfarin more than 10 mg (n = 20, 57%) were selected for further mutational analysis using Sanger sequencing (VKORC1) or real-time PCR genotyping (CYP2C9). The indications for anticoagulant treatment were venous thromboembolism (n = 28, 80%), atrial fibrillation (n = 6, 17%), or artificial heart valve (n = 1, 3%). Patients taking medication interfering with VKA were ineligible. Almost all of VKA-resistant patients (n = 34, 97%) possessed at least one VKORC1*3 (n = 29, 83%) or VKORC1*4 (n = 15, 43%) haplotypes. In a 70-year-old man atrial fibrillation patient on the daily acenocoumarol dose of 16 mg, a novel p.Ile123Met (c.369C>G) VKORC1 mutation was found. In-silico analysis showed that the p.Ile123Met can functionally underlie the acenocoumarol resistance, presumably by altering VKA binding. To our knowledge this is the first cohort of Polish patients resistant to VKA evaluated for the causal genetic background. We found one new detrimental mutation underlying VKA resistance. Our study highlights a key role of unidentified environmental factors in VKA resistance in daily clinical practice.

Influence of genetic and non-genetic factors on acenocoumarol maintenance dose requirement in a Tunisian population

PURPOSE

We aimed to study potential variables involved in interindividual variability to acenocoumarol (AC) response in order to establish a pharmacogenetic algorithm (PA) that includes clinical and genetic factors to predict adequate AC dose to stabilize anticoagulation in a cohort of Tunisian patients.

METHODS

Genotyping of the CYP2C9, VKORC1, CYP4F2, and CALU polymorphisms was conducted on 246 patients using PCR-RFLP technique. AC normalized maintenance dose (NMD): ((mean maintenance dose/international normalized ratio (INR)) equilibrium) was calculated. The statistical study was carried out with SPSS V20.

RESULTS

A significant correlation was found between age, BMI, and daily AC dose (r = - 0.397; p < 0.001 and r = 0.215; p = 0.001, respectively). The carriers of mutated alleles CYP2C9*2 or CYP2C9*3 or VKORC1 haplotypes (H1 and H7) were associated with AC hyper-sensibility. After adjustment to potential covariates, these patients presented supra-therapeutic INR during treatment period and needed low AC dose (ORs* = 0.28 [0.06-0.60], p = 0.004; ORs* = 0.12 [0.04-0.05], p < 0.001; ORs* = 0.45 [0.24-0.84], p = 0.01; and ORs* = 0.28 [0.06-0.98], p = 0.049, respectively). However, carriers of VKORC1 haplotypes (H3 and H12) or mutated alleles CYP4F2 (rs2108622) or CALU (rs1043550) tend to resist to treatment, hence long period of therapy initiation, and must be treated with high AC dose (ORs* = 2.67 [81.12-5.91], p = 0.013; ORs* = 8.76 [1.07-76.26], p = 0.019; ORs* = 3.12 [1.01-9.63], p = 0.047; and ORs* = 3.96 [1.41-11.09], p = 0.009, respectively). A final multivariate regression model explained 48.1% of the global interindividual variability in AC dose requirement.

CONCLUSION

The PA demonstrated that VKORC1 and CYP2C9 polymorphisms contribution was more important than clinical factors. Applying the PA would allow dose adjustment to treat patients in a personalized manner.

Role of CYP4F2, CYP2C19, and CYP1A2 polymorphisms on acenocoumarol pharmacogenomic algorithm accuracy improvement in the Greek population: need for sub-phenotype analysis

BACKGROUND

We have earlier developed a pharmacogenomic algorithm for acenocoumarol dose prediction in Greek patients that included CYP2C9/VKORC1 genetic information. This study aims at analyzing the potential effect of CYP4F2, CYP2C19, and CYP1A2 gene polymorphisms on acenocoumarol dose requirements and at further improving the Greek-specific pharmacogenomic algorithm.

METHODS

A total of 205 Greek patients taking acenocoumarol (140 who reached and 65 who did not reach stable dose), participants of acenocoumarol EU-PACT trial, were included in the study. CYP4F2, CYP2C19, and CYP1A2 polymorphisms were genotyped by use of the PCR-RFLP method. All patients were previously genotyped for CYP2C9/VKORC1 polymorphisms.

RESULTS

In the pooled sample, CYP4F2, CYP2C19, and CYP1A2 polymorphisms do not affect independently acenocoumarol dose requirements. For CYP4F2, significant effects were found on patients' ability to reach stable dose and on acenocoumarol dose requirements when CYP2C9/VKORC1 sub-phenotypes were analyzed. Specifically, when the patients were stratified according to their CYP2C9/VKORC1 functional bins, in sensitive responders, CYP4F2*3 allele carriers (CYP4F2 *1/*3 and *3/*3 genotypes) were more frequent in the patient group who reached stable dose (p=0.049). Additionally, in CYP2C9 intermediate metabolizers (IMs), after adjusting for age, weight, and VKORC1 genotypes, CYP4F2 genotypes were significantly associated with acenocoumarol stable dose (β: 0.07; 95% CI: 0.006-0.134; p=0.033).

CONCLUSIONS

CYP4F2 gene shows a prominent weak association with acenocoumarol dose requirements. Sub-phenotype analysis is potentially important in determining additional gene polymorphisms that are associated with acenocoumarol dose requirements.

Can pharmacogenetics help patients under chronic treatment with coumarin anticoagulants?

Vitamin K antagonists are highly effective antithrombotic drugs. However, appropriate dosing is difficult to establish owing to its narrow therapeutic window as well as widespread inter- and intra-individual variability in dosage. Compared with dosing solely based on clinical information, pharmacogenetics can help improve the therapy with coumarins by decreasing the time to reach a stable dose and reducing the risk of bleeding. Most of the studies about genotyping of patients using vitamin K antagonists have focused on predicting the stable dose. Two genes have been shown to have the most influence on dosing: VKORC1 and CYP2C9. Furthermore, genotyping of more genes, such as CYP4F2 and APOE, is also being included in some dosing algorithms. The role of genotype beyond the initial dose-titration phase is less clear. Thus, a proven genetically determined risk of unstable dose or bleeding could help with the selection of patients who require more frequent monitoring of dose. On the other hand, patients who have a genetically determined stable dose could self-monitor their international normalized ratio (INR), making the therapy less expensive and more convenient.

The impact of CYP4F2, ABCB1, and GGCX polymorphisms on bleeding episodes associated with acenocoumarol in Russian patients with atrial fibrillation

BACKGROUND

Oral anticoagulants are commonly used to treat patients with thromboembolic pathology. Genetic variations could influence personal response to anticoagulant drugs. Acenocoumarol (AC) is a vitamin K antagonist used in anticoagulant therapy and as a prophylaxis measure in Europe. In this study, we assessed the effect of CYP4F2 rs2108622, ABCB1, and GGCX polymorphisms on the safety profile and regime dosing of AC in patients with nonvalvular atrial fibrillation.

METHODS

Fifty patients aged 40-70 years were included. All patients received AC in the dose of 1-6 mg daily with a target international normalized ratio of 2.0-3.0. Genotyping for polymorphism markers C3435T for the ABCB1 gene, rs2108622 for the CYP4F2 gene, and rs11676382 for the GGCX gene were designed using polymerase chain reaction and restriction fragment length polymorphism. Statistical analysis was performed using the Fisher exact test and the Mann-Whitney U test.

RESULTS

We found that CYP4F2 rs2108622 CT carriers required a higher AC dose than CC (p=0.0366), and CT and TT carriers required a higher AC dose than CC (p=0.0314).

CONCLUSIONS

We found that ABCB1 CT and TT genotypes are associated with a higher risk of bleeding. No influence of ABCB1 and GGCX polymorphisms on the doses of AC was established. CYP4F2 could still be a genetic factor responsible for the personal variability of AC metabolism.

Impact of CYP2C9, VKORC1 and CYP4F2 genetic polymorphisms on maintenance warfarin dosage in Han-Chinese patients: A systematic review and meta-analysis

Introduction

Warfarin is the most commonly used antithrombotic drug. Single nucleotide polymorphisms (SNPs) of CYP2C9, CYP4F2, VKORC1 1173 and VKORC1-1639 influence warfarin maintenance dosage. We aimed to determine the impact of SNPs of these genes on mean daily warfarin dosage (MDWD) in Han-Chinese patients.

Methods

Strict literature inclusion criteria were established, and literature searching was performed on PubMed, Embase and Cochrane Library for English articles and CNKI, CBM and Wanfang database for Chinese articles before September 2, 2014. Revman 5.3 was used to analyze the relationship between gene SNPs and MDWD in Han-Chinese subjects.

Results

We included 33 studies researching the impact of gene SNPs on MDWD in Han-Chinese subjects. CYP2C9 *3/*3, *1/*3 and *3 carriers needed a 72% (95% confidence interval [CI]: 62.0%–81.0%), 28% (22.0%–33.0%) and 26% (21.0%–32.0%) lower MDWD, respectively, than CYP2C9 *1/*1 carriers. CYP4F2 TT, CT and T carriers required a 18% (7.0%–30.0%), 7% (7.0%–7.0%) and 11% (7.0%–14.0%) higher MDWD, respectively, than CYP4F2 CC carriers. VKORC1 1173 CC, CT and C carriers required a 98% (78.0%–118.0%), 49% (37.0%–62.0%) and 56% (44.0%–67.0%) higher MDWD, respectively, than VKORC1 1173 TT carriers. VKORC1-1639 GG, GA and G carriers needed a 101% (53.0%–149.0%), 40% (36.0%–45.0%) and 38% (35.0%–42.0%) higher MDWD, respectively, than VKORC1-1639 AA carriers.

Conclusions

This meta-analysis is the first to report the relationship between genotypes and MDWD among Han-Chinese patients. The results showed that SNPs of CYP2C9, CYP4F2, VKORC1 1173 and VKORC1-1639 significantly influenced the MDWD in Han-Chinese patients.

•

This meta-analysis examined the effects of genotype on mean daily warfarin dosage.

•

CYP2C9, CYP4F2 and VKORC1 genotypes were studied in Han-Chinese patients.

•

CYP2C9, CYP4F2, VKORC1-1173 and VKORC1-1639 polymorphisms affected warfarin dosage.

•

VKORC1-1173 C and VKORC1-1639 G mutations had similar frequencies and effects.

•

Either genotype can be tested for to guide drug usage and lower medical costs.