Effect of the VKORC1 genotype on warfarin dose requirements in Japanese pediatric patients

The primary aim of the present study was to evaluate the effect of the genotype of vitamin K epoxide reductase complex 1 (VKORC1) on warfarin dose requirements in Japanese pediatric patients. Forty-eight pediatric patients (0.42-19.25 years old) in whom stable anticoagulation was achieved by warfarin were enrolled in this study, and the polymorphic alleles of VKORC1 and CYP2C9 were determined for each subject. The relative impact of covariates on the anticoagulant effect of warfarin was evaluated by multiple regression analysis. It was found that VKORC1 genotype and age were major factors affecting the relationship between the weight-normalized warfarin dose and the therapeutic prothrombin time-international normalized ratio (PT-INR). Because only one patient had the CYP2C9*3 allele, we could not evaluate the effect of CYP2C9 polymorphisms on the anticoagulant effect of warfarin. In contrast, the anticoagulant effect of warfarin in patients with the VKORC1 1173CT or 1173CC genotype was 52.3% of that in patients with the 1173TT genotype. In addition, the anticoagulant effect of warfarin was shown to increase by 10.5% per year in Japanese pediatric patients. In conclusion, genotyping of VKORC1 will be useful in establishing individual anticoagulant therapy with warfarin, and it should be noted that a higher weight-normalized dose of warfarin is required in younger pediatric patients.     

Role of pharmacogenomics in the management of traditional and novel oral anticoagulants

Warfarin is the most commonly prescribed oral anticoagulant. However, it remains a difficult drug to manage mostly because of its narrow therapeutic index and wide interpatient variability in anticoagulant effects. Over the past decade, there has been substantial progress in our understanding of genetic contributions to variable warfarin response, particularly with regard to warfarin dose requirements. The genes encoding for cytochrome P450 (CYP) 2C9 (CYP2C9) and vitamin K epoxide reductase complex subunit 1 (VKORC1) are the major genetic determinants of warfarin pharmacokinetics and pharmacodynamics, respectively. Numerous studies have demonstrated significant contributions of these genes to warfarin dose requirements. The CYP2C9 gene has also been associated with bleeding risk with warfarin. The CYP4F2 gene influences vitamin K availability and makes minor contributions to warfarin dose requirements. Less is known about genes influencing warfarin response in African-American patients compared with other racial groups, but this is the focus of ongoing research. Several warfarin pharmacogenetic dosing algorithms and United States Food and Drug Administration-cleared genotyping tests are available for clinical use. Clinical trials are ongoing to determine the clinical utility and cost-effectiveness of genotypeguided warfarin dosing. Results from these trials will likely influence clinical uptake and third party payer reimbursement for genotype-guided warfarin therapy. There is still a lack of pharmacogenetic data for the newly approved oral anticoagulants, dabigatran and rivaroxaban, and with other oral anticoagulants in the research and development pipeline. These data, once known, could be of great importance as routine monitoring parameters for these agents are not available.     

胺碘酮和CYP2C9、VKORC1基因型对华法林抗凝效果的影响分析

分析胺碘酮在不同的CYP2C9和VKORC1分型患者对华法林的抗凝作用的影响。纳入从2008年9月至2009年11月某三甲医院应用华法林的入院患者,收集患者一般信息、合并用药及其他临床相关数据,检测患者VKORCl和CYP2C9基因型;比较使用或未使用胺碘酮治疗患者抗凝稳定期INR值及华法林用量,纳入基因分型进行华法林/胺碘酮相互作用的亚组分析。结果未发现胺碘酮应用患者华法林稳定期用量和INR值的统计学差异,基因型亚组差异无统计学意义。这说明院内短期合并使用胺碘酮患者对华法林稳定剂量和INR值无显著影响。     

<Emphasis Type="Italic">VKORC1</Emphasis> and <Emphasis Type="Italic">CYP2C9</Emphasis> polymorphisms are associated with warfarin dose requirements in Turkish patients

OBJECTIVES: The objective of this study was to determine the quantitative influence of vitamin K epoxide reductase complex subunit 1 (VKORC1) and cytochrome P450 2C9 (CYP 2C9) polymorphisms on warfarin dose requirements in Turkish patients. METHODS: A total of 205 patients taking warfarin for >2 months were enrolled in the study. Deoxyribonucleic acid (DNA) samples from these patients were genotyped for polymorphisms in VKORC1 and CYP2C9 genes. A linear regression analysis was used to determine the independent effects of genetic and non-genetic factors on mean warfarin dose requirements. RESULTS: The VKORC1 promoter polymorphism (3673 G>A) was associated with differences in weekly mean varfarin dose: for GG genotype the dose was 43.18 mg/week, for GA genotype 33.78 mg/week and for AA genoype 25.83 mg/week (P < 0.0001). Patients who carried VKORC1 and CYP2C9 variants needed a 40% lower mean weekly warfarin dose compared to wild types. Variables associated with lower warfarin dose requirements were VKORC1 3673 AA or GA genotype (both P < 0.0001), one or two CYP2C9 variant alleles (both P < 0.0001), increasing age (P < 0.0001) and non-indication of venous thromboembolism for warfarin therapy (P = 0.002). CONCLUSION: Polymorphisms in VKORC1 and CYP2C9 genes were important determinants of warfarin dose requirements in Turkish patients.     

华法林药物基因组学和个体化用药

华法林是临床使用最广泛的口服抗凝药,其治疗窗窄,剂量个体差异大,容易发生出血或栓塞的风险。CYP2C9和VKORC1基因多态性明显影响华法林剂量。其他参与维生素摄入和循环,华法林转运的基因变异,以及microRNA也可能影响华法林剂量。该文结合国内外各种华法林稳定剂量预测模型研究,总结影响华法林剂量相关基因的最新研究进展,旨在为华法林个体化治疗提供参考和指导依据。     

Changes in the urinary metabolites of phylloquinone (vitamin K1) in man following therapeutic anticoagulation with warfarin

The metabolism of [1′,2-′³H₂]phylloquinone was studied in five normal male volunteers both before and after treatment with therapeutic doses of warfarin for 8–10 days. Warfarin treatment caused an almost 2-fold increase in the urinary excretion of phylloquinone metabolites; a decrease in glucuronide conjugated metabolites and the excretion of an unidentified conjugate fraction resistant to hydrolysis by both β-glucuronidase and phenolsulphatase.In addition, excretion of the normal aglycones of phylloquinone was markedly reduced and was replaced by the excretion of more polar, hydroxylated metabolites which appeared to be derived from phylloquinone-2,3-epoxide.The results are consistent with the hypothesis that warfarin exerts its anticoagulant effect in man by blocking the regeneration of vitamin K from its 2,3-epoxide metabolite.     

Influence of CYP2C9 and vitamin k oxide reductase complex (VKORC)1 polymorphisms on time to determine the warfarin maintenance dose

Polymorphisms in cytochrome P450 (CYP) 2C9 and the vitamin K oxide reductase complex subunit 1 (VKORC1) greatly affect the maintenance dose of warfarin. To prevent adverse events, immediate dose adjustment is required. The purpose of this study was to investigate the influence of these polymorphisms on the time taken to determine the warfarin maintenance dose for individual patients, and to assess the advantages of genotype-based dosing on initial anticoagulant therapy. We analyzed the genotypes of CYP2C9 and VKORC1 from 72 patients. The number of days taken to determine the maintenance dose was compared with the genotypes. The time taken to determine the maintenance dose of warfarin in group A (CYP2C9*1/*1, VKORC1 -1639AA), B (*1/*1, - 1639GA), C (*1/*3, - 1639AA), and D (*1/*3, - 1639GA) patients was 19 +/- 19, 28 +/- 28, 27 +/- 20 and 7 days, respectively. We analyzed the relationship between the initial dose of warfarin and the number of days required to determine the maintenance dose based on the VKORC1 genotypes. Patients with the VKORC1 - 1639AA genotype and who were initially treated with more than 3mg warfarin, required approximately 2 weeks for the maintenance dose to be determined. Patients with the VKORC1 - 1639GA genotype and the same initial warfarin dosage required approximately a month; however, patients initially treated with 5 mg of warfarin only required 9.5 +/- 5.3 days. We found a tendency that the time taken to determine the warfarin maintenance dose depends on the genotypes. Genotype-based dosing may improve initial anticoagulant therapy.     

细胞色素P450酶2C9和维生素K环氧化物还原酶复合体1基因多态性对瓣膜置换术后华法林剂量影响分析

目的 分析细胞色素P450酶2C9（CYP2C9）和维生素K环氧化物还原酶复合体1（VKORC1）基因多态性对瓣膜置换术后华法林剂量的影响。方法 选取自2015年3月—2017年12月期间于漯河市中心医院行瓣膜置换术后口服华法林的127例患者为研究对象。采用PCR-RFLP法分别检测其CYP2C9和VKORC1基因型,同时记录患者的华法林日均服用剂量、血浆总浓度及游离浓度。对不同基因型及临床特征与华法林日常服用剂量进行直线相关及多元回归分析。结果 华法林日均服用剂量对比,CYP2C9（1061A/C）基因型AA患者显著高于基因型AC患者（P<0.05）,VKORC1（1639 G/A）基因型AA患者显著低于基因型AG患者（P<0.05）,VKORC1（1173 C/T）基因型TT患者显著低于基因型CT患者（P<0.05）。华法林血浆总浓度及游离浓度对比, VKORC1 （1639 G/A）基因型AA患者显著低于基因型AG患者（P<0.05）,VKORC1（1173 C/T）基因型TT患者显著低于基因型CT患者（P<0.05）。女性患者的华法林日均服用剂量显著低于男性患者（P<0.05）,≥70岁和60～69岁患者显著低于60岁以下各年龄段（P<0.05）。直线相关分析及多元回归分析结果提示,华法日均服用剂量与CYP2C9、VKORC1基因型和年龄、性别相关（P<0.05）。结论 CYP2C9和VKORC1基因多态性与瓣膜置换术后华法林日常服用剂量个体化相关,同时年龄和性别也是影响因素之一。     

Warfarin and vitamin K intake in the era of pharmacogenetics

The considerable variability in the warfarin dose–response relationship between individuals, is explained mainly by genetic variation in its major metabolic (CYP2C9) and target (VKORC1) enzymes. Despite the predominance of pharmacogenetics, environmental factors also affect the pharmacokinetics and pharmacodynamics of warfarin, and are often overlooked. Among these factors, dietary and supplemental vitamin K consumption is a controllable contributor to within-, and between-patient variability of warfarin sensitivity. In this commentary we review the current role of vitamin K in warfarin anticoagulation therapy, with emphasis on the following:

1. The effect of dietary and supplemental vitamin K on warfarin anticoagulation, beyond the impact of genetic variability in CYP2C9 and VKORC1. We deal separately with the effects of vitamin K on warfarin dose requirements during the induction of therapy, as opposed to its effect on stability of anticoagulation control during maintenance therapy.
2. The role of vitamin K supplementation in warfarin treated patients with vitamin K deficiency as well as in patients with unstable warfarin anticoagulation, and
3. The role of therapeutic vitamin K in cases of warfarin over-anticoagulation.

     

华法林的药物基因组学及其合理应用

华法林为香豆素类抗凝血药,广泛用于防治血栓栓塞性疾病。华法林治疗窗窄,剂量个体差异大,临床应用中易出现出血合并症。近年研究表明,华法林个体剂量差异与影响华法林代谢和作用的多个基因多态性如CYP2C9、VKORC等有关。本文回顾华法林的药物基因组学研究进展,为临床合理应用华法林提供参考。     

心房颤动患者CYP2C9、VKORC1基因多态性与华法林药物敏感度的关系

目的分析心房颤动(AF)患者CYP2C9、VKORC1基因多态性与华法林药物敏感度的关系。方法根据华法林给药累计剂量,将27例AF患者分为低起效剂量组和高起效剂量组;根据达标时间,分为短起效时间组和长起效时间组。比较高、低起效剂量组和长、短起效时间组CYP2C9、VKORC1不同基因型华法林的起效剂量和起效时间。结果高、低起效剂量组rs1057910(CYP2C9*3)及长、短起效时间组VKORC1 rs9923231基因构成差异有统计学意义(P<0.05)。与AA基因型比较,CYP2C9 rs1057910 AC基因型华法林起效剂量降低,VKORC1 rs9923231 GA基因型华法林起效时间缩短(P<0.05)。华法林药物敏感度可分为低度敏感、中度敏感和高度敏感3种。结论应结合临床实际对口服华法林行抗凝治疗的AF患者进行CYP2C9、VKORC1基因多态性检测,以便从基因类型角度合理分配华法林剂量。     

Influence of CYP4F2 rs2108622 (V433M) on warfarin dose requirement in Asian patients

Warfarin exhibits wide interpatient variability in dosing requirements. Recent studies have shown a novel polymorphism (rs2108622, V433M) in the CYP4F2 gene to be associated with variability in warfarin requirements in Caucasians. The purpose of this study was to evaluate the impact of rs2108622 on warfarin dose requirements in the Asian population. The mean warfarin dose was found to be significantly lower in patients carrying homozygous wild-type allele CC when compared with patients carrying variant alleles CT and TT (CC vs CT+TT: 3.0 mg/day vs 3.75 mg/day, p = 0.033). In patients harboring VKORC1 diplotypes associated with low warfarin requirements, a linear regression model which included age, weight, CYP2C9 and CYP4F2 variants accounted for 38% of the variability in warfarin dose. Approximately 11% of the dose variation was explained by CYP4F2 rs2108622 (p = 0.004). The influence of rs2108622 in patients harboring VKORC1 diplotypes associated with high warfarin requirements was not significant. This study suggests that CYP4F2 rs2108622 may significantly affect warfarin dose requirements in carriers of VKORC1 low-dose-associated diplotypes.     

Pharmacogenetics of oral anticoagulants: a basis for dose individualization

Coumarin derivatives, including warfarin, acenocoumarol and phenprocoumon, are the drugs of choice for long-term treatment and prevention of thromboembolic events. The management of oral anticoagulation is challenging because of a large variability in the dose-response relationship, which is in part caused by genetic polymorphisms. The narrow therapeutic range may result in bleeding complications or recurrent thrombosis, especially during the initial phase of treatment. The aim of this review is to systematically extract the published data reporting pharmacogenetic influences on oral anticoagulant therapy and to provide empirical doses for individual genotype combinations. To this end, we extracted all data from clinical studies of warfarin, phenprocoumon and acenocoumarol that reported genetic influences on either the dose demand or adverse drug effects, such as bleeding complications. Data were summarized for each substance, and the relative effect of each relevant gene was calculated across studies, assuming a linear gene-dose effect in Caucasians. Cytochrome P450 (CYP) 2C9, which is the main enzyme for rate-limiting metabolism of oral anticoagulants, had the largest impact on the dose demand. Compared with homozygous carriers of CYP2C9*1, patients homozygous for CYP2C9*3 were estimated to need 3.3-fold lower mean doses of warfarin to achieve the same international normalized ratio, with *2 carriers and heterozygous patients in between. Differences for acenocoumarol and phenprocoumon were 2.5-fold and 1.5-fold, respectively. Homozygosity of the vitamin K epoxide reductase complex subunit 1 (VKORC1) variant C1173T (*2) allele (VKORC1 is the molecular target of anticoagulant action) was related to 2.4-fold, 1.6-fold and 1.9-fold lower dose requirements compared with the wild-type for warfarin, acenocoumarol and phenprocoumon, respectively. Compared with CYP2C9 and VKORC1 homozygous wild-type individuals, patients with polymorphisms in these genes also more often experience severe overanticoagulation. An empirical dose table, which may be useful as a basis for dose individualization, is presented for the combined CYP2C9/VKORC1 genotypes. Genetic polymorphism in further enzymes and structures involved in the effect of anticoagulants such as gamma-glutamylcarboxylase, glutathione S-transferase A1, microsomal epoxide hydrolase and apolipoprotein E appear to be of negligible importance.Despite the clear effects of CYP2C9 and VKORC1 variants, these polymorphisms explain less than half of the interindividual variability in the dose response to oral anticoagulants. Thus, while individuals at the extremes of the dose requirements are likely to benefit, the overall clinical merits of a genotype-adapted anticoagulant treatment regimen in the entire patient populations remain to be determined in further prospective clinical studies.     

CYP2C9、VKORC1基因多态性对华法令抗凝治疗维持剂量的影响

目的：研究细胞色素P4502C9基因（CYP2C9）和维生素K环氧化物还原酶复合物1基因（VKORC1）在华法令抗凝治疗患者的多态性分布,并探讨其对抗凝剂量的影响。方法：收集74例服用华法令抗凝治疗病人的外周血,测定其凝血酶原时间国际标准化比值（INR）和CYP2C9、VKORC1基因类型,探讨基因多态性的分布特点,以及华法令维持剂量与基因多态性的关系。结果：CYP2C9基因分布主要为野生型,突变型较少,抗凝治疗的维持剂量野生型组与突变组无明显差别。 VKORC1基因型的分布AA型为主,AG型较少,GG型未见,抗凝治疗的维持剂量AG组明显高于AA组。结论：CYP2C9、VKORC1基因在中国汉族人群中具有遗传多态性, VKORC1基因的多态性在华法令抗凝治疗中具有显著意义。     

Pesticide resistance in wild mammals--mechanisms of anticoagulant resistance in wild rodents

Warfarin is commonly used worldwide as a rodenticide. It inhibits coagulation of blood by inhibiting vitamin K 2,3-epoxide reductase (VKOR) activity. An inadequate supply of vitamin K blocks the production of prothrombin and causes hemorrhage. It has been reported that repeated or long-term treatments with this drug cause resistance in wild rodents. However, the mechanism of warfarin resistance in rodents is still not known precisely. Recent studies reported and identified the function of the molecule, vitamin K epoxide reductase complex subunit 1 (VKORC1), which is the main unit of VKOR. An amino acid substitution in VKORC1 is one of the supposed mechanisms of warfarin resistance. An accelerated detoxification system involving cytochrome P450 (CYP) could also cause the rodenticide resistance. Administration of SKF-525A, a potent inhibitor for P450, increased the mortality due to reduction of warfarin metabolism in warfarin-resistant rats. Meanwhile, the appearance of warfarin-resistant rodents has led to the development of the more effective and toxic rodenticide superwarfarin, which is widely used in Europe and the USA. However, animals resistant to this second-generation rodenticide have already been reported in Europe. In this review, we focus on the mechanism and the pleiotropic effects of pesticide resistance in wild rodents.     

The relationship between inhibition of vitamin K1 2,3-epoxide reductase and reduction of clotting factor activity with warfarin.

1 The effect of low dose steady state warfarin (0.2 mg and 1 mg daily) on clotting factor activity and vitamin K1 metabolism was studied in seven healthy volunteers. 2 Steady state plasma warfarin concentrations were 41-99 ng ml-1 for the 0.2 mg dose and 157-292 ng ml-1 for the 1 mg dose. 3 There was a significant prolongation of the mean prothrombin time (0.9 s) after 1 mg warfarin daily, but no significant change in prothrombin time after 0.2 mg warfarin daily. There was no significant change in individual clotting factor activity (II, VII, IX or X) with either dose of warfarin. 4 Following the administration of a pharmacological dose of vitamin K1 (10 mg), all seven volunteers had detectable levels of vitamin K1 2,3-epoxide with both doses of warfarin (Cpmax 31-409 ng ml-1). 5 Both the Cpmax and the AUC for vitamin K1 2,3-epoxide were significantly greater on 1 mg of warfarin daily than 0.2 mg daily (P less than 0.01). 6 The apparent dissociation between inhibition of vitamin K1 2,3-epoxide reductase and reduction of clotting factor activity, produced by warfarin, may reflect the insensitivity of functional clotting factor assays to a small reduction in clotting factor concentration.     

影响华法林抗凝血作用的有关因素

华法林为口服抗凝血药,用于治疗和预防血栓栓塞性疾病。华法林抗凝血作用(增强或减弱)受多种因素影响。这些因素包括遗传、疾病、药物、草药以及食物等。CYP2C9多态性(主要为CYP2C9*2、CYP2C9*3)、肝功能低下、甲状腺功能亢进、心力衰竭以及阿司匹林、氯吡格雷、咪康唑、当归、茴香、芹菜、菠萝、洋葱、大蒜等和华法林的相互作用均能致华法林抗凝血作用增强。而VKORC1的基因突变以及利福平、卡马西平、人参、绿茶,富含维生素K的制剂或饮食等和华法林相互作用均能使华法林抗凝血作用减弱。另外,有些药物如:苯妥英钠,既能增强又能减弱华法林的抗凝血作用。了解这些因素对华法林抗凝血作用的影响,定期监测INR值,进行个体化给药,有利于华法林安全有效应用。     

APOE genotype makes a small contribution to warfarin dose requirements

Alterations in vitamin K availability can significantly influence anticoagulation response to warfarin. Apolipoprotein E (APOE) plays a part in the hepatic uptake of lipid-soluble vitamin K. This study aimed to determine the influence of common polymorphisms in the APOE gene on warfarin dose requirements. patients with stable anticoagulation control and with a target International Normalized Ratio (INR) 2.0-3.0 were genotyped for the APOE epsilon2, epsilon3 and epsilon4 variants. Mean +/- SD daily warfarin doses were significantly lower in patients carrying at least one epsilon4 allele compared to the epsilon3epsilon3 reference genotype (3.3 +/- 1.9 versus 4.0 +/- 1.8; P = 0.03; 95% CI: 0.1-1.2). Multivariate regression analysis showed that patient age, height and CYP2C9, VKORC1 and APOE genotypes significantly contributed to warfarin dose requirement (R = 57%). only the epsilon4 allele of APOE was found to make a significant (P = 0.002) but small contribution to warfarin dose requirement. There was no significant difference in fasted plasma vitamin K concentration between patients with the different APOE genotypes. This study suggests that APOE genotype is unlikely to have a clinically significant effect on warfarin dose requirements.     

CYP2C9和VKORC1基因多态性对华法林抗凝疗效的影响

目的:分析探讨CYP2C9和VKORC1基因多态性对华法林抗凝疗效的影响,为进一步指导临床精准合理化用药提供参考.方法:通过医院电子病历系统收集昆明市某三甲医院2019年1月至2020年9月住院期间患者服用华法林抗凝治疗的184例临床信息,并根据是否进行CYP2C9(1075A>C)、VKORC1(1639 G>A)基...     

基因多态性对华法林个体化药量作用的临床分析

目的探讨细胞色素氧化酶P450（CYP2C9）和环氧化物还原酶复合体（VKORC1）基因型与华法林个体化剂量的关系。方法应用PCR-RFLP方法,检测临床长期口服华法林患者（362例）的VKORC1-1639及CYP2C9-1061A/C多态性,并按其基因型分组,分别比较VKORC1和CYP2C9不同基因型间的平均华法林剂量。结果病例检测出VKORC1-1639 AA基因型273例（75.4%）、AC基因型81例（22.3%）及CC基因型8例（2.3%）。CYP2C9基因检测AA型321例（88.7%）、AG基因型34例（9.5%）、GG型7例（1.8%）。两组VKORC1和CYP2C9各基因型分布差异无统计学意义（P〉0.05）。VKORC1不同基因型间患者所需华法林平均剂量GA、GG组明显高于AA组（P〈0.01）。携带CYP2C9基因型的患者（AG＋GG）组华法林平均剂量要低于AA组（P〈0.05）。结论华法林应用剂量偏低可能与VKORC G-C和CYP2C9 A-G转变有关。VKORC1 AA型占多数可能是中国汉族人群所需华法林剂量普遍较低的重要原因。