The influence of VKORC1 gene polymorphism on warfarin maintenance dosage in pediatric patients: A systematic review and meta-analysis

Association of VKORC1 and CYP2C9 single-nucleotide polymorphisms with warfarin dose adjustment in Saudi patients

OBJECTIVES

Despite its wide usage, warfarin therapy remains challenging due to its narrow therapeutic index, inter-individual response variability, and risk of bleeding. Previous reports have suggested that polymorphisms in VKORC1 and CYP2C9 genes could influence warfarin therapy. Herein, we investigated whether VKORC1 -1173C>T, CYP2C9*2, and CYP2C9*3 gene polymorphisms are associated with warfarin dose adjustment and related bleeding events.

METHODS

This cross-sectional study was conducted on Saudi adults receiving warfarin for more than 1 month. Their demographics and relevant clinical data were obtained. Genotyping for VKORC1 -1173C>T, CYP2C9*2, and CYP2C9*2 genotypes was performed.

RESULTS

Patients who are homozygous for the mutant T allele VKORC1 T/T required the lowest warfarin daily maintenance dose, compared to VKORC1 C/T and VKORC1 C/C. Similarly, there was a significant reduction in warfarin daily maintenance dose among CYP2C9*1/*3 and CYP2C9*1/*2 groups compared to CYP2C9*1/*1. However, we found no significant correlation between the studied polymorphisms and warfarin-associated bleeding.

CONCLUSIONS

Similar to other populations, the VKORC1 and CYP2C9 gene polymorphisms are significantly associated with warfarin dosage in Saudi patients. The presence of at least one copy of the mutant alleles for VKORC1 -1173C>T, CYP2C9*2, and CYP2C9*3 is associated with a significant reduction in warfarin maintenance dose.

Association of VKORC1 and CYP2C9 single-nucleotide polymorphisms with warfarin dose adjustment in Saudi patients

OBJECTIVES

Despite its wide usage, warfarin therapy remains challenging due to its narrow therapeutic index, inter-individual response variability, and risk of bleeding. Previous reports have suggested that polymorphisms in VKORC1 and CYP2C9 genes could influence warfarin therapy. Herein, we investigated whether VKORC1 -1173C>T, CYP2C9*2, and CYP2C9*3 gene polymorphisms are associated with warfarin dose adjustment and related bleeding events.

METHODS

This cross-sectional study was conducted on Saudi adults receiving warfarin for more than 1 month. Their demographics and relevant clinical data were obtained. Genotyping for VKORC1 -1173C>T, CYP2C9*2, and CYP2C9*2 genotypes was performed.

RESULTS

Patients who are homozygous for the mutant T allele VKORC1 T/T required the lowest warfarin daily maintenance dose, compared to VKORC1 C/T and VKORC1 C/C. Similarly, there was a significant reduction in warfarin daily maintenance dose among CYP2C9*1/*3 and CYP2C9*1/*2 groups compared to CYP2C9*1/*1. However, we found no significant correlation between the studied polymorphisms and warfarin-associated bleeding.

CONCLUSIONS

Similar to other populations, the VKORC1 and CYP2C9 gene polymorphisms are significantly associated with warfarin dosage in Saudi patients. The presence of at least one copy of the mutant alleles for VKORC1 -1173C>T, CYP2C9*2, and CYP2C9*3 is associated with a significant reduction in warfarin maintenance dose.

Influence of NQO1 Polymorphisms on Warfarin Maintenance Dose: A Systematic Review and Meta-Analysis (rs1800566 and rs10517)

This meta-analysis was conducted to analyze the effect of NQO1 polymorphism on the warfarin maintenance dosage. Using strict inclusion and exclusion criteria, we searched PubMed, EMBASE, and the Cochrane Library for eligible studies published prior to July 7, 2021. The required data were extracted, and experts were consulted when necessary. Review Manager Version 5.4 software was used to analyze the relationship between NQO1 polymorphisms and the warfarin maintenance dosage. Four articles involving 757 patients were included in the meta-analysis. Patients who were NQO1 rs10517 G carriers (AG carriers or GG carriers) required a 48% higher warfarin maintenance dose than those who were AA carriers. Patients with NQO1 rs1800566 CT carriers required a 13% higher warfarin dose than those who were CC carriers, with no associations observed with the other comparisons of the NQO1 rs1800566 genotypes. However, the results obtained by comparing the NQO1 rs1800566 genotypes require confirmation, as significant changes in the results were found in sensitivity analyses. Our meta-analysis suggests that the NQO1 rs10517and NQO1 rs1800566 variant statuses affect the required warfarin maintenance dose.

Genetic Associations With Stable Warfarin Dose Requirements in Han Chinese Patients

ABSTRACT

Warfarin is a commonly prescribed anticoagulant for valvular heart disease that plays an important role in clinical management to prevent thrombotic events. In this study, we aim to perform a comprehensive study to investigate the genetic biomarkers of stable warfarin dose in the Han Chinese population. We performed an integrative study on 211 Han Chinese patients with valvular heart disease. A total of 40 single nucleotide polymorphisms (SNPs) in 10 important genes (CYP2C9, VKORC1, ABCB1, CYP4F2, APOE, PROC, GGCX, EPHX1, CALU, and SETD1A) which are involved in the warfarin metabolic pathway and equilibrium of coagulation and anticoagulation were selected. We applied MassARRAY technology to genotype the 40 SNPs identified in these Han Chinese patients. Our results showed that 13 SNPs on 6 genes (CYP2C9, VKORC1, ABCB1, PROC, EPHX1, and SETD1A) were associated with the individual stable warfarin dose. Two VKORC1 SNPs (rs9934438 and rs2359612) were the strongest genetic factors determining warfarin dose requirements (P = 8 × 10-6 and 9 × 10-6, respectively). Rs4889599 in SETD1A was first reported to be associated with warfarin dose at a significant level of 0.001 in our study (Padjust = 0.040 after Bonferroni correction). We discovered that genetic variants in CYP2C9, VKORC1, ABCB1, PROC, EPHX1, and SETD1A may affect the stable warfarin dose requirement in Han Chinese patients with valvular disease. The discovery of these potential genetic markers will facilitate the development of advanced personalized anticoagulation therapy in Han Chinese patients.

Deciphering Genetic Variants of Warfarin Metabolism in Children With Ventricular Assist Devices

Warfarin is prescribed in patients with ventricular assist devices (VADs). Dosage depends on several factors including the underlying genotype. These include polymorphisms of genes encoding cytochrome P450 enzymes, the main ones being CYP2C9, VKORC1, and CYP4F2. The objectives of this study were to evaluate the prevalence of CY2CP9 1*2*3*, VKORC1, and CYP4F2 in children with VADs and the time to reach the target international normalized ratio. We performed a retrospective/prospective study in children with VADs. We recorded polymorphisms, disease, type of VAD, ethnicity, age, gender, height, weight, INR values, bleeding, and thromboembolic episodes. Informed consent was obtained. We enrolled 34 children (19 male, 15 female), with a median age of 2 years (range 0.3-17 years) and median weight of 6.9Kg. The Berlin Heart was the most commonly implanted VAD (22/34; 64%), and the most common diagnosis was dilated cardiomyopathy. Statistical analysis confirmed a significant partial correlation with VKORC1 CC (p = 0.019). The CYP2C9*2 CT genotype showed a late rise in target INR values (p = 0.06), while the CYP2C9*2 CC showed a tendency toward an early INR rise (p = 0.024). We provide new information on the contribution of the warfarin polymorphisms in children with VAD implantation. Pharmacogenomic dosing for children using warfarin has the potential to improve clinical care in VAD patients. Patients with the CYP2C9*2 CT genotype may need more time or higher doses to reach target INR, while clinicians may need to be aware of the potential for a rapid rise in INR in patients with the CYP2C9*2 CC genotype.

Pharmacogenetic-Guided Algorithm to Improve Daily Dose of Warfarin in Elder Han-Chinese Population

Objectives

To verify the accuracy of the International Warfarin Pharmacogenetics Consortium (IWPC) algorithm, identify the effects of genetic and clinical factors on warfarin stable dose, and to establish a new warfarin stable dose prediction algorithm for the elderly Han-Chinese population under the guidance of pharmacogenetics.

Methods

According to the inclusion criteria, 544 non-valvular atrial fibrillation patients taking warfarin for anticoagulation treatment were enrolled. Data information of three groups including the whole population, people under 65 years old and over 65 years old were substituted into the IWPC algorithm respectively to verify its accuracy. The basic data and clinical information of 360 elderly people were collected for statistical analysis and the genotypes of VKORC1-G1639A and CYP2C9 were detected by Sanger sequencing. The new algorithm of the elder pharmacogenetics warfarin dosing was obtained by stepwise multiple regression. The determination coefficient (R2), root mean squared error (RMSE), and the proportion of the predicted value within the true value range of ±20%(20%-p) were used to evaluate the accuracy of the IWPC algorithm and the new algorithm.

Results

Among the three different age groups, the warfarin stable dose predictive accuracy of IWPC algorithm was the lowest in the elderly patients above 65-year-old. In this study, the important factors influencing the stable dose of warfarin in the elderly Han-Chinese were height, weight, body surface area, serum creatinine level, amiodarone usage, CYP2C9 (*1*2, *1*3), and VKORC1 (GG/GA) genotypes. By means of stepwise multiple regression analysis, we established a new elder warfarin dosing algorithm (R²=0.3714) containing height, creatinine, amiodarone usage, CYP2C9 (*1*2 or *1*3), and VKORC1 (GA or GG) genotypes. The prediction accuracy and clinical availability of the Elderly algorithm was significantly better than that of IWPC algorithm verified by RMSE, R2, and (20%-p) methods.

Conclusions

The IWPC model may not be suitable for the elder Han-Chinese population. Polymorphism of CYP2C9 and VKORC1 obviously affected warfarin stable dose of the elder Han-Chinese. Combination of genetic data with demographic and clinical factors could help to better improve warfarin doses in the elder Han-Chinese population.

The effect of warfarin knowledge on anticoagulation control among patients with heart valve replacement

Background Although novel oral anticoagulants have been applied into clinical practice, warfarin remains the only approved oral anticoagulant for heart valve replacement. Currently, an increasing number of Chinese clinical pharmacists provide patients with warfarin education. However, little research to date has been carried out to evaluate the relationship between warfarin knowledge level and anticoagulation control among patients with heart valve replacement. Objective To evaluate knowledge of warfarin and the relationship between knowledge level and anticoagulation control among patients with heart valve replacement. Setting Fujian Medical University Union Hospital, China. Method A prospective and cross-sectional study was designed to evaluate the warfarin education of inpatients new to warfarin therapy using a validated Anticoagulation Knowledge Assessment questionnaire. Included patients were followed up for at least 3 months. Data were retrieved from hospital databases and telephone follow up. Main outcome measure Spearman's rho correlation analysis was used to assess the relationships between time in therapeutic range and warfarin knowledge level. Results 383 patients were included. The mean age of patients was 50.3 ± 7.9 years. The mean knowledge questionnaire score was 62.3 ± 8.8%. The majority of incorrect answers related to drug-warfarin interaction. Five of the frequently incorrect questions covered drugs, herbs and diet that affect warfarin therapy. There were significant correlations between total questionnaire score and time in therapeutic range (rho = 0.539, P < 0.001), or percentage of international normalized ratio measurements within range (rho = 0.416, P < 0.001). There were significant correlations between patients' educational level and total questionnaire score (rho = 0.357, P = 0.001). No significant correlations were found between income or living area and total questionnaire score (rho = 0.110, P = 0.435; rho = 0.161, P = 0.149). Conclusion Patient knowledge level of anticoagulation therapy affects anticoagulation control. Education for patients new to warfarin and the evaluation of knowledge by validated questionnaire is recommended for better INR control.

Anticoagulant prophylaxis and therapy in children: current challenges and emerging issues

This review is aimed at describing the unique challenges of anticoagulant prophylaxis and treatment in children, and highlighting areas for research for improving clinical outcomes of children with thromboembolic disease. The evidence presented demonstrates the challenges of advancing the evidence base informing optimal management of thromboembolic disease in children. Recent observational studies have identified risk factors for venous thromboembolism in children, but there are few interventional studies assessing the benefit-risk balance of using thromboprophylaxis in risk-stratified clinical subgroups. A risk level-based framework is proposed for administering mechanical and pharmacological thromboprophylaxis. More research is required to refine the assignment of risk levels. The anticoagulants currently used predominantly in children are unfractionated heparin, low molecular weight heparin, and vitamin K antagonists. There is a paucity of robust evidence on the age-specific pharmacology of these agents, and their efficacy and safety for prevention and treatment of thrombosis in children. The available literature is heterogeneous, reflecting age-specific differences, and the various clinical settings for anticoagulation in children. Monitoring assays and target ranges are not well established. Nevertheless, weight-based dosing appears to achieve acceptable outcomes in most indications. Given the limitations of the classical anticoagulants for children, there is great interest in the direct oral anticoagulants (DOACs), whose properties appear to be particularly suitable for children. All DOACs currently approved for adults have Pediatric Investigation Plans ongoing or planned. These are generating age-specific formulations and systematic dosing information. The ongoing pediatric studies still have to establish whether DOACs have a positive benefit-risk balance in the various pediatric indications and age groups.

UNUSUAL WARFARIN DOSE TO ACHIEVE THERAPEUTIC INR IN A 4-MONTH OLD CHILD: NON-GENETICS RISK FACTORS ARE STILL A CHALLENGE

Objective:

To report a case of a 4-month old girl that required 0.7 mg/kg/day (5 mg) of warfarin and discuss relevant risk factors for requiring higher doses.

Case Description:

In November 2015, a 5 kg female infant (36-week preterm) was admitted to the hospital due to status epilepticus and fever. Diazepam, phenytoin and ceftriaxone were prescribed. Cerebrospinal fluid contained 7 leukocytes, 150 mg/dL proteins, 1 mg/dL glucose and gram positive cocci were observed. Cranial tomography suggested hypodense signs in the cerebellum, right temporal lobe and left basal nuclei, which was consistent with pneumococcal meningitis-induced infectious vasculitis. She required low molecular weight heparin and warfarin for post-encephalitis thrombosis. About 10 days were required to achieve therapeutic INR, and warfarin was adjusted five times since the initial prescription.

Comments:

The risk factors for higher warfarin doses were age and enteral tube feeding. Phenobarbital and prednisone might also have contributed with one of the highest warfarin dose ever reported. Despite current importance given to genetics testing, clinicians should attempt to identify common contributing factors for prolonged non-therapeutic INR, to minimize the risk of coagulation, and to reduce costs of hospital stay and laboratory exams.

Distribution of CYP2C8 and CYP2C9 amino acid substitution alleles in South Indian diabetes patients: A genotypic and computational protein phenotype study

The CYP2C8 and CYP2C9 are two major isoforms of the cytochrome P450 enzyme family, which is involved in drug response, detoxification, and disease development. This study describes the differential distribution of amino acid substitution variants of CYP2C8 (*2-I269F & *3-R139K) and CYP2C9 (*2-C144R & *3-L359A) genes in 234 type 2 diabetes mellitus (T2DM) patients and 218 healthy controls from Andhra Pradesh, South India. Single locus genotype analysis has revealed that homozygous recessive genotypes of 2C8*2-TT (P ≤ .03), 2C9*2-TT (P ≤ .02), and heterozygous 2C9*3-AC (P ≤ .006) are seen to be increasingly present in the case group, indicating a significant level of their association with diabetes in Andhra population. The statistical significance of these recessive genotypes has persisted even under their corresponding allelic forms (P ≤ .01). Genotype association results were further examined by computational protein structure and stability analysis to assess the deleteriousness of the amino acid changes. The mutant CYP 2C8 and 2C9 (both *2 and *3) proteins showed structural drifts at both amino acid residue (range 0.43Å-0.77Å), and polypeptide chain levels (range 0.68Å-1.81Å) compared to their wild-type counterparts. Furthermore, the free energy value differences (range -0.915 to -1.38 Kcal/mol) between mutant and native protein structures suggests the deleterious and destabilizing potential of amino acid substitution polymorphisms of CYP genes. The present study confirms the variable distribution of CYP2C8 (*2 and *3) and CYP2C9 (*2 and *3) allelic polymorphisms among South Indian diabetic populations and further warrants the serious attention of CYP gene family, as a putative locus for disease risk assessment and therapy.

Effect of CYP2C9, VKORC1, and CYP4F2 polymorphisms on warfarin maintenance dose in children aged less than 18 years: a protocol for systematic review and meta-analysis

BACKGROUND

Despite its shortcomings, warfarin is still the most commonly prescribed anticoagulant to prevent thromboembolism in children. In adults, numerous studies confirmed the robust relationship between warfarin maintenance doses and single nucleotide polymorphisms of cytochrome P450 2C9 (CYP2C9), vitamin K epoxide reductase (VKORC1), and cytochrome P450 4F2 (CYP4F2). However, their effect in children still remains to be determined. The primary objective of the present systematic review and meta-analysis is to assess the effect of genotypes of CYP2C9, VKORC1, and CYP4F2 on warfarin maintenance dose in children.

METHODS/DESIGN

A comprehensive literature review search using the OVID platform will be conducted by a specialized librarian, without language restrictions (i.e., MEDLINE/EMBASE/Cochrane Central Register of Controlled Trials), and all abstracts will be reviewed by two authors. Data abstraction from each eligible study will be extracted individually by two authors (MT and TK), and disagreements will be resolved through discussion with a third person (SI). Critical appraisal of the included analysis of the primary objective will follow the Newcastle-Ottawa Scale, in addition to the Strengthening the Reporting of Genetic Association study (STREGA) statement, and data reporting will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. For the meta-analysis, the presence vs. absence of each genetic polymorphism will be pursued, respectively, using a random effect model with effect size expressed as a mean difference plus 95 % confidence interval.

DISCUSSION

Our study will provide a comprehensive systematic review and meta-analysis on the potential effects of CYP2C9, VKORC1, or CYP4F2 on the warfarin maintenance dose in children, exploring the feasibility of the development of pharmacogenetic-guided warfarin dosing algorithm for children on oral vitamin K antagonists.

SYSTEMATIC REVIEW REGISTRATION

The review has been registered with PROSPERO (registration number CRD42015016172 ).