VKORC1 Genotypes Research Articles

Case report on Pharmacogenetic guided warfarin dosing in a postoperative valve replacement patient

Patient underwent mitral valve replacement with mechanical valve and was initiated on oral anticoagulation with standard dose of warfarin. She developed supra therapeutic INR levels. Genotyping of CYP2C9 and VKORC1 encoding genes revealed homozygous variation of CYP2C9*3*3 and heterozygous variation of VKORC1 G>A making her hypersensitive to warfarin. Based on this study result and Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline, a low dose of warfarin (0.5mg per day) was prescribed, to achieve a therapeutic INR of 2.5 to 3.5 and adverse drug effects were avoided.

Leveraging QSP Models for MIPD: A Case Study for Warfarin/INR.

Warfarin dosing remains challenging due to substantial inter-individual variability, which can lead to unsafe or ineffective therapy with standard dosing. Model-informed precision dosing (MIPD) can help individualize warfarin dosing, requiring the selection of a suitable model. For models developed from clinical data, the dependence on the study design and population raises questions about generalizability. Quantitative system pharmacology (QSP) models promise better extrapolation abilities; however, their complexity and lack of validation on clinical data raise questions about applicability in MIPD. We have previously derived a mechanistic warfarin/international normalized ratio (INR) model from a blood coagulation QSP model. In this article, we evaluated the predictive performance of the warfarin/INR model in the context of MIPD using an external dataset with INR data from patients starting warfarin treatment. We assessed the accuracy and precision of model predictions, benchmarked against an empirically based reference model. Additionally, we evaluated covariate contributions and assessed the predictive performance separately in the more challenging outpatient data. The warfarin/INR model performed comparably to the reference model across various measures despite not being calibrated with warfarin initiation data. Including CYP2C9 and/or VKORC1 genotypes as covariates improved the prediction quality of the warfarin/INR model, even after assimilating 4 days of INR data. The outpatient INR exhibited higher unexplained variability, and predictions slightly exceeded observed values, suggesting that model adjustments might be necessary when transitioning from an inpatient to an outpatient setting. Overall, this research underscores the potential of QSP-derived models for MIPD, offering a complementary approach to empirical model development.

Association between gene polymorphisms and initial warfarin therapy in patients after heart valve surgery.

Warfarin is widely used for the prevention and treatment of thrombotic events. This study aimed to examine the influence of gene polymorphisms on the early stage of warfarin therapy in patients following heart valve surgery. Nine single nucleotide polymorphisms were genotyped using microarray chips, categorizing patients into three groups: normal responders (Group I), sensitive responders (Group II), and highly sensitive responders (Group III). The primary clinical outcomes examined were time in therapeutic range (TTR) and international normalized ratio (INR) variability. To investigate potential influencing factors, a generalized linear regression model was employed. Among 734 patients, the prevalence of CYP2C9*3-1075A > C, CYP2C19*3-636G > A, and CYP2C19*17-806C > T variants were 11.2%, 9.9%, and 1.9% of patients, respectively. VKORC1-1639G > A or the linked -1173C > T variant was observed in 99.0% of the patients. Generalized linear model analysis revealed an impact of sensitivity grouping on INR variability. Compared to Group I, Group II showed higher TTR values (p = 0.023), while INR variability was poorer in Group II (p < 0.001) and Group III (p < 0.001). Individual gene analysis identified significant associations between CYP2C9*3-1075A > C (p < 0.001), VKORC1-1639G > A or the linked -1173 C > T (p = 0.009) and GGCX-3261G > A (p = 0.019) with INR variability. The genotypes of CYP2C9, VKORC1, and GGCX were found to have a significant impact on INR variability during the initial phase of warfarin therapy. However, no significant association was observed between TTR and gene polymorphisms. These findings suggest that focusing on INR variability is crucial in clinical practice, and preoperative detection of gene polymorphisms should be considered to assist in the initiation of warfarin therapy.

Acute kidney injury interacts with VKORC1 genotype on initiative warfarin dose among heart surgery recipients: a real-world research

Patients who receive heart valve surgery need anticoagulation prophylaxis to reduce the risk of thrombosis. Warfarin often is a choice but its dosage varies due to gene and clinical factors. We aim to study, among them, if there is an interaction between acute kidney injury and two gene polymorphisms from this study. We extracted data of heart valve surgery recipients from the electronic health record (EHR) system of a medical center. The primary outcome is about the average daily dose of warfarin, measured as an additive interaction effect (INTadd) between acute kidney injury (AKI) and warfarin-related gene polymorphisms. The confounders, including age, sex, body surface area (BSA), comorbidities (i.e., atrial fibrillation [AF], hypertension [HTN], congestive heart failure [CHF]), serum albumin level, warfarin-relevant gene polymorphism (i.e., CYP2C9, VKORC1), prosthetic valve type (i.e., metal, bio), and warfarin history were controlled via a multivariate-linear regression model. The study included 200 patients, among whom 108 (54.00%) are female. Further, the mean age is 54.45 years, 31 (15.50%) have CHF, and 40 (20.00%) patients were prescribed concomitant amiodarone, which potentially overlays with the warfarin prophylaxis period. During the follow-up, AKI occurred in 30 (15.00%) patients. VKORC1 mutation (1639G>A) occurred in 25 (12.50%) patients and CYPC29 *2 or *3 mutations presented in 20 patients (10.00%). We found a significant additive interaction effect between AKI and VKORC1 (− 1.17, 95% CI − 1.82 to − 0.53, p = 0.0004). This result suggests it is probable that there is an interaction between acute kidney injury and the VKORC1 polymorphism for the warfarin dose during the initial period of anticoagulation prophylaxis.

New insights into the role of VKORC1 polymorphisms for optimal warfarin dose selection in Caribbean Hispanic patients through an external validation of a population PK/PD model

Warfarin, an oral anticoagulant, has been used for decades to prevent thromboembolic events. The complex interplay between CYP2C9 and VKORC1 genotypes on warfarin PK and PD properties is not fully understood in special sub-groups of patients. This study aimed to externally validate a population pharmacokinetic/pharmacodynamic (PK/PD) model for the effect of warfarin on international normalized ratio (INR) and to evaluate optimal dosing strategies based on the selected covariates in Caribbean Hispanic patients. INR, and CYP2C9 and VKORC1 genotypes from 138 patients were used to develop a population PK/PD model in NONMEM. The structural definition of a previously published PD model for INR was implemented. A numerical evaluation of the parameter-covariate relationship was performed. Simulations were conducted to determine optimal dosing strategies for each genotype combinations, focusing on achieving therapeutic INR levels. Findings revealed elevated IC50 for G/G, G/A, and A/A VKORC1 haplotypes (11.76, 10.49, and 9.22 mg/L, respectively), in this population compared to previous reports. The model-guided dosing analysis recommended daily warfarin doses of 3–5 mg for most genotypes to maintain desired INR levels, although subjects with combination of CYP2C9 and VKORC1 genotypes * 2/* 2-, * 2/* 3- and * 2/* 5-A/A would require only 1 mg daily. This research underscores the potential of population PK/PD modeling to inform personalized warfarin dosing in populations typically underrepresented in clinical studies, potentially leading to improved treatment outcomes and patient safety. By integrating genetic factors and clinical data, this approach could pave the way for more effective and tailored anticoagulation therapy in diverse patient groups.

Exploring the complex relationship between vitamin K, gut microbiota, and warfarin variability in cardiac surgery patients.

Due to the high individual variability of anticoagulant warfarin, this study aimed to investigate the effects of vitamin K concentration and gut microbiota on individual variability of warfarin in 246 cardiac surgery patients. The pharmacokinetics and pharmacodynamics (PKPD) model predicted international normalized ratio (INR) and warfarin concentration. Serum and fecal samples were collected to detect warfarin and vitamin K [VK1 and menaquinone-4 (MK4)] concentrations and gut microbiota diversity, respectively. In addition, the patient's medical records were reviewed for demographic characteristics, drug history, and CYP2C9, VKORC1, and CYP4F2 genotypes. The PKPD model predicted ideal values of 62.7% for S-warfarin, 70.4% for R-warfarin, and 76.4% for INR. The normal VK1 level was 1.34±1.12nmol/ml (95% CI: 0.33-4.08nmol/ml), and the normal MK4 level was 0.22±0.18nmol/ml (95% CI: 0.07-0.63nmol/ml). The MK4 to total vitamin K ratio was 16.5±9.8% (95% CI: 4.3-41.5%). The S-warfarin concentration of producing 50% of maximum anticoagulation and the half-life of prothrombin complex activity tended to increase with vitamin K. Further, Prevotella and Eubacterium of gut microbiota identified as the main bacteria associated with individual variability of warfarin. The results suggest that an increase in vitamin K concentration can decrease anticoagulation, and gut microbiota may influence warfarin anticoagulation through vitamin K2 synthesis. This study highlights the importance of considering vitamin K concentration and gut microbiota when prescribing warfarin. The findings may have significant implications for the personalized use of warfarin. Further research is needed to understand better the role of vitamin K and gut microbiota in warfarin anticoagulation.

Lack of exposure to pharmacogenomics education among the health care providing students in the West Bank of Palestine.

Evaluating the knowledge in pharmacogenomics (PGx) is the first step toward the implementation of PGx testing in clinical practice. This survey aimed to evaluate the knowledge of PGx testing among healthcare providing students at the top-ranked university in the West Bank of Palestine. First an online questionnaire consisting of 30 questions regarding the demographic, knowledge, and attitude toward pharmacogenomics testing was structured and validated. Then the questionnaire was distributed to 1,000 current students from different fields. 696 responses was received. The results showed that almost half of the participants (n=355, 51.1%) have never took any courses about PGx during their university training. Only 81 (11.7%) of the students who took the PGx course stated that it helped them understanding how genetic variations affect drug response. The majority of the students were uncertain (n=352, 50.6%) or disagreed (n=143, 20.6%) that the lectures during university education described the effects of genetic variants on drug response. Although most of the students (70-80%) answered that genetic variants can indeed affect the drug's response, only 162 students (23.3%) responded that VKORC1 and CYP2C9 genotypes influence the response to warfarin. In addition, only 94 (13.5%) students were aware that many medicine labels include clinical information about PGx testing provided by the FDA. It is concluded from the results of this survey that there is a lack of exposure to PGx education associated with poor knowledge of PGx testing among the healthcare providing students in the West Bank of Palestine. It is recommended to include and improve the lectures and courses regarding PGx as this will have a major impact on precision medicine.

Time-to-event modeling for achieving a stable warfarin dose using genetic and non-genetic covariates.

Time-to-event modeling is gaining importance in drug dosage determination, particularly using pharmacometrics approaches. To evaluate the various time-to-event models for estimating the time to achieve a stable warfarin dose in the Bahraini population. A cross-sectional study evaluating the non-genetic and genetic covariates (single nucleotide polymorphisms (SNPs) in CYP2C9, VKORC1 and CYP4F2 genotypes) was conducted in patients receiving warfarin for at least 6 months. Time to achieving a stable dose of warfarin was defined as the duration (in days) from the day of initiating warfarin until 2 consecutive prothrombin time-international normalized ratio (PT-INR) values were observed in the therapeutic range with a gap of at least 7 days. Exponential, Gompertz, log-logistics, and Weibull models were tested, and the model with the lowest objective function value (OFV) was chosen. The covariate selection was carried out using the Wald test and OFV. A hazard ratio (HR) with a 95% confidence interval (95% CI) was estimated. A total of 218 participants were included in the study. The Weibull model was observed to have the lowest OFV (1989.82). The expected time to reach a stable dose in the population was 21.35 days. The CYP2C9 genotypes were identified as the only significant covariate. The HR (95% CI) for achieving a stable warfarin dose within 6 months of initiation for individuals with CYP2C9 *1/*2 was 0.2 (0.09, 0.3), 0.2 (0.1, 0.5) for CYP2C9 *1/*3, 0.14 (0.04, 0.6) for CYP2C9 *2/*2, 0.2 (0.03, 0.9) for CYP2C9 *2/*3, and 0.8 (0.45, 0.9) for those with the C/T genotype for CYP4F2. We estimated the population time-to-event parameters for achieving a stable warfarin dose in our population and observed CYP2C9 genotypes to be the main predictor covariate followed by CYP4F2. The influence of these SNPs needs to be validated in a prospective study and an algorithm to predict a stable warfarin dose and the time to achieve it needs to be developed.

Warfarin-Rifampin-Gene (WARIF-G) Interaction: ARetrospective, Genetic, Case-Control Study.

Warfarin is extensively metabolized by cytochrome P450 2C9 (CYP2C9). Concomitant use with the potent CYP2C9 inducer, rifampin, requires close monitoring and dosage adjustments. Although, in theory, warfarin dose increase should overcome this interaction, most reported cases over the last 50 years have not responded even to high warfarin doses, but some have responded to modest doses. To investigate the genetic polymorphisms' impact on this unexplained interpatient variability, we performed genotyping of CYP2C9, VKORC1, and CYP4F2 for warfarin and rifampin concomitant receivers from 2016 to 2022 at Hamad Medical Corporation, Doha, Qatar. We identified and included 36 patients: 22 responders and 14 nonresponders. Warfarin-responders were significantly more likely to have one or more warfarin-sensitizing CYP2C9/VKORC1 alleles than nonresponders (odds ratio=23.2, 95% confidence interval=3.2-195.6; P=0.0001). The mean genetic-based pre-interaction calculated dose was significantly lower for responders than for nonresponders (P < 0.001); and was negatively correlated with warfarin sensitivity index (WSI) (r=-0.58; P=0.0002). The median percentage time in therapeutic range and mean WSI were significantly higher in the warfarin-sensitizing CYP2C9/VKORC1 alleles carriers than noncarriers (P=0.017 and 0.0004, respectively). Whereas the warfarin-sensitizing CYP2C9/VKORC1 genotypes were associated with modest on-rifampin warfarin dose requirements, the noncarriers would have required more than double these doses to respond. Warfarin-sensitizing CYP2C9/VKORC1 genotypes and low genetic-based warfarin calculated doses were associated with higher warfarin sensitivity and better anticoagulation quality in patients receiving rifampin concomitantly.

The prevalence of pharmacogenetic variants of vitamin K epoxide reductase complex subunit 1 gene (rs9923231), cytochrome P450 family 2 subfamily C member 9 gene (rs1799853) and cytochrome P450 family 3 subfamily-A member-5 gene (rs776746) among 13 ethnic groups of Pakistan.

Pharmacogenomics (PGx) plays a central role in the selection of targeted therapies that underpins precision-medicine. We investigated the prevalence of three important pharmacogenetic variants of VKORC1, CYP2C9, and CYP3A5 genes among Pakistani populations. A total of 1104 individuals were included representing thirteen major ethnicities. Samples were genotyped by using PCR-RFLP analysis. The allelic and genotypic frequencies of the three SNV's were calculated and were compared with the world's population data (ALFA, gnomAD, and 1000Genome, 1K databases), using the chi-square test. We found overall frequencies of functional-alleles of VKORC1 0.43, CYP2C9 0.94, and CYP3A5 0.14 in our population. Data showed a low prevalence of homozygous functional genotypes of VKORC1 (0.18; 0.0-0.45) and CYP3A5 (0.04; 0.0-0.22), and a high frequency of CYP2C9 (0.885; 0.80-1.0) across ethnicities. Genotyping distribution of VKCOR1 functional genotype was varied across ethnic groups such as 0.0-0.10 in Brahuis and Mohanas, Sindhis, Rajputs, and Gujjars populations, 0.11-0.20 in Makranis, Parsis, and Burusho populations, and 0.20-0.30 in Kalash, Kashmiris and Baloch populations. The highest VKORC1 (CC) was found in Pathans (0.45) and Hazaras (0.39) populations. Interestingly, we found a high prevalence of functional genotype CYP2C9 (rs1799853; C) and non-functional genotype of CYP3A5 (rs776746; T) across various ethnic groups of Pakistan. Data regarding prevalence of clinically important pharmacogenomics SNVs could be useful in drug adjustment and avoiding adverse drug reactions in a specific ethnic population. This could help in moving current medical practices toward precision medicine in our part of the world.

Pharmacogenetics of warfarin dosing in Chinese adults with nonvalvular atrial fibrillation.

The guide for the use of genotype-guided warfarin dosing in patients for the treatment of non-valvular atrial fibrillation (AF) is still lacking. We aimed to evaluate whether genotype-guided warfarin dosing is superior to conventional clinical dosing for the outcomes of interest in Chinese patients. Our study consisted of 508 newly recruited and 471 existing Chinese AF patients. Among the total 979 patients, 585 patients received their dose of warfarin determined by a genetic and clinical factor (gene group), while the remaining 394 patients whose dosing was determined empirically in control group. We incorporated CYP2C9 and VKORC1 genotypes into the gene group. The international normalized ratio (INR) measurement and standard protocols were used for further dose adjustment in both groups. The primary outcomes were the percentage of time in the therapeutic range (%TTR) and INR during 12-month follow-up. Secondary safety outcome included bleeding and thrombotic events. Compared with the control group, the average TTR of the gene group was higher [68.4 ± 20.6% vs 48.5 ± 21.6%, P < 0.001]. The average INR monitoring times to reach the therapeutic time in the gene group was lower (P < 0.001). The risk ratios (RR) for cumulative incidence of total bleeding events, minor bleeding events, gastrointestinal bleeding, and intracerebral bleeding events were not significantly different between the two groups (P > 0.05). Comparing to the analysis using existing 471 patients, the analysis using total 979 patients showed that the gene group experienced a lower (RR 0.4 (95% CI 0.2 to 0.8), P = 0.008) incidence of cumulative ischemic stroke. Genotype-guided warfarin administration increases the average TTR, reaches higher TTR levels in the early anticoagulant phase, and significantly reduces the risk of ischemic stroke events.

Comparison of Maintenance Dose Predictions by Warfarin Dosing Algorithms Based on Chinese and Western Patients.

Warfarin has a long record of safe and effective clinical use, and it remains one of the most commonly prescribed drugs for the prevention and treatment of thromboembolic conditions even in the era of direct oral anticoagulants. To address its large interindividual variability and narrow therapeutic window, the Clinical Pharmacogenetics Implementation Consortium has recommended using pharmacogenetic dosing algorithms, such as the ones developed by the International Warfarin Pharmacogenetics Consortium (IWPC) and by Gage et al, to dose warfarin when genotype information is available. In China, dosing algorithms based on local patient populations have been developed and evaluated for predictive accuracy of warfarin maintenance doses. In this study, percentage deviations of doses predicted by 15 Chinese dosing algorithms from that by IWPC and Gage algorithms were systematically evaluated to understand the differences between Chinese and Western algorithms. In general, dose predictions by Chinese dosing algorithms tended to be lower than those predicted by IWPC or Gage algorithms for the most prevalent VKORC1 and CYP2C9 genotypes in the Chinese population. The extent of negative prediction deviation appeared to be largest in the younger age group with smaller body weight. Our findings are consistent with previous reports that Asians have a higher sensitivity to warfarin and require lower doses than Western populations.

Clinical significance of the series of CYP2C9*non3 variants, an unignorable predictor of warfarin sensitivity in Chinese population.

Gene polymorphisms are critical for variations in warfarin dose. To date, more than 70 CYP2C9 alleles have been identified. This study was designed to clarify the clinical significance of CYP2C9*non-3 variants to warfarin sensitivity in Chinese Han patients. The entire CYP2C9 gene region was sequenced in 1,993 individuals, and clinical data and VKORC1 genotypes were collected from 986 patients with atrial fibrillation treated with warfarin. The SKAT-O method was used to analyze the effects of CYP2C9*non-3 variants on warfarin sensitivity. A total of 20 CYP2C9 variants were identified, of which four were novel. Carriers with CYP2C9*non-3 variants may have lower warfarin dose requirements, and similar to CYP2C9*3, CYP2C9*non-3 variants are clearly relevant to warfarin-sensitive and highly sensitive responders. Our results showed that, besides CYP2C9*3, the series of CYP2C9*non-3 variants is an unignorable predictor for warfarin sensitivity in Chinese population. From a safety consideration, people carried such variants may need a preferred choice of NOACs when they started anticoagulation therapy.

Evaluation of supervised machine learning algorithms in predicting the poor anticoagulation control and stable weekly doses of warfarin.

Machine learning algorithms (MLAs) carry a huge potential in identifying predicting factors and are being explored for their utility in the field of personalized medicine. We aimed to investigate MLAs for identifying predictors (clinical and genetic) of poor anticoagulation status (ACS) and stable weekly warfarin dose (SWWD). Clinical factors, in addition to the CYP2C9, VKORC1, and CYP4F2 genotypes, were obtained for patients receiving warfarin for at least the previous six months. The C5.0 decision tree classification algorithm was used to predict poor ACS while classification and regression tree analysis (CART), in addition to the Chi-square automatic interaction detector (CHAID), was used to predict SWWD. The percentage of patients within 20% of the actual dose, root mean squared error (RMSE), and area under the receiver-operating characteristics curve (AUROC) were identified as performance indicators of the models. In the C5.0 classification decision tree, the CYP4F2 genotype was the strongest predictor of ACS (AUROC = 0.53). In the CART analysis of SWWD, VKORC1 polymorphisms were the most significant predictor, followed by the CYP2C9 genotype (percentage of patients within 20% of the actual dose = 38.2%, RMSE = 13.6). For the CHAID algorithm, the percentage of patients within 20% of the actual dose was 49%, while the RMSE was found to be 13.4. Genetic and non-genetic predictive factors were identified by the MLAs for ACS and SWWD. Further, the need to externally validate the MLAs in a prospective study was highlighted.

Efficacy and safety of warfarin therapy in patients with atrial fibrillation using genotype-guided dosing method

The aim. To evaluate the efficacy and safety of warfarin (WF) therapy in patients with atrial fibrillation (AF) using pharmacogenetic dosing method at an anticoagulant monitoring office according to the results of a one-year prospective follow-up. Materials and methods. The study involved 110 patients with AF (mean age 68.72 ± 0.79; men – 57, women – 53). By the method of stratified randomization, the patients with AF were divided into two groups: the main group – 50 patients with AF and genotype-guided dosing method, the control group – 60 patients with AF and clinical dosing method. The outcomes were examined after the one-year follow-up: excessive hypocoagulation episodes (INR &gt; 4) and bleeding. CYP2C9, CYP4F2, VKORC1 gene polymorphisms were determined using multiplex real time polymerase chain reaction; INR was controlled monthly; CHA2DS2-VASC, HAS-BLED, SAMe-TT2R2 scale scores were evaluated; TTR was calculated using the Rosendaal method. Results. The distribution of CYP2C9, CYP4F2, VKORC1 genotypes in the main and control groups were in accordance with the Hardy–Weinberg equilibrium. In patients with AF and genotype-guided dosing, the frequency and risk of excessive hypocoagulation episodes (χ2 = 5.11; P &lt; 0.05; RR = 0.50 (CI 0.27; 0.94)) and bleeding (χ2 = 9.57; P &lt; 0.05; RR = 0.41 (CI 0.22; 0.77)) were significantly lower. However, the groups did not differ in TTR. The validity of genetic-guided dosing was confirmed by the comparability of the medians and the direct correlation between the calculated and therapeutic WF doses (r = +0.57; P &lt; 0.05). There were no relationships between TTR, excessive hypocoagulation episodes, hemorrhagic complications and clinical and genetic factors in the main group. Conclusions. In patients with AF, the use of genotype-guided dosing method in the anticoagulant monitoring office helped to reduce the frequency and risk of excessive hypocoagulation episodes and bleeding as well as eliminate the influence of endogenous and exogenous factors in the personalized management of patients.

PHARMACOGENETIC TESTING AS AN ELEMENT OF PERSONALIZED MEDICINE IN REAL CLINICAL PRACTICE

Introduction . It has been proven that patients with thrombosis and with a high risk of systemic thromboembolic complications (TEС), including patients with non-valvular atrial fibrillation (AF) should receive effective and safe antithrombotic therapy [1–3]. A personalized approach to prolonged AVK therapy is associated with an improvement in hemostasiological markers of thrombinemia and clinical outcomes in patients with VTE and non-valvular AF [4–8]. Materials and methods . Prospective study was carried out on the basis of the anticoagulant clinic (AC) of the Department of hemostasis and atherothrombosis laboratory of the state budgetary health institution of the Arkhangelsk region “First city clinical hospital named after names E. E. Volosevich” (GBUZ AR FCCH). The object of the study is patients of the AVK registry who applied to the RCATT (n = 107) who underwent pharmacogenetic testing (CYP2C9, CYP4F2, VKORC1 genotype) with calculation of individual doses of warfarin and assessment of quality of life using validated questionnaires. The analysis of the effectiveness and safety of warfarin therapy was carried out. Results . It was found that complications of warfarin therapy developed regardless of the presence of the genotype (CYP2C9, CYP4F2, VKORC1) and the warfarin dosing algorithm under observation in AC. It has been shown that pharmacogenetic testing in patients with VTE and AF is an additional method under the condition of observation in AC. Conclusion . A personalized approach to prolonged VKA therapy using pharmacogenetic testing is appropriate for patients of the older age group, patients with a aggravated hemorrhagic history, frequent minor bleeding at target INR values and the presence of concomitant therapy with cytochrome P450 inhibitors.

Determination of Pleiotropic Effect of Warfarin in VKORC1 and CYP2C9 Genotypes in Patients With Heart Valve Replacement.

Warfarin has been widely used as an oral anticoagulant agent. In past, efforts have been done to study the contribution of genetic variation on warfarin dose requirements. The possible therapeutic dose determination of warfarin is very challenging, i.e., extremely low dose leading to unusable antithrombotic therapy or high dose causes particularly bleeding complications. Our study aimed to investigate these observations in more detail, we determined the correlation of interleukin-6 (IL-6), cyclooxygenase-2 (COX-2), and tumor necrosis factor-α (TNF-α) among VKORC1 and CYP2C9 genetic variants in patients with heart valve replacement who were treated with a range of warfarin doses and compared with levels in healthy controls. A total of 107 human subjects were recruited with low < 5 mg, medium 5–10 mg/day, and high > 10 mg/day warfarin doses. The genetic study of VKORC1–1639G/A, C1173T, 3730G > A, CYP2C9*2, and CYP2C9*3 was performed using TaqMan genotyping and DNA sequencing. The gene expression of IL-6, TNF-α, and COX-2 mRNA was analyzed. IL-6, TNF-α, and COX-2 protein expressions were determined by ELISA and Western blot analysis to evaluate the pro- and anti-inflammatory effects of warfarin. A statistically significant difference was found among the haplotypes of VKORC1 rs9934438 (C1173T), rs9923231 (−1639G > A), rs7294 (3730G > A) and CYP2C9 *2 p. Arg144 Cys (rs28371674), CYP2C9 *3 p. Ile359Leu (rs1057910) genotypes with warfarin dose requirements (p = 0.001). The increased levels of COX-2, IL-6, and TNF-α proteins were observed when a high dose of warfarin (>10 mg/ml) was administered. However, a lower concentration (1.0 mg/ml) was observed with decreased warfarin dose (<5 mg/day). The present study reported that in addition to its anticoagulant action, the genetic variants of warfarin may have a pleiotropic effect by influencing IL-6 depending on the dosing regimen and inducing the expression of COX-2.

Pharmacogenetic variants influence vitamin K anticoagulant dosing in patients with mechanical prosthetic heart valves.

Background: Vitamin K antagonists (VKAs) are class I oral anticoagulants that are widely prescribed following surgical heart valve implantation. The objective of this studywas to quantify the relative effects of VKORC1, CYP2C9 and CYP4F2 genotypes in predicting VKA dosing. Materials & methods: A total of 506 South Indian patients with mechanical prosthetic heart valves who were prescribed oral VKAs, such as warfarin or acenocoumarol, were genotyped. The discriminatory ability of mutant genotypes to predict dose categories and bleeding events was assessed using regression analysis. Results: The VKORC1 rs9923231, CYP2C9*3 and CYP4F2*3 mutant genotypes significantly influenced VKA-dose requirements and explained 27.47% of the observed dose variation. Conclusion: Theseresults support pharmacogenetic screening for initial VKA dosing among South Indian patients with mechanical prosthetic heart valves.

The influence of clinical and genetic factors on the stability of warfarin’s anticoagulant effect in patients with atrial fibrillation

The aim. To investigate the influence of clinical and genetic factors on the stability of warfarin’s anticoagulant effect in patients with atrial fibrillation (AF) during the year. Materials and methods. The study involved 60 patients with AF, age 70.50 (64.25; 76.25) years (32 men and 28 women). Coagulogram indexes with International Normalized Ratio (INR) were determined using Coag Chrome 3003 monthly; the CHA2DS2-VASC, HAS-BLED, SAMe-TT2R2 scales scores were evaluated; the calculation of TTR was performed using the Rosendaal method. CYP2C9, CYP4F2, VKORC1 genes polymorphisms were determined using multiplex real time polymerase chain reaction in CFX-96 thermocycler (BioRad). Results. Median TTR in groups of patients with SAMe-TT2R2 score &lt;2 (n = 33) and ≥2 (n = 27) did not differ significantly (74 % versus 68 % respectively, P &gt; 0.05). There were significantly more patients with TTR &lt;70 % in the group with predicted labile INR (59.36 % versus 30.30 %; χ2 = 5.07, P &lt; 0.05). SAMe-TT2R2 score ≥2 increased the risk of poor INR control by 1.96 times (CI 1.05–3.63). No association of TTR with CYP2C9, CYP4F2 and VKORC1 gene polymorphisms was found. Episodes of excessive hypocoagulation (INR &gt;4) were detected in 21 (40 %) patients during the year. Excessive hypocoagulation was significantly more common in patients carrying the allele A of the VKORC1 gene in comparison with non-carriers (51.43 % versus 24.00 %; χ2 = 4.57, P &lt; 0.05). The presence of mutant allele A was associated with 2.14-fold higher risk of excessive hypocoagulation (RR = 2.14; CI 1.06–4.69). Taking amiodarone (χ2 = 3.13; P &lt; 0.05) had a significant effect on the development of excessive hypocoagulation with a relative risk RR = 1.83 (CI 1.01–3.35). Conclusions. SAMe-TT2R2 score can be useful to predict poor INR control, while VKORC1 genotype estimating – to predict excessive hypocoagulation episodes. An integrated approach using clinical and genetic methods is needed to determine the potential efficacy and safety of warfarin therapy.

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

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