Effects of CYP4F2 and GGCX genetic variants on maintenance warfarin dose in a multi-ethnic Asian population

Estimation of the warfarin dose with a pharmacogenetic refinement algorithm in Chinese patients mainly under low-intensity warfarin anticoagulation

Pharmacogenetic (PG) dosing algorithms have been confirmed to predict warfarin therapeutic dose more accurately;however, most of them are based on standard intensity of warfarin anticoagulation, and their utility outside this range is limited. This study was designed to develop and validate a PG refinement algorithm in Chinese patients mainly under low-intensity warfarin anticoagulation. Consented Chinese-Han patients (n=310) under stable warfarin treatment were randomly divided into a derivation (n=207) and a validation cohort (n=103), with 83% and 80% of the patients under low-intensity anticoagulation, respectively. In the derivation cohort, a PG algorithm was constructed on the basis of genotypes (CYP2C9*3 and VKORC1–1639A/G) and clinical data. After integrating additional covariates of international normalised ratio (INR) values (INR on day 4 of therapy and target INR) and genotype of CYP4F2 (rs2108622), a PG refinement algorithm was established and explained 54% of warfarin dose variability. In the validation cohort, warfarin dose prediction was more accurate (p <0.01) with the PG refinement algorithm than with the PG algorithm and the fixed dose approach (3 mg/day). In the entire cohort, the PG refinement algorithm could accurately identify larger proportions of patients with lower dose requirement (≤2 mg/day) and higher dose requirement (≥4 mg/day) than did the PG algorithm. In conclusion, PG refinement algorithm integrating early INR response and three genotypes CYP2C9*3, VKORC1–1639A/G, CYP4F2 rs2108622) improves the accuracy of warfarin dose prediction in Chinese patients mainly under low-intensity anticoagulation.

Characteristics of Venous Thromboembolism in Pancreatic Adenocarcinoma in East Asian Ethnics: A Large Population-Based Observational Study

Pancreatic cancer (PC) is known to be frequently associated with venous thromboembolism (VTE). Although treatment and prophylaxis strategies for VTE in PC patients were updated recently, these were mainly based on data from Western populations and were not verified in East Asian ethnic populations.We investigated the clinical characteristics of VTE in East Asian PC patients. We reviewed electronic medical records (EMR) of 1334 patients diagnosed with pancreatic adenocarcinoma from 2005 to 2010 at single tertiary hospital in Korea. All the patients with newly diagnosed VTE were classified by anatomical site and manifestation of symptoms. The primary outcomes of interest were 2-year cumulative incidence of VTE events. Cox proportional hazards models were used to analyze associations between risk factors and clinical outcomes.A total of 1115 patients were eligible for enrollment. The 2-year cumulative VTE incidence was 9.2%. Major risk factors associated with VTE event were advanced cancer stage, major surgery, and poor performance status. Risk factors associated with mortality after PC diagnosis included advanced cancer stage, poor performance score, leukocytosis, and lower albumin level. The overall VTE did not affected mortality. However in subgroup analysis, symptomatic VTE and deep vein thrombosis/pulmonary thromboembolism (DVT/PTE) showed worse prognosis than incidental or intra-abdominal VTE.The overall incidence of VTE events in Korean PC patients was lower than previous studies. Advanced cancer stage was the most important factor for VTE event and mortality. Unlike Western population group, VTE event did not affect overall prognosis after PC diagnosis. However, symptomatic VTE and DVT/PTE showed higher mortality after VTE event.

A pharmacogenetics-based warfarin maintenance dosing algorithm from Northern Chinese patients

Inconsistent associations with warfarin dose were observed in genetic variants except VKORC1 haplotype and CYP2C9*3 in Chinese people, and few studies on warfarin dose algorithm was performed in a large Chinese Han population lived in Northern China. Of 787 consenting patients with heart-valve replacements who were receiving long-term warfarin maintenance therapy, 20 related Single nucleotide polymorphisms were genotyped. Only VKORC1 and CYP2C9 SNPs were observed to be significantly associated with warfarin dose. In the derivation cohort (n = 551), warfarin dose variability was influenced, in decreasing order, by VKORC1 rs7294 (27.3%), CYP2C9*3(7.0%), body surface area(4.2%), age(2.7%), target INR(1.4%), CYP4F2 rs2108622 (0.7%), amiodarone use(0.6%), diabetes mellitus(0.6%), and digoxin use(0.5%), which account for 45.1% of the warfarin dose variability. In the validation cohort (n = 236), the actual maintenance dose was significantly correlated with predicted dose (r = 0.609, P<0.001). Our algorithm could improve the personalized management of warfarin use in Northern Chinese patients.

Impact of the CYP4F2 p.V433M polymorphism on coumarin dose requirement: systematic review and meta-analysis

A systematic review and a meta-analysis were performed to quantify the accumulated information from genetic association studies investigating the impact of the CYP4F2 rs2108622 (p.V433M) polymorphism on coumarin dose requirement. An additional aim was to explore the contribution of the CYP4F2 variant in comparison with, as well as after stratification for, the VKORC1 and CYP2C9 variants. Thirty studies involving 9,470 participants met prespecified inclusion criteria. As compared with CC-homozygotes, T-allele carriers required an 8.3% (95% confidence interval (CI): 5.6-11.1%; P < 0.0001) higher mean daily coumarin dose than CC homozygotes to reach a stable international normalized ratio (INR). There was no evidence of publication bias. Heterogeneity among studies was present (I(2) = 43%). Our results show that the CYP4F2 p.V433M polymorphism is associated with interindividual variability in response to coumarin drugs, but with a low effect size that is confirmed to be lower than those contributed by VKORC1 and CYP2C9 polymorphisms.