华法林药物遗传学基因CYP2C9和VKORC1单核苷酸多态性在广东汉族人群的分布研究

目的探讨细胞色素P450(cytochrome P450, CYP450)家族中CYP2C9的单核苷酸多态性(single nucleotide polymorphisms, SNP)位点rs1057910和rs1799853以及维生素K环氧化物还原酶复合物亚基1(vitamin K epoxide reductase complex subunit 1, VKORC1)的rs9923231 SNP位点在广东汉族的分布,为华法林(warfarin)个体化用药(personalized medicine)提供循证医学依据.方法利用Sequenom MassArray? iPLEX GOLD系统对215例广东地区人群的rs1057910,rs1799853和rs9923231三个位点进行基因分型,并分析各基因型分布频率.结果 rs1799853和rs9923231在广东汉族中无多态性分布,分别只有CC基因型和CT基因型.rs1057910在广东汉族中有两种基因型AA和AC,分布频率分别为0.921和0.079;等位基因A的频率为0.9605,C的频率为0.0395.结论在本研究中由于rs1799853和rs9923231在广东汉族中无多态性分布,基于本研究数据建议广东汉族华法林药物的检测位点应以rs1057910为主.     

Pharmacogenetics of acenocoumarol in patients with extreme dose requirements

Summary. Background: There is currently intense debate as to whether pharmacogenetic algorithms for estimating the initial dose of coumarins provide a more accurate dose than the fixed‐dose approach. Recently, it has been suggested that the greatest benefit of pharmacogenetic algorithms is observed in patients with extreme dose requirements. Objectives: To identify clinical and genetic factors that better characterize patients who need extreme acenocoumarol doses for steady anticoagulation state. Patients/methods: We reviewed 9538 patients with a steady acenocoumarol dose from three Spanish hospitals, selecting 83 who took ≤ 5.00 mg week^?1 (percentile 5, p5) and 203 taking ≥ 30.00 mg week^?1 (p95). We also selected patients matched by gender and age taking 13.50–14.00 mg week^?1 (p50). We genotyped VKORC1 (rs9923231), CALU (rs1043550), GGCX (rs699664), CYP2C9 (rs1799853; rs1057910), CYP4F2 (rs2108622) and F7 (rs5742910) single‐nucleotide polymorphisms (SNPs). Results: Comparison between p5 and p95 revealed five parameters with significant differences: body surface area (BSA) (P = 0.006), age, VKORC1, CYP2C9 and CYP4F2 genotypes (all P < 0.001). First VKORC1, and second, CYP2C9 SNPs played a strong effect by determining extreme doses, particularly in p95. Only one out of 203 p95 had the VKORC1 A‐1639A genotype, but this subject was CYP2C9*1/*1. In contrast, nine out of 83 p5 carried the VKORC1 G‐1639G genotype, although six of them were CYP2C9*3 homozygotes and another two were heterozygotes. Surprisingly, CYP4F2 V433M SNP displayed prevalences that suggest that its influence might only be evident when patients are treated with high doses. Conclusion: Two clinical data, age and BSA, and three SNPs in the VKORC1, CYP2C9 and CYP4F2 genes strongly predict outlier patients treated with acenocoumarol.     

华法林相关基因SNPs在心脏瓣膜置换汉族患者中的分布调查

目的:探索心脏瓣膜置换的汉族患者中华法林相关基因SNPs的分布。方法:入选2012年至2013年上海市在中山医院行心脏瓣膜置换手术后,需长期服用华法林进行抗凝治疗的汉族患者110例,通过阅读文献筛选得到华法林相关基因及相应SNPs位点(CYP2C9 rs1799853 C/T、CYP2C9rs1057910 A/C、VKORC1 rs9923231 G/A、VKORC1 rs9934438 C/T、CYP4F2 rs2108622 C/T、GGCX rs12714145 A/G、EPHX1 rs1877724 C/T、EPHX1 rs2292566 A/G、EPHX1 rs4653436 A/G)。使用直接测序法检测SNPs,采用Hardy-Weinberg遗传平衡检验验证群体代表性。结果:CYP2C9基因rs1799853、rs1057910等位基因频率分别为0.45%、5.00%;VKORC1基因rs9923231、rs9934438等位基因频率均为91.36%;CYP4F2基因rs2108622等位基因频率为28.64%;GGCX基因rs12714145等位基因频率为33.18%;EPHX1基因rs1877724、rs2292566和rs4653436等位基因频率分别为30.00%、24.55%、26.36%。结论:探索华法林相关基因CYP2C9、VKORC1、CYP4F2、GGCX、EPHX1的9个SNPs的频率在行心脏瓣膜置换术的患者人群中的分布,对建立和实施华法林个体化治疗具有重要意义。     

CYP4F2 gene polymorphism as a contributor to warfarin maintenance dose in Japanese subjects

What is known and Objective: Polymorphisms in the gene encoding CYP4F2 may partly explain the variability in warfarin maintenance dose by altering the metabolism of vitamin K. To determine the genetic factors that cause large inter‐patient variability in warfarin efficacy, we investigated the relationship between serum warfarin concentration and CYP4F2 V433M (1347C>T, rs2108622) polymorphism in Japanese subjects. Methods: Gene variations in VKORC1, CYP2C9 and CYP4F2 were analysed in 126 Japanese patients treated with warfarin. The daily dosage of warfarin, concentration of S‐ and R‐warfarin in plasma, and prothrombin time international normalized ratio (PT‐INR) was used as the pharmacokinetic and pharmacodynamic indices. Results and Discussion: The maintenance dose of warfarin was larger in the CYP4F2 1347 CT genotype group (3·59 ± 1·80 mg/day, P = 0·027) than in the CYP4F2 CC genotype group (2·88 ± 1·00 mg/day). CYP4F2 1347C>T polymorphism significantly affected serum R‐warfarin concentration when the VKORC1‐1639 genotypes are AG and GG. What is new and Conclusion: Although a significant inter‐patient difference in warfarin maintenance dose was observed between the CYP4F2 CC and CT genotypes, serum S‐warfarin concentration was not significantly different between them. An effect of CYP4F2 V433M polymorphism on warfarin maintenance dose was observed but was relatively small when compared to the effects of CYP2C9 and VKOR polymorphism.     

Clinical relevance of VKORC1 (G-1639A and C1173T) and CYP2C9*3 among patients on warfarin

What is known and Objectives: Testing for cytochrome P450‐2C9 (CYP2C9) and vitamin K epoxide reductase complex subunit 1 (VKORC1) variant alleles is recommended by the FDA for dosing of warfarin. However, dose prediction models derived from data obtained in one population may not be applicable to another. We therefore studied the impact of genetic polymorphisms of CYP2C9 and VKORC1 on warfarin dose requirement in Malaysia. Methods: Patients who were attending clinics at our hospital and prescribed warfarin with stabilized INR levels of 2–4 were selected. DNA was extracted from blood samples and subsequently genotyped for CYP2C9*1, *2, *3, VKORC1 (G‐1639A) and VKORC1 C1173T. Linear regression modelling using age, CYP2C9 and VKORC1 genotypes, sex, weight and height was undertaken to define a warfarin dosing algorithm. An initial model was developed using data from one cohort of patients and validated using data from a second cohort. Results and Discussion: A model which included age and variants of CYP2C9 and VKORC1 account for about 37% of the variability in warfarin dose required to achieve INR of 2–4. Among the parameters evaluated, only VKORC1 (G‐1639A) and (C1173T) alleles, and age correlated with warfarin dose at 6 month. The mean dose predicted using the algorithm derived from cohort 1 was lower than the actual dose for cohort 2 (3·30 mg, SD 0·84 vs. 3·45 mg, SD 1·42). There was no relationship between INR values and the dose taken by the patients. Race, sex, weight and height did not correlate with dose. What is new and Conclusion: This study identifies factors which affect warfarin dosing in the Malaysia population. However, our best model does not account sufficiently for the variability in dose requirements for it to be used in dose prediction for the individual patient. Other important influential factors affecting warfarin dose requirement remain to be identified.     

An evaluation of gene–gene interaction between the CYP2C9 and VKORC1 genotypes affecting the anticoagulant effect of phenprocoumon and acenocoumarol

Background:  Previous studies have provided contradictory results regarding the interaction between the CYP2C9 and VKORC1 genotypes affecting various outcome measures. Objectives:  We aimed to provide a definite answer regarding the question whether there exists a gene–gene interaction between the CYP2C9 and VKORC1 genotypes affecting the anticoagulant effect of phenprocoumon and acenocoumarol. Patients/Methods:  The EU‐PACT cohort dataset, which contains data on 624 phenprocoumon and 471 acenocoumarol patients, was used. Patient characteristics, pharmacogenetic data, International Normalized Ratios (INRs) and dosages were available. We investigated whether there was an interaction between the CYP2C9 and VKORC1 genotypes affecting the maintenance dose, time to severe over‐anticoagulation and time to achieve stability during the first 180 days of phenprocoumon and acenocoumarol therapy, in addition to the effect of the separate genotypes. The interaction effect was investigated by adding the product term of the CYP2C9 and VKORC1 genotype classes for four different commonly used CYP2C9 classifications to the linear regression model – for the outcome measure maintenance dose – or to the Cox regression models – for the outcome measures time to severe over‐anticoagulation and time to achieve stability. Results:  No significant interactions – all P‐values above 0.23 for phenprocoumon and 0.30 for acenocoumarol – were observed for all outcome measures. Conclusions:  There are no interactions between the CYP2C9 and VKORC1 genotypes affecting the maintenance dose, time to severe over‐anticoagulation and time to achieve stability for phenprocoumon and acenocoumarol.     

Predicting the warfarin maintenance dose in elderly inpatients at treatment initiation: accuracy of dosing algorithms incorporating or not VKORC1/CYP2C9 genotypes

Summary. Background: Initiating warfarin is challenging in frail elderly patients because of low‐dose requirements and interindividual variability. Objectives: We investigated whether incorporating VKORC1 and CYP2C9 genotype information in different models helped to predict the warfarin maintenance dose when added to clinical data and INR values at baseline (Day 0), and during warfarin induction. Patients: We prospectively enrolled 187 elderly inpatients (mean age, 85.6 years), all starting on warfarin using the same ‘geriatric dosing‐algorithm’ based on the INR value measured on the day after three 4‐mg warfarin doses (INR₃) and on INR_{6 ± 1}. Results: On Day 0, the clinical model failed to accurately predict the maintenance dose (R² < 0.10). Adding the VKORC1 and CYP2C9 genotypes to the model increased R² to 0.31. On Day 3, the INR₃ value was the strongest predictor, completely embedding the VKORC1 genotype, whereas the CYP2C9 genotype remained a significant predictor (model‐ R² 0.55). On Day 6 ± 1, none of the genotypes predicted the maintenance dose. Finally, the simple ‘geriatric dosing‐algorithm’ was the most accurate algorithm on Day 3 (R² 0.77) and Day 6 (R² 0.81), under‐estimating (≥ 1 mg) and over‐estimating the dose (≥ 1 mg) in fewer than 10% and 2% of patients, respectively. Clinical models and the ‘geriatric dosing‐algorithm’ were validated on an independent sample. Conclusions: Before starting warfarin therapy, the VKORC1 genotype is the best predictor of the maintenance dose. Once treatment is started using induction doses tailored for elderly patients, the contribution of VKORC1 and CYP2C9 genotypes in dose refinement is negligible compared with two INR values measured during the first week of treatment.     

Implications of Polymorphisms in the BCKDK and GATA‐4 Gene Regions on Stable Warfarin Dose in African Americans

VKORC1 and CYP2C9 genotypes explain less variability in warfarin dose requirements in African Americans compared with Europeans. Variants in BCKDK and GATA‐4 gene regions, purported to regulate VKORC1 and CYP2C9 expression, have been shown to play an important role in warfarin dose requirements in Europeans and Asians, respectively. We sought to determine whether rs56314408 near BCKDK or GATA‐4 rs2645400 influence warfarin dose requirements in 200 African Americans. Unlike the strong linkage disequilibrium (LD) between rs56314408 and VKORC1 rs9923231 in Europeans, they were not in LD in African Americans. No associations were found on univariate analysis. On multivariable analysis, rs56314408 was associated (P = 0.027) with dose in a regression model excluding VKORC1 rs9923231, and GATA‐4 rs2645400 was associated (P = 0.032) with dose in a model excluding CYP2C (CYP2C9*2, *3, *5, *6, *8, and *11, CYP2C rs12777823) variants. Neither variant contributed to dose in the model that included both VKORC1 rs9923231 and CYP2C variants. Our results do not support contributions of the studied variants to warfarin dose requirements in African Americans. However, they illustrate the value of studies in African descent populations, who have low LD in their genome, in teasing out genetic variation underlying drug response associations. They also emphasize the importance of confirming associations in persons of African ancestry.

Study Highlights

• WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC?

The literature is limited in warfarin pharmacogenomic studies in African Americans. VKORC1 and CYP2C9 genotypes explain less variability in warfarin dose requirements in African Americans compared with those of European ancestry. Variants in BCKDK and GATA‐4 gene regions, purported to regulate VKORC1 and CYP2C9 expression, have been studied in Europeans and Asians, respectively, but not in African Americans.

• WHAT QUESTION DID THIS STUDY ADDRESS?

We sought to determine whether rs56314408 near BCKDK or GATA‐4 rs2645400 influence warfarin dose requirements in African Americans.

• WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE?

Our results do not support major contributions of studied variants to warfarin dose requirements in African Americans. However, our findings illustrate the value of studies in African descent populations, who have low linkage disequilibrium in their genome, in teasing out genetic variation underlying drug response associations. They also highlight the importance of confirming associations in persons of African ancestry.

• HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE?

Results do not support the inclusion of rs56314408 near BCKDK or GATA‐4 rs2645400 in pharmacogenomic dosing algorithms for African Americans.

Warfarin remains commonly prescribed despite the availability of direct‐acting oral anticoagulants. ¹ It is, however, a challenging drug to dose because of its narrow therapeutic index and pronounced interpatient variability in dose requirements. Warfarin dose requirements are influenced by VKORC1 and CYP 2C9 genotypes and clinical factors. ² VKORC1‐1639G>A (rs9923231) and CYP2C9*2 and *3 are the variants most commonly included in pharmacogenetic dosing algorithms and explain more than 30% of dose variability in Europeans, but only about 10% of the variability in African Americans. ³ , ⁴ , ⁵ , ⁶ The CYP2C9*5, *6, *8, and *11 and the rs12777823 variant in the CYP2C cluster explain an additional 11% of the dose variability in African Americans. ⁴ , ⁷ , ⁸ Pharmacogenomic studies on warfarin are mostly done in Europeans and Asians. There is, therefore, a gap in the literature on warfarin pharmacogenomic studies in minorities like African Americans who show differences in minor allele frequencies (MAF) and have a lower linkage disequilibrium (LD) pattern. ⁹ A recent study in a European population suggested that the rs56314408 C>T single nucleotide polymorphism (SNP), located on chromosome 16 in an enhancer upstream of the branched chain ketoacid dehydrogenase kinase (BCKDK) gene, could be a functional variant regulating VKORC1 gene expression. ¹⁰ However, rs56314408 is in high LD with VKORC1 rs9923231 in Europeans, and thus, whether this SNP influences warfarin dose independent of the VKORC1 rs9923231 variant could not be determined in Europeans. Therefore, Cavalli et al. mentioned that it is warranted to genotype rs56314408 in warfarin‐treated African Americans to see whether it improves warfarin dose predictions. ¹⁰ In another study, the GATA binding protein 4 (GATA‐4) rs2645400 T>G variant was significantly associated with stable warfarin dose in Asians with prosthetic cardiac valves having the homozygous wild‐type (i.e., *1/*1) CYP2C9 genotype. On multivariable analysis, rs2645400/rs4841588 combination increased contribution to the overall warfarin dose variability. This study, therefore, suggested that GATA‐4 plays a role in the regulation of CYP2C9 gene expression and can be predictive of stable warfarin dose. ¹¹ Neither rs56314408 nor rs2645400 has been studied in African Americans. Therefore, this study aimed to determine whether the rs56314408 variant near BCKDK, which is in low LD with VKORC1 rs9923231 in African Americans, and/or the GATA‐4 rs2645400 variant are associated with warfarin dose requirements in African Americans and explain additional variability in dose beyond that of the VKORC1 and CYP2C (CYP2C9*2, *3, *5, *6, *8, and *11 and CYP2C rs12777823) polymorphisms. In our study, we are using these two SNPs as cases to illustrate the importance of carrying out pharmacogenomic studies in African Americans.     

Assessment of CYP2C19 genetic polymorphisms in a Korean population using a simultaneous multiplex pyrosequencing method to simultaneously detect the CYP2C19*2, CYP2C19*3, and CYP2C19*17 alleles

Background and objective: CYP2C19 is a drug‐metabolizing enzyme showing various genetic polymorphisms that may cause marked interindividual and interethnic variability in the disposition of its substrates. We assessed CYP2C19 genetic polymorphisms in a Korean population using a newly developed multiplex pyrosequencing method. Method: A multiplex pyrosequencing method to simultaneously detect CYP2C19*2, *3, and *17 alleles was designed. We established the frequency of these CYP2C19 alleles in 271 Korean subjects using the multiplex pyrosequencing method. Results: The results showed 100% concordance between single and multiplex pyrosequencing methods. We also validated the polymorphisms identified by pyrosequencing with direct sequencing method. The allele frequencies of CYP2C19*2, CYP2C19*3, and CYP2C19*17 were 0·284, 0·101 and 0·015 respectively. These frequencies are similar to that reported for other Asian populations including Japanese and Chinese but different from that of Caucasians and Africans. Conclusions: The multiplex pyrosequencing method to detect CYP2C19*2, CYP2C19*3, and CYP2C19*17 concurrently, seems to be a rapid and reliable genotyping method for the detection of important CYP2C19 genetic polymorphisms. Similar to studies conducted on other Asian populations, this study reported that in the Korean population tested, the CYP2C19*2 and CYP2C19*3 alleles were relatively frequently found, whereas the frequency of CYP2C19*17 was very low.     

Pupillometry in healthy volunteers as a biomarker of tramadol efficacy

What is known and Objective: The opioid effect of tramadol, which can be detected by pupillary response, is predominantly mediated by the O‐demethylated metabolite, formed via CYP2D6. This study was designed to evaluate the effects of tramadol using different parameters of pupillometry as biomarkers. Methods: Sixty‐nine healthy volunteers received tramadol hydrochloride drops orally at a dose of 0·7 mg/kg. Pre‐dose and 2‐h post‐dose pupillometric measurements were performed. The polymorphism of CYP2D6 was analysed. Results and Discussion: Large interindividual variability was observed in the tramadol‐induced pupillary reaction. Miosis was induced in 69·6% and mydriasis in 30·4% of the subjects. The pupillary response differed in relation to the CYP2D6 genotype. A maximal difference in initial pupil diameter of 0·81 mm was found in extensive metabolizers. There were significant effects observed on the pupillary light reflex parameters with tramadol administration (P < 0·05) except for the reflex amplitude and constriction velocity. What is new and Conclusion: The pharmacodynamic effects of tramadol were easily detected using both static and dynamic pupil parameters. The pharmacodynamic profiles were markedly influenced by the CYP2D6 phenotype.     

Differences in genotype and allele frequency distributions of polymorphic drug metabolizing enzymes CYP2C19 and CYP2D6 in mainland Chinese Mongolian, Hui and Han populations

What is known and Objective: Cytochrome P450 2C19 (CYP2C19) and CYP2D6 are important xenobiotic metabolic enzymes and both show considerable genetic variability between Orientals and Caucasians. There are known marked heterogeneity in susceptibility to various cancers and hypertension among Chinese Mongolian, Hui and Han ethnic groups, but the molecular mechanisms are unknown. Our objective was to investigate the patterns of distribution of CYP2C19 and CYP2D6 polymorphisms among healthy Chinese subjects to determine whether any observed inter‐ethnic variability might be worth further investigation as possible contributors to the known differences in disease prevalence. Methods: Blood samples were collected from 454 unrelated Chinese healthy subjects (214 Han, 111 Hui, 129 Mongolian) for genotyping analysis. The single nucleotide polymorphisms (SNPs) CYP2C19*2 (681G>A in exon 5), CYP2C19*3 (636G>A in exon 4) and CYP2D6*10 (188C>T in exon 1) were determined by the polymerase chain reaction–restriction fragment length polymorphism (PCR‐RFLP) method. Results and Discussion: Significantly higher frequencies of the CYP2C19 poor metabolic genotypes were observed in Chinese Han (18·7%), Chinese Hui (25·0%) and Chinese Mongolian (10·9%) subjects than has been reported for Caucasians (1·7–3·0%, P < 0·01). The prevalent defective allele CYP2C19*2 occurred more frequently in both Chinese Hui (32·4%) and Han (29·7%) than in Chinese Mongolian (18·2%, P < 0·01) subjects. The CYP2C19*2 and CYP2C19*3 defective alleles were significantly more frequent in Chinese Han and Chinese Hui ethnic groups than have been reported for Caucasians (11·1–16·3% and 0–0·2%, P < 0·01). CYP2D6*1/*10 heterozygotes and CYP2D6*10/*10 homozygotes were observed more frequently in Chinese Han (43·1% and 27·2%), Hui (40·6% and 30·7%) and Mongolian subjects (31·3% and 9·6%, both P < 0·01) than have been reported for Caucasians (5·5% and 0·3%, P < 0·01). In Chinese Mongolians, the CYP2D6*10 allele occurred at a frequency (25·2%, P < 0·01) intermediate between those reported for Caucasians and the other two Chinese ethnic populations. What is new and Conclusions: This is first report of interethnic differences in frequencies of functional CYP2C19 and CYP2D6 genes among Chinese Mongolian, Hui and Han populations. These differences may be important in explaining reported inter‐ethnic differences in disease prevalence and response to drugs.     

Long‐term anticoagulant effects of the CYP2C9 and VKORC1 genotypes in acenocoumarol users

Summary. Background: The required acenocoumarol dose and the risk of underanticoagulation and overanticoagulation are associated with the CYP2C9 and VKORC1 genotypes. However, the duration of the effects of these genes on anticoagulation is not yet known. Objectives: In the present study, the effects of these polymorphisms on the risk of underanticoagulation and overanticoagulation over time after the start of acenocoumarol were investigated. Patients/methods: In three cohorts, we analyzed the relationship between the CYP2C9 and VKORC1 genotypes and the incidence of subtherapeutic or supratherapeutic International Normalized Ratio (INR) values (< 2 and > 3.5) or severe overanticoagulation (INR > 6) for different time periods after treatment initiation. Results: Patients with polymorphisms in CYP2C9 and VKORC1 had a higher risk of overanticoagulation (up to 74%) and a lower risk of underanticoagulation (down to 45%) in the first month of treatment with acenocoumarol, but this effect diminished after 1–6 months. Conclusions: Knowledge of the patient’s genotype therefore might assist physicians to adjust doses in the first month(s) of therapy.     

Pharmacogenetics of acenocoumarol pharmacodynamics

OBJECTIVE: The aim of this study was to investigate the respective contribution of the different cytochrome P450 (CYP) 2C9 genetic polymorphisms to the interindividual variability of acenocoumarol pharmacodynamic response. METHODS: A total of 263 healthy volunteers were genotyped for CYP2C9*2, CYP2C9*3, CYP2C9*4, and CYP2C9*5 alleles, as well as for the nicotinamide adenine dinucleotide phosphate, reduced, quinone oxidoreductase 1 genetic polymorphism (NQO1*2). Moreover, the 5'-flanking region of the CYP2C9 gene was investigated for new polymorphisms, and haplotype analysis was then performed. Finally, CYP2C9 phenotype was evaluated after a single oral dose of 4 mg of acenocoumarol. Factor VII coagulant activity was measured before and 24 hours after acenocoumarol intake. RESULTS: The CYP2C9*3 allele was the only nonsynonymous single nucleotide polymorphism (SNP) influencing acenocoumarol pharmacodynamics; the percentages of remaining factor VII were 60% +/- 19%, 39% +/- 17%, and 17% for CYP2C9*1/CYP2C9*1, CYP2C9*1/CYP2C9*3, and CYP2C9*3/CYP2C9*3 subjects, respectively (P =.001). Among the white subjects, the CYP2C9 promoter showed the existence of 6 SNPs at positions G-1538A, T-1189C, G-1097A, G-982A, T-640 del, and G-620T with allelic frequencies of 0.085, 0.0398, 0.136, 0.086, 0.005, and 0.0138, respectively. Four major haplotypes could be inferred among white subjects. The haplotype that contains the CYP2C9*3 allele was the only one influencing acenocoumarol pharmacodynamics, explaining 14.3% of its interindividual variability. Body weight explained 5% of acenocoumarol pharmacodynamic variability, whereas the NQO1*2 allele had no significant effect. CONCLUSION: Overall, CYP2C9-related genetic variability accounts for 14% of the interindividual variability in acenocoumarol pharmacodynamic response. The information found by haplotype analysis is mainly related to the CYP2C9*3 SNP.     

A multiplex assay to detect variations in the CYP2C9, VKORC1, CYP4F2 and APOE genes involved in acenocoumarol metabolism

ObjectivesWe have developed a genotyping system to determine the alleles of genes related to interindividual variability in acenocoumarol dosage requirements. This genotyping system is intended for routine clinical use and therefore it is essential that it be simple, fast and inexpensive.Design and methodsWe developed a PCR multiplex SNaPshot reaction that targets 6 SNPs (single nucleotide polymorphisms) in CYP2C9, CYP4F2, VKORC1 and APOE genes, which are associated with acenocoumarol dose requirements.ResultsWe tested the multiplex in 152 samples and found it to be 100% concordant with the results of other methods.ConclusionsWe successfully produced a reliable multiplex system for simultaneously typing 6 SNPs. This system may be used as a model for accurate, simple and inexpensive genotyping of SNPs related to dose requirements. This information allows the prediction of drug efficiency in patients prior to treatment with acenocoumarol and the prevention of adverse drug reactions.     

Pharmacogenetic determinants for interindividual difference of tacrolimus pharmacokinetics 1 year after renal transplantation

What is known and objective: Tacrolimus, a widely used immunosuppressive agent in organ transplantation, has a narrow therapeutic window. It has been suggested that its interaction with lansoprazole could be dependent on polymorphisms of CYP3A5 and CYP2C19. The objective of this study was to investigate how, 1 year after renal transplantation, CYP3A5 and CYP2C19 polymorphisms, biochemical parameters and coadministration with lansoprazole, influenced tacrolimus pharmacokinetics. Methods: The pharmacokinetics of tacrolimus was studied 1 year after renal transplantation, in 75 recipients who were all receiving continuation treatment with 12‐hourly oral tacrolimus, and 30 mg lansoprazole daily (Group 1; n = 20) or, 10 mg rabeprazole daily or no proton pump inhibitor (Group 2; n = 55). Results: There were no significant differences in the dose‐adjusted area under the plasma concentration–time curve (AUC_0–12) and maximum plasma concentration (C_max) of tacrolimus between CYP2C19 genotype groups, but there were significant differences between CYP3A5 genotypes groups (*1/*1 + *1/*3 vs. *3/*3 = 45·2 ± 20·0 vs. 71·0 ± 34·1 ng·h/mL/mg, P < 0·0001 and 6·3 ± 2·6 vs. 9·3 ± 7·0 ng/mL/mg, P = 0·0017, respectively) and between co‐administration with and without lansoprazole (74·5 ± 34·0 vs. 52·4 ± 27·4 ng·h/mL/mg, P = 0·0054 and 10·9 ± 8·8 vs. 6·7 ± 3·0 ng/mL/mg, P = 0·0024, respectively). In a multiple regression analysis, the dose‐adjusted AUC_0–12 and C_max of tacrolimus were associated with CYP3A5*3/*3 and co‐administration with lansoprazole. What is new and conclusion: CYP2C19 does not seem to contribute to the interaction between tacrolimus and lansoprazole. The long‐term combination of tacrolimus and lansoprazole requires careful monitoring of patients with the CYP3A5*3/*3 genotype.     

基质辅助激光解吸电离飞行时间质谱技术检测药物代谢酶基因多态性平台的建立

目的 建立基于基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)技术检测患者体内药物代谢酶基因多态性的平台。方法 选取2013年10月～2014年6月在北京协和医院门诊就诊患者53例EDTA抗凝外周血,提取全血基因组DNA,用MALDI-TOF-MS技术检测53例患者药物代谢酶基因CYP2C9*2(rs1799853),CYP2C9*3(rs1057910),CYP2C19*2(rs4244285),CYP2C19*3(rs4986893),CYP2C19*4(rs28399504),CYP2C19*5(rs56337013)和CYP2C19*17(rs12248560)的单核苷酸多态性(SNP)位点,并用Sanger测序法进行验证。结果 用 MALDI-TOF-MS 技术可以同时完成53份样本,2个药物代谢酶基因,7个SNP位点的检测。53例患者中,发现CYP2C19*2(rs4244285)AG型25例,AA型6例,GG型22例,A等位基因频率为34.9%。CYP2C19*3(rs4986893)AG型4例,GG型49例,A等位基因频率为3.8%。CYP2C9*3(rs1057910)CA型5例,AA型48例,C等位基因频率为4.7%。未发现 CYP2C9*2(rs1799853),CYP2C19*4(rs28399504),CYP2C19*5(rs56337013)和CYP2C19*17(rs12248560)位点突变。经与Sanger测序法比较,两种检测方法结果的符合率为100%。结论 成功建立MALDI-TOF-MS技术检测药物代谢酶基因多态性的平台,该平台具有高通量、准确的特点,对个性化用药治疗具有重要的临床应用价值。     

The association of CYP2C9 gene polymorphisms with colorectal carcinoma in Han Chinese

BACKGROUND: Cytochrome P450 (CYP) 2C9 is an important enzyme involved in xenobiotics metabolism. This study investigated the association of CYP2C9 gene coding region polymorphisms with colorectal cancer (CRC) in Chinese Han population. METHODS: Four hundred and eighty-three healthy controls and 286 sporadic CRC patients participated in this study. Direct sequencing was used to identify the sequence polymorphisms. RESULTS: We detected the significant association of 2 coding region SNPs, rs1057910 and rs1057911, of CYP2C9 with the risk of developing sporadic CRC for Han Chinese. These 2 SNPs showed a strong linkage disequilibrium (LD) (r(2)=0.97, D'=0.985). Significantly different minor allele frequencies were found for SNPs rs1057910 and rs1057911 between the cases (7% and 7.2%, respectively) and controls (3% and 2.9%, respectively) with adjusted P=0.0004 and 0.0002, respectively. Individuals heterozygous for rs1057910A/C or rs1057911A/T showed 2.589-fold (95% CI: 1.549-4.330) or 2.770-fold (95% CI 1.653-4.643) increased risk of developing sporadic CRC. We did not detect any homozygote minor allele carrier for either rs1057910 or rs1057911 in our study population. The CRC association appeared to be more evident for individuals over age 50 y, for men, and for rectum cancer site. CONCLUSION: There is an association of CYP2C9 coding region polymorphisms with the risk of developing CRC in Han Chinese after genotyping cases and controls recruited from different locations in China.     

Comparative performance of gene‐based warfarin dosing algorithms in a multiethnic population

Summary. Background: Gene‐based warfarin dosing algorithms have largely been developed in homogeneous populations, and their generalizability has not been established. Objectives: We sought to assess the performance of published algorithms in a racially diverse and multiethnic sample, and determine if additional clinical variables or genetic variants associated with dose could enhance algorithm performance. Patients and methods: In 145 compliant patients on warfarin with a goal international normalized ratio (INR) of 2–3, stable, therapeutic doses were compared with predicted doses using 12 reported algorithms that incorporated CYP2C9 and VKORC1 variants. Additional covariates tested with each model included race, concurrent medications, medications known to interact with warfarin and previously described CYP4F2, CALU and GGCX variants. Results: The mean patient age was 67 ± 14 years; 90 (62%) were male. Eighty‐two (57%) were Caucasian, 28 (19%) African‐American, 20 (14%) Hispanic and 15 (10%) Asian. The median warfarin dose was 35 mg per week (interquartile range 23–53 mg per week). Gene‐based dosing algorithms explained 37–55% of the variation in warfarin dose requirements. Neither the addition of race, number of concurrent medications nor the number of concurrent medications interacting with warfarin enhanced algorithm performance. Similarly, consideration of CYP4F2, CALU or GGCX variant genotypes did not improve algorithms. Conclusions: Existing gene‐based dosing algorithms explained between approximately one‐third and one‐half of the variability in warfarin dose requirements in this racially and ethnically diverse cohort. Additional clinical and recently described genetic variants associated with warfarin dose did not enhance prediction in our patient population.     

Frequency of CYP2C9 variant alleles, including CYP2C9*13 in a Korean population and effect on glimepiride pharmacokinetics

What is known and Objective: Cytochrome P450 (CYP) 2C9 is a clinically important enzyme involved in the metabolism of many drugs commonly used in humans. Of several allelic variants known to affect the catalytic activity of the CYP2C9 enzyme, the frequencies of the CYP2C9*3 and CYP2C9*13 alleles in the Korean population have been reported as 1·1% and 0·6%, respectively. Our objective was to re‐evaluate the frequencies of CYP2C9 allelic variants in the Korean population, including the CYP2C9*13 allele by pyrosequencing, and to investigate the pharmacokinetics of glimepiride in relation to CYP2C9 genotypes, including CYP2C9*3/*3. Methods: 295 subjects were genotyped for CYP2C9*2 and CYP2C9*3 using the TaqMan procedure, and for CYP2C9*13 using pyrosequencing. These data were combined with our previously reported data to assess the CYP2C9 allele and genotype frequencies in 869 Korean subjects. Data from 24 of the 295 genotyped subjects (22 CYP2C9*1/*1 homozygotes, one CYP2C9*1/*3 heterozygote and one CYP2C9*3/*3 homozygote) who had participated in a bioequivalence study were analysed retrospectively to examine the effects of CYP2C9 genotype on glimepiride pharmacokinetics. Results: The frequencies of the CYP2C9*1/*3, *3/*3, and *1/*13 genotypes in the study population (n = 295) were 0·081 (n = 24), 0·010 (n = 3) and 0·003 (n = 1), respectively. In the 869 subjects from the combined studies, allele frequencies for CYP2C9*3 and CYP2C9*13 were 0·025 (95% CI: 0·018, 0·033) and 0·002 (95% CI: 0·000, 0·010), respectively. Relative to CYP2C9*1 homozygotes, the one CYP2C9*3 homozygous subject was found to have a higher AUC_0–∞ value (490% of the reference value) and a lower oral clearance rate (18% of the reference). What is new and Conclusion: This study is the first examination of CYP2C9*3 homozygotes in the Korean population. Our data on the one subject with this genotype suggest that CYP2C9*3/*3 momozygotes have lower clearance of glimepiride and are exposed to higher levels of the drug than wild‐type homozygotes. Although we identified a subject with the CYP2C9*13 allele using a new pyrosequencing assay, we were unfortunately unable to investigate its effects on glimepiride pharmacokinetics.