Frequency of cytochrome P450 2C9 allelic variants in the Chinese and French populations

Identification of adverse drug reactions that may be related to pharmacogenetics in a public hospital in the South of Brazil

BACKGROUND

Adverse drug reactions (ADRs) are of great concern in clinical practice. Pharmacogenetics can identify individuals and groups at increased risk of developing ADRs, enabling treatment adjustments to improve outcomes. The study aimed to determine the prevalence of ADRs related to drugs with pharmacogenetic evidence level 1A in a public hospital in Southern Brazil.

RESEARCH DESIGN AND METHODS

ADR information was collected from the pharmaceutical registries from 2017 to 2019. Drugs that have pharmacogenetic evidence level 1A were selected. Public genomic databases were used to estimate the genotypes/phenotypes frequency.

RESULTS

During the period, 585 ADRs were spontaneously notified. Most were moderate (76.3%), whereas severe reactions accounted for 33.8%. Additionally, 109 ADRs caused by 41 drugs presented pharmacogenetic evidence level 1A, representing 18.6% of all notified reactions. Depending on the drug-gene pair, up to 35% of individuals from Southern Brazil could be at risk of developing ADRs.

CONCLUSIONS

Relevant amount of ADRs were related to drugs with pharmacogenetic recommendations on drug labels and/or guidelines. Genetic information could guide and improve clinical outcomes, decreasing ADR incidence and reducing treatment costs.

Pharmacogenetic Aspects of Drug Metabolizing Enzymes and Transporters in Pediatric Medicine: Study Progress, Clinical Practice and Future Perspectives

As the activity of certain drug metabolizing enzymes or transporter proteins can vary with age, the effect of ontogenetic and genetic variation on the activity of these enzymes is critical for the accurate prediction of treatment outcomes and toxicity in children. This makes pharmacogenetic research in pediatrics particularly important and urgently needed, but also challenging. This review summarizes pharmacogenetic studies on the effects of genetic polymorphisms on pharmacokinetic parameters and clinical outcomes in pediatric populations for certain drugs, which are commonly prescribed by clinicians across multiple therapeutic areas in a general hospital, organized from those with the most to the least pediatric evidence among each drug category. We also further discuss the research status of the gene-guided dosing regimens and clinical implementation of pediatric pharmacogenetics. More and more drug-gene interactions are demonstrated to have clinical validity for children, and pharmacogenomics in pediatrics have shown evidence-based benefits to enhance the efficacy and precision of existing drug dosing regimens in several therapeutic areas. However, the most important limitation to the implementation is the lack of high-quality, rigorous pediatric prospective clinical studies, so adequately powered interventional clinical trials that support incorporation of pharmacogenetics into the care of children are still needed.

Effects of CYP2C19, CYP2C9 and CYP3A4 gene polymorphisms on plasma voriconazole levels in Chinese pediatric patients

OBJECTIVES

Voriconazole is the most commonly used antifungal agent in clinical application. Previous studies suggested that voriconazole was extensively metabolized by CYP450 enzyme system, including CYP2C19, CYP2C9 and CYP3A4, which contributed to the individual variability of the pharmacokinetic process of voriconazole. This study aimed to investigate the effects of CYP2C19, CYP2C9 and CYP3A4 gene polymorphisms on plasma voriconazole concentrations in Chinese pediatric patients.

METHODS

This study prospectively evaluated pediatric patients administrating voriconazole for the treatment or prophylaxis of invasive fungal infections from October 2018 to July 2020. Seven single-nucleotide polymorphisms in CYP2C19 (CYP2C19*2, CYP2C19*3, and CYP2C19*17), CYP2C9 (CYP2C9*3, CYP2C9*13) and CYP3A4 (CYP3A4*22, rs4646437) were detected by real-time fluorescent PCR with TaqMan probes. The voriconazole trough plasma concentration was determined by UPLC-MS/MS.

RESULTS

A total of 68 pediatric patients were enrolled in this study. Our results showed that voriconazole plasma concentrations of patients with CYP2C19*2 or CYP2C19*3 allele were significantly higher than that with wild-type carriers (P < 0.0001, P = 0.004, respectively). However, CYP2C9*3 and CYP3A4 rs4646437 were not significantly associated with voriconazole plasma levels. The CYP2C19*17, CYP2C9*13 and CYP3A4*22 alleles were not observed in our study. Additionally, multiple linear regression analysis indicated that CYP2C19*2 and CYP2C19*3 alleles remained predictors of voriconazole plasma concentration (r2 = 0.428; P < 0.0001). For CYP2C19 metabolizer phenotype, trough concentration of voriconazole was significantly lower in NM group compared with IM (P < 0.0001) and PM (P = 0.004) groups.

CONCLUSION

Voriconazole plasma levels in pediatric patients are mainly affected by CYP2C19 gene polymorphisms.

Effects of genetic polymorphism of drug-metabolizing enzymes on the plasma concentrations of antiepileptic drugs in Chinese population

As a chronic brain disease, epilepsy affects ~50 million people worldwide. The traditional antiepileptic drugs (AEDs) are widely applied but showing various problems. Although the new AEDs have partially solved the problems of traditional AEDs, the current clinical application of traditional AEDs are not completely replaced by new drugs, particularly due to the large individual differences in drug plasma concentrations and narrow therapeutic windows among patients. Therefore, it is still clinically important to continue to treat patients using traditional AEDs with individualized therapeutic plans. To date, our understanding of the molecular and genetic mechanisms regulating plasma concentrations of AEDs has advanced rapidly, expanding the knowledge on the effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of AEDs. It is increasingly imperative to summarize and conceptualize the clinical significance of recent studies on individualized therapeutic regimens. In this review, we extensively summarize the critical effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of several commonly used AEDs as well as the clinical significance of testing genotypes related to drug metabolism on individualized drug dosage. Our review provides solid experimental evidence and clinical guidance for the therapeutic applications of these AEDs.

Metabolizer phenotype prediction in different Peruvian ethnic groups through CYP2C9 polymorphisms

OBJECTIVES

The CYP2C9 gene have three common alleles, CYP2C9*1, CYP2C9*2 and CYP2C9*3, associated with different homozygous (*1/*1, *2/*2 and *3/*3) and heterozygous (*1/*2 and *1/*3) genotypes, which in turn are related to extensive (gEM), intermediate (gIM) and poor (gPM) metabolizers. Likewise, the inter-ethnic variability was intimately associated with different drug metabolism. Therefore, the aim of the present study was predict the metabolizer phenotypes in different Peruvian ethnic groups from lowland (<2,500 m) and highland (>2,500 m).

METHODS

TaqMan genotyping assays were performed in a group of 174 healthy unrelated Peruvian individuals.

RESULTS

In this study, the allelic comparison between the three eco-regions showed that the CYP2C9*1 was the most common in Andean (96.32%); the *2 was the most frequent in Coast (7.45%, p<0.05). Regarding the *3 was the most common in Amazonian (6.25%, p<0.05). In a corroborative manner, the gEM was the most common in Andean (94.74%), the gIM in Coast (17.02%) and gPM in Amazonian (6.25%) populations.

CONCLUSIONS

Our study provides a valuable source of information about to metabolizer phenotype drugs in different Peruvian ethnic groups. In this way, it could be established suitable genetic-dosage medicaments for various common diseases in these heterogenetic populations.

Hypoglycemia and Glycemic Control With Glyburide in Women With Gestational Diabetes and Genetic Variants of Cytochrome P450 2C9 and/or OATP1B3

Glyburide is mainly metabolized by the cytochrome P450 2C9 (CYP2C9) enzyme and enters the liver via the transporter OATP1B3. The variants OATP1B3*4 (699 G>A; rs7311358) and CYP2C9*2 and *3 are known to have a significant influence on the hepatic uptake and metabolism of glyburide, with lower clearance than in the wild type. In an ancillary study of the INDAO trial, we selected 117 pregnant women with gestational diabetes treated by glyburide and assessed the role of the combined CYP2C9 and OATP1B3 genetic polymorphisms in hypoglycemia and glycemic control. Three groups were constituted: (1) the wild-type genotype group (wild-type allele genotype for both CYP2C9*1 and OATP1B3*1 (699G)), (2) the intermediate group (carriers of CYP2C9*2 allele or OATP1B3*4 (699G>A) heterozygous), and (3) the variant group (carriers of CYP2C9*3 allele and/or OATP1B3*4 (699G>A) homozygous variant). We found that the risk of hypoglycemia was significantly higher in the variant genotype at the second week of treatment: 20.0% (4/20) vs. 8.1% (3/37) in the intermediate group and 4.1% (2/49) in the wild-type genotype group (P = 0.03). The last daily dose of glyburide during pregnancy was lower for patients in the variant genotype group: 4.7 mg (SD 3.5) vs. 8.7 mg (SD 5.7) in the wild-type group and 5.7 mg (SD 3.7) in the intermediate group (P < 0.01). In conclusion, the no-function variants CYP2C9*3 and OATP1B3*4 are associated with a higher risk of hypoglycemia and a lower dose of glyburide in women with gestational diabetes treated with glyburide, which is consistent with the pharmacokinetic roles of both CYP2C9 and OATP1B3.

Genetic polymorphisms of CYP2C9, CYP2C19, and CYP3A5 in Kosovar population

Cytochrome P450 genetic polymorphisms are responsible for individual variations in drug metabolism and drug-drug interactions. They are very important for pharmacogenetics, and their frequency varies across different populations. There is a big gap in the knowledge about the CYP gene family polymorphisms in the population of Kosovo, and the aim of our study was to fill that gap by determining the frequency of the most important variant alleles of CYP2C9, CYP2C19, and CYP3A5 in 234 nonrelated Kosovars. The allele frequencies of CYP2C9*2 and 2C9*3 were 17.52 %, and 10.89 %, respectively. Sixteen participants (6.81 %) were CYP2C9 poor metabolisers. The CYP2C19*2 and *17 variant frequencies were 13.03 % and 19.01 %, respectively. There were 2.13 % CYP2C19 poor and 4.27 % ultra-rapid metabolisers (homozygous carriers of the *17 allele). With regard to CYP3A5, the frequency of the *3 variant allele was 98.29 % (non-expressors), while the remaining participants (1.70 %) were expressors of CYP3A5. These findings are comparable with other European ethnicities, specifically those of Southeast Europe.

Association between genetic polymorphisms of CYP2C9 and VKORC1 and safety and efficacy of warfarin: Results of a 5 years audit

Objective

Genetic polymorphisms of CYP2C9 and VKORC1 play major role in pharmacokinetics and pharmacodynamics of warfarin, respectively. Purpose of our study was to assess the utility of pretesting patients for the above mutations in predicting tendency for bleeding and achieving target INR.

Methods

This was an audit of data collected between July 2011 and December 2016. For safety and efficacy, patients were divided into two subgroups: those with or without bleeding and those who achieved target INR or not. Chi square test was applied to compare the between group differences and crude Odds Ratio (cOR) calculated.

Results

Among 521 patients evaluated, most common indication for warfarin therapy was valvular heart disease (210/521 = 40%); 36% (187/521) had at least one bleeding episode; 56% (269/479) had below target INR. 26% (136/521) had polymorphic alleles of CYP2C9 and 69% (358/521) had the GG haplotype of VKORC1. Polymorphic alleles of CYP2C9 or AG/AA haplotype had twice the odds of bleeding (cOR = 2.14 and 2.44 respectively) relative to those with wild CYP2C9 allele or GG haplotype. Combined CYP2C9 mutant alleles and/or AG/AA haplotypes had thrice the odds of bleeding (cOR = 3.12) relative to those with wild CYP2C9 alleles and GG haplotype. Those with GG haplotype had twice the odds (cOR = 1.81) and those with GG haplotype along with wild CYP2C9 allele had four times the odds (cOR = 4.27) of not achieving the target INR relative to those with other haplotype/alleles. All these associations were statistically significant (p < 0.05).

Conclusions

Pretesting patients for genetic polymorphisms could aid in individualizing warfarin therapy.

Early post-traumatic seizures are associated with valproic acid plasma concentrations and UGT1A6/CYP2C9 genetic polymorphisms in patients with severe traumatic brain injury

BACKGROUND

Seizure is a common complication for severe traumatic brain injury (TBI). Valproic acid (VPA) is a first-line antiepileptic drug, though its metabolism is affected by genetic polymorphisms and varies between individuals. The aim of this study was to investigate such association and to explore its influence on the occurrence of early post-traumatic seizure.

METHODS

A prospective case control study was conducted from 2012 to 2016 recruiting adult patients with severe TBI. Electroencephalograph (EEG) monitoring was performed approximately 4 h for each patient from day 1 to day 7 after injury. If seizures were detected, EEG monitoring was extended until 12 h after seizures being controlled. Genetic polymorphisms in UGT1A6, UGT2B7, CYP2C9, and CYP2C19 were analyzed in association with daily VPA plasma concentrations, adjusted dosages, and occurrence of seizures.

RESULTS

Among the 395 recruited patients, eighty-three (21%) had early post-traumatic seizure, of which 30 (36.14%) were non-convulsive. Most seizures were first detected on day 1 (34.94%) and day 2 (46.99%) after injury. Patients with seizure had longer ICU length of stay and relatively lower VPA plasma concentrations. Patients with UGT1A6_19T > G/541A > G/552A > C double heterozygosities or CYP2C9 extensive metabolizers (EMs) initially had lower adjusted VPA plasma concentrations (power >0.99) and accordingly require higher VPA dosages during later time of treatment (power >0.99). The odds ratio indicated a higher risk of early post-traumatic seizure occurrence in male patients (OR 1.96, 95% CI 1.01-3.81, p = 0.043), age over 65 (OR 2.13, 95% CI 1.01-4.48), and with UGT1A6_19T > G/541A > G/552A > C double heterozygosities (OR 2.38, 95% CI 1.11-5.10, p = 0.02), though the power of the difference was between 0.54 to 0.61.

DISCUSSION

Due to limited facility, the actual frequency of non-convulsive seizures is suspected to be higher than identified. There has been discrepancy regarding to genetic polymorphisms and VPA metab olism between this study and some previous reports. This could be related to confounders such as sample size, race, and patient age. Another limitation is that the case numbers of certain genotypes are limited in this study.

CONCLUSIONS

Continuous EEG monitoring is necessary to detect both convulsive and non-convulsive early post-traumatic seizures in severe TBI patients. UGT1A6/CYP2C9 polymorphisms have influence on VPA metabolism. UGT1A6_19T > G/541A > G/552A > C double heterozygositie is associated with occurrence of early post-traumatic seizures in addition to patients' age and gender. Further investigations with larger sample size are required to confirm the difference.

TRIAL REGISTRATION

Retrospectively registered with Chinese Clinical Trail Registry on 1st Jan 2016 ( ChiCTR-OPC-16007687 ).

The allele frequency of CYP2C9 and VKORC1 in the Southern Khorasan population

The genetic factors are determinants in required dosage changes of warfarin among which are polymorphisms of CYP2C9 and VKORC1 genes. The present study aimed to determine the allele and genotype frequency of CYP2C9 and VKORC1 genes in Birjand population. This study was conducted on 120 individuals who referred to Imam Reza and Vali-Asr hospitals for PT/INR test. After extracting the genomic DNA, the considered sequences were amplified by PCR, and restriction fragment length polymorphism analysis was done by AvaII and KpnI enzymes to determine allele polymorphisms. Moreover, related sequences of VKORC1, after amplification, were sequenced for determining the genotype. Allelic and genotypic frequencies as well as Hardy-Weinberg equilibrium, observed heterozygosity, expected heterozygosity, and polymorphism information content were calculated by PowerMarker V 3.25 software. Amongst 120 individuals in this study with the mean age of 58.12 ± 12.7 years, 80.8%, 9.1%, and 10% exhibited the alleles of 1, 2, and 3 CYP2C9 gene, respectively. The genotype frequencies of 1/1, 1/2, 2/2, 3/1, 3/2, and 3/3 of this gene were found to be 64.1, 15.8, 0, 17.5, 2.5, and 0 %, respectively. In -1639 G>A region, VKORC1 had normal homozygote genotype (GG) and in 1173 C>T region, heterozygote (CT) with the frequency of 48.7% and 45.9% had the most prevalence. Compared with other populations, there is a considerable difference between the allele frequency of CYP2C9 and VKORC1 genetic variance. Since 35.8% of the selected populations carry an abnormal allele causing sensitivity to warfarin, the specialists at medical centers must be informed about the genotypes of patients before prescribing warfarin.

Pharmacogenomic Effect of Cytochrome P450 2C9 Polymorphisms in Different Populations

Presently, warfarin sodium or coumadin is the therapeutic drug of choice for maintenance anticoagualtion therapy. One of several factors underlying the variability in warfarin dose response in the patients receiving this oral anticoagulant is a genetic predisposition, especially the CYP2C9 polymorphisms. The pharmacogenomic effect of CYP2C9 polymorphisms is assessed in different racial populations. A retrospective review was performed with an electronic search engine on this topic to get the data for further meta-analysis. A significant correlation between population ethnicity and gene frequencies was detected in this study. A significant low frequency of CYP2C9 variants among the Asian can be demonstrated. The clinical correlation between CYP2C9 polymorphism and warfarin metabolism was also assessed. Four available case-control reports were selected for this meta-analysis. CYP2C9 variants are strongly associated with low-dose warfarin requirement. In summary, the CYP2C9 variants strongly affect the warfarin dose requirement. This phenomenon is ethnically dependent. Due to the high variant frequency among whites in the West, the investigation for CYP2C9 might be useful for this population, not the Asians, whose variant frequency is very low.

Genetic polymorphism analysis of the drug-metabolizing enzyme CYP2C9 in a Chinese Tibetan population

OBJECTIVES

The enzymatic activity of CYP2C9 results in broad inter-individual variability in response to certain pharmacotherapies. The present study aimed to screen Tibetan volunteers for CYP2C9 genetic polymorphisms. Previous research has focused on Han Chinese patients, while little is known about the genetic variation of CYP2C9 in Tibetan populations.

METHODS

We used DNA sequencing to investigate the promoter, exons and surrounding introns, and 3'-untranslated region of the CYP2C9 gene in 96 unrelated healthy Tibetan individuals.

RESULTS

We identified 26 different CYP2C9 polymorphisms in the Tibetan population, including two novel variants detected in exon 9 (50193G>A and 50197G>C). In addition, we determined the allele frequencies of CYP2C9*1 and *3 were 93.75% and 5.73%, respectively. The rare CYP2C9*55 allele was also found in 0.52% of the study population.

CONCLUSIONS

Our results provide information on CYP2C9 polymorphisms in Tibetan individuals, which may help to optimize pharmacotherapy effectiveness by providing personalized medicine to this ethnic group.

In vitro and in vivo characterization of 13 CYP2C9 allelic variants found in Chinese Han population

Our previous study detected totally 35 CYP2C9 allelic variants in 2127 Chinese subjects, of whom 21 novel alleles were reported for the first time in Chinese populations. The aim of the present study was to characterize the 13 CYP2C9 allelic variants both in vitro and in vivo. Different types of CYP2C9 variants were highly expressed in COS-7 cells, and 50 μM tolbutamide was added as the probing substrate to evaluate their metabolic abilities in vitro. Subsequently, the concentrations of tolbutamide and its metabolite in the plasma and urine within individuals with different types of genotypes were determined by HPLC to evaluate the catalytic activity of the 13 mutant CYP2C9 proteins in vivo. Our results showed that compared with *1/*1 wild-type subjects, subjects with *1/*40 genotype showed increased oral clearance (CL/F), whereas individuals with *1/*3, *1/*13, *3/*3, *3/*13, *1/*16, *1/*19, *1/*34, *1/*42, *1/*45, *1/*46, and *1/*48 genotype exhibited significantly decreased CL/F, and those with *1/*27, *1/*29, *1/*40, and *1/*41 genotype presented similar CL/F value. When expressed in COS-7 cells, the CYP2C9 variants showed similar pattern to the results in clinical study. The study suggests that, besides two typical defective alleles, *3 and *13, seven CYP2C9 allelic variants (*16, *19, *34, *42, *45, *46, and *48) cause defective effects on the enzymatic activities both in vitro and in vivo. In clinic, patients with these defective alleles should be paid close attention to.

Search for genetic determinants of sulfonylurea efficacy in type 2 diabetic patients from China

AIMS/HYPOTHESIS

The aim of this study was to investigate whether genetic variance can influence the efficacy of glibenclamide in patients with type 2 diabetes.

METHODS

A total of 747 patients with type 2 diabetes was enrolled from the Xiaoke Pills Clinical Trial, which is a double-blind, randomised controlled trial. All the patients had been treated with glibenclamide for 48 weeks, with strict drug dose adjustment and data collection. Treatment failure was confirmed when patients reached the criteria for terminating their participation in the study (fasting blood glucose level ≥ 7.0 mmol/l on two consecutive tests 4 weeks after reaching the pre-set maximal dose or maximal tolerated dose). Using this cohort, we tested 44 single-nucleotide polymorphisms (SNPs) in 27 gene regions. The genes in our study were involved in the metabolism of sulfonylureas, islet beta cell function, insulin resistance and beta cell growth and differentiation. A logistic regression model was used to evaluate the relationship between genetic variants and treatment failure over a period of 48 weeks.

RESULTS

We found that no SNP reached the significance level of p < 0.00125 if Bonferroni correction was performed for multiple testing in the logistic regression model used in this pharmacogenetic study. Participants with the minor allele C of rs10811661 in CDKN2A/CDKN2B showed a significantly greater reduction in fasting blood glucose (TT vs TC vs CC: 9.3% (0-20.0%) vs 9.2% (0.9-20.5%) vs 12.7% (5.2-24.4%), p = 0.008) after the initial 4 weeks of treatment independent of age, sex and BMI. There was a significant difference in beta cell function among carriers of different genotypes of rs10811661.

CONCLUSIONS/INTERPRETATION

Our study demonstrated that the CDKN2A/CDKN2B gene may be nominally associated with the efficacy of glibenclamide, and that CDKN2A/CDKN2B is associated with beta cell function.

Analysis of CYP2C9*2, CYP2C9*3 and VKORC1 -1639 G>A polymorphisms in a population from South-Eastern Europe

The CYP2C9 enzyme metabolizes a wide range of relevant drugs, among which are oral anticoagulants. VKORC1 is the pharmacodynamic target of the oral anticoagulants. The genetic polymorphisms CYP2C9*2, CYP2C9*3 and VKORC1 -1639 G>A are the major determinants of the inter-individual variability in the dosage requirements of oral anticoagulants. This study provides a first evaluation of these 3 polymorphisms in a Romanian population. A total of 332 Romanian individuals were genotyped for the CYP2C9*2, CYP2C9*3 and VKORC1 -1639 G>A polymorphisms using the PCR-RFLP technique. Sixty-two individuals (18.7%) were heterozygous for CYP2C9*2, whereas 47 individuals (14.1%) were heterozygous for CYP2C9*3. Fourteen individuals (4.2%) had a CYP2C9*2 homozygous, CYP2C9*3 homozygous or CYP2C9*2/CYP2C9*3 compound heterozygous genotype. These individuals are predicted to have the lowest CYP2C9 enzymatic activity. The allele frequencies of the CYP2C9*2 and CYP2C9*3 polymorphisms were 11.3% and 9.3% respectively. For the VKORC1 -1639 G>A polymorphism, there were 170 heterozygotes (51.2%) and 55 (16.6%) homozygotes for the A allele. The frequency of the A allele was 42.2%. Overall, the distribution of the CYP2C9*2, CYP2C9*3 and VKORC1 -1639 G>A polymorphisms observed in our cohort is in accordance with other Caucasian populations. A large number of Romanians are expected to harbour at least one CYP2C9 variant allele and/or one VKORC1 -1639 G>A allele. This frequency has major implications in the pharmacogenomics of oral anticoagulants in Romanians.

In vitro assessment of 36 CYP2C9 allelic isoforms found in the Chinese population on the metabolism of glimepiride

Of the 57 reported CYP2C9 alleles, to date, 36 of them have been identified in the Chinese population. The aim of this study was to assess the catalytic characteristics of these allelic isoforms and their effects on the metabolism of glimepiride in vitro. Baculovirus-mediated expressing system was used to highly express wild-type and the 35 CYP2C9 allelic variants in insect cell microsomes. Then, the enzymatic characteristics of each variant were evaluated using glimepiride as the substrate. Reactions were performed at 37°C with the insect microsomes and 0.125-10 μM glimepiride for 40 min. After termination, the products were extracted and used for signal collection by LC-MS/MS. Of the 36 tested CYP2C9 allelic isoforms, only four variants (CYP2C9.40, CYP2C9.47, CYP2C9.51 and CYP2C9.54) exhibited similar relative clearance values to that of wild-type CYP2C9.1. In addition, one variant (CYP2C9.36) showed a higher intrinsic clearance value than the wild-type protein, while the remaining 30 CYP2C9 allelic isoforms exhibited significantly decreased clearance values (from 0.1% to 87.2%) compared to CYP2C9.1. This study provided the most comprehensive data on the enzymatic activities of all reported CYP2C9 variants in the Chinese population with regard to the commonly used antidiabetic drug, glimepiride. Our results indicate that most of the tested rare alleles significantly decrease the catalytic activity of CYP2C9 variants towards glimepiride hydroxylation in vitro.

Genotype-phenotype correlation of cytochrome P450 2C9 polymorphism in Indian National Capital Region

Identification of polymorphism of cytochrome P450 2C9 (CYP2C9) enzymes in different ethnic populations is important to understand the differences in clinical responses to drugs. This study determines the CYP2C9 genetic polymorphism in Indian National Capital Region and correlates the phenotype-genotype. Losartan (25 mg) was administered to 107 volunteers to assess CYP2C9 activity, and, on the basis of results, volunteers were categorized as rapid and poor metabolizers. Molecular typing of CYP2C9*1 (wild type), CYP2C9*2, and CYP2C9*3 (the most common variant) was carried out by single-base primer extension technology for 37 subjects, of which 9 were poor metabolizers, and 28 were rapid metabolizers. 14.28 % of the studied population was identified as poor metabolizer for the category of drugs metabolized by CYP2C9. Significant difference was observed between the mean ratio (drug/metabolite) of poor (11.38 ± 5.88) and rapid (1.18 ± 1.11) drug metabolizers. The study suggests that phenotyping of CYP2C9 is desirable before enrollment of subjects for clinical trials or for deciding drug dose regimen as 14.28 % of study population was found to be poor metabolizer for the category of drugs metabolized by CYP2C9. This study establishes phenotype-genotype correlation, and proposes to use genotyping or phenotyping to evaluate the status of drug metabolizing capacity of CYP2C9 as a primary screening procedure before enrolling subjects in clinical trials or in clinical practice.

Lipid-lowering effect of fluvastatin in relation to cytochrome P450 2C9 variant alleles frequently distributed in the Czech population

Background

CYP2C9*3 allele has been reported to correlate with increased plasma concentration of fluvastatin active form in healthy volunteers. We analyzed the correlation between the CYP2C9 genotype and cholesterol-lowering effect of fluvastatin in human hypercholesterolemic patients.

Material/Methods

The study was prospective, without any interventions to standard procedures of hypolipidemic treatment. CYP2C9 genotype was determined by PCR–RFLP assay in 87 patients on concomitant fluvastatin therapy, in 48 patients on monotherapy, and in a control group of 254 healthy volunteers of Czech nationality. Biochemical and clinical data were collected before the initiation of fluvastatin treatment and 12 weeks later.

Results

The frequency of CYP2C9 alleles did not differ significantly among groups of patients and volunteers. The most frequently observed allele was CYP2C9*2.

Treatment with 80 mg of fluvastatin daily of 48 patients on monotherapy for 12 weeks resulted in mean low-density lipoprotein cholesterol (LDL-C) reduction by 25%, mean serum total cholesterol (TC) reduction by 21%, and mean triglyceride (TG) reduction by 28%. The CYP2C9*1/*3 genotype was associated with a decrease in LDL-C levels (by 40.0% for CYP2C9*1/*3, but only by 22.4% for CYP2C9*1/*1), and with the reduction of TC (by 28.6% in CYP2C9*1/*3 versus 20.2% in CYP2C9*1/*1).

Conclusions

In hypercholesterolemic patients, LDL-C serum concentration was decreased more significantly in fluvastatin-treated subjects bearing the CYP2C9*1/*3 genotype compared to CYP2C9*1/*1 genotype. However, due to rare occurrence of some CYP genotypes, it was impossible to report a definitive positive genotype-fluvastatin effect association.

Interethnic and Intraethnic Variability of CYP2C8 and CYP2C9 Polymorphisms in Healthy Individuals

Cytochrome P450 (CYP) superfamily members CYP2C8 and CYP2C9 are polymorphically expressed enzymes that are involved in the metabolic inactivation of several drugs, including, among others, antiepileptics, NSAIDs, oral hypoglycemics, and anticoagulants. Many of these drugs have a narrow therapeutic index, and growing evidence indicates a prominent role of CYP2C8 and CYP2C9 polymorphisms in the therapeutic efficacy and in the development of adverse effects among patients treated with drugs that are CYP2C8 or CYP2C9 substrates. In this review, we summarize present knowledge on human variability in the frequency of variant CYP2C8 and CYP2C9 alleles. Besides an expected interethnic variability in allele frequencies, a large intraethnic variability exists. Among Asian subjects, for example, statistically significant differences (p < 0.0001) in CYP2C9*3 allele frequencies between Chinese and Japanese individuals have been reported. In addition, individuals from East Asia present different allele frequencies for CYP2C9*2 and CYP2C9*3 compared with South Asian subjects (p < 0.0001). Among Caucasian Europeans, statistically significant differences for the frequency of CYP2C8*3, CYP2C9*2, and CYP2C9*3 exist (p < 0.0001). This indicates that Asian individuals or Caucasian European individuals cannot be considered as homogeneous groups regarding CYP2C8 or CYP2C9 allele frequencies. Caucasian American subjects also show a large variability in allele frequencies, which is likely to be related to ethnic ancestry. A higher frequency of variant CYP2C8 and CYP2C9 alleles is expected among Caucasian Americans with South European ancestry than in individuals with North European ancestry. The findings summarized in this review suggest that among individuals with Asian or European ancestry, intraethnic differences in the risk of developing adverse effects with drugs that are CYP2C8 or CYP2C9 substrates are to be expected. In addition, the observed intraethnic variability reinforces the need for proper selection of control subjects and points against the use of surrogate control groups for studies involving association of CYP2C8 or CYP2C9 alleles with adverse drug reactions or spontaneous diseases.

Allele and genotype frequencies of CYP2C9 within an Iranian population (Mazandaran)

Cytochrome P450 2C9 (CYP2C9) is a polymorphic enzyme responsible for the metabolism of different drugs, some with low therapeutic index. The frequency of functionally important mutations and alleles of the gene coding for CYP2C9 shows wide ethnic variations. The present study aimed to determine the prevalence of the most common allelic variants of the CYP2C9 enzyme and to predict the genotype frequency in the Mazandarani ethnic group among the Iranian population. Genotyping of CYP2C9 allelic variants was carried out in 103 unrelated subjects by polymerase chain reaction and restriction fragment length pattern analysis. The frequencies for CYP2C9 alleles *1, *2, and *3 were 78%, 12%, and 10%, respectively. No subjects were found carrying the CYP2C19*11 allele. The frequencies of CYP2C9 genotypes *1/*1, *1/*2, *1/*3, *2/*2, *2/*3, and *3/*3 were 61%, 19%, 16%, 1.5%, 2.5%, and 0.0%, respectively. The result of the present study showed that the two inactive alleles of CYP2C9 accounted for 22% of CYP2C9 alleles in our sample versus 1.5%-29% reported in other populations. The frequencies of the studied alleles resulted in significant differences between our sample and African and Eastern Asian populations.

Population differences in major functional polymorphisms of pharmacokinetics/pharmacodynamics-related genes in Eastern Asians and Europeans: implications in the clinical trials for novel drug development

Drug lag, recently discussed extensively in Japan, can be divided into two phases: clinical development time and application review time. The former factor is still an important problem that might be improved by promoting multi-regional clinical trials and considering the results from other similar populations with Japanese, such as Koreans and Chinese. In this review, we compare the allelic or genotype frequencies of 30 relatively common functional alleles mainly between Eastern Asians and Europeans as well as among 3 major populations in Eastern Asian countries, Japan, Korea, and China, in 12 pharmacokinetics (PK)/pharmacodynamics (PD)-related genes; CYP2C9 (*2 and *3), CYP2C19 (*2, *3 and *17), 13 CYP2D6 haplotypes including *4, *5 and *10, CYP3A5 (*3), UGT1A1 (*28 and *6), NAT2 (*5, *6 and *7), GSTM1 and GSTT1 null genotypes, SLCO1B1 521T>C, ABCG2 421C>A, and HLA-A*31:01 and HLA-B*58:01. In this review, differences in allele frequencies (AFs) or genotype frequencies (GFs) less than 0.1 (in the cases of highest AF (GF) ≥0.1) or less than 0.05 (in the cases of lowest AF (GF) <0.1) were regarded as similar. Between Eastern Asians and Europeans, AFs (or GFs) are regarded as being different for many alleles such as CYP2C9 (*2), CYP2C19 (*2, *3 and *17), CYP2D6 (*4 and *10), CYP3A5 (*3), UGT1A1 (*28 and *6), NAT2 (*5*7), GSTT1 null and ABCG2 421C>A. Among the 3 Eastern Asian populations, however, only AFs of CYP2C19*3, CYP2D6*10, HLA-A*31:01 and HLA-B*58:01 are regarded as dissimilar. For CYP2C19*3, the total functional impact on CYP2C19 could be small if the frequencies of the two null alleles CYP2C19*2 and *3 are combined. Regarding CYP2D6*10, frequency difference over 0.1 is observed only between Japanese and Chinese (0.147). Although environmental factors should be considered for PK/PD differences, we could propose that among Japan, Korea, and China, genetic differences are very small for the analyzed common PK-related gene polymorphisms. On the other hand, AFs of the two HLA alleles important for cutaneous adverse drug reactions are diverse even among Eastern Asians and thus should be taken into account.

Frequency of CYP2C9 alleles in Koreans and their effects on losartan pharmacokinetics

AIM

CYP2C9 enzyme metabolizes numerous clinically important drugs. The aim of this study is to investigate the frequencies of CYP2C9 genotypes and the effects of selected alleles on losartan pharmacokinetics in a large sample of the Korean population.

METHODS

The CYP2C9 gene was genotyped in 1796 healthy Korean subjects. CYP2C9 alleles (CYP2C9*1, *2, *3 and *13 alleles) were measured using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay and direct sequencing assay. The enzymatic activity of each CYP2C9 genotype was evaluated using losartan as the substrate.

RESULTS

The frequencies of CYP2C9*1, *3 and *13 allele were 0.952 (95% confidence interval 0.945-0.959), 0.044 (95% CI 0.037-0.051) and 0.005 (95% CI 0.003-0.007), respectively. The frequencies of the CYP2C9*1/*1, *1/*3, *1/*13 and *3/*3 genotypes were 0.904 (95% CI 0.890-0.918), 0.085 (95% CI 0.072-0.098), 0.009 (95% CI 0.005-0.013) and 0.001 (95% CI 0.000-0.002), respectively. In the pharmacokinetics studies, the AUC(0-∞) of losartan in CYP2C9*3/*3 subjects was 1.42-fold larger than that in CYP2C9*1/*1 subjects, and the AUC(0-∞) of E-3174, a more active metabolite of losartan, in CYP2C9*3/*3 subjects was only 12% of that in CYP2C9*1/*1 subjects.

CONCLUSION

The results confirmed the frequencies of CYP2C9 genotypes in a large cohort of Koreans, and detected the CYP2C9*3/*3 genotype. CYP2C9*3/*3 subjects metabolized much less losartan into E-3174 than CYP2C9*1/*1 subjects.

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.

Influence of CYP2C9 polymorphism on metabolism of valproate and its hepatotoxin metabolite in Iranian patients

Sodium valproate (VPA) has 16 known metabolites in humans. The 2-ene-VPA has anti-convulsant efficacy and 4-ene-VPA is reported to contribute in VPA hepatotoxicity. The formation of 4-ene-VPA is catalyzed by cytochrome P450 2C9 (CYP2C9). CYP2C9 allele mutation is closely related to the attenuation of the enzymatic activity and 4-ene-VPA production. In the present work, VPA, 2-ene-VPA, and 4-ene-VPA in serum of patients receiving VPA were determined and the correlation between CYP2C9 polymorphism and 4-ene-VPA concentration was examined. Blood samplings in 68 patients were performed at two time-points (peak and trough) and one sample blood obtained from 50 healthy volunteers for genotype evaluation. Patients were divided into three groups (22 cases of monotherapy, 19 cases of enzyme inducer therapy, and 27 cases of polytherapy). There was a significant reduction in concentration of VPA and 4-ene-VPA between peak and trough time. In peak concentration, there was a significant correlation between 2-ene-VPA and VPA in all groups. The concentration of 4-ene-VPA in the enzyme inducer and polytherapy group was significantly higher than that of the monotherapy group. The allele frequencies of CYP2C9*1, CYP2C9*2, and CYP2C9*3 were 88.97%, 8.09%, and 2.94% in the patient group and 91%, 6%, and 3% in the normal group, respectively. There was no significant difference in allele frequency in two groups. Mutated alleles didn't have any significant effect on 4-ene-VPA production. No patient showed toxic level of 4-ene-VPA or saturation of ß-oxidation pathway. In conclusion, the role of CYP2C9*2 and CYP2C9*3 in attenuation of 4-ene-VPA formation cannot be confirmed.

Implementing genotype-guided antithrombotic therapy

Genotyping has the potential to improve the efficacy and safety of major antithrombotic drugs. For warfarin, the stable maintenance dose varies from 1-10 mg/day. The VKORC1 -1639G>A allele and the CYP2C9*2 and *3 alleles (cumulative frequency: 90% in Asians, 65% in Europeans and 20% in Africans), explain 45% of response variability in European and 30% in African populations. The large clinical trials COAG and EU-PACT will define the extent to which pharmacogenetic dosing affects the safety and efficacy of warfarin and coumarin derivatives. The platelet inhibitor clopidogrel requires activation by the CYP2C19 enzyme. CYP2C19*2 and *3 alleles (cumulative frequency: 20-50%) produce null enzyme activity, and their presence attenuates platelet inhibition and increases cardiovascular events. The US FDA-mandated drug labeling recognizes the relevance of genotyping in the selection and dosing of both warfarin and clopidogrel.

Patterns of pharmacogenetic diversity in African populations: role of ancient and recent history

AIMS

The knowledge that genetic variation influencing drug response is clearly structured among human populations has prompted many studies aimed at obtaining pharmacogenetic profiles in specific populations. While large amounts of data are being produced for populations from developed countries, the African continent still remains very poorly studied. To help to fill this gap, this work characterized three previously uncharacterized African populations for a set of pharmacogenetically relevant polymorphisms.

MATERIALS & METHODS

Seven polymorphic variations in four genes that encode enzymes from phase I (CYP2C9, CYP3A4 and CYP3A5) or phase III (ABCB1) of drug metabolism were analyzed in population samples from Cabinda (n = 107), Mozambique (n = 109) and São Tomé e Príncipe (n = 126). All three populations shared strong recent historical links with Portugal.

RESULTS

The majority of the screened variations displayed large contrasts in allele frequencies between European and African populations, and this study identified a substantial higher European influence in São Tomé e Príncipe than in Cabinda or Mozambique. Admixture analysis demonstrated that the European contribution to the population of São Tomé e Príncipe amounted to 13.3 +/- 3.3%. Furthermore, the proportion of African or European pharmacogenetic ancestry varied widely across each São Tomean individual.

DISCUSSION & CONCLUSION

This implies that genetic association studies conducted in São Tomé e Príncipe should take into account the confounding factor of admixture to avoid spurious positive or negative results. Our findings also indicate that drug dosage requirements may be different in São Tomé e Príncipe than in other African populations. Thus, the search for pharmacogenetic risk factors should be assessed at an individual level, therefore fulfilling the perspective of personalized medicine. This study further indicates that the common notion of 'African population' might hide a pattern of pharmacogenetic heterogeneity whose real extent still needs to be evaluated by means of a refined sampling of the entire continent.

Novel DNA sequence variations of cytochrome P450 genes in the Han Chinese population

Aim: Cytochrome P450 is an important monooxygenase responsible for the metabolism of a large variety of structurally diverse compounds. The aim of this study was to systematically investigate the DNA sequence variations in 14 cytochrome P450 genes relevant to drug metabolism in the Han Chinese population. Materials & methods: We sequenced these 14 genes in 23 subjects and determined the allele frequencies. Results: We identified a total of 312 genetic variants, which included 80 (25.6%) novel variants. These novel variants included 67 noncoding variants, four synonymous and nine nonsynonymous variants. Among these variants, an 11-nucleotide insertion in the 3´-flanking site of intron 6 in CYP2E1 (c.968-77_-76insGATGGGTGGAT) had the highest allele frequency of 0.565. A total of 16 of these novel variants were predicted to have potential functional consequences; however, among them only c.-1299T>A in CYP2C18 and c.-498C>A in CYP2D6 reached a frequency of 4.9%. Conclusions: This study establishes a genetic database of cytochrome P450 genes in the Han Chinese population and suggests further genetic diversity throughout this important gene family.

Genetic determinants of statin-associated myopathy

Lipid-lowering drugs, especially 3-hydroxy-3-methylglutaryl coenzyme A inhibitors (statins), are widely used in the treatment of patients with increased risk of cardiovascular disease, with well-documented benefits. However, in rare cases, lipid-lowering drugs may cause myopathy or rhabdomyolysis, the risk of which is increased by certain drug–drug interactions. Polymorphisms of metabolizing pathways, including CYP, and efflux transporters, such as MDR1 and SLCO1B1, may cause intersubject variability in plasma statin levels and therefore may be responsible for susceptibility to myopathy. The aim of this review is to summarize selected genetic polymorphisms that predispose to statin-related myopathy (including combined studies of myopathy and myalgia). Genome-wide studies suggest that there is a strong candidate variant within the SLCO1B1 gene (rs4149056) for statin-associated myopathy in a UK (European) population. An enhanced understanding of statin-related myopathy may lead to safer drug development and use.

CYP2C9 polymorphism in non-steroidal anti-inflammatory drugs-induced gastropathy

OBJECTIVE

Non-steroidal anti-inflammatory drugs (NSAID) induce gastroduodenal mucosal injury and are metabolized by cytochrome P450 2C9 (CYP2C9). It is postulated that CYP2C9 genotype is associated with NSAID-induced gastropathy. This study aims to determine whether individuals with a CYP2C9 allele mutation are susceptible to NSAID-induced gastropathy.

METHODS

A total of 109 patients diagnosed as having rheumatic diseases and taking NSAID were appraised as having gastropathy by endoscopy, stool occult blood test and questionnaire two weeks after entering the study. Their peripheral blood was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

A total of 47.7% gastropathy (33% erosions, 14.7% ulcers, 2.75% ulcer bleeding) and 56% dyspeptic symptoms were presented. Only one CYP2C9*2 heterozygote (*1/*2) was found in the group with gastropathy and two variant alleles (CYP2C9*2 and CYP2C9* 3) could not be found in the group without gastropathy. There was no significant difference in both CYP2C9 genotype (0.96%vs 0%) and CYP2C9 variant allele frequency (1.92%vs 0%) between patients with and without gastropathy.

CONCLUSION

These results confirm the high prevalence of NSAID-induced gastropathy but do not support the postulation that CYP2C9*2 and CYP2C9*3 contribute to the development of NSAID-induced gastropathy. This may be due to the low frequency of the two alleles in the population studied.

Pharmacogenetically relevant polymorphisms in Portugal

OBJECTIVE

Most drugs are developed based on data from European-derived 'reference' populations; however, clinically relevant DNA polymorphisms often demonstrate population-specific patterns of allele frequencies. Given that the knowledge of the frequency distribution of functional polymorphisms in a population may guide national planning for selection of therapeutic options, in the present study we examined the allele frequencies of enzymes responsible for drug disposition in Portugal.

PATIENTS & METHODS

Using PCR- and Pyrosequencing-based methods, the current study assessed the frequencies of 15 key polymorphisms from genes encoding enzymes involved in Phases I, II and III of drug metabolism, DNA repair and intracellular metabolism in 135 healthy individuals from Portugal.

RESULTS

Allele frequencies were derived for cytochrome P450 (CYP)2C9*2 (13.2%), CYP2C9*3 (8%), CYP2C19*2 (14%), CYP3A4*1B (7%), CYP3A5*3C (87.5%), glutathione S-transferase (GST)M1*0 (77.9%), GSTP1 313A>G (33%), inosine triphosphatase 94C>A (7%), UDP-glucuronosyltransferase (UGT)1A1*28 (28%), UGT1A1 -3156G>A (23%), ATP-binding cassette (ABC)B1 1236C>T (46%), ABCB1 2677G>A/T (2 and 42%), ABCG2 421C>A (8%), excision repair cross-complementing rodent repair deficiency 2 2251A>C (3%) and thymidylate synthetase 1494del (31%).

CONCLUSION

Although, on the whole, the frequency distributions among the Portuguese fitted the patterns commonly found in other Europeans well, evidence for some degree of African influence was observed. This is the most comprehensive study on pharmacogenetically relevant variations in Portugal to date, and the baseline of pharmacogenetic data might be important for determining policy guidelines for cancer prevention and drug treatments in the Portuguese population.

Pharmacogenetics of glucose-lowering drug treatment: a systematic review

Intensive blood glucose lowering can significantly reduce the risk of micro- and macrovascular complications in patients with diabetes mellitus. However, 30% of all treated patients do not achieve optimal blood glucose levels. Genetic factors may influence the response to glucose-lowering medication. A search of MEDLINE-indexed literature published between January 1966 and July 2007 revealed 37 studies reporting data on genetic polymorphisms and response to glucose-lowering drugs. Most studies involving cytochrome P450 (CYP) genes had small sample sizes (21 studies <50 subjects) and were among healthy volunteers. Multiple studies indicated that the CYP2C9 *3 allele (Ile359Leu polymorphism) was associated with decreased clearance of sulfonylurea drugs. Supporting this, one study reported an increased insulin secretion in CYP2C9*3 allele carriers when using the sulfonylurea agent glyburide. The CYP2C9*3 allele was also associated with a decreased clearance of meglitinides, whereas the CYP2C8*3 (Arg139Lys; Lys399Arg) variant increased the clearance of meglitinides. Polymorphisms in genes encoding the inwardly rectifying potassium channel Kir6.2 (KCNJ11) and the insulin receptor substrate-1 (IRS1) were reported to be associated with an increased risk of (secondary) failure to respond to sulfonylurea therapy. A significant decrease in fasting plasma glucose and hemoglobin A(1c) (HbA(1c)) in response to rosiglitazone was seen in subjects carrying the Pro12Ala polymorphism of the peroxisome proliferator-activated receptor-gamma (PPARG) gene. Conversely, carriers of this polymorphism also had a higher conversion to diabetes mellitus when treated with acarbose; this effect was also seen in adiponectin (ADIPOQ) gene polymorphism carriers. Future studies with adequate sample sizes in which several SNPs in multiple candidate genes are genotyped in patients with diabetes should provide reliable information on genetic variants and response to glucose-lowering drugs.