Genetic polymorphisms of the drug-metabolizing enzyme CYP2C19 in the Uyghur population in northwest China

1.?CYP2C19 is a clinically important enzyme and is involved in the metabolism of approximately 10% of drugs used in daily clinical practice. Previous studies mainly focused on Chinese Han populations or other ethnic groups, little is known about Uyghur populations.

2.?The present study was designed to determine the genetic basis of CYP2C19 polymorphisms.

3.?We used direct sequencing to investigate the promoter, exons and surrounding introns, and 3′-untranslated region of the CYP2C19 gene in 96 unrelated healthy Uyghur individuals.

4.?A total of 31 different CYP2C19 polymorphisms were identified in the Uyghur population, three of which were novel, including two nonsynonymous variants (57807A?>?M, Gln279Pro and 19257G?>?R, Asp262Asn) and one synonymous variants in exon 5 (19184T?>?Y, Leu237Leu). In addition, CYP2C19*1, *2 and *3 alleles showed frequencies of 83.34%, 14.06% and 2.08%, respectively.

5.?This is the first study that systematically screened the polymorphisms of the whole CYP2C19 gene in Uyghur population. Hence, our results provided important information on CYP2C19 polymorphisms in Uyghur population and could be helpful for future personalized medicine studies in Uyghur population generally.     

Genetic polymorphism analysis of the drug-metabolizing enzyme CYP1A2 in a Uyghur Chinese population: a pilot study

1.?CYP1A2 is a highly polymorphic gene and CYP1A2 enzyme results in broad inter-individual variability in response to certain pharmacotherapies, while little is known about the genetic variation of CYP1A2 in Uyghur Chinese population. The aim of the present study was to screen Uyghur volunteers for CYP1A2 genetic polymorphisms.

2.?We used DNA sequencing to investigate promoter, exons, introns, and 3’ UTR of the CYP1A2 gene in 96 unrelated healthy Uyghur individuals. We also used SIFT (Sorting Intolerant From Tolerant) and PolyPhen-2 (Polymorphism Phenotyping v2) to predict the protein function of the novel non-synonymous mutation in CYP1A2 coding regions.

3.?We identified 20 different CYP1A2 polymorphisms in the Uyghur Chinese population, including two novel variants (119A?>?G and 2410G?>?A). Variant 119A?>?G was predicted to be probably damaging on protein function by PolyPhen-2, by contrast, 2410G?>?A was identified as benign. The allele frequencies of CYP1A2*1A, *1B, *1F, *1G, *1J, *1M, *4, and *9 were 23.4%, 53.1%, 3.7%, 2.6%, 2.6%, 13.5%, 0.5%, and 0.5%, respectively. The frequency of *1F, a putative high inducibility allele, was higher in our sample population compared with that in the Caucasian population (p?<?0.05). The most common genotype combinations were *1A/*1B (46.9%) and *1B/*1M (27.1%).

4.?Our results provide basic information on CYP1A2 polymorphisms in Uyghur individuals and suggest that the enzymatic activities of CYP1A2 may differ among the diverse ethnic populations of the world.     

Effects of cytochrome P450 3A4 and non-genetic factors on initial voriconazole serum trough concentrations in hematological patients with different cytochrome P450 2C19 genotypes

1.?Polymorphisms of cytochrome P450 2C19 (CYP2C19) is an important factor contributing to variability of voriconazole pharmacokinetics. Polymorphisms of CYP3A4, CYP3A5, CYP2C9 and non-genetic factors such as age, gender, body mass index (BMI), transaminase levels, concomitant medications might also affect voriconazole initial steady serum trough concentration (VIC_min) in haematological patients, but the effects were not clear.

2.?Eighteen single-nucleotide polymorphisms in CYP2C19, CYP3A4, CYP3A5, CYP2C9 were genotyped. Patients were stratified into two groups according to CYP2C19 genotype. Group 1 were patients with CYP2C19*2 or CYP2C19*3, and Group 2 were homozygous extensive metabolizers. The effects were studied in different groups. VIC_min was adjusted on daily dose (VIC_min/D) for overcoming effect of dose.

3.?A total of 106 blood samples from 86 patients were included. In final optimal scaling regression models, polymorphisms of rs4646437 (CYP3A4), age, BMI was identified to be factors of VIC_min/D in Group 1 (R^2?=^?.255, p?<?.001). Only age was confirmed as a factor of VIC_min/D in Group 2 (R^2?=^?0.144, p?=?.021).

4.?Besides polymorphisms of CYP2C19, in individualized medication of voriconazole in haematological patients, polymorphisms of CYP3A4, and non-genetic factors as BMI, age should also be taken into account, especially for individuals with CYP2C19*2 or CYP2C19*3.     

Impact of CYP2C8*3 polymorphism on in vitro metabolism of imatinib to N-desmethyl imatinib

Abstract

1.?Imatinib is metabolized to N-desmethyl imatinib by CYPs 3A4 and 2C8. The effect of CYP2C8*3 genotype on N-desmethyl imatinib formation was unknown.

2.?We examined imatinib N-demethylation in human liver microsomes (HLMs) genotyped for CYP2C8*3, in CYP2C8*3/*3 pooled HLMs and in recombinant CYP2C8 and CYP3A4 enzymes. Effects of CYP-selective inhibitors on N-demethylation were also determined.

3.?A single-enzyme Michaelis–Menten model with autoinhibition best fitted CYP2C8*1/*1 HLM (n?=?5) and recombinant CYP2C8 kinetic data (median?±?SD K_i?=?139?±?61?µM and 149?µM, respectively). Recombinant CYP3A4 showed two-site enzyme kinetics with no autoinhibition. Three of four CYP2C8*1/*3 HLMs showed single-enzyme kinetics with no autoinhibition. Binding affinity was higher in CYP2C8*1/*3 than CYP2C8*1/*1 HLM (median?±?SD K_m?=?6?±?2 versus 11?±?2?µM, P=0.04). CYP2C8*3/*3 (pooled HLM) also showed high binding affinity (K_m?=?4?µM) and single-enzyme weak autoinhibition (K_i?=?449?µM) kinetics. CYP2C8 inhibitors reduced HLM N-demethylation by 47–75%, compared to 0–30% for CYP3A4 inhibitors.

4.?In conclusion, CYP2C8*3 is a gain-of-function polymorphism for imatinib N-demethylation, which appears to be mainly mediated by CYP2C8 and not CYP3A4 in vitro in HLM.     

Identification of human cytochrome P450 enzymes involved in the metabolism of IN-1130, a novel activin receptor-like kinase-5 (ALK5) inhibitor

1.?The in vitro metabolism of 3-((5-(6-methylpyridin-2-yl)-4-(quinoxalin-6-yl)-1H-imidazol-2-yl)methyl)benzamide (IN-1130), a selective activin receptor-like kinase-5 (ALK5) inhibitor and a candidate drug for fibrotic disease, was studied.

2.?The cytochrome P450s (CYPs) responsible for metabolism of IN-1130 in liver microsomes of rat, mouse, dog, monkey and human, and in human CYP supersomes?, were identified using specific CYP inhibitors. The order of disappearance of IN-1130 in various liver microsomal systems studied was as follows: monkey, mouse, rat, human, and dog.

3.?Five distinct metabolites (M1–M5) were identified in all the above microsomes and their production was substantially inhibited by CYP inhibitors such as SKF-525A and ketoconazole. Among nine human CYP supersomes? examined, CYP3A4, CYP2C8, CYP2D6*1, and CYP2C19 were involved in the metabolism of IN-1130, and the production of metabolites were significantly inhibited by specific CYP inhibitors. IN-1130 disappeared fastest in CYP2C8 supersomes. CYP3A4 produced four metabolites of IN-1130 (M1–M4), whereas supersomes expressing human FMO cDNAs, such as FMO1, FMO3, and FMO5, produced no metabolites.

4.?Hence, it is concluded that metabolism of IN-1130 is mediated by CYP3A4, CYP2C8, CYP2D6*1, and CYP2C19.     

Genetic polymorphisms analysis of drug-metabolizing enzyme CYP2C9 in the Uyghur population

1. Genetic variations in cytochrome P450 2C9 are known to contribute to interindividual and interethnic variability in response to clinical drugs, but little is known about the genetic variation of CYP2C9 in the Uyghur population.

2. We directly sequenced the whole CYP2C9 gene in 96 unrelated, healthy Uyghur from Xinjiang Uygur Autonomous Region of China and screened for genetic variants in the promoter, exons, introns and 3′-UTR.

3. Thirty five previously reported alleles and six genotypes were detected in this study. The allele frequencies of CYP2C9*1, *2, *11, *12, *29 and *33 were 89.58, 7.81, 0.52, 0.52, 1.04 and 0.52%, respectively. We detected one non-synonymous novel variant at position 329 from Arg to Cys and this mutation is predicted to be intolerant by SIFT.

4. Our results provide basic information about CYP2C9 alleles in Uyghur, which may help to optimize pharmacotherapy effectiveness by providing personalized medicine to this ethnic group.

     

The effect of resveratrol on pharmacokinetics of aripiprazole in vivo and in vitro

1.?The objective of this study were to investigate the effect of orally administered resveratrol on the pharmacokinetics of aripiprazole (APZ) in rat, and the inhibitory effects of resveratrol on APZ dehydrogenation activity in liver microsomes and human cytochrome P450 3A4 and 2D6.

2.?Twenty-five healthy male Sprague–Dawley rats were randomly divided into five groups: A (control group), B (multiple dose of 200?mg/kg resveratrol), C (multiple dose of 100?mg/kg resveratrol), D (a single dose of 200?mg/kg resveratrol) and E (a single dose of 100?mg/kg resveratrol). A single dose of 3?mg/kg APZ administered orally 30?min after administration of resveratrol. In addition, CYP2D6*1, CYP3A4*1, human and rat liver microsomes were performed to determine the effect of resveratrol on the metabolism of APZ in vitro.

3.?The multiple dose of 200 or 100?mg/kg resveratrol significantly increased the AUC and C_max of APZ. The resveratrol also obviously decreased the CL, but without any significant difference on t_1/2 in vivo. On the other hand, resveratrol showed inhibitory effect on CYP3A4*1, CYP2D6*1, human and rat microsomes, the IC₅₀ of resveratrol was 6.771, 87.87, 45.11 and 35.59?μmol?l^?1, respectively.

4.?Those results indicated more attention should be paid when APZ was administrated combined with resveratrol.     

Homology modelling of CYP3A4 from the CYP2C5 crystallographic template: analysis of typical CYP3A4 substrate interactions

1.?The results of homology modelling of cytochrome P4503A4 (CYP3A4), which is a human enzyme of major importance for the Phase 1 metabolism of drug substrates, from the CYP2C5 crystal structure is reported.

2.?The overall homology between the two protein sequences was generally good (46%) with 24%?of amino acid residues being identical and a 22%?similarity between matched pairs in the CYP3A4 and CYP2C5 aligned sequences, thus indicating that CYP2C5 represents a viable template for modelling CYP3A4 by homology.

3.?The CYP3A4 model appears to show consistency with the reported findings from the extensive site-directed mutagenesis studies already published.

4.?Typical CYP3A4 substrates, such as midazolam, testosterone, nifedipine and verapamil, are shown to fit the putative active site of the enzyme structure in a manner consistent with their known positions of metabolism.     

Impact of CYP3A5 polymorphism on platelet reactivity at percutaneous coronary intervention and after 9 months of aspirin and clopidogrel therapy in Japanese patients with coronary artery disease

Background

High residual platelet reactivity in patients receiving clopidogrel is associated with an increased risk of a cardiovascular event after coronary stenting. The aim of our study was to evaluate the impact of the cytochrome P450 (CYP) 3A5 and CYP2C19 polymorphisms on platelet reactivity during dual antiplatelet therapy.

Methods

We determined the CYP2C19 and CYP3A5 genotypes of 101 angina patients (65 male patients, mean age 64 years) receiving dual antiplatelet therapy with aspirin and clopidogrel and evaluated the effect of these polymorphism on platelet reactivity at the early and late phases of treatment using a conventional light transmission aggregometry. Early and late phases were defined as 24 h after the loading dose and after 9 months on a maintenance dose of 75 mg daily, respectively.

Results

The distribution of the CYP2C19 genotype was 30 % in extensive metabolizers (EM; CYP2C19*1/*1), 46 % in intermediate metabolizers (IM; *1/*2, *1/*3), and 25 % in poor metabolizers (PM; *2/*2, *2/*3, *3/*3). Platelet reactivity levels in during the early and late phases were 3,793?±?1,476 and 2,960?±?1,410, respectively, in EM, 4,706?±?1,417 and 3,239?±?1,479, respectively, in IM, and 5,402?±?776 and 4,736?±?1,356 aggregation units (AU)?min, respectively in EM. The distribution of the CYP3A5 genotype was 33 % in patients carrying the wild-type or one loss-of-function allele (Expressor phenotype; *1/*1 and *1/*3, respectively) and 67 % in those carrying two loss-of-function alleles (Non-expressor; *3/*3). In total, eight patients were EM+Expressor, 22 were EM+Non-expressor, 18 were IM+Expressor, 28 were IM+Non-expressor, eight were PM+Expressor, and 17 were PM+Non-expressor. In the late phase of PM with the CYP2C19 polymorphism, the levels of platelet reactivity according to CYP3A5 genotype were 3,963?±?1,436 and 5,100?±?1,190 AU?min in Expressor and Non-expressor, respectively (P?<?0.05), however, there was no difference in platelet reactivity between Expressor and Non-expressor in EM and IM.

Conclusions

Our results suggest that antiplatelet response to clopidogrel in the late phase depends on the CYP3A5 polymorphism in PM with CYP2C19.     

CYP2A13 genetic polymorphism in French Caucasian,Gabonese and Tunisian populations

Since human CYP2A13 is expressed in the respiratory tract and is involved in the activation of tobacco-specific nitrosamines, some of the previously reported sequence variations may contribute to inter-individual and inter-ethnic differences in the susceptibility of tobacco-related tumorigenesis. The aim was to compare the frequencies of the 578C?>?T (Arg¹⁰¹Stop), 3375C?>?T (Arg²⁵⁷Cys) and 7520C?>?G (3′-untranslated region) mutations in several populations. The frequencies of the 578C?>?T polymorphism were 3.8, 0 and 1.0% in French Caucasians, Gabonese and Tunisians, respectively. In the same populations, the frequencies of the 3375C?>?T mutation were 0, 15.3 and 4.2%, respectively, whereas the frequencies of the 7520C?>?G mutation were 1.0, 20.8 and 7.3%, respectively. Marked inter-ethnic variations in CYP2A13 were identified and confirmed. These findings provide data for further studies that associate CYP2A13 haplotypes with an incidence of smoking-related tumours in respect of ethnicity.     

Cytochrome P450 2A6 and other human P450 enzymes in the oxidation of flavone and flavanone

1.?We previously reported that flavone and flavanone interact spectrally with cytochrome P450 (P450 or CYP) 2A6 and 2A13 and other human P450s and inhibit catalytic activities of these P450 enzymes. In this study, we studied abilities of CYP1A1, 1A2, 1B1, 2A6, 2A13, 2C9 and 3A4 to oxidize flavone and flavanone.

2.?Human P450s oxidized flavone to 6- and 5-hydroxylated flavones, seven uncharacterized mono-hydroxylated flavones, and five di-hydroxylated flavones. CYP2A6 was most active in forming 6-hydroxy- and 5-hydroxyflavones and several mono- and di-hydroxylated products.

3.?CYP2A6 was also very active in catalyzing flavanone to form 2′- and 6-hydroxyflavanones, the major products, at turnover rates of 4.8?min^?1 and 1.3?min^?1, respectively. Other flavanone metabolites were 4′-, 3′- and 7-hydroxyflavanone, three uncharacterized mono-hydroxylated flavanones and five mono-hydroxylated flavones, including 6-hydroxyflavone. CYP2A6 catalyzed flavanone to produce flavone at a turnover rate of 0.72?min^?1 that was ～3-fold higher than that catalyzed by CYP2A13 (0.29?min^?1).

4.?These results indicate that CYP2A6 and other human P450s have important roles in metabolizing flavone and flavanone, two unsubstituted flavonoids, present in dietary foods. Chemical mechanisms of P450-catalyzed desaturation of flavanone to form flavone are discussed.     

Interaction of isoflavonoids with human liver microsomal cytochromes P450: inhibition of CYP enzyme activities

1.?The possibility of interaction of isoflavonoids with concomitantly taken drugs to determined isoflavonoids safety was studied. Inhibition of nine forms of cytochrome P450 (CYP3A4, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2C9, CYP2D6 and CYP2E1) by 12 isoflavonoids (daidzein, genistein, biochanin A, formononetin, glycitein, equol and six glucosides, daidzin, puerarin, genistin, sissotrin, ononin and glycitin) was studied systematically.

2.?The most potent inhibitors were genistein and daidzein inhibiting noncompetitively the CYP2C9 with K_i of 35.95?±?6.96 and 60.56?±?3.53?μmol/l and CYP3A4 (inhibited by genistein with K_i of 23.25?±?5.85?μmol/l also by a noncompetitive mechanism). Potent inhibition of CYP3A4 was observed also with biochanin A (K_i of 57.69?±?2.36?μmol/l) and equol (K_i of 38.47?±?2.32?μmol/l).

3.?Genistein and daidzein inhibit noncompetitively CYP3A4 and CYP2C9. With plasma levels in micromolar range, a clinically important interaction with concomitantly taken drugs does not seem to be probable.     

Inhibitory effect of six herbal extracts on CYP2C8 enzyme activity in human liver microsomes

Abstract

1.?Herbal supplements widely used in the US were screened for the potential to inhibit CYP2C8 activity in human liver microsomes. The herbal extracts screened were garlic, echinacea, saw palmetto, valerian, black cohosh and cranberry. N-desethylamodiaquine (DEAQ) and hydroxypioglitazone metabolite formation were used as indices of CYP2C8 activity.

2.?All herbal extracts showed inhibition of CYP2C8 activity for at least one of three concentrations tested. A volume per dose index (VDI) was calculated to determine the volume in which a dose should be diluted to obtain IC₅₀ equivalent concentration. Cranberry and saw palmetto had a VDI value >5.0?l per dose unit, suggesting a potential for interaction.

3.?Inhibition curves were constructed and the IC₅₀ (mean?±?SE) values were 24.7?±?2.7?μg/ml for cranberry and 15.4?±?1.7?μg/ml for saw palmetto.

4.?The results suggest a potential for cranberry or saw palmetto extracts to inhibit CYP2C8 activity. Clinical studies are needed to evaluate the significance of this interaction.     

Inhibitory effects of curculigoside on human liver cytochrome P450 enzymes

1.?Curculigoside possesses numerous pharmacological activities, and however, little data available for the effects of curculigoside on the activity of human liver cytochrome P450 (CYP) enzymes.

2.?This study investigates the inhibitory effects of curculigoside on the main human liver CYP isoforms. In this study, the inhibitory effects of curculigoside on the eight human liver CYP isoforms 1A2, 2A6, 2E1, 2D6, 2C9, 2C19, 2C8, and 3A4 were investigated in human liver microsomes.

3.?The results indicated that curculigoside could inhibit the activity of CYP1A2, CYP2C8, and CYP3A4, with IC₅₀ values of 15.26, 11.93, and 9.47?μM, respectively, but that other CYP isoforms were not affected. Enzyme kinetic studies showed that curculigoside was not only a noncompetitive inhibitor of CYP1A2, but also a competitive inhibitor of CYP2C8 and CYP3A4, with Ki values of 5.43, 3.54, and 3.35?μM, respectively. In addition, curculigoside is a time-dependent inhibitor for CYP1A2, with kinact/K_I values of 0.056/6.15?μM^?1?min^?1.

4.?The in vitro studies of curculigoside with CYP isoforms suggest that curculigoside has the potential to cause pharmacokinetic drug interactions with other coadministered drugs metabolized by CYP1A2, CYP2C8, and CYP3A4. Further in vivo studies are needed in order to evaluate the significance of this interaction.     

The potent mechanism-based inactivation of CYP2D6 and CYP3A4 with fusidic acid in in vivo bioaccumulation

1.?The accumulation of fusidic acid (FA) after multiple doses of FA has been reported on in previous studies but the related mechanisms have not been clarified fully. In the present study, we explain the mechanisms related to the mechanism-based inactivation of CYP2D6 and CYP3A4.

2.?The irreversible inhibitory effects of FA on CYP2D6 and CYP3A4 were examined via a series of experiments, including: (a) time-, concentration- and NADPH-dependent inactivation, (b) substrate protection in enzyme inactivation and (c) partition ratio with recombinant human CYP enzymes. Metoprolol α-hydroxylation and midazolam 1′-hydroxylation were used as marker reactions for CYP2D6 and CYP3A4 activities, and HPLC-MS/MS measurement was also utilised.

3.?FA caused to the time- and concentration-dependent inactivation of CYP2D6 and CYP3A4. About 55.8% of the activity of CYP2D6 and 75.8% of the activity of CYP3A4 were suppressed after incubation with 10?μM FA for 15?min. K_I and k_inact were found to be 2.87?μM and 0.033?min^?1, respectively, for CYP2D6, while they were 1.95?μM and 0.029?min^?1, respectively, for CYP3A4. Inhibition of CYP2D6 and CYP3A4 activity was found to require the presence of NADPH. Substrates of CYP2D6 and CYP3A4 showed that the enzymes were protected against the inactivation induced by FA. The estimated partition ratio for the inactivation was 7 for CYP2D6 and 12 for CYP3A4.

4.?FA is a potent mechanism-based inhibitor of CYP2D6 and CYP3A4, which may explain the accumulation of FA in vivo.     

Effects of CYP3A5 genotypes,ABCB1 C3435T and G2677T/A polymorphism on pharmacokinetics of Tacrolimus in Chinese adult liver transplant patients

Abstract

1.?The purpose of this study was to establish a population pharmacokinetic (PK) model of tacrolimus and evaluate the influence of clinical covariates, including the genetic polymorphisms of the cytochrome P450 3A5 gene (CYP3A5) and gene-encoding P-glycoprotein (ABCB1), on the PK parameters in Chinese adult liver transplant recipients.

2.?Details of drug dose, sampling times and concentrations were collected retrospectively from routine therapeutic drug monitoring data early after liver transplant. Tacrolimus PKs was studied by a non-linear mixed-effect modeling (NONMEM) method. CYP3A5 genotypes, ABCB1 C3435T and G2677T/A polymorphism and a number of clinical covariates were tested for their influence on TAC PKs.

3.?A one-compartment model with first-order absorption and elimination adequately described the data. Apparent clearance (CL/F) and apparent volumes of distribution (V/F) in final population model were 17.6?L/h and 225?L, respectively. The absorption rate constant (K_a) was fixed at 4.48?h^?1. The inter-individual variability in CL/F and V/F was 53.9 and 68%, respectively. In the final model, CYP3A5 genotype, post-operative day, alanine aminotransferase, total bilirubin, hematocrit and blood urea nitrogen were found to significantly influence the CL/F, whereas POD and HB influence V/F.

4.?Population PK analysis of tacrolimus in Chinese adult liver transplant patients resulted in identification of the CYP3A5 genotype, POD, BUN, ALP, HCT, TBIL and HB as significant covariates on the PK parameters of tacrolimus.     

VKORC1 −1639G>A and CYP2C9*3 are the major genetic predictors of phenprocoumon dose requirement

Purpose

Phenprocoumon, similar to other coumarin-derived anticoagulants, is associated with a large variation in the individual dose requirement to achieve stable anticoagulation. Polymorphisms in the vitamin K epoxide reductase complex subunit 1 (VKORC1) and the liver enzyme cytochrome P450 2C9 (CYP2C9) effectively account for the variability in warfarin and acenocoumarol response but are less well-defined pharmacogenetic predictors in phenprocoumon therapy.

Methods

A retrospective study was performed on 185 outpatients attending anticoagulation clinics in Austria and Germany. These patients were genotyped for the VKORC1 ?1639G>A and 3730G>A polymorphisms as well as for the CYP2C9 *2 and *3 polymorphisms using a reverse hybridisation-based teststrip assay.

Results

The VKORC1 ?1639A allele, which was present at a frequency of 41.4% in the study cohort, significantly reduced the mean weekly phenprocoumon dose by 3 mg (19%) in the heterozygous and by 6.7 mg (43%) in the homozygous state compared to wild-type carriers (15.5?±?6.8 mg, p?<?0.0001). A stepwise multiple regression analysis revealed that VKORC1 ?1639G>A, age and CYP2C9*3 were the major independent determinants of phenprocoumon dose, accounting for 14.2, 9.1 and 4.7% of its variability, respectively (p?≤?0.0007). The CYP2C9*2 polymorphism had a marginal influence (1.4%) and failed to reach statistical significance (p?=?0.062). The VKORC1 3730G>A genotype had no additional predictive power for individual dose variability.

Conclusion

Similar to warfarin and acenocoumarol, the VKORC1 ?1639G>A polymorphism had the highest impact on the maintenance dose of phenprocoumon. The factor age was the second most important predictor and explained a greater percentage of the variability than CYP2C9 genotype.     

The different metabolism of morusin in various species and its potent inhibition against UDP-glucuronosyltransferase (UGT) and cytochrome p450 (CYP450) enzymes

1.?The aim of this study was to investigate the inhibitory effect of morusin on Glucuronosyltransferase (UGT) isoforms and cytochrome P450 enzymes (CYP450s). We also investigated the metabolism of morusin in human, rat, dog, monkey, and minipig liver microsomes.

2.?100?μM of morusin exhibited strong inhibition on all UGTs and CYP450s. The half inhibition concentration (IC₅₀) values for CYP3A4, CYP1A2, CYP2C9, CYP2E1, UGT1A6, UGT1A7, and UGT1A8 were 2.13, 1.27, 3.18, 9.28, 4.23, 0.98, and 3.00?μM, and the inhibition kinetic parameters (K_i) were 1.34, 1.16, 2.98, 6.23, 4.09, 0.62, and 2.11?μM, respectively.

3.?Metabolism of morusin exhibited significant species differences. The quantities of M₁ from minipig, monkey, dog, and rat were 7.8, 11.9, 2.0, and 6.3-fold of human levels. The K_m values in HLMs, RLMs, MLMs, DLMs, and PLMs were 7.84, 22.77, 14.32, 9.13, and 22.83?μM, and V_max for these species were 0.09, 1.23, 1.43, 0.15, and 0.75?nmol/min/mg, respectively. CL_int (intrinsic clearance) values (V_max/K_m) for morusin obeyed the following order: monkey?>?rat?>?minipig?>?dog?>?human. CL_H (hepatic clearance) values for humans, dogs, and rats were calculated to be 8.28, 17.38, and 35.12?mL/min/kg body weight, respectively.

4.?This study provided vital information to understand the inhibitory potential and metabolic behavior of morusin among various species.     

Identification of the human liver cytochrome P450 isoenzymes responsible for the 5-methylhydroxylation of the novel anti-fibrotic drug AKF-PD

1. Identification of cytochrome P450 isoforms (CYPs) involved in flourofenidone (5-methyl-1-(3-fluorophenyl)-2-[1H]-pyridone, AKF-PD) 5-methylhydroxylation was carried out using human liver microsomes and cDNA-expressed human CYPs (supersomes). The experiments were performed in the following in vitro models: (A) a study of AKF-PD metabolism in liver microsomes: (a) correlations study between the rate of AKF-PD 5-methylhydroxylation and activity of CYPs; (b) the effect of specific CYPs inhibitors on the rate of AKF-PD 5-methylhydroxylation; (B) AKF-PD biotransformation by cDNA-expressed human CYPs (1A2, 2D6, 2C9, 2C19, 2E1, 3A4).

2. In human liver microsomes, the formation of AKF-PD 5-methylhydroxylation metabolite significantly correlated with the caffeine N3-demethylase (CYP1A2), chlorzoxazone 6-hydroxylase (CYP2E1), midazolam 1’- hydroxylase (CYP3A4), tolbutamide 4-hydroxylase (CYP2C9), and debrisoquin 4-hydroxylase (CYP2D6) activities. The production of AKF-PD 5-methylhydroxylation metabolite was completely inhibited by a-naphthoflavone (a CYP1A2 inhibitor) with the IC50 value of 0.12 μM in human liver microsomes. The cDNA-expressed human CYPs generated different amounts of AKF-PD 5-methylhydroxylation metabolites, but the preference of CYP isoforms to catalyze AKF-PD metabolism was as follows: 2D6?>?2C19?>?1A2?>?2E1?>?2C9?>?3A4.

3. The results demonstrated that CYP1A2 is the main isoform catalyzing AKF-PD 5-methylhydroxylation while CYP3A4, CYP2C9, CYP2E1, CYP2C19, and CYP2D6 are engaged to a lesser degree. Potential drug–drug interactions involving CYP1A2 may be noticed when AKF-PD is used combined with CYP1A2 inducers or inhibitors.

     

Enantiospecific effects of chiral drugs on cytochrome P450 inhibition in vitro

1.?The aim of this work was to examine the differences in the inhibitory potency of individual enantiomers and racemic mixtures of selected chiral drugs on human liver microsomal cytochromes P450.

2.?The interaction of enantiomeric forms of six drugs (tamsulosin, tolterodine, citalopram, modafinil, zopiclone, ketoconazole) with nine cytochromes P450 (CYP3A4, CYP2E1, CYP2D6, CYP2C19, CYP2C9, CYP2C8, CYP2B6, CYP2A6, CYP1A2) was examined. HPLC methods were used to estimate the extent of the inhibition of specific activity in vitro.

3.?Tamsulosin (TAM) and tolterodine (TOL) inhibited CYP3A4 activity with an enantiospecific pattern. The inhibition of CYP3A4 activity differed for R-TAM (K_i 2.88?±?0.12?µM) and S-TAM (K_i 14.22?±?0.53?µM) as well as for S-TOL (K_i 1.71?±?0.03?µM) and R-TOL (K_i 4.78?±?0.17?µM). Also, the inhibition of CYP2C19 by ketoconazole (KET) cis-enantiomers exhibited enantioselective behavior: the (+)-KET (IC₅₀ 23.64?±?6.25?µM) was more potent than (?)-KET (IC₅₀ 66.12?±?12.6?µM). The inhibition of CYP2C19 by modafinil (MOD) enantiomers (R-MOD IC₅₀?=?51.79?±?8.58?µM, S-MOD IC₅₀?=?48.62?±?9.74?µM) and the inhibition of CYP2D6 by citalopram (CIT) enantiomers (R-CIT IC₅₀?=?68.17?±?5.70?µM, S-CIT IC₅₀?=?62.63?±?7.89?µM) was not enantiospecific.

4.?Although enantiospecific interactions were found (TAM, TOL, KET), they are probably not clinically relevant as the plasma levels are generally lower than the drug concentration needed for prominent inhibition (at least 50% of CYP activity).