The CYP3A4*18 allele, the most frequent coding variant in asian populations, does not significantly affect the midazolam disposition in heterozygous individuals

The influence of drug-induced metabolic enzyme activity inhibition and CYP3A4 gene polymorphism on aumolertinib metabolism

The purpose of this study is to clarify the drug interaction profile of aumolertinib, and the influence of CYP3A4 genetic polymorphism on aumolertinib metabolic characteristics. Through microsomal enzyme reactions, we screened 153 drugs and identified 15 that significantly inhibited the metabolism of aumolertinib. Among them, telmisartan and carvedilol exhibited potent inhibitory activities in rat liver microsomes (RLM) and human liver microsomes (HLM). In vivo, the pharmacokinetic parameters of aumolertinib, including AUC and Cmax, were significantly altered when co-administered with carvedilol, with a notable decrease in the clearance rate CLz/F. Interestingly, the pharmacokinetic parameters of the metabolite HAS-719 exhibited a similar trend as aumolertinib when co-administered. Mechanistically, both telmisartan and carvedilol exhibited a mixed-type inhibition on the metabolism of aumolertinib. Additionally, we used a baculovirus-insect cell expression system to prepare 24 recombinant CYP3A4 microsomes and obtained enzymatic kinetic parameters using aumolertinib as a substrate. Enzyme kinetic studies obtained the kinetic parameters of various CYP3A4 variant-mediated metabolism of aumolertinib. Based on the relative clearance rates, CYP3A4.4, 5, 7, 8, 9, 12, 13, 14, 17, 18, 19, 23, 24, 33, and 34 showed significantly lower clearance rates compared to the wild-type. Among the different CYP3A4 variants, the inhibitory potency of telmisartan and carvedilol on the metabolism of aumolertinib also varied. The IC50 values of telmisartan and carvedilol in CYP3A4.1 were 6.68 ± 1.76 μM and 0.60 ± 0.25 μM, respectively, whereas in CYP3A4.12, the IC50 exceeded 100 μM. Finally, we utilized adeno-associated virus to achieve liver-specific high expression of CYP3A4*1 and CYP3A4*12. In the group with high expression of the less active CYP3A4*12, the magnitude of the drug-drug interaction was significantly attenuated. In conclusion, CYP3A4 genetic polymorphism not only influences the pharmacokinetic characteristics of aumolertinib, but also the inhibitory potency of telmisartan and carvedilol on it.

Metabolism of the antipsychotic drug olanzapine by CYP3A43

1. Olanzapine is an atypical antipsychotic primarily used to treat schizophrenia and bipolar disorder. An intronic single nucleotide polymorphism (SNP) that highly significantly predicts increased olanzapine clearance (rs472660) was previously identified in the CYP3A43 gene, which encodes a cytochrome P450 enzyme. But until now there was no experimental evidence for the metabolism of olanzapine by the CYP3A43 enzyme.2. In the present study we provide this evidence, together with a thorough analysis of olanzapine metabolism by all human CYP3A enzymes. We also rationalize our findings by molecular docking experiments. Moreover, we describe the activities of several CYP3A43 mutants and present the first enzymatic activity data for the CYP3A43.3 variant; with respect to prostate cancer, this polymorphic variant is associated with both increased risk and increased mortality. The catalytic properties of the wild type enzyme and the tumor mutant were analyzed by molecular dynamics simulations, which fit very well with the observed experimental results.3. Our finding suggests that the SNP rs472660 likely causes an increased CYP3A43 expression level and demonstrate that, depending on the substrate under study, the tumor mutant CYP3A43.3 can have increased activity in comparison to the wild type enzyme CYP3A43.1.

Significance of Ethnic Factors in Immunosuppressive Therapy Management After Organ Transplantation

Clinical outcomes after organ transplantation have greatly improved in the past 2 decades with the discovery and development of immunosuppressive drugs such as calcineurin inhibitors, antiproliferative agents, and mammalian target of rapamycin inhibitors. However, individualized dosage regimens have not yet been fully established for these drugs except for therapeutic drug monitoring-based dosage modification because of extensive interindividual variations in immunosuppressive drug pharmacokinetics. The variations in immunosuppressive drug pharmacokinetics are attributed to interindividual variations in the functional activity of cytochrome P450 enzymes, UDP-glucuronosyltransferases, and ATP-binding cassette subfamily B member 1 (known as P-glycoprotein or multidrug resistance 1) in the liver and small intestine. Some genetic variations have been found to be involved to at least some degree in pharmacokinetic variations in post-transplant immunosuppressive therapy. It is well known that the frequencies and effect size of minor alleles vary greatly between different races. Thus, ethnic considerations might provide useful information for optimizing individualized immunosuppressive therapy after organ transplantation. Here, we review ethnic factors affecting the pharmacokinetics of immunosuppressive drugs requiring therapeutic drug monitoring, including tacrolimus, cyclosporine, mycophenolate mofetil, sirolimus, and everolimus.

Pharmacokinetics, Safety, and Tolerability of Ledipasvir/Sofosbuvir and Sofosbuvir/Velpatasvir in Healthy Chinese Subjects

PURPOSE

Ledipasvir/sofosbuvir and sofosbuvir/velpatasvir have been approved worldwide for the treatment of chronic hepatitis C virus (HCV) infection. Although both have been approved in China, there are currently no data on their pharmacokinetic profiles in Chinese individuals. Two studies investigated the pharmacokinetic properties, safety, and tolerability of ledipasvir/sofosbuvir and sofosbuvir/velpatasvir, respectively, in healthy Chinese subjects.

METHODS

Two Phase I, open-label, single- and multiple-dose studies were conducted in healthy Chinese subjects. Ledipasvir/sofosbuvir (90/400 mg) or sofosbuvir/velpatasvir (400/100 mg), respectively, was administered orally once daily under fasted conditions. Subjects received a single dose (day 1) and multiple doses (days 8-17 [ledipasvir/sofosbuvir]; days 8-14 [sofosbuvir/velpatasvir]). Plasma pharmacokinetic parameters were estimated by using noncompartmental models, and safety was assessed through clinical evaluation and monitoring of adverse events.

FINDINGS

Fourteen subjects were enrolled in each study (7 men, 7 women each; mean age, 30 years [ledipasvir/sofosbuvir] and 29 years [sofosbuvir/velpatasvir]). The pharmacokinetic parameters for sofosbuvir, GS-566500, GS-331007, and ledipasvir or velpatasvir were similar to historical values in non-Chinese subjects. Consistent with the t_1/2 of ledipasvir relative to 24-h dosing, accumulation of 177% (AUC) and 107% (C_max) was observed. There was no significant accumulation of velpatasvir, sofosbuvir, GS-566500, or GS-331007. Both drugs were generally well tolerated; no serious adverse events or discontinuations due to adverse events were reported.

IMPLICATIONS

Overall, ledipasvir/sofosbuvir and sofosbuvir/velpatasvir exhibited pharmacokinetic and safety profiles in healthy Chinese subjects similar to those in non-Chinese subjects in historical studies, supporting their use in the Chinese population with HCV infection. ChinaDrugTrials.org.cn identifiers: CTR20160149 (ledipasvir/sofosbuvir); CTR20160602 (sofosbuvir/velpatasvir).

Enzymatic Activities of CYP3A4 Allelic Variants on Quinine 3-Hydroxylation In Vitro

Cytochrome P450 3A4 (CYP3A4) enzyme activity is known to show considerable ethnic heterogeneity and inter-individual differences, affecting the outcome of drug treatment. CYP3A4 genetic polymorphisms are believed to be one of the important causes, leading to inter-individual variability in drug metabolism. Quinine is an antipyretic drug with antimalarial properties that is metabolized primarily by CYP3A4. Quinine 3-hydroxylation has been proven as a biomarker reaction for evaluating CYP3A4 ability. Quinine has frequent adverse effects and there are distinct inter-individual differences in quinine sensitivity. The open reading frame for 30 CYP3A4 allelic variants were constructed from wild-type CYP3A4*1A by an overlap extension polymerase chain reaction. Recombinant CYP3A4 variants were expressed using baculovirus-insect cell expression system, and their catalytic activities towards quinine hydroxylation were determined and evaluated. Of the 30 CYP3A4 allelic variants, 23 variants exhibited significantly reduced intrinsic clearance towards quinine, 2 variants showed increased intrinsic clearance for quinine, 2 variants possessed no significant differences towards quinine, compared with CYP3A4*1A, and 3 variants had no detected expression and enzyme activity. Our assessment on the enzymatic activities of CYP3A4 variants towards quinine may contribute to laying an experimental foundation for further clinical studies so as to accelerate the process of determining the associations between genetic variations and clinical phenotypes.

Systematic screening for CYP3A4 genetic polymorphisms in a Han Chinese population

Aim: To systematically investigate the genetic polymorphisms of the CYP3A4 gene in a Han Chinese population. Materials & methods: The promoter and exons of CYP3A4 gene in 1114 unrelated, healthy Han Chinese subjects were amplified and genotyped by direct sequencing. Results: In total, five previously reported alleles (*1G, *4, *5, *18B and *23) were detected, of which one allele (*23) was reported for the first time in Han Chinese population. Additionally, seven novel exonic variants were also identified and designated as new alleles CYP3A4*28–*34. Conclusion: This study provides the most comprehensive data of CYP3A4 polymorphisms in Han Chinese population and detects the largest number of novel CYP3A4 alleles in one ethnic group.

Impact of CYP3A4*18 and CYP3A5*3 Polymorphisms on Imatinib Mesylate Response Among Chronic Myeloid Leukemia Patients in Malaysia

Introduction

Imatinib mesylate (IM), a selective inhibitor of the BCR-ABL tyrosine kinase, is a well-established first-line treatment for chronic myeloid leukemia (CML). IM is metabolized mainly by cytochrome P450 (CYP) in the liver, specifically the CYP3A4 and CYP3A5 enzymes. Polymorphisms in these genes can alter the enzyme activity of IM and may affect its response. In this study, the impact of two single-nucleotide polymorphisms (SNPs), CYP3A5*3 (6986A>G) and CYP3A4*18 (878T>C), on IM treatment response in CML patients (n = 270; 139 IM resistant and 131 IM good responders) was investigated.

Methods

Genotyping of CYP3A4*18 and CYP3A5*3 was performed using the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) technique. The association between allelic variants and treatment response was assessed by means of odds ratio (OR) with 95% confidence intervals calculated by logistic regression.

Results

Our results indicated that CML patients carrying the heterozygous (AG) and homozygous variant (GG) genotype of CYP3A5*3 were associated with a significantly lower risk of acquiring resistance with OR 0.171; 95% CI: 0.090–0.324, p < 0.001 and OR 0.257; 95% CI: 0.126–0.525, p < 0.001, respectively. Although CML patients carrying the heterozygous (TC) genotype of CYP3A4*18 showed a lower risk of acquiring resistance toward IM (OR 0.648; 95% CI: 0.277–1.515), the association was not statistically significant (p = 0.316). No homozygous variant (CC) genotype of CYP3A4*18 was detected among the CML patients.

Conclusion

It is concluded that polymorphism of CYP3A5*3 is associated with IM treatment response in Malaysian CML patients with carriers of CYP3A5*1/*3 and CYP3A5*3/*3 genotypes posing lower risk for development of resistance to IM.

Drug-induced liver injury in a chronic hepatitis C patient treated by peginterferon, ribavirin and simeprevir

A 56-year-old male patient with chronic hepatitis C was treated with pegylated interferon (PEG IFN)-α-2b and ribavirin (RBV) for 72 weeks in 2006. The patient achieved an early virological response (EVR); however, hepatitis C relapsed 12 weeks after discontinuation of PEG IFN and RBV. In 2012, the patient was treated with a PEG IFN/RBV/telaprevir combination therapy. After 5 days of treatment, he suffered from a telaprevir-associated skin rash on his body and four limbs. He chose to be treated with PEG IFN and RBV until 60 weeks. He again achieved EVR but no sustained virological response. In 2014, he was treated with PEG IFN/RBV/simeprevir combination therapy. He achieved rapid virological response, but after 6 weeks of therapy, a striking elevation of serum aminotransferase level was recorded with no accompanying skin rash; he was admitted to our hospital. PEG IFN/RBV/simeprevir was stopped, but sodium valproate (400 mg/day), which had been administrated for more than 10 years to prevent epilepsy was continued. Liver biopsy revealed typical features of drug-induced liver injury. After stopping PEG IFN/RBV/simeprevir, serum aminotransferase levels soon returned to the normal range. We diagnosed this case to be simeprevir-induced hepatitis clinically and histologically. Physicians need to stay alert to the possibility of drug-induced liver injury in using simeprevir.

Screening of Genetic Polymorphisms of CYP3A4 and CYP3A5 Genes

Given the CYP3A4 and CYP3A5's impact on the efficacy of drugs, the genetic backgrounds of individuals and populations are regarded as an important factor to be considered in the prescription of personalized medicine. However, genetic studies with Korean population are relatively scarce compared to those with other populations. In this study, we aimed to identify CYP3A4/5 polymorphisms and compare the genotype distributions among five ethnicities. To identify CYP3A4/5 SNPs, we first performed direct sequencing with 288 DNA samples which consisted of 96 Koreans, 48 European-Americans, 48 African-Americans, 48 Han Chinese, and 48 Japanese. The direct sequencing identified 15 novel SNPs, as well as 42 known polymorphisms. We defined the genotype distributions, and compared the allele frequencies among five ethnicities. The results showed that minor allele frequencies of Korean population were similar with those of the Japanese and Han Chinese populations, whereas there were distinct differences from European-Americans or African-Americans. Among the pharmacogenetic markers, frequencies of CYP3A4*1B (rs2740574) and CYP3A5*3C (rs776742) in Asian groups were different from those in other populations. In addition, minor allele frequency of CYP3A4*18 (rs28371759) was the highest in Korean population. Additional in silico analysis predicted that two novel non-synonymous SNPs in CYP3A5 (+27256C>T, P389S and +31546T>G, I488S) could alter protein structure. The frequency distributions of the identified polymorphisms in the present study may contribute to the expansion of pharmacogenetic knowledge.

Identification of human cytochrome P450 enzymes involved in the metabolism of a novel к-opioid receptor agonist, nalfurafine hydrochloride

Nalfurafine hydrochloride (TRK-820) exhibits strong к-opioid agonistic activity and is a new antipruritic agent for uremic pruritus. This study was performed to identify the human hepatic cytochrome P450 isoforms involved in the metabolic conversion of nalfurafine to the decyclopropylmethylated form, de-CPM, using human liver microsomes and E. coli membrane fractions expressing human P450 isoforms. Samples were analysed by liquid chromatography with a radioactivity detector and liquid chromatography-tandem mass spectrometry. The metabolism of nalfurafine by human liver microsomes exhibited a biphasic kinetic profile. Experiments examining the metabolism by E. coli membrane fractions expressing human P450 isoforms indicated that CYP1A1, 2C8, 2C19 and 3A4 had the ability to produce de-CPM. In experiments with human liver microsomes that examined the inhibition of nalfurafine metabolism by anti-human P450 antibodies, anti-CYP3A4 antibody predominantly, and anti-CYP2C8 and 2C19 antibodies moderately, inhibited de-CPM formation. From these results, CYP3A4 appeared to be the major isoform involved in the metabolic decyclopropylmethylation of nalfurafine, while CYP2C8 and 2C19 most likely play a minor role in the formation of de-CPM.

Effect of CYP2C19 genetic polymorphism on pharmacokinetics and pharmacodynamics of a new proton pump inhibitor, ilaprazole

It is well known that the CYP2C19 genetic polymorphism influences the pharmacokinetics and pharmacodynamics of proton pump inhibitors (PPIs), but no report has addressed the effects on ilaprazole, a newly developed PPI. To investigate the effects of the CYP2C19 genetic polymorphism on the disposition and pharmacodynamics of ilaprazole, multiple doses of once-daily 10 mg ilaprazole were repeatedly administered for 7 days to 27 healthy Korean participants, comprising 9 homozygous CYP2C19 extensive metabolizers (homo EMs), 10 heterozygous EMs (hetero EMs), and 8 homozygous poor metabolizers (PMs). The plasma concentration and pharmacodynamic response were measured in the last dose interval. Each genotype group was matched for gender and thus was composed of 4 male and 4 female participants when the analysis was conducted. The pharmacokinetic parameters estimated from the plasma concentrations of ilaprazole and its metabolite ilaprazole sulfone, the serum gastrin level, and the 24-hour intragastric pH were compared among the CYP2C19 genotype groups. No statistically significant differences in the maximum plasma concentration at steady state(C(ss,max)) and the area under the concentration-time curve from zero to 24 hours (AUC(τ)) of ilaprazole and ilaprazole sulfone were observed among the homo EM, hetero EM, and PM CYP2C19 genotypes. In addition, the mean 24-hour intragastric pH, the percentage of time at pH >4, and the AUC(τ) of serum gastrin showed no significant differences among the CYP2C19 genotype groups. The data suggests that the pharmacokinetics and pharmacodynamics of ilaprazole are not significantly influenced by the CYP2C19 genetic polymorphism in healthy participants.

Analysis of CYP3A4 genetic polymorphisms in Han Chinese

Our study aimed to comprehensively investigate the genetic polymorphisms of CYP3A4 in Han Chinese. We sequenced the gene regions of CYP3A4, including its promoter, exons, surrounding introns and 3' untranslated region (3'UTR), from 100 unrelated-healthy Han Chinese individuals. We detected 11 SNPs, three of which are novel. According to in silico functional prediction of novel variants, 20148 A>G in exon 10, resulting in substitution of Tyr319 with Cys (CYP3A4*21), may induce dramatic alteration of protein conformation, and 26908 G>A in 3'UTR may disrupt post-transcriptional regulation. We identified five alleles in Han Chinese, the allele frequencies of CYP3A4*1, *5, *6, *18 and *21 are 97, 0.5, 1, 1 and 0.5%, respectively. Haplotype inference revealed 14 haplotypes, of which the major haplotype CYP3A4*1A constitutes 59% of the total chromosomes. We also examined the possible role of natural selection in shaping the variation of CYP3A4 and confirmed a trend, consistent with the action of positive selection. We systematically screened the genetic polymorphisms of CYP3A4 in Han Chinese, highlighted possible functional impairment of the novel allele and summarized the distinct allele and haplotype frequency distribution, with an emphasis on detecting the footprint of recent positive selection on the CYP3A4 gene in Han Chinese.

A haplotype of CYP2C9 associated with warfarin sensitivity in mechanical heart valve replacement patients

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT * CYP2C9 single nucleotide polymorphisms (SNPs) are important in safe and effective oral anticoagulation with warfarin use. * Although CYP2C9*2 and *3 are important genetic factors for the warfarin dose, one of the CYP2C9 SNPs, IVS-65G>C, has been suggested to be associated with warfarin sensitivity. However, as of yet, there has been no explanation about the possible mechanism and linkage analysis. WHAT THIS PAPER ADDS * New information on CYP2C9 SNPs and their occurrences in common haplotype structures in healthy unrelated Koreans and in individuals who require low warfarin dose after mechanical heart valve replacements (MHVRs) were studied. * Additional evidence showed that an Asian dominant haplotype consisting of -1565C>T, -1188T>C, IVS3+197G>A, IVS3-334C>T, IVS3-65G>C, IVS4-115A>G and IVS5-73A>G could be associated with a low warfarin maintenance dose in mechanical heart valve replacement (MHVR) patients. AIMS The objectives of this study were to determine the distribution of CYP2C9 variants in Koreans and investigate their association with warfarin dose requirements in patients who received MHVRs. METHODS All nine exons, intron-exon junction, and promoter region of CYP2C9 were amplified and directly sequenced in 50 healthy normal Koreans. Additional direct DNA sequencing of the CYP2C9 gene was conducted in 36 of the 267 MHVR patients who required low maintenance warfarin doses without carrying CYP2C9*3 and VKORC1 1173T mutations. The effects of CYP2C9 genetics on warfarin maintenance dose were assessed in 267 MHVR patients. RESULTS Thirty-nine single nucleotide polymorphisms (SNPs) including seven previously unidentified SNPs were identified in 50 Koreans by direct DNA sequencing. One of the CYP2C9 haplotypes exhibited an association with warfarin low dose requirement. The adjusted odds ratio for the haplotype between the low dose group and the normal subjects was 2.5 (95% confidence interval 1.05, 6.16). This haplotype consisting of -1565C>T, -1188T>C, IVS3+197G>A, IVS3-334C>T, IVS3-65G>C, IVS4-115A>G, and IVS5-73A>G was found in 15% of 36 MHVR patients who required low warfarin doses, while 4% of 50 normal healthy subjects exhibited this haplotype. One of the SNPs comprising this haplotype, -1565C>T, apparently changed a protein binding pattern as observed in electrophoretic mobility shift assay. CONCLUSION The haplotype including -1565C>T, -1188T>C, IVS3+197G>A, IVS3-334C>T, IVS3-65G>C, IVS4-115A>G, and IVS5-73A>G seems to be associated with low warfarin dose requirement and this haplotype could be considered in the development of a warfarin dose prediction model for Asian populations.

Impact of CYP3A5 and CYP3A4 gene polymorphisms on dose requirement of calcineurin inhibitors, cyclosporine and tacrolimus, in renal allograft recipients of North India

The present study investigated pharmacogenetic associations of common cytochrome P450 3A (CYP3A5 and CYP3A4) polymorphisms with dose requirements of calcineurin inhibitors, cyclosporine (CsA) and tacrolimus (Tac) in renal transplant recipients of North India. Two hundred twenty four patients on CsA and 73 patients on Tac-based immunosuppression regimen were genotyped for CYP3A5*3 (6986A>G) and CYP3A4*1B (-290A>G) and correlated with CsA/Tac dose requirement (mg/kg/day) and dose-adjusted CsA (C(2))/Tac (T (0)) blood levels (concentration/dose ratio) at 1 month and 3 months posttransplantation. The dose-adjusted levels were significantly lower in CYP3A5 expressers for CsA (p = 0.037; 3 months) and Tac (p < 0.001; 1 month and p < 0.001; 3 months) compared to the non-expressers, suggesting that for a given dose their CsA/Tac blood concentration is lower. The CYP3A5 non-expresser genotype was associated with reduced risk for allograft rejection (HR-0.18, 95% CI 0.03-0.99). No influence of CYP3A4*1B on CsA/Tac pharmacokinetics was observed. CYP3A5 expressers were associated with significantly lower dose-adjusted CsA/Tac concentrations and higher allograft rejection episodes in patients on Tac therapy.

An NH2-terminal truncated cytochrome P450 CYP3A4 showing catalytic activity is present in the cytoplasm of human liver cells

Cytochrome P450 3A4 (CYP3A4), is the dominant human liver hemoprotein enzyme localized in the endoplasmic reticulum (ER), and is responsible for the metabolism of more than 50% of clinically relevant drugs. While we were studying CYP3A4 expression and activity in human liver, we found that anti-CYP3A4 antibody cross-reacted with a lower band in liver cytoplasmic fraction. We assessed the activities of CYP3A4 and its truncated form in the microsomal and cytoplasmic fraction, respectively. In the cytoplasmic fraction, truncated CYP3A4 showed catalytic activity when reconstituted with NADPH-cytochrome P-450 reductase and cytochrome b5. In order to determine which site was deleted in the truncated form in vitro, we transfected cells with N-terminal tagged or C-terminal tagged human CYP3A4 cDNA. The truncated CYP3A4 is the N-terminal deleted form and was present in the soluble cytoplasmic fraction. Our result shows, for the first time, that N-terminal truncated, catalytically active CYP3A4 is present principally in the cytoplasm of human liver cells.