Major Cytochrome P450 Isozymes Research Articles

CYPlebrity: Machine learning models for the prediction of inhibitors of cytochrome P450 enzymes

The vast majority of approved drugs are metabolized by the five major cytochrome P450 (CYP) isozymes, 1A2, 2C9, 2C19, 2D6 and 3A4. Inhibition of CYP isozymes can cause drug-drug interactions with severe pharmacological and toxicological consequences. Computational methods for the fast and reliable prediction of the inhibition of CYP isozymes by small molecules are therefore of high interest and relevance to pharmaceutical companies and a host of other industries, including the cosmetics and agrochemical industries. Today, a large number of machine learning models for predicting the inhibition of the major CYP isozymes by small molecules are available. With this work we aim to go beyond the coverage of existing models, by combining data from several major public and proprietary sources. More specifically, we used up to 18815 compounds with measured bioactivities to train random forest classification models for the individual CYP isozymes. A major advantage of the new data collection over existing ones is the better representation of the minority class, the CYP inhibitors. With the new data collection we achieved inhibitor-to-non-inhibitor ratios in the order of 1:1 (CYP1A2) to 1:3 (CYP2D6). We show that our models reach competitive performance on external data, with Matthews correlation coefficients (MCCs) ranging from 0.62 (CYP2C19) to 0.70 (CYP2D6), and areas under the receiver operating characteristic curve (AUCs) between 0.89 (CYP2C19) and 0.92 (CYPs 2D6 and 3A4). Importantly, the models show a high level of robustness, reflected in a good predictivity also for compounds that are structurally dissimilar to the compounds represented in the training data. The best models presented in this work are freely accessible for academic research via a web service.

Investigation of the inhibition of eight major human cytochrome P450 isozymes by a probe substrate cocktail in vitro with emphasis on CYP2E1

1. A protocol has been developed and validated for the high-throughput screening of eight major human cytochrome P450 (CYP) isozymes inhibition (CYP 1A2, 2C9, 2C19, 2D6, 3A4, 2B6, 2C8 and 2E1) using an in vitro probe cocktail containing eight substrates by overcoming the unfavorable effect of assay conditions on CYP2E1 inhibition data.2. The cocktail consisting of selective probe substrates like tacrine (CYP1A2), diclofenac (CYP2C9), S-mephenytoin (CYP2C19), dextromethorphan (CYP2D6), midazolam (CYP3A4), bupropion (CYP2B6), paclitaxel (CYP2C8) and chlorzoxazone (CYP2E1) was incubated with human liver microsomes.3. The method was investigated by incubating well-known CYP inhibitors {alphanaphthoflavone (CYP1A2), sulfaphenazole (CYP2C9), N-3-benzylnirvanol (CYP2C19), quinidine (CYP2D6), ketoconazole (CYP3A4), ticlopidine (CYP2B6), quercetin (CYP2C8) and 4-methylpyrazole (CYP2E1)} with the substrate cocktail. A fast gradient liquid chromatography tandem mass spectrometry (LC-MS/MS) was used for this study.4. The IC50 values determined for typical CYP inhibitors were reproducible and consistent with those in the literature. DMSO has significant effect and itself inhibits CYP2E1. DMSO should not exceed 0.1% for the determination of reliable CYP2E1 inhibition profile. This cocktail assay offers an efficient and robust method to determine the CYP450 isoforms inhibition profiles of large numbers of compounds in a quick turnaround time.

Safety assessment of Gyejibokryeong-hwan water extract: Study of acute and subacute toxicity, and influence on drug metabolizing enzymes

Ethnopharmacological relevanceGyejibokryeong-hwan is a traditional herbal medicine and is reported to have various pharmacological actions. Despite many reports of previous studies, there is limited scientific evidence concerning its safety and few drug-metabolism profiles to support the continued therapeutic application of Gyejibokryeong-hwan. Aim of the studyThe purpose of the present study was to investigate the acute and subacute toxicity profile of a Gyejibokryeong-hwan water extract (GBHW) in vivo, and its effects on the activities of drug-metabolizing enzymes in vitro. Materials and methodsAcute and subacute toxicity was evaluated by giving GBHW to rats. In a study of acute toxicity, the rats were given GBHW by single oral gavage administration at 0 and 5000 mg/kg. In a study of subacute toxicity, rats were given GBHW by oral gavage at 0, 1000, 2000, and 5000 mg/kg/day daily for 28 days. The activities of the major human microsomal cytochrome P450 (CYP450) and UDP-glucuronosyltransferase (UGT) isozymes were investigated using fluorescence- and luminescence-based enzyme assays in vitro, respectively. ResultsGBHW did not cause any mortality in the study of acute toxicity. In the study of subacute toxicity, GBHW at more than 2000 mg/kg/day was observed with minor changes in the absolute and relative organ weight, hematology, serum biochemistry and urinalysis parameters in rats of either sex. However, these changes were not considered to be important toxicologically. GBHW moderately inhibited the activities of CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2E1, CYP3A4, and UGT1A1. ConclusionsOur present data suggest that GBHW does not cause toxicologically important adverse events at doses up to 2000 mg/kg/day in the 4-week repeated dose toxicity study and provide valuable information concerning its potential to interact with conventional medicine.

In vitro modulation of cytochrome P450 isozymes and pharmacokinetics of caffeine by extracts of Hibiscus sabdariffa Linn calyx.

Background Hibiscus sabdariffa beverage (HSB) is widely consumed as a medicinal herb and sometimes used concomitantly with drugs. This study evaluated the in vitro inhibitory potential of the aqueous extract of H. sabdariffa calyces (AEHS) on selected cytochrome P450 (CYP) isozymes and the effect of HSB on the pharmacokinetics of caffeine in vivo. Methods In vitro inhibitions of eight major CYP isozymes by AEHS were estimated by monitoring CYP-specific model reactions of 10 CYP probe substrates using N-in-one assay method. Subsequently, an open, randomized, two-period crossover design was used to evaluate the effect of HSB on the pharmacokinetics of single-dose 200 mg caffeine in six healthy human volunteers. Blood samples were obtained at specific times over a 24 h period. Probe drugs and metabolites were analyzed in their respective matrices with ultra-performance liquid chromatography/mass spectrometer/mass spectrometer and reversed-phase high-performance liquid chromatography/ultraviolet detection. Results The H. sabdariffa aqueous extract weakly inhibited the selected CYP isozymes in vitro, with IC50 of >100 μgmL-1 in the order of CYP1A2 > CYP2C8 > CYP2B6 >> CYP2D6 > CYP2C19 > CYP3A4 > CYP2A6 > CYP2C9. HSB decreased terminal t1/2 and Tmax of caffeine by 13.6% and 13.0%, respectively, and increased Cmax by 10.3%. Point estimates of primary pharmacokinetic endpoints, Cmax = 1.142 (90% confidence interval (CI) = 0.882, 1.480) and AUC0-∞ = 0.992 (90% CI = 0.745, 1.320), were outside the 90% CI of 0.8-1.25 bioequivalence limits. Conclusion The aqueous extract of H. sabdariffa weakly inhibited eight CYP isozymes in vitro, but HSB modified the exposure to caffeine in human. Caution should be exercised in administering HSB with caffeine or similar substrates of CYP1A2 until more clinical data are available.

Inhibitory potential of three Yin-tonification herbal formulas on the activities of human major cytochrome P450 and UDP- glucuronosyltransferases isozymes in vitro

OBJECTIVETo investigate the influence of Yin-tonification herbal formulas Jaeumganghwa-tang (Ziyin Jianghuo Tang, JEGHT), Ssanghwa-tang (Shuanghe Tang, SHT) and Yukmijihwang-tang (Liuwei Di huang Tang, YMJHT) on the activities of human major cytochrome P450 (CYP450s) and UDP-glucuronosyltransferases isozymes (UGTs) in vitro. METHODSThe activities of CYP450s (CYP1A2, CYP3A4, CYP2B6, CYP2C9, CYP2C19, CYP2D6 and CYP2E1) and UGTs (UGT1A1, UGT1A4 and UGT2B7) were assessed using in vitro fluorescence- and luminescence-based enzyme assays, respectively. The effects of herbal formulas on the activities of CYP450s and UGTs were presented as IC50 values. RESULTSJEGHT showed the potent inhibition of the CYP2D6 activity, with weak inhibition on the activities of CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2E1, CYP3A4, UGT1A1, UGT1A4 and UGT2B7. SHT inhibited the activities of CYP1A2 and CYP2E1, whereas the negligible inhibition of the activities of CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4, UGT1A1, UGT1A4 and UGT2B7 through SHT was observed. YMJHT inhibited CYP2E1 activity, with a negligible inhibition on the activities of CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4, UGT1A1, UGT1A4 and UGT2B7. CONCLUSIONThese findings provide information about the potential interactions between three Yin-tonification herbal formulas and conventional drugs.

Abstract LB-268: Discovery of clinical candidate methyl (5-(6-((4-(methylsulfonyl)piperazin-1-yl)methyl)-4-morpholinopyrrolo[2,1-f][1,2,4]triazin-2-yl)-4-(trifluoromethyl)pyridin-2-yl)carbamate (CYH33) : A highly potent and selective PI3K alpha inhibitor for the treatment of advanced solid tumors

Abstract Phosphatidylinositol 3-kinaseα isoform (PI3Kα) is frequently deregulated in a wide variety of human solid tumors. A series of new pyrrolo[2,1-f][1,2,4]triazines has been prepared in an effort to discover new PI3Kα-selective inhibitors. Intensive structure-activity relationship (SAR) and structure-pharmacokinetic relationship (SPR) studies on this new series led to the discovery of compound 40 (CYH33), a potent and highly selective PI3Kα inhibitor. CYH33 displays the most potent activity against PI3Kα among the class I PI3K isoforms, with IC50s of 5.9 nM/598 nM/ 78.7 nM/225 nM against α/β/δ/γ isoform respectively. Kinome profiling revealed that CYH33 showed little activity among more than 300 kinases. The selectivity of CYH33 against PI3Kα was further confirmed with a panel of Rh30-Myr-p110s isogenic cells, which express constitutively active PI3K isoform respectively. Accordingly, CYH33 inhibited PI3K/AKT/mTOR signaling in glioblastoma U87MG and rhabdomyosarcoma Rh30 cells, which is associated with its potent anti-proliferative activity in against cell proliferation in a panel cancer cell lines originated from breast, lung, ovary and colon, prostate etc. It is noteworthy that most of sensitive cells were originated from breast cancer, which was consistent with the fact that PI3K is frequently hyper-activated in breast cancer. Oral administration of CYH33 to mice bearing ovarian cancer SKOV-3 xenografts resulted in decreased phosphorylation of AKT in tumor tissue, which is consistent with the significant efficacy of CYH33 to inhibit the growth of SKOV-3 xenograft. Moreover, CYH33 did not cause significant weight loss and toxic symptoms during the treatment period. We also detected the glucose tolerance after mice bearing SKOV-3 xenografts were administered with CYH33 for 18 days. Though CYH33 treatment delayed the restoration of blood glucose to normal level, blood glucose of the CYH33-treated groups were similar to that of control group 2 h after the injection of glucose. CYH33 displays a favorable pharmacokinetic profile with an oral bioavailability of 36.9% and little activity against the major cytochrome P450 isozymes. In summary, CYH33 emerged as a novel selective PI3Kα inhibitor with potent activity against human solid tumors and favorable pharmaceutical profile, which makes it a promising drug candidate and enter clinical trials in China. Citation Format: Haoyue Xiang, Xiang Wang, Yanhong Chen, Xi Zhang, Yi Chen, Cun Tan, Yi Wang, Jian Ding, Ling-Hua Meng, Chunhao Yang. Discovery of clinical candidate methyl (5-(6-((4-(methylsulfonyl)piperazin-1-yl)methyl)-4-morpholinopyrrolo[2,1-f][1,2,4]triazin-2-yl)-4-(trifluoromethyl)pyridin-2-yl)carbamate (CYH33) : A highly potent and selective PI3K alpha inhibitor for the treatment of advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-268.

An Automated High-Throughput Metabolic Stability Assay Using an Integrated High-Resolution Accurate Mass Method and Automated Data Analysis Software.

Advancement of in silico tools would be enabled by the availability of data for metabolic reaction rates and intrinsic clearance (CLint) of a diverse compound structure data set by specific metabolic enzymes. Our goal is to measure CLint for a large set of compounds with each major human cytochrome P450 (P450) isozyme. To achieve our goal, it is of utmost importance to develop an automated, robust, sensitive, high-throughput metabolic stability assay that can efficiently handle a large volume of compound sets. The substrate depletion method [in vitro half-life (t1/2) method] was chosen to determine CLint The assay (384-well format) consisted of three parts: 1) a robotic system for incubation and sample cleanup; 2) two different integrated, ultraperformance liquid chromatography/mass spectrometry (UPLC/MS) platforms to determine the percent remaining of parent compound, and 3) an automated data analysis system. The CYP3A4 assay was evaluated using two long t1/2 compounds, carbamazepine and antipyrine (t1/2 > 30 minutes); one moderate t1/2 compound, ketoconazole (10 < t1/2 < 30 minutes); and two short t1/2 compounds, loperamide and buspirone (t½ < 10 minutes). Interday and intraday precision and accuracy of the assay were within acceptable range (∼12%) for the linear range observed. Using this assay, CYP3A4 CLint and t1/2 values for more than 3000 compounds were measured. This high-throughput, automated, and robust assay allows for rapid metabolic stability screening of large compound sets and enables advanced computational modeling for individual human P450 isozymes.

In vitro metabolism of a novel synthetic cannabinoid, EAM-2201, in human liver microsomes and human recombinant cytochrome P450s

In vitro metabolism of a new synthetic cannabinoid, EAM-2201, has been investigated with human liver microsomes and major cDNA-expressed cytochrome P450 (CYP) isozymes using liquid chromatography–high resolution mass spectrometry (LC–HRMS). Incubation of EAM-2201 with human liver microsomes in the presence of NADPH resulted in the formation of 37 metabolites, including nine hydroxy-EAM-2201 (M1-M9), five dihydroxy-EAM-2201 (M10-M14), dihydrodiol-EAM-2201 (M15), oxidative defluorinated EAM-2201 (M16), two hydroxy-M16 (M17 and M18), three dihydroxy-M16 (M19-M21), N-dealkyl-EAM-2201 (M22), two hydroxy-M22 (M23 and M24), dihydroxy-M22 (M25), EAM-2201 N-pentanoic acid (M26), hydroxy-M26 (M27), dehydro-EAM-2201 (M28), hydroxy-M28 (M29), seven dihydroxy-M28 (M30-M36), and oxidative defluorinated hydroxy-M28 (M37). Multiple CYPs, including CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, 2J2, 3A4, and 3A5, were involved in the metabolism of EAM-2201. In conclusion, EAM-2201 is extensively metabolized by CYPs and its metabolites can be used as an indicator of EAM-2201 abuse.

Size- and time-dependent alteration in metabolic activities of human hepatic cytochrome P450 isozymes by gold nanoparticles via microsomal coincubations.

Nano-sized particles are known to interfere with drug-metabolizing cytochrome P450 (CYP) enzymes, which can be anticipated to be a potential source of unintended adverse reactions, but the mechanisms underlying the inhibition are still not well understood. Herein we report a systematic investigation of the impacts of gold nanoparticles (AuNPs) on five major CYP isozymes under in vitro incubations of human liver microsomes (HLMs) with tannic acid (TA)-stabilized AuNPs in the size range of 5 to 100 nm. It is found that smaller AuNPs show more pronounced inhibitory effects on CYP2C9, CYP2C19, CYP2D6, and CYP3A4 in a dose-dependent manner, while 1A2 is the least susceptible to the AuNP inhibition. The size- and dose-dependent CYP-specific inhibition and the nonspecific drug-nanogold binding in the coincubation media can be significantly reduced by increasing the concentration ratio of microsomal proteins to AuNPs, probably via a noncompetitive mode. Remarkably, AuNPs are also found to exhibit a slow time-dependent inactivation of 2D6 and 3A4 in a β-nicotinamide adenine dinucleotide 2′-phosphate reduced tetrasodium salt hydrate (NADPH)-independent manner. During microsomal incubations, UV–vis spectroscopy, dynamic light scattering, and zeta-potential measurements were used to monitor the changes in particle properties under the miscellaneous AuNP/HLM/CYP dispersion system. An improved stability of AuNPs by mixing HLM with the gold nanocolloid reveals that the stabilization via AuNP-HLM interactions may occur on a faster time scale than the salt-induced nanoaggregation by incubation in phosphate buffer. The results suggest that the AuNP induced CYP inhibition can be partially attributed to its adhesion onto the enzymes to alter their structural conformations or onto the HLM membrane therefore impairing the integral membrane proteins. Additionally, AuNPs likely block the substrate pocket on the CYP surface, depending on both the particle characteristics and the structural diversity of the isozymes. These findings may represent additional mechanisms for the differential inhibitory effects arising from the coincubated AuNPs on the metabolic activities of the hepatic CYP isozymes.

In vitro oxidative metabolism of cajaninstilbene Acid by human liver microsomes and hepatocytes: involvement of cytochrome p450 reaction phenotyping, inhibition, and induction studies.

Cajaninstilbene acid (CSA, 3-hydroxy-4-prenyl-5-methoxystilbene-2-carboxylic acid), an active constituent of pigeonpea leaves, an important tropical crop, is known for its clinical effects in the treatment of diabetes, hepatitis, and measles and its potential antitumor effect. In this study, the effect of the cytochrome P450 isozymes on the activity of CSA was investigated. Two hydroxylation metabolites were identified in the study. The reaction phenotype study showed that CYP3A4, CYP2C9, and CYP1A2 were the major cytochrome P450 isozymes in the metabolism of CSA. The metabolic food-drug interaction potential was also evaluated in vitro. The effect of CSA inhibition/induction of enzymatic activities of seven drug-metabolizing CYP450 isozymes in vitro was estimated by high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry analytical techniques. CSA showed different inhibitory effects on different isozymes. CSA reversibly inhibited CYP3A4 and CYP2C9 activities in human liver microsomes with IC50 values of 28.3 and 31.3 μM, respectively, but exhibited no inhibition activities to CYP1A2, CYP2A6, CYP2C19, CYP2D6, and CYP2E1. CSA showed a weak effect on CYP450 enzymes in a time-dependent manner. CSA did not substantially induce CYP1A2, CYP2A6, CYP2B6, CYP2E1, CYP2C9, CYP2C19, CYP2D6, or CYP3A4 at concentrations up to 30 μM in primary human hepatocytes. The results of our experiments may be helpful to predict clinically significant food-drug interactions when other drugs are administered in combination with CSA.

The Potential ofSutherlandia frutescensfor Herb-Drug Interaction

In Africa, Sutherlandia frutescens is a popular medicinal herb widely consumed by people living with human immunodeficiency virus/AIDS. Concomitant use with antiretroviral drugs has generated concerns of herb-drug interaction (HDI). This study investigated the inhibitory effects of the crude extracts of S. frutescens on the major cytochrome P450 isozymes with the use of pooled human liver microsomes. Its effect on the metabolic clearance of midazolam using cryopreserved hepatocytes was also monitored. The potential of S. frutescens to inhibit human ATP-binding cassette transporters (P-gp and BCRP) and the human organic anion transporting polypeptide (OATP1B1 and OATP1B3) activity was assessed using cell lines overexpressing the transporter proteins. S. frutescens showed inhibitory potency for CYP1A2 (IC(50) = 41.0 µg/ml), CYP2A6 (IC(50) = 160 µg/ml), CYP2B6 (IC(50) = 20.0 µg/ml), CYP2C8 (IC(50) = 22.4 µg/ml), CYP2C9 (IC(50) = 23.0 µg/ml), CYP2C19 (IC(50) = 35.9 µg/ml), and CYP3A4/5 (IC(50) = 17.5 µg/ml [with midazolam1'-hydroxylation]; IC(50) = 28.3 µg/ml [with testosterone 6β-hydroxylation]). Time-dependent (irreversible) inhibition by S. frutescens was observed for CYP3A4/5 (K(I) = 296 µg/ml, k(inact) = 0.063 min(-1)) under the conditions of this study. S. frutescens also delays the production of midazolam metabolites in the hepatocytes, decreasing its clearance by 40%. Furthermore, S. frutescens inhibited P-gp (IC(50) = 324.8 µg/ml), OATP1B1 (IC(50) = 10.4 µg/ml), and OATP1B3 (IC(50) = 6.6 µg/ml). The result indicates the potential for HDI between S. frutescens and the substrates of the affected enzymes, if sufficient in vivo concentration of the extract is attained.

Enzyme kinetic and molecular docking studies for the inhibitions of miltirone on major human cytochrome P450 isozymes

Previous studies have shown that major tanshinones isolated from Danshen (Salvia miltiorrhiza) inhibited human and rat CYP450 enzymes-mediated metabolism of model probe substrates, with potential in causing herb–drug interactions. Miltirone, another abietane type-diterpene quinone isolated from Danshen, has been reported for its anti-oxidative, anxiolytic and anti-cancer effects. The aim of this study was to study the effect of miltirone on the metabolism of model probe substrates of CYP1A2, 2C9, 2D6 and 3A4 in pooled human liver microsomes. Miltirone showed moderate inhibition on CYP1A2 (IC50=1.73μM) and CYP2C9 (IC50=8.61μM), and weak inhibition on CYP2D6 (IC50=30.20μM) and CYP3A4 (IC50=33.88μM). Enzyme kinetic studies showed that miltirone competitively inhibited CYP2C9 (Ki=1.48μM), and displayed mixed type inhibitions on CYP1A2, CYP2D6 and CYP3A4 with Ki values of 3.17μM, 24.25μM and 35.09μM, respectively. Molecular docking study further confirmed the ligand-binding conformations of miltirone in the active sites of these human CYP450 isoforms, and provided some information on structure–activity relationships for the CYPs inhibition by tanshinones. Taken together, CYPs inhibitions of miltirone were weaker than dihydrotanshinone, but stronger than cryptotanshinone, tanshinone I and tanshinone IIA.

Cytochrome P450 inhibitory potential of selected Indian spices — possible food drug interaction

Spices constitute an important group of food which is virtually indispensable in the culinary art. In a view, these spices feared to pose a probability to affect the disposition of conventional pharmaceuticals through inhibition of human cytochrome P450 (CYPs) enzymes. In the present study an approach has been made to evaluate the possible CYP inhibition potential with some Indian spices (Capsicum annuum, Murraya koenigii, Zingiber officinale) and their major bioactive compounds, in combination with pooled microsome; as well as commercially available recombinant human CYP3A4, CYP2D6, CYP2C9 and CYP1A2. Quantification of the bioactive compound was determined through RP-HPLC, in order to standardize the plant material. CYP–carbon monoxide (CYP–CO) complex assay result indicated that all the plants and their bioactive compounds have an interaction potential with CYPs. Fluoregenic assay results indicated that the spice extracts have higher inhibition potential comparing to their single bioactive molecule. The higher enzyme inhibition potential by the extracts may be related to the synergistic effects due to the presence of other constituents in the extract. Capsaicin and C. annuum showed the lowest IC50 value and 6-gingerol and Z. officinale extract showed the highest IC50 value among the entire sample tested. The entire sample showed significantly less (P<0.001, P<0.01) interaction potential than known inhibitors. These findings indicate that selected spices are unlikely to cause clinically relevant drug interactions involving the inhibition of major CYP isozymes.

Human cytochrome P450 and UDP-glucuronosyltransferase reaction phenotyping of MPC-3100, an oral HSP90 inhibitor.

e13019 Background: MPC-3100 is an oral synthetic inhibitor of HSP90, in a phase I safety study in cancer patients. Major cytochrome P450 (CYP450) and UDP-glucuronosyltransferase (UGT) isozymes were identified to define the inclusion and exclusion criteria necessary to ensure patient safety. Methods: CYP450 isozymes responsible for the metabolism of MPC-3100 were assessed by two methods. The first entailed the use of recombinant human Supersomes (1A2, 2C8, 2C9, 2C19, 2D6 and 3A4) suspended in phosphate buffer (pH 7.4) with 40 pmoles of CYP450. An NADPH regenerating system was used with a 5 minute pre-incubation prior to adding 10 µM MPC-3100. The second used human donor liver microsomes suspended in phosphate buffer (pH 7.4) with 0.5 mg/mL of protein. The microsomes were pre-incubated with CYP450 isozyme selective chemical inhibitors prior to addition of 10 µM MPC-3100 and NADPH. UGT isozymes responsible for glucuronidation of MPC-3100 and a major oxidative metabolite were identified using recombinant UGT Supersomes suspended in Tris-HCl buffer (pH 7.5) at a final protein concentration of 1 mg/mL. The UGT Supersomes were pre-incubated with alamethicin and the reaction was initiated with UDPGA. The disappearance of MPC-3100 and formation of metabolites was monitored by HPLC-ESI-MS/MS. Results: MPC-3100 was metabolized by CYP450 1A2, 2C19, 2D6 and 3A4, but not by 2C8 or 2C9. With the use of selective chemical inhibitors in pooled human liver microsomes, the percent of MPC-3100 metabolized at 40 minutes was inhibited greatest by azamulin (31.4%), ketoconazole (20.9%) and quinidine (5.5%). MPC-3100 was glucuronidated by UGT 1A3, 1A8 and 1A4, but not by 1A1, 1A6, 1A7, 1A9, 1A10, 2B4, 2B5, 2B15, and 2B17. The major oxidative metabolite of MPC-3100 was a substrate for UGT 1A3, 1A7, 1A9, 1A10, 2B4, 2B17 with 1A1, 1A8, and 2B7 predominating. Conclusions: CYP450 3A4 is the primary isozyme involved in the metabolism of MPC-3100. UGT 1A4 is the major isozyme responsible for direct glucuronidation of MPC-3100; whereas multiple UGTs (1A1, 1A8, and 2B7) are capable of glucuronidating the major oxidative metabolite. Therefore current clinical studies preclude co-administration of potent CYP3A4 inhibitors with MPC-3100.

In Vitro Metabolism of 17-(Dimethylaminoethylamino)-17-demethoxygeldanamycin in Human Liver Microsomes

The objective of this study was to investigate the oxidative metabolism pathways of 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG), a geldanamycin (GA) derivative and 90-kDa heat shock protein inhibitor. In vitro metabolic profiles of 17-DMAG were examined by using pooled human liver microsomes (HLMs) and recombinant CYP450 isozymes in the presence or absence of reduced GSH. In addition to 17-DMAG hydroquinone and 19-glutathionyl 17-DMAG, several oxidative metabolites of 17-DMAG were detected and characterized by liquid chromatography-tandem mass spectrometry. Different from previously reported primary biotransformations of GA and GA derivatives, 17-DMAG was not metabolized primarily through the reduction of benzoquinone and GSH conjugation in HLMs. In contrast, the primary biotransformations of 17-DMAG in HLMs were hydroxylation and demethylation on its side chains. The most abundant metabolite was produced by demethylation from the methoxyl at position 12. The reaction phenotyping study showed that CYP3A4 and 3A5 were the major cytochrome P450 isozymes involved in the oxidative metabolism of 17-DMAG, whereas CYP2C8, 2D6, 2A6, 2C19, and 1A2 made minor contributions to the formation of metabolites. On the basis of the identified metabolite profiles, the biotransformation pathways for 17-DMAG in HLMs were proposed.

Effect of Hydrocotarnine on Cytochrome P450 and P-glycoprotein

The injectable form of oxycodone contains hydrocotarnine that is supposed to potentiate the analgesic effect of oxycodone with unknown mechanism(s). In this study, the effects of hydrocotarnine on the cytochrome P450 (CYP) and P-glycoprotein (P-gp) were investigated. Hydrocotarnine did not induce a significant change in the metabolic activities of CYP2C9, 2C19, and 2E1 in an in vitro study using human CYP recombinants. Although weak inhibitory effects were observed on CYP3A4 and 2D6, these interactions did not seem to be clinically relevant. Hydrocotarnine also did not cause a significant change in the ATPase activity of human P-gp membranes, suggesting that it is not an inhibitor of P-gp. Furthermore, mice were intraperitoneally injected with hydrocotarnine for 14 days and the mRNA levels of major CYP isozymes and P-gp in the liver and small intestine were determined by real-time RT-PCR. As a result, none of the mRNAs investigated showed a significant change in their levels by hydrocotarnine treatment. In conclusion, it is unlikely that the potentiation of oxycodone effect by hydrocotarnine involves its effect on CYP and P-gp. The findings also demonstrate that hydrocotarnine is unlikely to cause drug interactions via CYP or P-gp.

Effects of Kampo Medicines on CYP and P-gp Activity in Vitro

The Kampo medicines are more and more often used in recent years, usually together with the Western drugs. The need for the investigation of drug interactions between Kampo medicines and Western drugs are, therefore, widely recognized. In the present study, the effects of 3 Kampo medicines (Rikkunshito, Yokukansan and Boiogito) on the activity of cytochrome P450 (CYP), a superfamily of drug-metabolizing enzymes, were investigated in an in vitro study using human CYP recombinants. Their effects on the P-glycoprotein (P-gp), one of the major drug transporters, were also evaluated by the ATPase assay using human P-gp membranes and verapamil as a substrate. The inhibition rate of Rikkunshito, Yokukansan and Boiogito on human CYP3A4, 2C9, 2C19, 2D6 and 2E1 was less than 50% at the concentrations below 0.1 mg/ml except for the inhibition of CYP2D6 by Boiogito. Furthermore, none of the Kampo medicines affected the ATPase activity at the concentrations lower than 0.1 mg/ml, either in the absence or presence of verapamil, indicating their low inhibitory potency against P-gp. These findings indicate that Rikkunshito, Yokukansan and Boiogito are unlikely to cause clinically relevant drug interactions involving the inhibition of major CYP isozymes and P-gp.

Metabolism And Excretion of the Dipeptidyl Peptidase 4 Inhibitor [14C]Sitagliptin in Humans

The metabolism and excretion of [(14)C]sitagliptin, an orally active, potent and selective dipeptidyl peptidase 4 inhibitor, were investigated in humans after a single oral dose of 83 mg/193 muCi. Urine, feces, and plasma were collected at regular intervals for up to 7 days. The primary route of excretion of radioactivity was via the kidneys, with a mean value of 87% of the administered dose recovered in urine. Mean fecal excretion was 13% of the administered dose. Parent drug was the major radioactive component in plasma, urine, and feces, with only 16% of the dose excreted as metabolites (13% in urine and 3% in feces), indicating that sitagliptin was eliminated primarily by renal excretion. Approximately 74% of plasma AUC of total radioactivity was accounted for by parent drug. Six metabolites were detected at trace levels, each representing <1 to 7% of the radioactivity in plasma. These metabolites were the N-sulfate and N-carbamoyl glucuronic acid conjugates of parent drug, a mixture of hydroxylated derivatives, an ether glucuronide of a hydroxylated metabolite, and two metabolites formed by oxidative desaturation of the piperazine ring followed by cyclization. These metabolites were detected also in urine, at low levels. Metabolite profiles in feces were similar to those in urine and plasma, except that the glucuronides were not detected in feces. CYP3A4 was the major cytochrome P450 isozyme responsible for the limited oxidative metabolism of sitagliptin, with some minor contribution from CYP2C8.

Differential Regulation of Hepatic Cytochrome P450 Monooxygenases

Cytochrome P450 (CYP) is a superfamily of hemoproteins that are able to metabolize a large number of xenobiotics through oxidative, reductive, and peroxidative mechanisms. Many intermediary metabolites of carbohydrates and lipids are produced in diabetes that are known to modulate the cytochrome P450 monooxygenases. During the oxidation of its substrates, the cytochrome P450 monooxygenases generate reactive oxygen species. The present study investigated the expression of major cytochrome P450 isozymes in streptozotocin-induced diabetes with concomitant insulin therapy. Male rats were randomly assigned to untreated control, streptozotocin-induced diabetic, insulin-treated groups and monitored for 4 wk. Uncontrolled hyperglycemia in the early phase of diabetes was associated with differential regulation of cytochrome P450 isozymes, including upregulation of CYP1A2-dependent 7-ethoxyresorufin O-deethylase (EROD) activity and expression of CYP1A2, CYP1B1 and heme oxygenase (HO)-2 proteins. Insulin therapy ameliorated the EROD activity and the expression of CYP1A2, CYP1B1 and HO-2 proteins. In addition, CYP2B1 and 2E1 proteins were markedly induced in the diabetic group. Insulin therapy resulted in complete amelioration of CYP2E1 protein and partial amelioration of CYP2B1 protein. By contrast, CYP2C11 and CYP3A1 protein expression were decreased over 99% and 95%, respectively, in the diabetic group. CYP2C11 protein was partially ameliorated by insulin therapy, whereas CYP3A1 was not affected.

Differential regulation of hepatic cytochrome P450 monooxygenases in streptozotocin-induced diabetic rats

The present investigation was carried out to study the expression of major cytochrome P450 (CYP) isozymes in streptozotocin-induced diabetes with concomitant insulin therapy. Male Sprague-Dawley rats were randomly assigned to untreated control, streptozotocin-induced diabetic, insulin-treated groups and monitored for 4 weeks. Uncontrolled hyperglycemia in the early phase of diabetes resulted in differential regulation of cytochrome P450 isozymes. CYP1B1, CYP1A2, heme oxygenase (HO)-2 proteins and CYP1A2-dependent 7-ethoxyresorufin O-deethylase (EROD) activity were upregulated in the hepatic microsomes of diabetic rats. Insulin therapy ameliorated EROD activity and the expression of CYP1A2, CYP1B1 and HO-2 proteins. In addition, CYP2B1 and 2E1 proteins were markedly induced in the diabetic group. Insulin therapy resulted in complete amelioration of CYP2E1 whereas CYP2B1 protein was partially ameliorated. By contrast, CYP2C11 protein was decreased over 99% in the diabetic group and was partially ameliorated by insulin therapy. These results demonstrate widespread alterations in the expression of CYP isozymes in diabetic rats that are ameliorated by insulin therapy.