Inhibition of Human UDP-Glucuronosyltransferase Enzyme by Entrectinib: Implications for Drug-Drug Interactions

As a new type of oral tyrosine kinase inhibitor, entrectinib can act on multiple targets and exert efficacy and has been approved for the treatment of non-small cell lung cancer (NSCLC) and solid tumors. However, whether entrectinib affects the activities of recombinant human UDP-glucuronosyltransferases (UGTs) remains unclear. Herein, we aimed to investigate the inhibitory effects of entrectinib on human UGTs and to assess the potential risk of causing drug-drug interactions (DDIs) based on the inhibition against UGTs. High-performance liquid chromatography (HPLC) was used to evaluate the inhibitory effects of entrectinib on UGTs according to the product formation rate of UGT substrate with or without entrectinib, and the inhibition kinetics experiment was conducted to assess the inhibitory type of entrectinib on UGTs. Our results showed that entrectinib exhibited extensive inhibitory effects on most human UGTs, and especially inhibited the activities of UGT1A7, UGT1A8, and UGT2B15 with Ki (Inhibition constant) of lower than 5 μM (0.95 - 4.38 μM). Furthermore, the results from quantitative prediction research suggested that the combination of entrectinib at 600 mg/day with substrates primarily metabolized by hepatic UGT2B15 or intestinal UGT1A7 and UGT1A8 might cause clinical DDIs. Thus, special attention should be paid to avoid adverse reactions induced by DDIs when co-administration of entrectinib and drugs metabolized by UGTs.

The potential impact of CYP and UGT drug-metabolizing enzymes on brain target site drug exposure

Drug metabolism is one of the critical determinants of drug disposition throughout the body. While traditionally associated with the liver, recent research has unveiled the presence and functional significance of drug-metabolizing enzymes (DMEs) within the brain. Specifically, cytochrome P-450 enzymes (CYPs) and UDP-glucuronosyltransferases (UGTs) enzymes have emerged as key players in drug biotransformation within the central nervous system (CNS). This comprehensive review explores the cellular and subcellular distribution of CYPs and UGTs within the CNS, emphasizing regional expression and contrasting profiles between the liver and brain, humans and rats. Moreover, we discuss the impact of species and sex differences on CYPs and UGTs within the CNS. This review also provides an overview of methodologies for identifying and quantifying enzyme activities in the brain. Additionally, we present factors influencing CYPs and UGTs activities in the brain, including genetic polymorphisms, physiological variables, pathophysiological conditions, and environmental factors. Examples of CYP- and UGT-mediated drug metabolism within the brain are presented at the end, illustrating the pivotal role of these enzymes in drug therapy and potential toxicity. In conclusion, this review enhances our understanding of drug metabolism's significance in the brain, with a specific focus on CYPs and UGTs. Insights into the expression, activity, and influential factors of these enzymes within the CNS have crucial implications for drug development, the design of safe drug treatment strategies, and the comprehension of drug actions within the CNS. To that end, CNS pharmacokinetic (PK) models can be improved to further advance drug development and personalized therapy.

Comparative metabolism of fargesin in human, dog, monkey, mouse, and rat hepatocytes

Fargesin, a bioactive lignan derived from Flos Magnoliae, possesses anti-inflammatory, anti-oxidative, anti-melanogenic, and anti-apoptotic effects. This study compared the metabolic profiles of fargesin in human, dog, monkey, mouse, and rat hepatocytes using liquid chromatography-high resolution mass spectrometry. In addition, we investigated the human cytochrome P450 (CYP), UDP-glucuronosyltransferase (UGT), and sulfotransferase (SULT) enzymes responsible for fargesin metabolism. The hepatic extraction ratio of fargesin among the five species ranged from 0.59 to 0.78, suggesting that it undergoes a moderate-to-extensive degree of hepatic metabolism. During metabolism, fargesin generates three phase 1 metabolites, including fargesin catechol (M1) and O-desmethylfargesin (M2 and M3), and 11 phase 2 metabolites, including O-methyl-M1 (M4 and M5) via catechol O-methyltransferase (COMT), glucuronides of M1, M2, M4, and M5, and sulfates of M1-M5. The production of M1 from fargesin via O-demethylenation is catalyzed by CYP2C9, CYP3A4, CYP2C19, and CYP2C8 enzymes, whereas the formation of M2 and M3 (O-desmethylfargesin) is catalyzed by CYP2C9, CYP2B6, CYP2C19, CYP3A4, CYP1A2, and CYP2D6 enzymes. M4 is metabolized to M4 glucuronide by UGT1A3, UGT1A8, UGT1A10, UGT2B15, and UGT2B17 enzymes, whereas M4 sulfate is generated by multiple SULT enzymes. Fargesin is extensively metabolized in human hepatocytes by CYP, COMT, UGT, and SULT enzymes. These findings help to elucidate the pharmacokinetics and drug interactions of fargesin.

Comprehensive mRNA and microRNA analysis revealed the effect and response strategy of freshwater fish, grass carp (Ctenopharyngodon idella) under geosmin exposure

Geosmin is an environmental pollutant that causes off-flavor in water and aquatic products. The high occurrence of geosmin contamination in aquatic systems and aquaculture raises public awareness, however, few studies have investigated the response pathways of geosmin stress on freshwater fish. In this research, grass carp were exposed to 50 μg/L geosmin for 96 h, liver tissue was sequenced and validated using real-time qPCR. In total of 528 up-regulated genes and 488 down-regulated genes were observed, includes cytochrome P450 and uridine diphosphate (UDP)-glucuronosyltransferase related genes. KEGG analysis showed that chemical carcinogenesis-DNA adducts, metabolism of xenobiotics by cytochrome P450, drug metabolism-cytochrome P450 pathway was enriched. Common genes from the target genes of microRNAs and differential expression genes are enriched in metabolism of xenobiotics cytochrome P450 pathway. Two miRNAs (dre-miR-146a and miR-212-3p) down regulated their target genes (LOC127510138 and adh5, respectively) which are enriched cytochrome P450 related pathway. The results present that geosmin is genetoxic to grass carp and indicate that cytochrome P450 system and UDP-glucuronosyltransferase play essential roles in biotransformation of geosmin. MicroRNAs regulate the biotransformation of geosmin by targeting specific genes, which contributes to the development of strategies to manage its negative impacts in both natural and artificial environments.

Predicting routes of phase I and II metabolism based on quantum mechanics and machine learning

1. Unexpected metabolism could lead to the failure of many late-stage drug candidates or even the withdrawal of approved drugs. Thus, it is critical to predict and study the dominant routes of metabolism in the early stages of research. In this study, we describe the development and validation of a 'WhichEnzyme' model that accurately predicts the enzyme families most likely to be responsible for a drug-like molecule's metabolism. Furthermore, we combine this model with our previously published regioselectivity models for Cytochromes P450, Aldehyde Oxidases, Flavin-containing Monooxygenases, UDP-glucuronosyltransferases and Sulfotransferases - the most important Phase I and Phase II drug metabolising enzymes - and a 'WhichP450' model that predicts the Cytochrome P450 isoform(s) responsible for a compound's metabolism. The regioselectivity models are based on a mechanistic understanding of these enzymes' actions, and use quantum mechanical simulations with machine learning methods to accurately predict sites of metabolism and the resulting metabolites. We train heuristic based on the outputs of the 'WhichEnzyme', 'WhichP450', and regioselectivity models to determine the most likely routes of metabolism and metabolites to be observed experimentally. Finally, we demonstrate that this combination delivers high sensitivity in identifying experimentally reported metabolites and higher precision than other methods for predicting in vivo metabolite profiles.

UDP-glucuronosyltransferase is involved in susceptibility of Chironomus kiiensis Tokunaga, 1936 (Diptera: Chironomidae) to insecticides

UDP-glucuronosyltransferases (UGTs) could transform various exogenous and endogenous compounds, which help detoxification of pesticides in insects. To investigate the role of UGTs in the detoxification metabolism of insecticides in Chironomus kiiensis, CkUGT302M1, CkUGT302N1, CkUGT308N1 and CkUGT36J1 genes were identified with 1449-1599 bp encoding 482-532 amino acids. Four UGT genes shared 40.86∼53.36% identity with other homologous insect species, and expressed in all developmental stages, notably in the larval and adult stages. Expression of CkUGTs was higher in the gastric caecum, midgut and head. Moreover, CkUGTs expression and activity were significantly increased in C. kiiensis larvae in exposure to sublethal concentrations of carbaryl, deltamethrin and phoxim, respectively. To further explore the functions of UGT genes, the CkUGT308N1 was effectively silenced in 4th instar C. kiiensis larvae by RNA interference, which resulted in the mortality of dsCkUGT308N1 treated larvae increased by 71.43%, 111.11% and 62.50% under sublethal doses of carbaryl, deltamethrin and phoxim at the 24-h time point, respectively. The study revealed that the CkUGT308N1 gene in C. kiiensis could contribute to the metabolism of pesticides and provide a scientific basis for evaluating the water pollution of pesticides.

Chlorpyrifos and chlorfenapyr resistance in Spodoptera frugiperda (Lepidoptera: Noctuidae) relies on UDP-glucuronosyltransferases

Fall armyworm, Spodoptera frugiperda (J. E. Smith), has become an important agricultural pest worldwide. S. frugiperda is mainly controlled by the chemical insecticides, whereas the frequent application of insecticides would result in the resistance development. Insect uridine diphosphate-glucuronosyltransferases (UGTs), as phase II metabolism enzymes, play vital roles in the breakdown of endobiotic and xenobiotics. In this study, 42 UGT genes were identified by RNA-seq, including 29 UGT genes were elevated compared to the susceptible population, and the transcript levels of 3 UGTs (UGT40F20, UGT40R18, and UGT40D17) were increased by more than 2.0-fold in the field populations. Expression pattern analysis revealed that S. frugiperda UGT40F20, UGT40R18, and UGT40D17 were increased by 6.34-, 4.26-, and 8.28-fold, compared the susceptible populations, respectively. The expression of UGT40D17, UGT40F20, and UGT40R18 was affected after exposure to phenobarbital, chlorpyrifos, chlorfenapyr, sulfinpyrazone, and 5-nitrouracil. The induced expression of UGT genes may have improved UGT enzymatic activity, while the inhibition of UGTs genes expression may decreased UGT enzymatic activity. Sulfinpyrazone, and 5-nitrouracil, significantly increased the toxicity of chlorpyrifos and chlorfenapyr, as well as phenobarbital significantly reduced the toxicity of chlorpyrifos and chlorfenapyr against the susceptible populations and field populations of S. frugiperda. The suppression of UGTs (UGT40D17, UGT40F20, and UGT40R18) significantly increased the insensitivity of the field populations to chlorpyrifos and chlorfenapyr. These findings strongly supported our viewpoint that UGTs may play a critical role in insecticide detoxification. This study provides a scientific basis for the management of S. frugiperda.

Drug-drug interactions that alter the exposure of glucuronidated drugs: Scope, UDP-glucuronosyltransferase (UGT) enzyme selectivity, mechanisms (inhibition and induction), and clinical significance

Drug-drug interactions (DDIs) arising from the perturbation of drug metabolising enzyme activities represent both a clinical problem and a potential economic loss for the pharmaceutical industry. DDIs involving glucuronidated drugs have historically attracted little attention and there is a perception that interactions are of minor clinical relevance. This review critically examines the scope and aetiology of DDIs that result in altered exposure of glucuronidated drugs. Interaction mechanisms, namely inhibition and induction of UDP-glucuronosyltransferase (UGT) enzymes and the potential interplay with drug transporters, are reviewed in detail, as is the clinical significance of known DDIs. Altered victim drug exposure arising from modulation of UGT enzyme activities is relatively common and, notably, the incidence and importance of UGT induction as a DDI mechanism is greater than generally believed. Numerous DDIs are clinically relevant, resulting in either loss of efficacy or an increased risk of adverse effects, necessitating dose individualisation. Several generalisations relating to the likelihood of DDIs can be drawn from the known substrate and inhibitor selectivities of UGT enzymes, highlighting the importance of comprehensive reaction phenotyping studies at an early stage of drug development. Further, rigorous assessment of the DDI liability of new chemical entities that undergo glucuronidation to a significant extent has been recommended recently by regulatory guidance. Although evidence-based approaches exist for the in vitro characterisation of UGT enzyme inhibition and induction, the availability of drugs considered appropriate for use as 'probe' substrates in clinical DDI studies is limited and this should be research priority.

Central metabolism as a potential origin of sex differences in morphine antinociception but not induction of antinociceptive tolerance in mice

BACKGROUND AND PURPOSE

In rodents, morphine antinociception is influenced by sex. However, conflicting results have been reported regarding the interaction between sex and morphine antinociceptive tolerance. Morphine is metabolised in the liver and brain into morphine-3-glucuronide (M3G). Sex differences in morphine metabolism and differential metabolic adaptations during tolerance development might contribute to behavioural discrepancies. This article investigates the differences in peripheral and central morphine metabolism after acute and chronic morphine treatment in male and female mice.

EXPERIMENTAL APPROACH

Sex differences in morphine antinociception and tolerance were assessed using the tail-immersion test. After acute and chronic morphine treatment, morphine and M3G metabolic kinetics in the blood were evaluated using LC-MS/MS. They were also quantified in several CNS regions. Finally, the blood-brain barrier (BBB) permeability of M3G was assessed in male and female mice.

KEY RESULTS

This study demonstrated that female mice showed weaker morphine antinociception and faster induction of tolerance than males. Additionally, female mice showed higher levels of M3G in the blood and in several pain-related CNS regions than male mice, whereas lower levels of morphine were observed in these regions. M3G brain/blood ratios after injection of M3G indicated no sex differences in M3G BBB permeability, and these ratios were lower than those obtained after injection of morphine.

CONCLUSION

These differences are attributable mainly to morphine central metabolism, which differed between males and females in pain-related CNS regions, consistent with weaker morphine antinociceptive effects in females. However, the role of morphine metabolism in antinociceptive tolerance seemed limited.

LINKED ARTICLES

This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

Inhibition of human UDP-glucuronosyltransferase enzyme by ripretinib: Implications for drug-drug interactions

Ripretinib, a tyrosine kinase inhibitor (TKI), is the first FDA approved fourth-line therapy for adults with advanced gastrointestinal stromal tumor (GIST). Studies have shown that several TKIs for treating GIST were potent inhibitors of human UDP- glucosyltransferase (UGTs) enzymes. However, whether ripretinib affects the activity of UGTs remains unclear. The aim of this study was to investigate the effects of ripretinib on major UGT isoforms, as well as to evaluate its potential drug-drug interactions (DDIs) risk caused by the inhibition of UGTs activities. The inhibitory effects and inhibition modes of ripretinib on UGTs were systematically evaluated using high-performance liquid chromatography (HPLC) and enzyme kinetic studies, respectively. Our data showed that ripretinib exhibited potent inhibition against UGT1A1, UGT1A3, UGT1A4, UGT1A7 and UGT1A8. Enzyme kinetic studies indicated that ripretinib was not only a competitive inhibitor of UGT1A1, UGT1A4 and UGT1A7, but also a noncompetitive inhibitor of UGT1A3, as well as a mixed inhibitor of UGT1A8. The prediction results of in vitro-in vivo extrapolation (IVIVE) demonstrated that ripretinib might bring the potential risk of DDIs when combined with substrates of UGT1A1, UGT1A3, UGT1A4, UGT1A7 or UGT1A8. Therefore, special attention should be paid when ripretinib is used in conjunction with other drugs metabolized by UGTs to avoid risk of DDIs in clinic.

Mutual Influence of Human Cytochrome P450 Enzymes and UDP-Glucuronosyltransferases on Their Respective Activities in Recombinant Fission Yeast

Cytochromes P450 (CYPs) and UDP-glucuronosyltransferases (UGTs) are the most important human drug metabolizing enzymes, but their mutual interactions are poorly understood. In this study, we recombinantly co-expressed of each one of the 19 human members of the UGT families 1 and 2 with either CYP2C9, CYP2D6, or CYP4Z1 in fission yeast. Using these strains, we monitored a total of 72 interactions: 57 cases where we tested the influence of UGT co-expression on CYP activity and 15 cases of the opposite approach. In the majority of cases (88%), UGT co-expression had a statistically significant (p < 0.05) effect on P450 activity (58% positive and 30% negative). Strong changes were observed in nine cases, including one case with an activity increase by a factor of 23 (CYP2C9 activity in the presence of UGT2A3) but also four cases with a complete loss of activity. When monitoring the effect of CYP co-expression on the activity of five UGTs, activity changes were generally not so pronounced and, if observed, always detrimental. UGT2B7 activity was not influenced by CYP co-expression, while the other UGTs were affected to varying degrees. These data suggest the notion that mutual influence of CYPs and UGTs on each other's activity is a widespread phenomenon.

Significance of UGT1A6, UGT1A9, and UGT2B7 genetic variants and their mRNA expression in the clinical outcome of renal cell carcinoma

UDP-glucuronosyltransferase (UGT) metabolizes a number of endogenous and exogenous substrates. Renal cells express high amounts of UGT; however, the significance of UGT in patients with renal cell carcinoma (RCC) remains unknown. In this study, we profile the mRNA expression of UGT subtypes (UGT1A6, UGT1A9, and UGT2B7) and their genetic variants in the kidney tissue of 125 Japanese patients with RCC (Okayama University Hospital, Japan). In addition, we elucidate the association between the UGT variants and UGT mRNA expression levels and clinical outcomes in these patients. The three representative genetic variants, namely, UGT1A6 541A > G, UGT1A9 i399C > T, and UGT2B7-161C > T, were genotyped, and their mRNA expression levels in each tissue were determined. We found that the mRNA expression of the three UGTs (UGT1A6, UGT1A9, and UGT2B7) are significantly downregulated in RCC tissues. Moreover, in patients with RCC, the UGT2B7-161C > T variant and high UGT2B7 mRNA expression are significantly correlated with preferable cancer-specific survival (CSS) and overall survival (OS), respectively. As such, the UGT2B7-161C > T variant and UGT2B7 mRNA expression level were identified as significant independent prognostic factors of CSS and CSS/OS, respectively. Taken together, these findings indicate that UGT2B7 has a role in RCC progression and may, therefore, represent a potential prognostic biomarker for patients with RCC.

The Somatic Mutation Landscape of UDP-Glycosyltransferase (UGT) Genes in Human Cancers

The human UDP-glycosyltransferase (UGTs) superfamily has a critical role in the metabolism of anticancer drugs and numerous pro/anti-cancer molecules (e.g., steroids, lipids, fatty acids, bile acids and carcinogens). Recent studies have shown wide and abundant expression of UGT genes in human cancers. However, the extent to which UGT genes acquire somatic mutations within tumors remains to be systematically investigated. In the present study, our comprehensive analysis of the somatic mutation profiles of 10,069 tumors from 33 different TCGA cancer types identified 3427 somatic mutations in UGT genes. Overall, nearly 18% (1802/10,069) of the assessed tumors had mutations in UGT genes with huge variations in mutation frequency across different cancer types, ranging from over 25% in five cancers (COAD, LUAD, LUSC, SKCM and UCSC) to less than 5% in eight cancers (LAML, MESO, PCPG, PAAD, PRAD, TGCT, THYM and UVM). All 22 UGT genes showed somatic mutations in tumors, with UGT2B4, UGT3A1 and UGT3A2 showing the largest number of mutations (289, 307 and 255 mutations, respectively). Nearly 65% (2260/3427) of the mutations were missense, frame-shift and nonsense mutations that have been predicted to code for variant UGT proteins. Furthermore, about 10% (362/3427) of the mutations occurred in non-coding regions (5' UTR, 3' UTR and splice sites) that may be able to alter the efficiency of translation initiation, miRNA regulation or the splicing of UGT transcripts. In conclusion, our data show widespread somatic mutations of UGT genes in human cancers that may affect the capacity of cancer cells to metabolize anticancer drugs and endobiotics that control pro/anti-cancer signaling pathways. This highlights their potential utility as biomarkers for predicting therapeutic efficacy and clinical outcomes.

Characterization of Clofazimine Metabolism in Human Liver Microsomal Incubation In Vitro

Clofazimine [N,5-bis(4-chlorophenyl)-3-[(propane-2-yl)rimino]-3,5-dihydrophenazin-2-amine] is an antimycobacterial agent used as a second-line antituberculosis (anti-TB) drug. Nonetheless, little information is known about the metabolic routes of clofazimine, and the enzymes involved in metabolism. This study aimed to characterize the metabolic pathways and enzymes responsible for the metabolism of clofazimine in human liver microsomes. Eight metabolites, including four oxidative metabolites, three glucuronide conjugates, and one sulfate conjugate were identified, and their structures were deduced based on tandem mass spectrometry (MS/MS) spectra. Hydroxylated clofazimine and hydrated clofazimine was generated even in the absence of the NADPH generating system presumably via a nonenzymatic pathway. Hydrolytic-dehalogenated clofazimine was catalyzed mainly by CYP1A2 whereas hydrolytic-deaminated clofazimine was formed by CYP3A4/A5. In case of glucuronide conjugates, UGT1A1, UGT1A3, and UGT1A9 showed catalytic activity toward hydroxylated and hydrated clofazimine glucuronide whereas hydrolytic-deaminated clofazimine glucuronide was catalyzed by UGT1A4, UGT1A9, UGT1A3, and UGT2B4. Our results suggested that CYP1A2 and CYP3A are involved in the formation of oxidative metabolites while UGT1A1, 1A3, 1A4, 1A9, and 2B4 are involved in the formation of glucuronide conjugates of oxidative metabolites of clofazimine.

Use of a Baculovirus-Mammalian Cell Expression-System for Expression of Drug-Metabolizing Enzymes: Optimization of Infection With a Focus on Cytochrome P450 3A4

Heterologous expression systems are important for analyzing the effects of genetic factors including single nucleotide polymorphisms on the functions of drug-metabolizing enzymes. In this study, we focused on a baculovirus-mammalian cell (Bac-Mam) expression system as a safer and more efficient approach for this purpose. The baculovirus-insect cell expression system is widely utilized in large-scale protein expression. Baculovirus has been shown to also infect certain mammalian cells, although the virus only replicates in insect cells. With this knowledge, baculovirus is now being applied in a mammalian expression system called the Bac-Mam system wherein a gene-modified baculovirus is used whose promotor is replaced with one that can function in mammalian cells. We subcloned open-reading frames of cytochrome P450 3A4 (CYP3A4), UDP-glucuronosyltransferase (UGT) 1A1, and UGT2B7 into a transfer plasmid for the Bac-Mam system, and prepared recombinant Bac-Mam virus. The obtained virus was amplified in insect Sf9 cells and used to infect mammalian COS-1 cells. Expression of CYP3A4, UGT1A1, and UGT2B7 in COS-1 cell homogenates were confirmed by immunoblotting. Optimum infection conditions including the amount of Bac-Mam virus, culture days before collection, and concentration of sodium butyrate, an enhancer of viral-transduction were determined by monitoring CYP3A4 expression. Expressed CYP3A4 showed appropriate activity without supplying hemin/5-aminolevulinic acid or co-expressing with NADPH-cytochrome P450 reductase. Further, we compared gene transfer efficiency between the Bac-Mam system and an established method using recombinant plasmid and transfection reagent. Our results indicate that the Bac-Mam system can be applied to introduce drug-metabolizing enzyme genes into mammalian cells that are widely used in drug metabolism research. The expressed enzymes are expected to undergo appropriate post-translational modification as they are in mammalian bodies. The Bac-Mam system may thus accelerate pharmacogenetics and pharmacogenomics research.

Assessment of susceptibility to phthalate and DINCH exposure through CYP and UGT single nucleotide polymorphisms

Single nucleotide polymorphisms (SNPs) of cytochrome P450 (CYPs) and UDP-glucuronosyltransferase (UGTs) genes have been proposed to influence phthalates and 1,2-cyclo-hexanedicarboxylic acid diisononyl ester (DINCH) biotransformation but have not been investigated on a populational level. We investigated the role of SNPs in CYP2C9, CYP2C19, CYP2D6, UGT2B15, and UGT1A7 genes in the biotransformation of phthalates (DEHP, DEP, DiBP, DnBP, BBzP, DiNP, DidP) and DINCH by determining their urine metabolites. From the Slovenian study population of 274 men and 289 lactating primiparous women we obtained data on phthalate and DINCH urine metabolite levels (MEHP, 5OH-MEHP, 5oxo-MEHP, 5cx-MEPP, MEP, MiBP, MnBP, MBzP, cx-MINP, OH-MiDP, MCHP, MnPeP, MnOP, 5OH-MINCH, 5oxo-MINCH), SNP genotypes (rs1057910 = CYP2C9*3, rs1799853 = CYP2C9*2, rs4244285 = CYP2C19*2, rs12248560 = CYP2C19*17, rs3892097 = CYP2D6*4, rs1902023 = UGT2B15*2, and rs11692021 = UGT1A7*3) and questionnaires. Associations of SNPs with levels of metabolites and their ratios were assessed by multiple linear regression and ordinary logistic regression analyses. Significant associations were observed for CYP2C9*2, CYP2C9*3, CYP2C19*17, and UGT1A7*3 SNPs. The most pronounced was the influence of CYP2C9*2 and *3 on the reduced DEHP biotransformation, with lower levels of metabolites and their ratios in men and women. In contrast, carriers of CYP2C19*17 showed higher urine levels of DEHP metabolites in both genders, and in women also in higher DiNP, DiDP, and DINCH metabolite levels. The presence of UGT1A7*3 was associated with increased metabolite levels of DINCH in men and of DiBP and DBzP in women. Statistical models explained up to 27% of variability in metabolite levels or their ratios. Our observations confirm the effect of CYP2C9*2 and *3 SNPs towards reduced DEHP biotransformation. We show that CYP2C9*2, CYP2C9*3, CYP2C19*17, and UGT1A7*3 SNPs might represent biomarkers of susceptibility or resilience in phthalates and DINCH exposure that have been so far unrecognised.

UGT1A1 genotype-guided dosing of irinotecan: A prospective safety and cost analysis in poor metaboliser patients

AIM

To determine the safety, feasibility, pharmacokinetics, and cost of UGT1A1 genotype-guided dosing of irinotecan.

PATIENTS AND METHODS

In this prospective, multicentre, non-randomised study, patients intended for treatment with irinotecan were pre-therapeutically genotyped for UGT1A1∗28 and UGT1A1∗93. Homozygous variant carriers (UGT1A1 poor metabolisers; PMs) received an initial 30% dose reduction. The primary endpoint was incidence of febrile neutropenia in the first two cycles of treatment. Toxicity in UGT1A1 PMs was compared to a historical cohort of UGT1A1 PMs treated with full dose therapy, and to UGT1A1 non-PMs treated with full dose therapy in the current study. Secondary endpoints were pharmacokinetics, feasibility, and costs.

RESULTS

Of the 350 evaluable patients, 31 (8.9%) patients were UGT1A1 PM and received a median 30% dose reduction. The incidence of febrile neutropenia in this group was 6.5% compared to 24% in historical UGT1A1 PMs (P = 0.04) and was comparable to the incidence in UGT1A1 non-PMs treated with full dose therapy. Systemic exposure of SN-38 of reduced dosing in UGT1A1 PMs was still slightly higher compared to a standard-dosed irinotecan patient cohort (difference: +32%). Cost analysis showed that genotype-guided dosing was cost-saving with a cost reduction of €183 per patient.

CONCLUSION

UGT1A1 genotype-guided dosing significantly reduces the incidence of febrile neutropenia in UGT1A1 PM patients treated with irinotecan, results in a therapeutically effective systemic drug exposure, and is cost-saving. Therefore, UGT1A1 genotype-guided dosing of irinotecan should be considered standard of care in order to improve individual patient safety.

Adenine-related compounds modulate UDP-glucuronosyltransferase (UGT) activity in mouse liver microsomes

Adenine-related compounds are allosteric inhibitors of UDP-glucuronosyltransferase (UGT) in rat liver microsomes (RLM) and human UGT isoforms treated with detergent or pore-forming peptide, alamethicin.To clarify whether the same is true beyond species, the effects of adenine-related compounds on 4-methylumbelliferone (4-MU) glucuronidation were examined using detergent-treated mouse liver microsomes (MLM).Brij-58 treatment of MLM increased the V_max and the Michaelis constant, K_m, of 4-MU. This study was performed using Brij-58-treated MLM as an enzyme source. ATP- and ADP-inhibited 4-MU glucuronidation. In contrast, AMP caused a 1.5-fold increase in glucuronidation. Oxidised forms, NAD⁺ and NADP⁺, potently inhibited 4-MU glucuronidation, whereas the reduced forms, NADH and NADPH, did not. Furthermore, the IC₅₀ values of ATP, ADP, NAD⁺, and NADP⁺ were approximately 15 μM.In our previous study, ATP was the strongest inhibitor of UGT activity in RLM. However, in this study, the above-mentioned compounds inhibited 4-MU UGT in a comparable and non-competitive manner. Furthermore, AMP antagonised the inhibitory effects of ATP and ADP.These results suggest that ATP, ADP, NAD⁺, and NADP⁺ are common endogenous inhibitors of UGT beyond species.

Development of a microplate method for the determination of hepatic UDP-glucuronosyltransferase activity in rainbow trout (Oncorhynchus mykiss) and Nile tilapia (Oreochromis niloticus)

Hepatic glucuronidation represents an important phase II biotransformation reaction in both mammals and fish. The kinetic characteristics of uridine 5'-diphosphate (UDP) glucuronosyltransferases (UDPGTs) in rainbow trout liver microsomes were examined using p-nitrophenol (p-NP) as an aglycone and UDP-glucuronic acid (UDPGA) as a glucuronyl donor according to an existing protocol. The kinetic data obtained with varying concentrations of p-NP best fit the Hill equation and UDPGT activity was successfully induced following an i.p. injection of β-naphthoflavone (β-NF). The assay was subsequently adapted to a microplate method for determination of UDPGT activity in microsomal samples obtained from rainbow trout as well as Nile tilapia. In contrast to rainbow trout, UDPGT activity of Nile tilapia was best described by Michaelis-Menten kinetics. Based on the linearity of p-NP glucuronide formation, a p-NP concentration of 0.60 mM and a UDPGA concentration of 6.89 mM were determined to be suitable for assaying UDPGT activity in samples from rainbow trout and Nile tilapia. The microplate method offers several advantages over the historical assay; most notably it enables the observation of successive kinetics which ensures that enzyme activity is calculated in the most linear (initial) rate of the reaction. It also provides practical advantages in terms of ease-of-use and efficiency. This may be relevant to researchers investigating exposure of wild or farmed fish to environmental or feed-borne contaminants which are substrates of UDPGTs.

The Expression Profiles and Deregulation of UDP-Glycosyltransferase (UGT) Genes in Human Cancers and Their Association with Clinical Outcomes

The human UDP-glycosyltransferase (UGTs) superfamily has 22 functional enzymes that play a critical role in the metabolism of small lipophilic compounds, including carcinogens, drugs, steroids, lipids, fatty acids, and bile acids. The expression profiles of UGT genes in human cancers and their impact on cancer patient survival remains to be systematically investigated. In the present study, a comprehensive analysis of the RNAseq and clinical datasets of 9514 patients from 33 different TCGA (the Genome Cancer Atlas) cancers demonstrated cancer-specific UGT expression profiles with high interindividual variability among and within individual cancers. Notably, cancers derived from drug metabolizing tissues (liver, kidney, gut, pancreas) expressed the largest number of UGT genes (COAD, KIRC, KIRP, LIHC, PAAD); six UGT genes (1A6, 1A9, 1A10, 2A3, 2B7, UGT8) showed high expression in five or more different cancers. Kaplan-Meier plots and logrank tests revealed that six UGT genes were significantly associated with increased overall survival (OS) rates [UGT1A1 (LUSC), UGT1A6 (ACC), UGT1A7 (ACC), UGT2A3 (KIRC), UGT2B15 (BLCA, SKCM)] or decreased OS rates [UGT2B15 (LGG), UGT8 (UVM)] in specific cancers. Finally, differential expression analysis of 611 patients from 12 TCGA cancers identified 16 UGT genes (1A1, 1A3, 1A6, 1A7, 1A8, 1A9, 1A10, 2A1, 2A3, 2B4, 2B7, 2B11, 2B15, 3A1, 3A2, UGT8) that were up/downregulated in at least one cancer relative to normal tissues. In conclusion, our data show widespread expression of UGT genes in cancers, highlighting the capacity for intratumoural drug metabolism through the UGT conjugation pathway. The data also suggests the potentials for specific UGT genes to serve as prognostic biomarkers or therapeutic targets in cancers.

Inhibition of human UDP-glucuronosyltransferase enzyme by Dabrafenib: Implications for drug-drug interactions

Dabrafenib is a novel small molecule tyrosine kinase inhibitor (TKI) which is used to treat metastatic melanoma. The aim of this research was to survey the effects of dabrafenib on human UDP-glucuronosyltransferases (UGTs) and to evaluate the risk of drug-drug interactions (DDIs). The formation rates for 4-methylumbelliferone (4-MU) glucuronide and trifluoperazine-glucuronide in 12 recombinant human UGT isoforms with or without dabrafenib were measured and HPLC was used to investigate the inhibitory effects of dabrafenib on UGTs. Inhibition kinetic studies were also conducted. In vitro-in vivo extrapolation approaches were further used to predict the risk of DDI potentials of dabrafenib via inhibition of UGTs. Our data indicated that dabrafenib had a broad inhibitory effect on 4-MU glucuronidation by inhibiting the activities of UGTs, especially on UGT1A1, UGT1A7, UGT1A8, and UGT1A9, and dabrafenib could increase the area under the curve of co-administered drugs. Dabrafenib is a strong inhibitor of several UGTs and the co-administration of dabrafenib with drugs primarily metabolized by UGT1A1, 1A7, 1A8 or 1A9 may induce potential DDIs.

Metabolism of 2,3-Dehydrosilybin A and 2,3-Dehydrosilybin B: A Study with Human Hepatocytes and Recombinant UDP-Glucuronosyltransferases and Sulfotransferases

2,3-Dehydrosilybin A and 2,3-dehydrosilybin B are a pair of enantiomers formed by the oxidation of the natural flavonolignans silybin A and silybin B, respectively. However, the antioxidant activity of 2,3-dehydrosilybin molecules is much stronger than that of their precursors. Here, we investigated the biotransformation of pure 2,3-dehydrosilybin A and 2,3-dehydrosilybin B in isolated human hepatocytes, and we also aimed to identify human UDP-glucuronosyltransferases (UGTs) and sulfotransferases (SULTs) with activity toward their respective enantiomers. After incubation with hepatocytes, both 2,3-dehydrosilybin A and 2,3-dehydrosilybin B were converted to hydroxyl derivatives, methylated hydroxyl derivatives, methyl derivatives, sulfates, and glucuronides. The products of direct conjugations predominated over those of oxidative metabolism, and glucuronides were the most abundant metabolites. Furthermore, we found that recombinant human UGTs 1A1, 1A3, 1A7, 1A8, 1A9, and 1A10 were capable of catalyzing the glucuronidation of both 2,3-dehydrosilybin A and 2,3-dehydrosilybin B. UGTs 1A1 and 1A7 showed the highest activity toward 2,3-dehydrosilybin A, and UGT1A9 showed the highest activity toward 2,3-dehydrosilybin B. The sulfation of 2,3-dehydrosilybin A and B was catalyzed by SULTs 1A1*1, 1A1*2, 1A2, 1A3, 1B1, 1C2, 1C4, and 1E1, of which SULT1A3 exhibited the highest activity toward both enantiomers. We conclude that 2,3-dehydrosilybin A and B are preferentially metabolized by conjugation reactions, and that several human UGT and SULT enzymes may play a role in these conjugations.

Comparison of the drug-drug interactions potential of ibrutinib and acalabrutinib via inhibition of UDP-glucuronosyltransferase

Ibrutinib and acalabrutinib are two Bruton's tyrosine kinase (BTK) inhibitors which have gained Food and Drug Administration (FDA) approval for the treatment of various B cell malignancies. Herein, we investigated the effects of the two drugs on UDP-glucuronosyltransferase (UGT) activities to evaluate their potential risk for drug-drug interactions (DDIs) via UGT inhibition. Our data indicated that ibrutinib exerted broad inhibition on most of UGTs, including a potent competitive inhibition against UGT1A1 with a K_i value of 0.90 ± 0.03 μM, a noncompetitive inhibition against UGT1A3 and UGT1A7 with K_i values of 0.88 ± 0.03 μM and 2.52 ± 0.23 μM, respectively, while acalabrutinib only exhibited weak UGT inhibition towards all tested UGT isoforms. DDI risk prediction suggested that the inhibition against UGT1A1 and UGT1A3 by ibrutinib might bring a potential DDIs risk, while acalabrutinib was unlikely to trigger clinically significant UGT-mediated DDIs due to its weak effects. Our study raises an alarm bell about potential DDI risk associated with ibrutinib, however, the extrapolation from in vitro data to in vivo drug interactions should be taken with caution, and additional systemic study is needed.

Identification of human uridine diphosphate-glucuronosyltransferase isoforms responsible for the glucuronidation of 10,11-dihydro-10-hydroxy-carbazepine

OBJECTIVES

To determine the kinetics of the formation of 10,11-dihydro-10-hydroxy-carbazepine (MHD)-O-glucuronide in human liver microsomes (HLMs), human intestine microsomes (HIMs), human kidney microsomes (HKMs) and recombinant human UDP-glucuronosyltransferase (UGTs), and identify the primary UGT isoforms catalyzing the glucuronidation of MHD.

METHODS

The kinetics of the glucuronidation of MHD was determined in HLMs, HIMs as well as HKMs. Screening assays with 13 recombinant human UGTs, inhibition studies and correlation analysis were performed to identify the main UGTs involved in the glucuronidation of MHD.

KEY FINDINGS

MHD-O-glucuronide was formed in HLMs, HIMs as well as HKMs, HLMs showed the highest intrinsic clearance of MHD. Among 13 recombinant human UGTs, UGT2B7 and UGT1A9 were identified to be the principal UGT isoforms mediating the glucuronidation of MHD, while UGT1A4 played a partial role. In addition, inhibition studies and correlation analysis further confirmed that UGT2B7 and UGT1A9 participated in the formation of MHD-O-glucuronide.

CONCLUSIONS

MHD could be metabolized by UGTs in the liver, intestine and kidney, and the hepatic glucuronidation was the critical metabolic pathway. UGT2B7 and UGT1A9 were the primary UGT isoforms mediating the formation of MHD-O-glucuronide in the liver.

Tetrahydrofurofuranoid Lignans, Eudesmin, Fargesin, Epimagnolin A, Magnolin, and Yangambin Inhibit UDP-Glucuronosyltransferase 1A1 and 1A3 Activities in Human Liver Microsomes

Eudesmin, fargesin, epimagnolin A, magnolin, and yangambin are tetrahydrofurofuranoid lignans with various pharmacological activities found in Magnoliae Flos. The inhibition potencies of eudesmin, fargesin, epimagnolin A, magnolin, and yangambin on six major human uridine 5'-diphospho-glucuronosyltransferase (UGT) activities in human liver microsomes were evaluated using liquid chromatography-tandem mass spectrometry and cocktail substrates. Eudesmin, fargesin, epimagnolin A, magnolin, and yangambin inhibited UGT1A1 and UGT1A3 activities, but showed negligible inhibition of UGT1A4, UGT16, UGT1A9, and UGT2B7 activities at 200 μM in pooled human liver microsomes. Moreover, eudesmin, fargesin, epimagnolin A, magnolin, and yangambin noncompetitively inhibited UGT1A1-catalyzed SN38 glucuronidation with K_i values of 25.7, 25.3, 3.6, 26.0, and 17.1 μM, respectively, based on kinetic analysis of UGT1A1 inhibition in pooled human liver microsomes. Conversely, the aforementioned tetrahydrofurofuranoid lignans competitively inhibited UGT1A3-catalyzed chenodeoxycholic acid 24-acyl-glucuronidation with 39.8, 24.3, 15.1, 37.6, and 66.8 μM, respectively in pooled human liver microsomes. These in vitro results suggest the necessity of evaluating whether the five tetrahydrofurofuranoid lignans can cause drug-drug interactions with UGT1A1 and UGT1A3 substrates in vivo.

Stratification of Volunteers According to Flavanone Metabolite Excretion and Phase II Metabolism Profile after Single Doses of 'Pera' Orange and 'Moro' Blood Orange Juices

Large interindividual variations in the biological response to citrus flavanones have been observed, and this could be associated with high variations in their bioavailability. The aim of this study was to identify the main determinants underlying interindividual differences in citrus flavanone metabolism and excretion. In a randomized cross-over study, non-obese and obese volunteers, aged 19-40 years, ingested single doses of Pera and Moro orange juices, and urine was collected for 24 h. A large difference in the recovery of the urinary flavanone phase II metabolites was observed, with hesperetin-sulfate and hesperetin-sulfo-O-glucuronide being the major metabolites. Subjects were stratified according to their total excretion of flavanone metabolites as high, medium, and low excretors, but the expected correlation with the microbiome was not observed at the genus level. A second stratification was proposed according to phase II flavanone metabolism, whereby participants were divided into two excretion groups: Profiles A and B. Profile B individuals showed greater biotransformation of hesperetin-sulfate to hesperetin-sulfo-O-glucuronide, as well as transformation of flavanone-monoglucuronide to the respective diglucuronides, suggestive of an influence of polymorphisms on UDP-glucuronosyltransferase. In conclusion, this study proposes a new stratification of volunteers based on their metabolic profiles. Gut microbiota composition and polymorphisms of phase II enzymes may be related to the interindividual variability of metabolism.

Evaluation of inhibitors of intestinal UDP-glucuronosyltransferases 1A8 and 1A10 using raloxifene as a substrate in Caco-2 cells: Studies with four flavonoids of Scutellaria baicalensis

UDP glucuronosyltransferases (UGTs) of the gastrointestinal tract play a crucial role in protection against the toxic effects of xenobiotics in the environment. UGTs such as UGT1A8 and UGT1A10 are predominantly expressed in gastrointestinal tissues. In this study, we examined the phase II metabolism of raloxifene in differentiated Caco-2 monolayers by inducing UGT1A8 and UGT1A10 expression in these cells. The present study evaluated the following four flavonoids of Scutellaria baicalensis as model herbal compounds: scutellarein, salvigenin, baicalein, and wogonin. All test compounds, endpoint substrates, and their metabolites were quantified using liquid chromatography and high-resolution mass spectrometry. The transepithelial electrical resistance values for the individual compounds were comparable regardless of whether they were measured individually. Salvigenin significantly inhibited UGT1A8 and UGT1A10 activities in a concentration-dependent manner. All individual compounds except scutellarein inhibited UGT1A8 and UGT1A10 activity at a concentration of 100 μM. In addition, all individual flavonoids at 100 μM, except wogonin, significantly increased the amount of raloxifene in the basolateral chambers. The positive control, canagliflozin, significantly inhibited both UGT1A8 and UGT1A10 activities. These findings suggest that the Caco-2 assay can be utilized for identifying UGT1A8 and UGT1A10 inhibitors and indicate the potential of salvigenin for enhancing the pharmacological effects of UGT substrate drugs.

Regulation of uridine diphosphate-glucuronosyltransferase 1A expression by miRNA-214-5p and miRNA-486-3p

Aim: This study aimed to identify novel miRNAs (miRs) as regulators of UGT1A gene expression and to evaluate them as potential risk factors for the development of liver fibrosis/cirrhosis. Materials & methods: miRNA target sites in UDP-glucuronosyltransferase 1A (UGT1A) 3'-UTR were predicted and confirmed by luciferase assays, quantitative real-time PCR and western blot using HEK293, HepG2 and Huh7 cells. UGT1A and miRNA expression were analyzed in cirrhotic patients and a mouse model of alcoholic liver fibrosis. Results: miR-214-5p and miR-486-3p overexpression reduced UGT1A mRNA, protein levels and enzyme activity in HepG2 and Huh7 cells. miR-486-3p was upregulated in cirrhotic patients and fibrotic mice livers, whereas UGT1A mRNA levels were reduced. Conclusion: In conclusion, we identified two novel miRNAs capable to repress UGT1A expression in vitro and in vivo. Furthermore, miR-486-3p may represent a potential risk factor for the development or progression of liver fibrosis/cirrhosis by means of a reduced UGT1A-mediated detoxification activity.

Enzyme Kinetics of Uridine Diphosphate Glucuronosyltransferases (UGTs)

Glucuronidation, catalyzed by uridine diphosphate glucuronosyltransferases (UGTs), is an important process for the metabolism and clearance of many lipophilic chemicals, including drugs, environmental chemicals, and endogenous compounds. Glucuronidation is a bisubstrate reaction that requires the aglycone and the cofactor, UDP-GlcUA. Accumulating evidence suggests that the bisubstrate reaction follows a compulsory-order ternary mechanism. To simplify the kinetic modeling of glucuronidation reactions in vitro, UDP-GlcUA is usually added to incubations in large excess. Many factors have been shown to influence UGT activity and kinetics in vitro, and these must be accounted for during experimental design and data interpretation. While the assessment of drug-drug interactions resulting from UGT inhibition has been challenging in the past, the increasing availability of UGT enzyme-selective substrate and inhibitor "probes" provides the prospect for more reliable reaction phenotyping and assessment of drug-drug interaction potential. Although extrapolation of the in vitro intrinsic clearance of a glucuronidated drug often underpredicts in vivo clearance, careful selection of in vitro experimental conditions and inclusion of extrahepatic glucuronidation may improve the predictivity of in vitro-in vivo extrapolation. Physiologically based pharmacokinetic (PBPK) modeling has also shown to be of value for predicting PK of drugs eliminated by glucuronidation.

Inhibition of human UDP-glucuronosyltransferase enzyme by belinostat: Implications for drug-drug interactions

Belinostat is a pan-histone deacetylase (HDAC) inhibitor which recently approved for the treatment of relapsed/refractory Peripheral T-cell lymphomas (PTCL). To assess drug-drug interactions (DDIs) potential of belinostat via inhibition of UDP-glucuronosyltransferases (UGTs), the effects of belinostat on UGTs activities were investigated using the non-selective probe substrate 4-methylumbelliferone (4-MU) and trifluoperazine (TFP) by UPLC-MS/MS. Belinostat exhibited a wide range of inhibition against UGTs activities, particularly a potent non-competitive inhibition against UGT1A3, and weak inhibition against UGT1A1, 1A7, 1A8, 2B4 and 2B7. Further, in vitro-in vivo extrapolation (IVIVE) approaches were used to predict the risk of DDI arising from inhibition of UGTs. Our data indicate that the intravenous infusion of belinostat at clinical available dose can contribute a significant increase to the AUC of co-administrated drugs primarily cleared by UGT1A3 or UGT1A1, which will result in potential DDIs. In contrast, oral administrated belinostat is unlikely to cause significant DDIs through inhibition of glucuronidation.

Characterization of the Ontogeny of Hepatic UDP-Glucuronosyltransferase Enzymes Based on Glucuronidation Activity Measured in Human Liver Microsomes

An understanding of the postnatal development of hepatic UDP-glucuronosyltransferase (UGT) enzymes is required for accurate prediction of the age-dependent changes in pharmacokinetics of many drugs used in children. However, the maturation rate of hepatic UGT isoforms remains a major knowledge gap. This study aimed to establish the age-associated changes in glucuronidation activity of 10 major hepatic UGT isoforms in humans, namely, UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B4, UGT2B7, UGT2B10, UGT2B15, and UGT2B17. Human liver microsomes from pediatric and adult donors were incubated under optimized incubation conditions to assess the activity rates of hepatic UGT isoforms using a panel of 19 in vitro UGT probe substrates and clinically used drugs. Statistically strong correlations of glucuronidation activities allowed the ontogeny of UGT1A1, UGT1A4, UGT2B7, UGT2B10, and UGT2B15 to be established using multiple selective UGT substrates and matched human liver microsome samples. The postnatal development of hepatic UGTs is isoform-dependent using either individual or cross-correlated selective isoform substrates. Maximal adult activity was reached at different times ranging from within a month (UGT1A1, UGT2B4, UGT2B7, UGT2B10, and UGT2B15), during infancy (UGT1A3, UGT1A4, and UGT1A9), to adolescence (UGT1A6 and UGT2B17). This study provides an extensive characterization of the postnatal ontogeny profiles of hepatic UGT enzymes that are instrumental for predicting drug disposition via in vitro-in vivo extrapolation algorithms and verifying pharmacokinetic predictions against in vivo observations via pediatric physiologically based pharmacokinetic modeling in pediatric patients.

Dosage Adjustment of Irinotecan in Patients with UGT1A1 Polymorphisms: A Review of Current Literature

Objective:

To review available literature regarding pharmacogenomics (PGx) effects on the metabolism of irinotecan by the UGT1A1 gene and the resulting dose adjustments based on PGx genetic variant.

Summary:

Irinotecan is a chemotherapy agent commonly used in treatment of various cancers such as metastatic colorectal cancer (mCRC) and others. The extent of decreased function of UGT1A1 varies based on genotype so irinotecan dose adjustments may be needed. Those with UGT1A1 homozygous *28/*28 genotype may experience 70% reduction in activity, while heterozygous genotypes with *1/*28 may only experience 30% loss. UGT1A1*6 variants may also play a role in decreased function. The incidence of *28 and *6 alleles varies among ethnic populations resulting in the need for dosage adjustments to avoid toxicities.

Conclusion:

These findings add to a growing body of literature that suggest patients with UGT1A1 *28 or *6 variant alleles benefit from lower doses of irinotecan. However, due to the heterogeneity of currently available studies, more evidence that investigates various regimens in different patient populations is needed to determine the most appropriate dosing strategies. Although other factors, as well as efficacy considerations will likely influence clinical decision making, genotype may be an important factor when determining dose.

Multiple circulating alkaloids and saponins from intravenous Kang-Ai injection inhibit human cytochrome P450 and UDP-glucuronosyltransferase isozymes: potential drug-drug interactions

BACKGROUND

Kang-Ai injection is widely used as an adjuvant therapy drug for many cancers, leukopenia, and chronic hepatitis B. Circulating alkaloids and saponins are believed to be responsible for therapeutic effects. However, their pharmacokinetics (PK) and excretion in vivo and the risk of drug-drug interactions (DDI) through inhibiting human cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) enzymes remain unclear.

METHODS

PK and excretion of circulating compounds were investigated in rats using a validated ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS) method. Further, the inhibitory effects of nine major compounds against eleven CYP and UGT isozymes were assayed using well-accepted specific substrate for each enzyme.

RESULTS

After dosing, 9 alkaloids were found with C max and t 1/2 values of 0.17-422.70 μmol/L and 1.78-4.33 h, respectively. Additionally, 28 saponins exhibited considerable systemic exposure with t 1/2 values of 0.63-7.22 h, whereas other trace saponins could be negligible or undetected. Besides, over 90% of alkaloids were excreted through hepatobiliary and renal excretion. Likewise, astragalosides and protopanaxatriol (PPT) type ginsenosides also involved in hepatobiliary and/or renal excretion. Protopanaxadiol (PPD) type ginsenosides were mainly excreted to urine. Furthermore, PPD-type ginsenosides were extensively bound (f u-plasma approximately 1%), whereas astragalosides and PPT-type ginsenosides displayed f u-plasma values of 12.35% and 60.23-87.36%, respectively. Moreover, matrine, oxymatrine, astragaloside IV, ginsenoside Rg1, ginsenoside Re, ginsenoside Rd, ginsenoside Rc, and ginsenoside Rb1 exhibited no inhibition or weak inhibition against several common CYP and UGT enzymes IC50 values between 8.81 and 92.21 μM. Through kinetic modeling, their inhibition mechanisms towards those CYP and UGT isozymes were explored with obtained Ki values. In vitro-in vivo extrapolation showed the inhibition of systemic clearance for CYP or UGT substrates seemed impossible due to [I]/Ki no more than 0.1.

CONCLUSIONS

We summarized the PK behaviors, excretion characteristics and protein binding rates of circulating alkaloids, astragalosides and ginsenosides after intravenous Kang-Ai injection. Furthermore, weak inhibition or no inhibition towards these CYP and UGT activities could not trigger harmful DDI when Kang-Ai injection is co-administered with clinical drugs primarily cleared by these CYP or UGT isozymes.

UDP-glycosyltransferases contribute to spirotetramat resistance in Aphis gossypii Glover

Uridine diphosphate (UDP)-glycosyltransferases (UGTs) catalyze the conjugation of small lipophilic endogenous and exogenous compounds with sugars to produce water-soluble glycosides, playing an important role in insect endobiotic regulation and xenobiotic detoxification. In this study, two UGT-inhibitors, sulfinpyrazone and 5-nitrouracil, significantly increased spirotetramat toxicity against third instar nymphs of resistant Aphis gossypii, whereas there were no synergistic effects in apterous adult aphids, suggesting UGT involvement in spirotetramat resistance in cotton aphids. Furthermore, the UHPLC-MS/MS was employed to determine the content of spirotetramat and its four metabolites (S-enol, S-glu, S-mono, S-keto) in the honeydew of resistant cotton aphids under spirotetramat treatment. No residual spirotetramat was detected in the honeydew, while its four metabolites were detected at a S-enol: S-glu: S-mono: S-keto ratio of 69.30: 6.54: 1.44: 1.00. Therefore, glycoxidation plays a major role in spirotetramat inactivation and excretion in resistant aphids. Compared with the susceptible strain, the transcriptional levels of UGT344M2 were significantly upregulated in nymphs and adults of the resistant strain. RNA interference of UGT344M2 dramatically increased spirotetramat toxicity in nymphs, but no such effect were found in the resistant adult aphids. Overall, UGT-mediated glycoxidation were found to be involved in spirotetramat resistance. The suppression of UGT344M2 significantly increased the sensitivity of resistant nymphs to spirotetramat, suggesting that UGT344M2 upregulation might be associated with spirotetramat detoxification. This study provides an overview of the involvement of metabolic factors, UGTs, in the development of spirotetramat resistance.

In-Depth Characterization of EpiIntestinal Microtissue as a Model for Intestinal Drug Absorption and Metabolism in Human

The Caco-2 model is a well-accepted in vitro model for the estimation of fraction absorbed in human intestine. Due to the lack of cytochrome P450 3A4 (CYP3A4) activities, Caco-2 model is not suitable for the investigation of intestinal first-pass metabolism. The purpose of this study is to evaluate a new human intestine model, EpiIntestinal microtissues, as a tool for the prediction of oral absorption and metabolism of drugs in human intestine. The activities of relevant drug transporters and drug metabolizing enzymes, including MDR1 P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), CYP3A4, CYP2J2, UDP-glucuronosyltransferases (UGT), carboxylesterases (CES), etc., were detected in functional assays with selective substrates and inhibitors. Compared to Caco-2, EpiIntestinal microtissues proved to be a more holistic model for the investigation of drug absorption and metabolism in human gastrointestinal tract.

SLC35B1 significantly contributes to the uptake of UDPGA into the endoplasmic reticulum for glucuronidation catalyzed by UDP-glucuronosyltransferases

The transport of UDP-glucuronic acid (UDPGA), a co-substrate of UDP-glucuronosyltransferase (UGT), to the intraluminal side of the endoplasmic reticulum (ER) is an essential step in the glucuronidation of exogenous and endogenous compounds. According to a previous study, the expression of recombinant SLC35B1, SLC35B4, or SLC35D1, nucleotide sugar transporters, in V79 cells has the potential to transport UDPGA into the lumen of microsomes. The purpose of this study is to examine whether the transport of UDPGA by these transporters substantially affects UGT activity. Since the knockdown of UDP-glucose 6-dehydrogenase, a synthetase of UDPGA, in HEK293 cells stably expressing UGT1A1 (HEK/UGT1A1 cells) resulted in a significant decrease in 4-methylumbelliferone (4-MU) glucuronosyltransferase activity, supplementation of a sufficient amount of UDPGA is required for UGT activity. By performing qRT-PCR using cDNA samples from 21 human liver samples, we observed levels of the SLC35B1 and SLC35D1 mRNAs that were 15- and 14-fold higher, respectively, than the levels of the SLC35B4 mRNA, and SLC35B1 showed the largest (37-fold) interindividual variability. Interestingly, 4-MU glucuronosyltransferase activity was significantly decreased upon the knockdown of SLC35B1 in HEK/UGT1A1 cells, and this phenomenon was also observed in HepaRG cells. Using siRNAs targeting 23 different SLC35 subfamilies, the knockdown of SLC35B1 and SLC35E3 decreased 4-MU glucuronosyltransferase activity in HEK/UGT1A1 cells. However, the 4-MU glucuronosyltransferase activity was not altered by SLC35E3 knockdown in HepaRG cells, suggesting that SLC35B1 was the main transporter of UDPGA into the ER in the human liver. In conclusion, SLC35B1 is a key modulator of UGT activity by transporting UDPGA to the intraluminal side of the ER.

Unveiling the Impact of Morphine on Tamoxifen Metabolism in Mice in vivo

Background: Tamoxifen is used to treat breast cancer and cancer recurrences. After administration, tamoxifen is converted into two more potent antitumor compounds, 4OH-tamoxifen and endoxifen by the CYP3A4/5 and 2D6 enzymes in human. These active compounds are inactivated by the same UDP-glucuronosyltransferase isoforms as those involved in the metabolism of morphine. Importantly, cancer-associated pain can be treated with morphine, and the common metabolic pathway of morphine and tamoxifen suggests potential clinically relevant interactions.

Methods: Mouse liver microsomes were used to determine the impact of morphine on 4OH-tamoxifen metabolism in vitro. For in vivo experiments, female mice were first injected with tamoxifen alone and then with tamoxifen and morphine. Blood was collected, and LC-MS/MS was used to quantify tamoxifen, 4OH-tamoxifen, N-desmethyltamoxifen, endoxifen, 4OH-tamoxifen-glucuronide, and endoxifen-glucuronide.

Results:In vitro, we found increased K_m values for the production of 4OH-tamoxifen-glucuronide in the presence of morphine, suggesting an inhibitory effect on 4OH-tamoxifen glucuronidation. Conversely, in vivo morphine treatment decreased 4OH-tamoxifen levels in the blood while dramatically increasing the formation of inactive metabolites 4OH-tamoxifen-glucuronide and endoxifen-glucuronide.

Conclusions: Our findings emphasize the need for caution when extrapolating results from in vitro metabolic assays to in vivo drug metabolism interactions. Importantly, morphine strongly impacts tamoxifen metabolism in mice. It suggests that tamoxifen efficiency could be reduced when both drugs are co-administered in a clinical setting, e.g., to relieve pain in breast cancer patients. Further studies are needed to assess the potential for tamoxifen-morphine metabolic interactions in humans.

Hetero-oligomer formation of mouse UDP-glucuronosyltransferase (UGT) 2b1 and 1a1 results in the gain of glucuronidation activity towards morphine, an activity which is absent in homo-oligomers of either UGT

UDP-Glucuronosyltransferase (UGT, Ugt) is a major drug metabolizing enzyme family involved in the glucuronidation and subsequent elimination of drugs and small lipophilic molecules. UGT forms homo- and hetero-oligomers that enhance or suppress UGT activity. In our previous study, we characterized mouse Ugt1a1 and all the Ugt isoform belonging to the Ugt2b subfamily and revealed that mouse Ugt2b1 and Ugt1a1 cannot metabolize morphine. Mouse Ugt2b1 had been believed to function similarly to rat UGT2B1, which plays a major role in morphine glucuronidation in rat liver. Thus, in this study, we hypothesized that hetero-oligomerization with another Ugt isoform may affect Ugt2b1 catalytic ability. We co-expressed Ugt1a1 and Ugt2b1 in a baculovirus-insect cell system, and confirmed hetero-oligomer formation by co-immunoprecipitation. As reported previously, microsomes singly expressing Ugt1a1 or Ugt2b1 were inactive towards the glucuronidation of morphine. Interestingly, in contrast, morphine-3-glucuronide, a major metabolite of morphine was formed, when Ugt2b1 and Ugt1a1 were co-expressed. This effect of hetero-oligomerization of Ugt1a1 and Ugt2b1 was also observed for 17β-estradiol glucuronidation. This is the first report demonstrating that UGT acquires a novel catalytic ability by forming oligomers. Protein-protein interaction of Ugts may contribute to robust detoxification of xenobiotics by altering the substrate diversity of the enzymes.

Kanechlor 500-mediated changes in serum and hepatic thyroxine levels primarily occur in a transthyretin-unrelated manner

The effects of Kanechlor-500 (KC500) on the levels of serum total thyroxine (T₄ ) and hepatic T₄ in wild-type C57BL/6 (WT) and its transthyretin (TTR)-deficient (TTR-null) mice were comparatively examined. Four days after a single intraperitoneal injection with KC500 (100 mg/kg body weight), serum total T₄ levels were significantly decreased in both WT and TTR-null mice. The KC500 pretreatment also promoted serum [¹²⁵ I]T₄ clearance in both strains of mice administrated with [¹²⁵ I]T₄ , and the promotion of serum [¹²⁵ I]T₄ clearance in WT mice occurred without inhibition of the [¹²⁵ I]T₄ -TTR complex formation. Furthermore, the KC500 pretreatment led to significant increases in liver weight, steady-state distribution volume of [¹²⁵ I]T₄ , hepatic accumulation level of [¹²⁵ I]T₄ , and concentration ratio of the liver to serum in both strains of mice. The present findings indicate that the KC500-mediated decrease in serum T₄ level occurs in a TTR-unrelated manner and further suggest that KC500-promoted T₄ accumulation in the liver occurs through the development of liver hypertrophy and the promotion of T₄ transportation from serum to liver.

Characterization of UDP-Glucuronosyltransferases and the Potential Contribution to Nicotine Tolerance in Myzus persicae

Uridine diphosphate (UDP)-glycosyltransferases (UGTs) are major phase II detoxification enzymes involved in glycosylation of lipophilic endobiotics and xenobiotics, including phytoalexins. Nicotine, one of the most abundant secondary plant metabolites in tobacco, is highly toxic to herbivorous insects. Plant-herbivore competition is the major impetus for the evolution of large superfamilies of UGTs and other detoxification enzymes. However, UGT functions in green peach aphid (Myzus persicae) adaptation are unknown. In this study, we show that UGT inhibitors (sulfinpyrazone and 5-nitrouracil) significantly increased nicotine toxicity in M. persicae nicotianae, suggesting that UGTs may be involved in nicotine tolerance. In total, 101 UGT transcripts identified in the M. persicae genome/transcriptome were renamed according to the UGT Nomenclature Committee guidelines and grouped into 11 families, UGT329, UGT330, UGT339, UGT341-UGT345, and UGT348-UGT350, with UGT344 containing the most (57). Ten UGTs (UGT330A3, UGT339A2, UGT341A6, UGT342B3, UGT343C3, UGT344D5, UGT344D8, UGT348A3, UGT349A3, and UGT350A3) were highly expressed in M. persicae nicotianae compared to M. persicae sensu stricto. Knockdown of four UGTs (UGT330A3, UGT344D5, UGT348A3, and UGT349A3) significantly increased M. persicae nicotianae sensitivity to nicotine, suggesting that UGT expression in this subspecies may be associated with nicotine tolerance and thus host adaptation. This study reveals possible UGTs relevant to nicotine adaptation in tobacco-consuming M. persicae nicotianae, and the findings will facilitate further validation of the roles of these UGTs in nicotine tolerance.

Identification of Catalposide Metabolites in Human Liver and Intestinal Preparations and Characterization of the Relevant Sulfotransferase, UDP-glucuronosyltransferase, and Carboxylesterase Enzymes

Catalposide, an active component of Veronica species such as Catalpa ovata and Pseudolysimachion lingifolium, exhibits anti-inflammatory, antinociceptic, anti-oxidant, hepatoprotective, and cytostatic activities. We characterized the in vitro metabolic pathways of catalposide to predict its pharmacokinetics. Catalposide was metabolized to catalposide sulfate (M1), 4-hydroxybenzoic acid (M2), 4-hydroxybenzoic acid glucuronide (M3), and catalposide glucuronide (M4) by human hepatocytes, liver S9 fractions, and intestinal microsomes. M1 formation from catalposide was catalyzed by sulfotransferases (SULTs) 1C4, SULT1A1*1, SULT1A1*2, and SULT1E1. Catalposide glucuronidation to M4 was catalyzed by gastrointestine-specific UDP-glucuronosyltransferases (UGTs) 1A8 and UGT1A10; M4 was not detected after incubation of catalposide with human liver preparations. Hydrolysis of catalposide to M2 was catalyzed by carboxylesterases (CESs) 1 and 2, and M2 was further metabolized to M3 by UGT1A6 and UGT1A9 enzymes. Catalposide was also metabolized in extrahepatic tissues; genetic polymorphisms of the carboxylesterase (CES), UDP-glucuronosyltransferase (UGT), and sulfotransferase (SULT) enzymes responsible for catalposide metabolism may cause inter-individual variability in terms of catalposide pharmacokinetics.

Comparative review of drug-drug interactions with epidermal growth factor receptor tyrosine kinase inhibitors for the treatment of non-small-cell lung cancer

The development of small-molecule tyrosine kinase inhibitors (TKIs) that target the epidermal growth factor receptor (EGFR) has revolutionized the management of non-small-cell lung cancer (NSCLC). Because these drugs are commonly used in combination with other types of medication, the risk of clinically significant drug–drug interactions (DDIs) is an important consideration, especially for patients using multiple drugs for coexisting medical conditions. Clinicians need to be aware of the potential for clinically important DDIs when considering therapeutic options for individual patients. In this article, we describe the main mechanisms underlying DDIs with the EGFR-TKIs that are currently approved for the treatment of NSCLC, and, specifically, the potential for interactions mediated via effects on gastrointestinal pH, cytochrome P450-dependent metabolism, uridine diphosphate-glucuronosyltransferase, and transporter proteins. We review evidence of such DDIs with the currently approved EGFR-TKIs (gefitinib, erlotinib, afatinib, osimertinib, and icotinib) and discuss several information sources that are available online to aid clinical decision-making. We conclude by summarizing the most clinically relevant DDIs with these EFGR-TKIs and provide recommendations for managing, minimizing, or avoiding DDIs with the different agents.

Interethnic Variations of UGT1A1 and UGT1A7 Polymorphisms in the Jordanian Population

BACKGROUND

Glucuronidation is one of the most important phase II metabolic pathways. It is catalyzed by a family of UDP-glucuronosyltransferase enzymes (UGTs). UGT1A1 and UGT1A7 catalyze the glucuronidation of a diverse range of medications, environmental chemicals and endogenous compounds. Polymorphisms in the UGT1A gene could potentially be significant for the pharmacological, toxicological and physiological effects of the enzymes.

OBJECTIVE

The UGT1A gene is polymorphic among ethnic groups and the aim of this study was to investigate the different UGT1A1 and UGT1A7 polymorphisms in Circassians, Chechens and Jordanian-Arabs.

METHODS

A total of 168 healthy Jordanian-Arabs, 56 Circassians and 54 Chechens were included in this study. Genotyping of 20 different Single-nucleotide polymorphism (SNPs) was done by using polymerase chain reaction- DNA sequencing.

RESULTS

We found that Circassians and Chechens have significantly higher allele frequencies of UGT1A7*2, UGT1A7*3 and UGT1A7*4 than the Jordanian-Arab population, but all three populations have similar frequencies of UGT1A1*28. Therefore, Circassians and Chechens are expected to have significantly lower levels of the UGT1A7 enzyme with almost 90% of these populations having genes that encode low or intermediate enzyme activity.

CONCLUSION

This inter-ethnic variation in the UGT1A alleles frequencies may affect drug response and susceptibility to cancers among different subethnic groups in Jordan. Our results can also provide useful information for the Jordanian population and for future genotyping of Circassian and Chechen populations in general.

Allometric scaling of hepatic biotransformation in rainbow trout

Biotransformation may substantially impact the toxicity and accumulation of xenobiotic chemicals in fish. However, this activity can vary substantially within and among species. In this study, liver S9 fractions from rainbow trout (4-400 g) were used to evaluate relationships between fish body mass and the activities of phase I and phase II metabolic enzymes. An analysis of log-transformed data, expressed per gram of liver (g liver-1), showed that total cytochrome P450 (CYP) concentration, UDP-glucuronosyltransferase (UGT) activity, and glutathione S-transferase (GST) activity exhibited small but significant inverse relationships with fish body weight. In contrast, in vitro intrinsic clearance rates (CLIN VITRO,INT) for three polycyclic aromatic hydrocarbons (PAHs) increased with increasing body weight. Weight normalized liver mass also decreased inversely with body weight, suggesting a need to express hepatic metabolism data per gram of body weight (g BW-1) in order to reflect the metabolic capabilities of the whole animal. When the data were recalculated in this manner, negative allometric relationships for CYP concentration, UGT activity, and GST activity became more pronounced, while CLIN VITRO,INT rates for the three PAHs showed no significant differences across fish sizes. Ethoxyresorufin O-deethylase (EROD) activity normalized to tissue weight (g liver-1) or body weight (g BW-1) exhibited a non-monotonic pattern with respect to body weight. The results of this study may have important implications for chemical modeling efforts with fish.

Effects of Herbal Formulas Bojungikgi-tang and Palmijihwang-hwan on Inflammation in RAW 264.7 Cells and the Activities of Drug-Metabolizing Enzymes in Human Hepatic Microsomes

In the present study, Bojungikgi-tang (BJIKT: Buzhongyiqi-tang, Hochuekki-to) and Palmijihwang-hwan (PMJHH: Baweidìhuang-wan, Hachimijio-gan), traditional herbal formulas, investigated anti-inflammatory efficacies in murine macrophage cell line and the influence on the activities of drug-metabolizing enzymes (DMEs). The anti-inflammatory potentials of the herbal formulas were evaluated to inhibit the production of the inflammatory mediators and cytokines and the protein expression of inducible nitric oxide and cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-treated RAW 264.7 cells. The activities of the major human DMEs, cytochrome P450 isozymes (CYP450s) and UDP-glucuronosyltransferase isozymes (UGTs), were measured by in vitro enzyme assay systems. BJIKT and PMJHH significantly suppressed the prostaglandin E₂ (PGE₂) production (IC₅₀ = 317.3 and 282.2 μg/mL, respectively) and the protein expression of COX-2 in LPS-treated RAW264.7 cells. On the human microsomal DMEs, BJIKT inhibited the activities of CYP1A2 (IC₅₀ = 535.05 μg/mL), CYP2B6 (IC₅₀ > 1000 μg/mL), CYP2C9 (IC₅₀ = 800.78 μg/mL), CYP2C19 (IC₅₀ = 563.11 μg/mL), CYP2D6 (IC₅₀ > 1000 μg/mL), CYP2E1 (IC₅₀ > 1000 μg/mL), CYP3A4 (IC₅₀ = 879.60 μg/mL), UGT1A1 (IC₅₀ > 1000 μg/mL), and UGT1A4 (IC₅₀ > 1000 μg/mL), but it showed no inhibition of the UGT2B7 activity at doses less than 1000 μg/mL. PMJHH inhibited the CYP2D6 activity (IC₅₀ = 280.89 μg/mL), but IC₅₀ values of PMJHH exceeded 1000 μg/mL on the activities of CYP1A2, CYP2C19, CYP2E1, and CYP3A4. At concentrations less than 1000 μg/mL, PMJHH did not affect the activities of CYP2B6, CYP2C9, UGT1A1, UGT1A4, and UGT2B7. The results indicate that both BJIKT and PMJHH may be potential candidates to prevent and treat PGE₂- and COX-2-mediated inflammatory diseases. In addition, this study will expand current knowledge about herb-drug interactions by BJIKT and PMJHH.

Association of nephrotoxicity during platinum-etoposide doublet therapy with UGT1A1 polymorphisms in small cell lung cancer patients

OBJECTIVES

Etoposide is a key agent in the treatment of small cell lung cancer (SCLC). Uridine diphosphate (UDP)-glucuronosyltransferase 1A1 (UGT1A1) is thought to be largely responsible for the glucuronidation of etoposide as well as that of irinotecan, suggesting that polymorphisms of UGT1A1 might be predictive of etoposide toxicity. We therefore examined the relation between UGT1A1 polymorphisms and toxicity profile during platinum-etoposide doublet therapy in SCLC patients.

MATERIALS AND METHODS

SCLC patients who underwent platinum-etoposide doublet therapy and molecular testing for UGT1A1 genotype were reviewed for the occurrence of adverse events during treatment.

RESULTS

A total of 41 SCLC patients received platinum-etoposide doublet therapy and were genotyped for UGT1A1*6 and UGT1A1*28 alleles. These alleles were detected in 15 (36.6%) patients, with the genotypes of *6/-, *6/*6, *28/-, *28/*28, or *6/*28 being observed in 9 (22.0%), 2 (4.9%), 2 (4.9%), 1 (2.4%), and 1 (2.4%) patients, respectively. The presence of these alleles was significantly associated with an increase in serum creatinine concentration of grade ≥2 (incidence of 66.7% for patients with the alleles versus 11.5% for those without, P <  0.001). Multivariate analysis also showed that these UGT1A1 alleles were significantly associated with therapy-induced nephrotoxicity (odds ratio of 19.30, 95% confidence interval of 2.50-149.00, P <  0.005). Although the differences did not achieve statistical significance, the incidence of other severe toxicities including febrile neutropenia was also slightly higher in patients with the UGT1A1*6 or UGT1A1*28 alleles than in those without them.

CONCLUSION

Our results reveal an association between UGT1A1 polymorphisms and toxicity of platinum-etoposide doublet therapy in SCLC patients, suggesting that close monitoring for toxicity, especially nephrotoxicity, is warranted for patients with such variant alleles receiving this treatment.

In Silico Prediction of Major Clearance Pathways of Drugs among 9 Routes with Two-Step Support Vector Machines

PURPOSE

The clearance pathways of drugs are critical elements for understanding the pharmacokinetics of drugs. We previously developed in silico systems to predict the five clearance pathway using a rectangular method and a support vector machine (SVM). In this study, we improved our classification system by increasing the number of clearance pathways available for our prediction (CYP1A2, CYP2C8, CYP2C19, and UDP-glucuronosyl transferases (UGTs)) and by accepting multiple major pathways.

METHODS

Using the four default descriptors (charge, molecular weight, logD at pH 7.0, and unbound fraction in plasma), three kinds of SVM-based predictors based on traditional single-step approach or two-step focusing approaches with subset or partition clustering were developed. The two-step approach with subset clustering resulted in the highest prediction performance. The feature-selection of additional descriptors based on a greedy algorithm was employed to further improve the predictability.

RESULTS

The prediction accuracy for each pathway was increased to more than 0.83 with the exception of CYP2C19 and UGTs pathways, whose accuracies were below 0.7. Prediction performance of CYP1A2, CYP3A4 and renal excretion pathways were found to be acceptable using external dataset.

CONCLUSIONS

We successfully constructed a novel SVM-based predictor for the multiple major clearance pathways based on chemical structures.

Safety assessment of Oryeong-san, a traditional herbal formula: Study of subacute toxicity and influence of cytochrome P450s and UDP-glucuronosyltransferases

Oryeong-san is a traditional herbal formula that is used for the treatment of common genitourinary diseases in Korea and other Asian countries. However, little is known about its safety and influence on drug metabolism. In the present study, we investigated the subacute toxicity of an Oryeong-san water extract (OSWE) in rats and its effects on activities of drug-metabolizing enzymes. Subacute toxicity was modeled in animals exposed to treatment with the extract at multiple doses. Rats were given OSWE by oral gavage at 0, 1000, 2000 and 5000 mg/kg/day for 4 weeks. We checked general observations and investigated any changes of body/organ weight, food consumption, hematology, serum biochemistry, and urinalysis in vivo; and the activities of human microsomal cytochrome P450s (CYP450s) and UDP-glucuronosyltransferase (UGT) isozymes in vitro. We found that OSWE caused no significant toxicological changes at the doses tested. Therefore, the no observed adverse effect level of OSWE was more than 5000 mg/kg/day for male and female rats. OSWE inhibited the activities of CYP2C19 (IC₅₀: 737.69 μg/mL) and CYP2E1 (IC₅₀: 177.77 μg/mL). These results indicate that OSWE may be safe with no drug-related toxicity for up to 4 weeks and provide useful information concerning its potential to interact with conventional drugs or other herbal medicines.

In vitrometabolic mapping of neobavaisoflavone in human cytochromes P450 and UDP-glucuronosyltransferase enzymes by ultra high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry

Neobavaisoflavone (NBIF), a phenolic compound isolated from Psoralea corylifolia L., possesses several significant biological properties. However, the pharmacokinetic behaviors of NBIF have been characterized as rapid oral absorption, high clearance, and poor oral bioavailability. We found that NBIF underwent massive glucuronidation and oxidation by human liver microsomes (HLM) in this study with the intrinsic clearance (CL_int) values of 12.43, 10.04, 2.01, and 6.99 μL/min/mg for M2, M3, M4, and M5, respectively. Additionally, the CL_int values of G1 and G2 by HLM were 271.90 and 651.38 μL/min/mg, respectively, whereas their respective parameters were 59.96 and 949.01 μL/min/mg by human intestine microsomes (HIM). Reaction phenotyping results indicated that CYP1A1, 1A2, 2C8, and 2C19 were the main contributors to M4 (34.96 μL/min/mg), M3 (29.45 μL/min/mg), M3 (13.16 μL/min/mg), and M2 (63.42 μL/min/mg), respectively. UGT1A1, 1A7, 1A8, and 1A9 mainly catalyzed the formation of G1 (250.87 μL/min/mg), G2 (438.15 μL/min/mg), G1 (92.68 μL/min/mg), and G2 (1073.25 μL/min/mg), respectively. Activity correlation analysis assays showed that phenacetin-N-deacetylation was strongly correlated to M3 (r = 0.860, p = 0.003) and M4 (r = 0.775, p = 0.014) in nine individual HLMs, while significant activity correlations were detected between paclitaxel-6-hydroxylation and M2 (r = 0.675, p = 0.046) and M3 (r = 0.829, p = 0.006). There was a strong correlation between β-estradiol-3-O-glucuronide and G1 (r = 0.822, p = 0.007) and G2 (r = 0.689, p = 0.040), as well as between propofol-O-glucuronidation and G1 (r = 0.768, p = 0.016) and G2 (r = 0.860, p = 0.003). Moreover, the phase I metabolism and glucuronidation of NBIF revealed marked species differences, and mice are the best animal model for investigating the metabolism of NBIF in humans. Taken together, characterization of NBIF-related metabolic pathways involving in CYP1A1, 1A2, 2C8, 2C19, and UGT1A1, 1A7, 1A8, 1A9 are helpful for understanding the pharmacokinetic behaviors and conducting in-depth pharmacological studies.

In Vitro Inhibitory Effects of Synthetic Cannabinoid EAM-2201 on Cytochrome P450 and UDP-Glucuronosyltransferase Enzyme Activities in Human Liver Microsomes

EAM-2201, a synthetic cannabinoid, is a potent agonist of the cannabinoid receptors that is widely abused as an illicit recreational drug in combination with other drugs. To evaluate the potential of EAM-2201 as a perpetrator of drug–drug interactions, the inhibitory effects of EAM-2201 on major drug-metabolizing enzymes, cytochrome P450s (CYPs) and uridine 5′-diphospho-glucuronosyltransferases (UGTs) were evaluated in pooled human liver microsomes using liquid chromatography–tandem mass spectrometry (LC-MS/MS). EAM-2201 at doses up to 50 µM negligibly inhibited the activities of eight major human CYPs (1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4) and five UGTs (1A1, 1A4, 1A6, 1A9 and 2B7) in human liver microsomes. EAM-2201 exhibited time-dependent inhibition of CYP2C8-catalyzed amodiaquine N-deethylation, CYP2C9-catalyzed diclofenac 4′-hydroxylation, CYP2C19-catalyzed [S]-mephenytoin 4′-hydroxylation and CYP3A4-catalyzed midazolam 1′-hydroxylation with K_i values of 0.54 µM (k_inact: 0.0633 min⁻¹), 3.0 µM (k_inact: 0.0462 min⁻¹), 3.8 µM (k_inact: 0.0264 min⁻¹) and 4.1 µM (k_inact: 0.0250 min⁻¹), respectively and competitively inhibited UGT1A3-catalyzed chenodeoxycholic acid 24-acyl-glucuronidation, with a K_i value of 2.4 µM. Based on these in vitro results, we conclude that EAM-2201 has the potential to trigger in vivo pharmacokinetic drug interactions when co-administered with substrates of CYP2C8, CYP2C9, CYP2C19, CYP3A4 and UGT1A3.