Drug Metabolism and Disposition最新文献

Pirfenidone (PIR) is used to treatment of idiopathic pulmonary fibrosis. After oral administration, it is metabolized by cytochrome P450 1A2 to 5-hydroxylpirfenidone (5-OH PIR) and further oxidized to 5-carboxylpirfenidone (5-COOH PIR), a major metabolite excreted in the urine (90% of the dose). This study aimed to identify enzymes that catalyze the formation of 5-COOH PIR from 5-OH PIR in the human liver. 5-COOH PIR was formed from 5-OH PIR in the presence of NAD⁺ by human liver microsomes (HLM) more than by human liver cytosol (HLC), with the concomitant formation of the aldehyde form (5-CHO PIR) as an intermediate metabolite. By purifying enzymes from HLM, alcohol dehydrogenases (ADHs) were identified as candidate enzymes catalyzing 5-CHO PIR formation, although ADHs are localized in the cytoplasm. Among constructed recombinant ADH1-5 expressed in HEK293T cells, only ADH4 efficiently catalyzed 5-CHO PIR formation from 5-OH PIR with a K _m value (29.0 {plus minus} 4.9 µM), which was close to that by HLM (59.1 {plus minus} 4.6 µM). In contrast to commercially available HLC, in-house prepared HLC clearly showed substantial 5-CHO PIR formation, and ADH4 protein levels were significantly (rs = 0.772, P < 0.0001) correlated with 5-CHO PIR formation in 25 in-house prepared HLC samples. Some components of the commercially available HLC may inhibit ADH4 activity. Disulfiram, an inhibitor of aldehyde dehydrogenases (ALDH), decreased 5-COOH PIR formation and increased 5-CHO PIR formation from 5-OH PIR in HLM. ALDH2 knockdown in HepG2 cells by siRNA decreased 5-COOH PIR formation by 61%. Significance Statement This study clarified that 5-COOH PIR formation from 5-OH PIR proceeds via a two-step oxidation reaction catalyzed by ADH4 and disulfiram-sensitive enzymes, including ALDH2. Inter-individual differences in the expression levels or functions of these enzymes could cause variations in the pharmacokinetics of PIR.

Tanimilast is an inhaled phosphodiesterase-4 inhibitor currently in phase 3 clinical development for treating chronic obstructive pulmonary disease (COPD) and asthma. This trial aimed to characterize the pharmacokinetics, mass balance, and metabolite profiling of tanimilast. Eight healthy male volunteers received a single dose of non-radiolabeled tanimilast via powder inhaler (NEXThaler^® (3200μg)), followed by a concomitant intravenous (IV) infusion of a microtracer ([¹⁴C]-tanimilast: 18.5μg and 500nCi). Plasma, whole blood, urine, and feces samples were collected up to 240 hours post-dose to quantify non-radiolabeled tanimilast, [¹⁴C]-tanimilast, and total-[¹⁴C]. The inhaled absolute bioavailability of tanimilast was found to be approximately 50%. Following IV administration of [¹⁴C]-tanimilast, plasma clearance was 22 L/h, the steady-state volume of distribution was 201 L, and the half-life was shorter compared to inhaled administration (14 vs. 39 hours, respectively), suggesting that plasma elimination is limited by the absorption rate from the lungs. 79% (71% in feces; 8% in urine) of the IV dose was recovered in excreta as total-[¹⁴C]. [¹⁴C]-tanimilast was the major radioactive compound in plasma, while no recovery was observed in urine and only 0.3% was recovered in feces, indicating predominant elimination through metabolic route. Importantly, as far as no metabolites accounting for more than 10% of the circulating drug-related exposure in plasma or the administered dose in excreta were detected, no further qualification is required according to regulatory guidelines. This study design successfully characterized the absorption, distribution, and elimination of tanimilast, providing key pharmacokinetic parameters to support its clinical development and regulatory application. Significance Statement This trial investigates PK and ADME profile of tanimilast, an inhaled PDE4 inhibitor for COPD and asthma. Eight male volunteers received a dose of non-radiolabeled tanimilast via NEXThaler^® and a microtracer IV dose. Results show pivotal PK results for the characterization of tanimilast, excretion route and quantification of significant metabolites, facilitating streamlined clinical development and regulatory approval.

The placenta acts as a barrier, excluding noxious substances whilst actively transferring nutrients to the fetus, mediated by various transporters. This study quantified the expression of key placental transporters in term human placenta (n=5) and BeWo, BeWo b30, and JEG-3 placenta cell lines. Combining these results with pregnancy physiologically-based pharmacokinetic (PBPK) modeling, we demonstrate the utility of proteomic analysis for predicting placental drug disposition and fetal exposure. Using targeted proteomics with QconCAT standards, we found significant expression of P-gp, BCRP, MRP2, MRP4, and MRP6 in the human placenta (0.05 - 0.25 pmol/mg membrane protein) with only regional differences observed for P-gp. Unexpectedly, both P-gp and BCRP were below the limit of quantification in the regularly used BeWo cells, indicating that this cell line may not be suitable for the study of placental P-gp and BCRP-mediated transport. In cellular and vesicular overexpression systems, P-gp and BCRP were detectable as expected. Vesicle batches showed consistent P-gp expression correlating with functional activity (N-methyl-quinidine (NMQ) transport). However, BCRP activity (Estrone 3-sulfate (E1S) transport) did not consistently align with expression levels. Incorporating in vitro transporter kinetic data, along with placental transporter abundance, into a PBPK model enabled the evaluation of fetal exposure. Simulation with a hypothetical drug indicated that estimating fetal exposure relies on the intrinsic clearances of relevant transporters. To minimize interlaboratory discrepancies, expression data was generated using consistent proteomic methodologies in the same lab. Integration of this data in pregnancy-PBPK modeling offers a promising tool to investigate maternal, placental and fetal drug exposure. Significance Statement This study quantified the expression of key transporters in human placenta and various placental cell lines, revealing significant expression variations. By integrating these data with PBPK modeling, the study highlights the importance of transporter abundance data in understanding and predicting placental drug disposition.

Many factors cause inter-person variability in the activity and expression of liver cytochrome P450 (CYP) drug-metabolizing enzymes, leading to variable drug exposure and treatment outcomes. Several liver-enriched transcription factors (TFs) are associated with CYP expression, with estrogen receptor alpha (ESR1) and constitutive androstane receptor (CAR or NR1I3) being the two top factors. ESR1 and NR1I3 undergo extensive alternative splicing that results in numerous splice isoforms, but how these splice isoforms associate with CYP expression is unknown. Here, we quantified 18 NR1I3 splice isoforms and the three most abundant ESR1 isoforms in 260 liver samples derived from African Americans (AA, n=125) and European Americans (EA, n=135). Our results showed variable splice isoform populations in the liver for both NR1I3 and ESR1. Multiple linear regression analyses revealed that, compared to gene-level NR1I3, isoform-level NR1I3 expression better predicted the mRNA expression of most CYPs and three UDP-glucuronosyltransferases (UGTs), while ESR1 isoforms improved predictive models for the UGTs and CYP2D6, but not for most CYPs. Also, different NR1I3 isoforms were associated with different CYPs, and the associations varied depending on sample ancestry. Surprisingly, non-canonical NR1I3 isoforms having retained introns (introns 2 or 6) were abundantly expressed and associated with the expression of most CYPs and UGTs, whereas the reference isoform (NR1I3-205) only associated with CYP2D6. Moreover, NR1I3 isoform diversity increased during the differentiation of induced pluripotent stem cells to hepatocytes, paralleling increasing CYP expression. These results suggest that isoform-level TF expression may help to explain variation in CYP or UGT expression between individuals. Significance Statement We quantified 18 NR1I3 splice isoforms and three ESR1 splice isoforms in 260 liver samples derived from AA and EA donors and found variable NR1I3 and ESR1 splice isoform expression in the liver. Multiple linear regression analysis showed that, compared to gene-level expression, isoform-level expression of NR1I3 and ESR1 better predicted the mRNA expression of some CYPs and UGTs, highlighting the importance of isoform-level analyses to enhance our understanding of gene transcriptional regulatory networks controlling the expression of drug-metabolizing enzymes.

Environmentally persistent free radicals (EPFRs) are a recently recognized component of particulate matter that cause respiratory and cardiovascular toxicity. The mechanism of EPFR toxicity appears to be related to their ability to generate reactive oxygen species (ROS), causing oxidative damage. EPFRs were shown to affect P450 function, inducing the expression of some forms through the Ah receptor. However, another characteristic of EPFRs lies in their ability to inhibit P450 activities. CYP2E1 is one of the P450s that is inhibited by EPFR (MCP230) exposure. As CYP2E1 is also known to generate ROS, it is important to understand the ability of EPFRs to influence the function of this enzyme and to identify the mechanisms involved. CYP2E1 was shown to be inhibited by EPFRs, and to a lesser extent by non-EPFR particles. As EPFR-mediated inhibition was more robust at subsaturating NADPH-cytochrome P450 reductase (POR) concentrations, disruption of POR·CYP2E1 complex formation and electron transfer were examined. Surprisingly, neither complex formation nor electron transfer between POR and CYP2E1 were inhibited by EPFRs. Examination of ROS production showed that MCP230 generated a greater amount of ROS than the non-EPFR CuO-Si. When a POR/CYP2E1-containing reconstituted system was added to the pollutant-particle systems there was a synergistic stimulation of ROS production. The results indicate that EPFRs cause inhibition of CYP2E1-mediated substrate metabolism, yet do not alter electron transfer and actually stimulate ROS generation. Taken together, the results are consistent with EPFRs affecting CYP2E1 function by inhibiting substrate metabolism and increasing the generation of ROS. Significance Statement Environmentally persistent free radicals affect CYP2E1 function by inhibition of monooxygenase activity. This inhibition is not due to disruption of the POR·CYP2E1 complex or inhibition of electron transfer, but due to uncoupling of NADPH and oxygen consumption from substrate metabolism to the generation of ROS. These results show that EPFRs block the metabolism of foreign compounds, and also synergistically stimulate the formation of reactive oxygen species that lead to oxidative damage within the organism.

Silybin, extracted milk thistle, was a flavonolignan compound with hepatoprotective effect. Now it is commonly used in dietary supplements, functional foods, and nutraceuticals. However, the metabolism of silybin has not been systematically characterized in organisms to date. Therefore, we established a novel HPLC-Q-TOF/MS method to analyze and identify the prototype and metabolites of silybin in rats. Totally, 29 (out of 32) new metabolic pathways and 56 (out of 59) unreported metabolite products were detected. Moreover, we found that the liver had a high first-pass effect of 63.30%{plus minus}13.01 for silybin and only one metabolite was detected. And the metabolites identified in gastrointestinal tract possessed 88% of all (52 out of 59). At the same time, the high concentration of silybin in the livers also indicated large amounts of silybin may be accumulated in liver instead of being metabolized. These results indicated the primary metabolizing organ of silybin in rats was intestine rather than liver, which would also offer solid chemical foundation for exploring more promising health care products of silybin. Significance Statement This study confirmed the main metabolism place of silybin in rats were gastrointestinal tracts instead of livers and the intestinal microbes were closely involved. Then 29 (out of 32) metabolism pathways and 56 (out of 59) metabolites were identified for the first time in rats. And to further study the liver disposition of silybin, its hepatic first-pass effect was determined for the first time.

Early detection of drug-drug interactions (DDIs) can facilitate timely drug development decisions, prevent unnecessary restrictions on patient enrollment, resulting in clinical study populations that are not representative of the indicated study population, and allow for appropriate dose adjustments to ensure safety in clinical trials. All of these factors contribute to a streamlined drug approval process and enhanced patient safety. Here we describe a new approach for early prediction of the magnitude of change in exposure for cytochrome P450 (P450) CYP3A4-related DDIs of small-molecule anticancer drugs based on the model-based extrapolation of human-CYP3A4-transgenic mice pharmacokinetics to humans. Victim drugs brigatinib and lorlatinib were evaluated with the new approach in combination with the perpetrator drugs itraconazole and rifampicin. Predictions of the magnitude of change in exposure deviated at most 0.99- to 1.31-fold from clinical trial results for inhibition with itraconazole, whereas exposure predictions for the induction with rifampicin were less accurate, with deviations of 0.22- to 0.48-fold. Results for the early prediction of DDIs and their clinical impact appear promising for CYP3A4 inhibition, but validation with more victim and perpetrator drugs is essential to evaluate the performance of the new method. SIGNIFICANCE STATEMENT: The described method offers an alternative for the early detection and assessment of potential clinical impact of CYP3A4-related drug-drug interactions. The model was able to adequately describe the inhibition of CYP3A4 metabolism and the subsequent magnitude of change in exposure. However, it was unable to accurately predict the magnitude of change in exposure of victim drugs in combination with an inducer.

ATP-binding cassette transporter subfamily G member 2 (ABCG2) is a membrane-bound transporter responsible for the efflux of various xenobiotics and endobiotics, including protoporphyrin IX (PPIX), an intermediate in the heme biosynthesis pathway. Certain genetic mutations and chemicals impair the conversion of PPIX to heme and/or increase PPIX production, leading to PPIX accumulation and toxicity. In mice, deficiency of ABCG2 protects against PPIX-mediated phototoxicity and hepatotoxicity by modulating PPIX distribution. In addition, in vitro studies revealed that ABCG2 inhibition increases the efficacy of PPIX-based photodynamic therapy by retaining PPIX inside target cells. In this review, we discuss the roles of ABCG2 in modulating the tissue distribution of PPIX, PPIX-mediated toxicity, and PPIX-based photodynamic therapy. SIGNIFICANCE STATEMENT: This review summarized the roles of ABCG2 in modulating PPIX distribution and highlighted the therapeutic potential of ABCG2 inhibitors for the management of PPIX-mediated toxicity.

The precision medicine initiative has driven a substantial change in the way scientists and health care practitioners think about diagnosing and treating disease. While it has long been recognized that drug response is determined by the intersection of genetic, environmental, and disease factors, improvements in technology have afforded precision medicine guided dosing of drugs to improve efficacy and reduce toxicity. Pharmacometabolomics aims to evaluate small molecule metabolites in plasma and/or urine to help evaluate mechanisms that predict and/or reflect drug efficacy and toxicity. In this mini review, we provide an overview of pharmacometabolomic approaches and methodologies. Relevant examples where metabolomic techniques have been used to better understand drug efficacy and toxicity in major depressive disorder and cancer chemotherapy are discussed. In addition, the utility of metabolomics in drug development and understanding drug metabolism, transport, and pharmacokinetics is reviewed. Pharmacometabolomic approaches can help describe factors mediating drug disposition, efficacy, and toxicity. While important advancements in this area have been made, there remain several challenges that must be overcome before this approach can be fully implemented into clinical drug therapy. SIGNIFICANCE STATEMENT: Pharmacometabolomics has emerged as an approach to identify metabolites that allow for implementation of precision medicine approaches to pharmacotherapy. This review article provides an overview of pharmacometabolomics including highlights of important examples.

Pregnane X receptor (PXR) belongs to the nuclear receptor superfamily that plays a crucial role in hepatic physiologic and pathologic conditions. Phase separation is a process in which biomacromolecules aggregate and condense into a dense phase as liquid condensates and coexist with a dilute phase, contributing to various cellular and biologic functions. Until now, whether PXR could undergo phase separation remains unclear. This study aimed to investigate whether PXR undergoes phase separation. Analysis of the intrinsically disordered regions (IDRs) using algorithm tools indicated a low propensity of PXR to undergo phase separation. Experimental assays such as hyperosmotic stress, agonist treatment, and optoDroplets assay demonstrated the absence of phase separation for PXR. OptoDroplets assay revealed the inability of the fusion protein of Cry2 with PXR to form condensates upon blue light stimulation. Moreover, phase separation of PXR did not occur even though the mRNA and protein expression levels of PXR target, cytochrome P450 3A4, changed after sorbitol treatment. In conclusion, for the first time, these findings suggested that exogenous PXR does not undergo phase separation following activation or under hyperosmotic stress in nucleus of cells. SIGNIFICANCE STATEMENT: PXR plays a critical role in hepatic physiological and pathological processes. The present study clearly demonstrated that exogenous PXR does not undergo phase separation after activation by agonist or under hyperosmotic stress in nucleus. These findings may help understand PXR biology.