Characterization of Enzymes Involved in Nintedanib Metabolism in Humans.

Nintedanib, which is used to treat idiopathic pulmonary fibrosis and non-small cell lung cancer, is metabolized to a pharmacologically inactive carboxylate derivative, BIBF1202, via hydrolysis and subsequently by glucuronidation to BIBF1202 acyl-glucuronide (BIBF1202-G). Since BIBF1202-G contains an ester bond, it can be hydrolytically cleaved to BIBF1202. In this study, we sought to characterize these metabolic reactions in the human liver and intestine. Nintedanib hydrolysis was detected in human liver microsomes (HLMs) (Clearance [CL int]: 102.8 ± 18.9 µL/min per mg protein) but not in small intestinal preparations. CES1 was suggested to be responsible for nintedanib hydrolysis according to experiments using recombinant hydrolases and hydrolase inhibitors as well as proteomic correlation analysis using 25 individual HLM. BIBF1202 glucuronidation in HLM (3.6 ± 0.3 µL/min per mg protein) was higher than that in human intestinal microsomes (1.5 ± 0.06 µL/min per mg protein). UGT1A1 and gastrointestinal UGT1A7, UGT1A8, and UGT1A10 were able to mediate BIBF1202 glucuronidation. The impact of UGT1A1 on glucuronidation was supported by the finding that liver microsomes from subjects homozygous for the UGT1A1*28 allele showed significantly lower activity than those from subjects carrying the wild-type UGT1A1 allele. Interestingly, BIBF1202-G was converted to BIBF1202 in HLS9 at 70-fold higher rates than the rates of BIBF1202 glucuronidation. An inhibition study and proteomic correlation analysis suggested that ß-glucuronidase is responsible for hepatic BIBF1202-G deglucuronidation. In conclusion, the major metabolic reactions of nintedanib in the human liver and intestine were quantitatively and thoroughly elucidated. This information could be helpful to understand the inter- and intraindividual variability in the efficacy of nintedanib. SIGNIFICANCE STATEMENT: To our knowledge, this is the first study to characterize the enzymes responsible for each step of nintedanib metabolism in the human body. This study found that ß-glucuronidase may contribute to BIBF1202-G deglucuronidation.

Hepatic differentiation of human iPSCs in different 3D models: A comparative study.

Human induced pluripotent stem cells (hiPSCs) are a promising source from which to derive distinct somatic cell types for in vitro or clinical use. Existent protocols for hepatic differentiation of hiPSCs are primarily based on 2D cultivation of the cells. In the present study, the authors investigated the generation of hiPSC-derived hepatocyte-like cells using two different 3D culture systems: A 3D scaffold-free microspheroid culture system and a 3D hollow-fiber perfusion bioreactor. The differentiation outcome in these 3D systems was compared with that in conventional 2D cultures, using primary human hepatocytes as a control. The evaluation was made based on specific mRNA expression, protein secretion, antigen expression and metabolic activity. The expression of α-fetoprotein was lower, while cytochrome P450 1A2 or 3A4 activities were higher in the 3D culture systems as compared with the 2D differentiation system. Cells differentiated in the 3D bioreactor showed an increased expression of albumin and hepatocyte nuclear factor 4α, as well as secretion of α-1-antitrypsin as compared with the 2D differentiation system, suggesting a higher degree of maturation. In contrast, the 3D scaffold-free microspheroid culture provides an easy and robust method to generate spheroids of a defined size for screening applications, while the bioreactor culture model provides an instrument for complex investigations under physiological-like conditions. In conclusion, the present study introduces two 3D culture systems for stem cell derived hepatic differentiation each demonstrating advantages for individual applications as well as benefits in comparison with 2D cultures.

Usefulness of A Model-Based Approach for Estimating In Vitro P-Glycoprotein Inhibition Potency in a Transcellular Transport Assay.

In vitro half-maximal inhibitory concentration (IC50) is a key parameter for accurately predicting the potential risk for P-glycoprotein (P-gp)--mediated drug--drug interactions. We aimed to compare the IC50 values estimated by different approaches and determine the usefulness of model-based approaches. Transcellular transport of digoxin across Caco-2 monolayer was investigated using various concentrations of P-gp inhibitors, quinidine, verapamil, and zosuquidar. To calculate IC50 values, 3 traditional parameters were used: apical-to-basal (AtoB) and basal-to-apical (BtoA) clearance (CL) with inhibitors (CLAtoB,i and CLBtoA,i) and the difference between the efflux ratios (ERs) with P-gp inhibitors (ERi) and those under complete P-gp inhibition [ER(-P-gp)]. Furthermore, a new model-based approach was applied that uses the difference between the reciprocals of CLAtoB with P-gp inhibitors (1/CLAtoB,i) and those under complete P-gp inhibition [1/CLAtoB(-P-gp)] as parameters. IC50 values obtained from 2 model-based approaches [ERi - ER(-P-gp) and 1/CLAtoB,i - 1/CLAtoB(-P-gp)] were comparable, whereas 2.6- to 6.6-fold larger IC50 values were estimated from empirical approaches (CLAtoB,i and CLBtoA,i). The reason for such difference in IC50 values is that indicators for model-based approaches, but not empirical approaches, directly reflect the P-gp function. Our new approach [1/CLAtoB,i - 1/CLAtoB(-P-gp)] based on only AtoB transcellular transport could substitute for current estimation methods using ER.

Sex-, Species-, and Tissue-Specific Metabolism of Empagliflozin in Male Mouse Kidney Forms an Unstable Hemiacetal Metabolite (M466/2) That Degrades to 4-Hydroxycrotonaldehyde, a Reactive and Cytotoxic Species.

Following oral administration of empagliflozin (1000 mg/kg/day) to male and female CD-1 mice for 2 years, renal tubular injury was identified in male mice. Renal injury was not detected in male mice (≤300 mg/kg/day), in female mice (1000 mg/kg/day), or in male or female Han Wistar rats (700 mg/kg/day). Using transfected HEK293 cells and Xenopus oocytes, empagliflozin was found to be a substrate of various mouse and rat organic anion transporters (oat/Oat) and organic anion transporting polypeptide (oatp/Oatp) transporters: mouse oat3, rat Oat3, mouse oatp1a1, and rat Oatp1a1. However, using isolated kidney slices from male and female mice and rats, no sex-based difference in the extent of uptake of empagliflozin occurred. Metabolism studies using hepatic and renal microsomes from male and female mice, rats, and humans revealed a hemiacetal metabolite of empagliflozin (M466/2), predominantly formed in male mouse kidney microsomes. Formation of M466/2 in male mouse kidney microsomes was 31-fold higher compared to that in female mouse kidney microsomes and was ∼29- and ∼20-fold higher compared to that in male and female mouse liver microsomes, respectively. M466/2 is unstable and degrades to form a phenol metabolite (M380/1) and 4-hydroxycrotonaldehyde (4-OH CTA). Formed 4-OH CTA was trapped by reduced GSH, and the structure of the GSH adduct was confirmed by mass spectrometry. Stoichiometric formation of M380/1 from M466/2 was observed (93-96% at 24 h); however, formation of 4-OH CTA was considerably lower (∼17.5% at 40 h), which is consistent with 4-OH CTA being a highly reactive species. These data represent a highly selective tissue-, species-, and sex-specific lesion in male CD-1 mice associated with a cytotoxic metabolite product, 4-OH CTA. In humans, glucuronidation of empagliflozin is the most prevalent metabolic pathway, and oxidation is a minor pathway. Thus, renal toxicity due to the formation of 4-OH CTA from empagliflozin is not expected in humans.

Impact of endogenous esterase activity on in vitro p-glycoprotein profiling of dabigatran etexilate in Caco-2 monolayers.

Dabigatran etexilate, a double prodrug of dabigatran, is a reversible, competitive, direct thrombin inhibitor that has been approved for use in many countries. A recent guideline from the European Medicines Agency on drug-drug interactions proposed dabigatran etexilate as a sensitive in vivo and in vitro probe substrate for intestinal P-glycoprotein (P-gp) inhibition. We therefore performed a series of in vitro studies to determine the best experimental conditions for evaluation of P-gp involvement on the transport process of dabigatran etexilate across colorectal adenocarcinoma Caco-2 cell monolayers. Experiments using expressed carboxylesterase 1 (CES1) and CES2 bactosomes revealed that dabigatran etexilate was hydrolyzed into BIBR 1087 by CES1 expressed in our Caco-2 cells. The impact of CES1-mediated BIBR 1087 formation during transcellular transport experiments was assessed by comparing several combinations of three experimental approaches: radioactivity detection using [(14)C]dabigatran etexilate as substrate, liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantification of dabigatran etexilate, and in the presence and absence of a CES inhibitor bis(p-nitrophenyl) phosphate (BNPP). The experimental approach that was based on the use of nonlabeled dabigatran etexilate together with LC-MS/MS quantification and the addition of BNPP was selected as the most favorable condition in which to correctly evaluate the permeability coefficient (Papp) of dabigatran etexilate and its transcellular transport by P-gp. The in vitro Caco-2 study at the selected condition revealed that dabigatran etexilate is a P-gp substrate with an efflux ratio of 13.8 and an intrinsic Papp, which is the Papp under the condition of complete blockage of P-gp by P-gp inhibitor, of 29 × 10(-6) cm/s.

In vitro predictability of drug-drug interaction likelihood of P-glycoprotein-mediated efflux of dabigatran etexilate based on [I]2/IC50 threshold.

Dabigatran etexilate, an oral, reversible, competitive, and direct thrombin inhibitor, is an in vitro and in vivo substrate of P-glycoprotein (P-gp). Dabigatran etexilate was proposed as an in vivo probe substrate for intestinal P-gp inhibition in a recent guidance on drug-drug interactions (DDI) from the European Medicines Agency (EMA) and the Food and Drug Administration (FDA). We conducted transcellular transport studies across Caco-2 cell monolayers with dabigatran etexilate in the presence of various P-gp inhibitors to examine how well in vitro IC50 data, in combination with mathematical equations provided by regulatory guidances, predict DDI likelihood. From a set of potential P-gp inhibitors, clarithromycin, cyclosporin A, itraconazole, ketoconazole, quinidine, and ritonavir inhibited P-gp-mediated transport of dabigatran etexilate over a concentration range that may hypothetically occur in the intestine. IC50 values of P-gp inhibitors for dabigatran etexilate transport were comparable to those of digoxin, a well established in vitro and in vivo P-gp substrate. However, IC50 values varied depending whether they were calculated from efflux ratios or permeability coefficients. Prediction of DDI likelihood of P-gp inhibitors using IC50 values, the hypothetical concentration of P-gp inhibitors, and the cut-off value recommended by both the FDA and EMA were in line with the DDI occurrence in clinical studies with dabigatran etexilate. However, it has to be kept in mind that validity of the cut-off criteria proposed by the FDA and EMA depends on in vitro experimental systems and the IC50-calculation methods that are employed, as IC50 values are substantially influenced by these factors.

Simultaneous absolute protein quantification of transporters, cytochromes P450, and UDP-glucuronosyltransferases as a novel approach for the characterization of individual human liver: comparison with mRNA levels and activities.

The purpose of the present study was to determine the absolute protein expression levels of multiple drug-metabolizing enzymes and transporters in 17 human liver biopsies, and to compare them with the mRNA expression levels and functional activities to evaluate the suitability of the three measures as parameters of hepatic metabolism. Absolute protein expression levels of 13 cytochrome P450 (P450) enzymes, NADPH-P450 reductase (P450R) and 6 UDP-glucuronosyltransferase (UGT) enzymes in microsomal fraction, and 22 transporters in plasma membrane fraction were determined using liquid chromatography/tandem mass spectrometry. CYP2C9, CYP2E1, CYP3A4, CYP2A6, UGT1A6, UGT2B7, UGT2B15, and P450R were abundantly expressed (more than 50 pmol/mg protein) in human liver microsomes. The protein expression levels of CYP3A4, CYP2B6, and CYP2C8 were each highly correlated with the corresponding enzyme activity and mRNA expression levels, whereas for other P450s, the protein expression levels were better correlated with the enzyme activities than the mRNA expression levels were. Among transporters, the protein expression level of organic anion-transporting polypeptide 1B1 was relatively highly correlated with the mRNA expression level. However, other transporters showed almost no correlation. These findings indicate that protein expression levels determined by the present simultaneous quantification method are a useful parameter to assess differences of hepatic function between individuals.

The metabolism and disposition of the oral dipeptidyl peptidase-4 inhibitor, linagliptin, in humans.

The pharmacokinetics and metabolism of linagliptin (BI1356, 8-(3R-amino-piperidin-1-yl)-7-but-2-ynyl-3-methyl-1-(4-methyl-quinazolin-2-ylmethyl)-3,7-dihydro-purine-2,6-dione) were investigated in healthy volunteers. The 10- and 5-mg (14)C-labeled drug was administered orally or intravenously, respectively. Fecal excretion was the dominant excretion pathway with 84.7% (p.o.) and 58.2% (i.v.) of the dose. Renal excretion accounted for 5.4% (p.o.) and 30.8% (i.v.) of the dose. Unchanged linagliptin was the most abundant radioactive species in all matrices investigated. The exposure (area under the curve 0-24 h) to the parent compound in plasma accounted for 191 nM . h (p.o.) and 356 nM . h (i.v.), respectively. The main metabolite 7-but-2-ynyl-8-(3S-hydroxy-piperidin-1-yl)-3-methyl-1-(4-methyl-quinazolin-2-ylmethyl)-3,7-dihydro-purine-2,6-dione (CD1790) was observed with >10% of parent compound systemic exposure after oral administration. The metabolite was identified as S-3-hydroxypiperidinly derivative of linagliptin. Experiments that included stable-labeled isotope techniques indicated that CD1790 was formed by a two-step mechanism via the ketone 7-but-2-yn-1-yl-3-methyl-1-[(4-methylquinazolin-2-yl)methyl]-8-(3-oxopiperidin-1-yl)-3,7-dihydro-1H-purine-2,6-dione (CD10604). The initial ketone formation was CYP3A4-dependent and rate-limiting for the overall reaction to CD1790. Aldo-keto reductases with minor contribution of carbonyl reductases were involved in the subsequent stereoselective reduction of CD10604 to CD1790. The antipodes of linagliptin and CD1790 were not observed with adequate enantioselective liquid chromatography-tandem mass spectrometry methods. Other minor metabolites were identified by mass spectrometry and NMR investigations. However, it was concluded that the metabolites of linagliptin only play a minor role in the overall disposition and elimination of linagliptin.

The metabolism and disposition of the oral direct thrombin inhibitor, dabigatran, in humans.

The pharmacokinetics and metabolism of the direct thrombin inhibitor dabigatran (BIBR 953 ZW, beta-alanine, N-[[2-[[[4-(aminoiminomethyl)phenyl]amino]methyl]-1-methyl-1H-benzimidazol-5-yl]carbonyl]-N-2-pyridinyl) were studied in 10 healthy males, who received 200 mg of [(14)C]dabigatran etexilate (BIBR 1048 MS, the oral prodrug of dabigatran) or an i.v. infusion of 5 mg of [(14)C]dabigatran. Radioactivity was measured in plasma, urine, and feces over 1 week. The metabolite pattern was analyzed by high-performance liquid chromatography with on-line radioactivity detection, and metabolite structures were elucidated by mass spectrometry. Dabigatran etexilate was rapidly converted to dabigatran, with peak plasma dabigatran concentrations being attained after approximately 1.5 h; the bioavailability of dabigatran after p.o. administration of dabigatran etexilate was 7.2%. Dabigatran was predominantly excreted in the feces after p.o. treatment and in the urine after i.v. treatment. The mean terminal half-life of dabigatran was approximately 8 h. The predominant metabolic reaction was esterase-mediated hydrolysis of dabigatran etexilate to dabigatran. Phase I metabolites accounted for