Development of Caco-2 cells co-expressing CYP3A4 and NADPH-cytochrome P450 reductase using a human artificial chromosome for the prediction of intestinal extraction ratio of CYP3A4 substrates

The Caco-2 cells co-expressing cytochrome P450 (CYP) 3A4 and NADPH-cytochrome P450 reductase (CPR) were developed using a human artificial chromosome (HAC) vector. The CYP3A4 and CPR genes were cloned into the HAC vector in CHO cells using the Cre-loxP system, and the microcell-mediated chromosome transfer technique was used to transfer the CYP3A4-CPR-HAC vector to Caco-2 cells. After seeding onto semipermeable culture inserts, the CYP3A4-CPR-HAC/Caco-2 cells were found to form tight monolayers, similar to the parental cells, as demonstrated by the high transepithelial electrical resistance (TEER) value and comparable permeability of non-CYP3A4 substrates between parent and CYP3A4-CPR-HAC/Caco-2 cell monolayers. The metabolic activity of CYP3A4 (midazolam 1'-hydroxylase activity) in the CYP3A4-CPR-HAC/Caco-2 cells was constant from 22 to 35 passages, indicating that HAC vectors conferred sufficient and sustained CYP3A4 activity to CYP3A4-CPR-HAC/Caco-2 cells. The strong relationship between the metabolic extraction ratios (ER) obtained from the CYP3A4-CPR-HAC/Caco-2 cells and calculated intestinal extraction ratios in humans (Eg) from reported intestinal availability (Fg) was found for 17 substrates of CYP3A4 (r² = 0.84). The present study suggests that the CYP3A4-CPR-HAC/Caco-2 cell monolayer can serve as an in vitro tool that facilitates the prediction of intestinal extraction ratio (or availability) in humans.

Human small intestinal epithelial cells differentiated from adult intestinal stem cells as a novel system for predicting oral drug absorption in humans

Adult intestinal stem cells (ISCs) possess both a long-term proliferation ability and differentiation capability into enterocytes. As a novel in vitro system for the evaluation of drug absorption, we characterized a human small intestinal epithelial cell (HIEC) monolayer that differentiated from adult ISCs. Continuous proliferation/differentiation from ISCs consistently conferred the capability of maturation of enterocytes to HIECs over 25 passages. The morphologically matured HIEC monolayer consisted of polarized columnar epithelia with dense microvilli, tight junctions, and desmosomes 8 days after seeding onto culture inserts. Transepithelial electrical resistance across the monolayer was 9-fold lower in HIECs (98.9 Ω × cm(2)) than in Caco-2 cells (900 Ω × cm(2)), which indicated that the looseness of the tight junctions in the HIEC monolayer was similar to that in the human small intestine (approximately 40 Ω × cm(2)). No significant differences were observed in the overall gene expression patterns of the major drug-metabolizing enzymes and transporters between the HIEC and Caco-2 cell monolayers. Furthermore, the functions of P-glycoprotein and breast cancer resistance protein in the HIEC monolayer were confirmed by the vectorial transport of marker substrates and their disappearance in the presence of specific inhibitors. The apparent drug permeability values of paracellularly transported compounds (fluorescein isothiocyanate-dextran 4000, atenolol, and terbutaline) and nucleoside transporter substrates (didanosine, ribavirin, and doxifluridine) in the HIEC monolayer were markedly higher than those of Caco-2 cells, whereas transcellularly transported drugs (pindolol and midazolam) were equally well permeated. In conclusion, the HIEC monolayer can serve as a novel and superior alternative to the conventional Caco-2 cell monolayer for predicting oral absorption in humans.

Abstract A273: TAS-5567, a highly potent and selective inhibitor of SYK kinase, demonstrated antitumor activity in diffuse large B-cell lymphoma (DLBCL) cellsin vitro and in vivo

Background: Chronic activation of the B-cell receptor (BCR) pathway is critical for proliferation and survival of malignant B cells, and is implicated in the pathogenesis of B-cell lymphomas. Spleen tyrosine kinase (SYK) is a central regulator of the BCR pathway. Although there are several reports of SYK inhibitory compounds in development, there appears to still be a need for a highly selective SYK inhibitor. Here we report on a novel SYK inhibitor, TAS-5567, which displays high potency with excellent kinase selectivity. In this study, we characterized the in vitro cytotoxic effect and the mechanism of action of TAS-5567 in DLBCL cells, and evaluated in vivo antitumor activity in DLBCL xenograft models.

Materials and Methods: In vitro enzyme inhibition of SYK was determined by using purified SYK and the peptide substrate. Selectivity for kinases of TAS-5567 was determined in a panel of 196 kinases. To evaluate the target engagement of TAS-5567, the cellular phosphorylation of BLNK(Y84), a substrate of SYK kinase, was examined by Flow cytometry. For a growth inhibition assay, DLBCL cells were treated with TAS-5567 for 3 days, and the number of living cells was determined by measuring cellular ATP. In order to demonstrate TAS-5567’s mechanism of action in DLBCL cells, a cell cycle analysis was conducted by Flow cytometry. For evaluation of pharmacokinetics (PK), pharmacodynamics (PD), and antitumor effect of TAS-5567 in vivo, we orally dosed TAS-5567 in human DLBCL xenograft models.

Results: TAS-5567 was a potent inhibitor of SYK with an IC50 value of 0.37nM, and demonstrated little activities against the other 196 kinases. In SU-DHL10 DLBCL cells, TAS-5567 potently inhibited the phosphorylation of BLNK (IC50 = 10 nM), and inhibited cell proliferation in a concentration-dependent manner (IC50 = 68 nM). Cell cycle arrest at G1 phase and apoptosis were observed in the DLBCL cells by continuous exposure to TAS-5567 at 300 nM. Also, TAS-5567 exhibited broad antiproliferation activity across various DLBCL cell lines in vitro. In vivo, TAS-5567 demonstrated favorable oral PK properties in mice, and exhibited a sustained and robust inhibition of the pharmacodynamics marker pBLNK in tumor tissues of SU-DHL10 DLBCL xenograft model. Consistent with the results of the pharmacodynamics study, TAS-5567 displayed significant antitumor effect in the SU-DHL10 xenograft models at PD effective doses with minimum body weight changes.

Conclusion: TAS-5567 is an orally available, highly potent, and selective inhibitor of SYK. TAS-5567 demonstrated substantial antitumor activity in DLBCL cells both in vitro and in vivo, with an accompanying sustained and robust inhibition of SYK in the cells. These data suggest that TAS-5567 may be a promising SYK inhibitor for the treatment of DLBCL.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A273.

Citation Format: Hiroki Irie, Aki Kawagishi, Keiko Ishihara, Shingo Tsuji, Yoko Nakatsuru, Jiro Kuze, Naoko Fujino, Yoshio Ogino, Hideya Komatani, Teruhiro Utsugi. TAS-5567, a highly potent and selective inhibitor of SYK kinase, demonstrated antitumor activity in diffuse large B-cell lymphoma (DLBCL) cellsin vitro and in vivo. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A273.

Utility of cryopreserved hepatocytes suspended in serum to predict hepatic clearance in dogs and monkeys

An in vitro-in vivo correlation analysis between observed and predicted metabolic clearance in multiple preclinical species including dogs and monkeys constitutes an integral part of prediction for the pharmacokinetics in humans by using liver-derived in vitro preparations. Empirical values of the scaling factor for the extrapolation of metabolic (intrinsic) clearance in the in vitro preparation to that for whole liver were calculated for each preparation of 8 and 5 cryopreserved dog and monkey hepatocytes, respectively, by optimizing the objective function of average fold error between predicted and observed metabolic (intrinsic) clearance for eight and 11 standard compounds for dogs and monkeys, respectively. Thus obtained values of the scaling factor ranged from 5.46 × 10(9) to 19.9 × 10(9) cells/kg body weight with an average of 10.3 × 10(9) cells/kg body weight in dogs, and the value ranged from 2.36 × 10(9) to 4.21 × 10(9) cells/kg body weight with an average of 3.17 × 10(9) cells/kg body weight in monkeys, which were both consistent with biologically calculated values in corresponding species. These results demonstrated the utility of commercially available cryopreserved preparations of dog and monkey hepatocytes for the in vitro-in vivo correlation analyses with the aid of empirically or biologically obtained scaling factors at the early development stage of new drug candidates.

Evaluation of animal models for intestinal first-pass metabolism of drug candidates to be metabolized by CYP3A enzymes via in vivo and in vitro oxidation of midazolam and triazolam

1. To search an appropriate evaluation methodology for the intestinal first-pass metabolism of new drug candidates, grapefruit juice (GFJ)- and vehicle (tap water)-pretreated mice or rats were orally administered midazolam (MDZ) or triazolam (TRZ), and blood levels of the parent compounds and their metabolites were measured by liquid chromatography/MS/MS. A significant effect of GFJ to elevate the blood levels was observed only for TRZ in mice. 2. In vitro experiments using mouse, rat and human intestinal and hepatic microsomal fractions demonstrated that GFJ suppressed the intestinal microsomal oxidation of MDZ and especially TRZ. Substrate inhibition by MDZ caused reduction in 1'-hydroxylation but not 4-hydroxylation in both intestinal and hepatic microsomal fractions. The kinetic profiles of MDZ oxidation and the substrate inhibition in mouse intestinal and hepatic microsomal fractions were very similar to those in human microsomes but were different from those in rat microsomes. Furthermore, MDZ caused mechanism-based inactivation of cytochrome P450 3A-dependent TRZ 1'-hydroxylation in mouse, rat and human intestinal microsomes with similar potencies. 3. These results are useful information in the analysis of data obtained in mouse and rat for the evaluation of first-pass effects of drug candidates to be metabolized by CYP3A enzymes.

N3-phenacyluridine, a novel hypnotic compound, interacts with the benzodiazepine receptor

N3-Phenacyluridine (3-phenacyl-1-beta-D-ribofuranosyluracil) has potent sedative and hypnotic activities following intracerebroventricular injection in mice. To study the mechanism of action of N3-phenacyluridine, the interaction of this compound with the benzodiazepine receptor has been investigated. Results obtained showed that this compound inhibited specific binding of [3H]flunitrazepam to synaptic membranes of bovine cortex in a concentration-dependent fashion (IC50 = 129 microM). Scatchard analysis of [3H]flunitrazepam binding revealed that N3-phenacyluridine interacted with the ligand at the benzodiazepine receptor binding site in a competitive manner. Ro15-1788 (8-fluoro-3-carboethoxy-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5a ]1, 4-benzodiazepine), a benzodiazepine receptor antagonist, also inhibited the specific binding of [3H]flunitrazepam in the presence of the compound. The results suggest that the pharmacological activity of N3-phenacyluridine may be partially mediated through the benzodiazepine receptor.

Central nervous system depressant effects of N3-substituted derivatives of deoxyuridine in mice

N3-Substituted derivatives of deoxyuridine (1) were synthesized and their pharmacological effects were evaluated by intracerebroventricular (i.c.v.) injection in mice. Eleven derivatives, including the methyl (2), ethyl (3), propyl (4), allyl (5), butyl (6), benzyl (7), o, m and p-xylyls (8, 9, 10), alpha-phenylethyl (11) and phenacyl (12) derivatives, of 1 were prepared and their pharmacological effects were evaluated by using hypnotic activity, pentobarbital-induced sleep prolongation, spontaneous activity and motor incoordination as indices of central nervous system (CNS) depressant effects. At a dose of 2.0 mumol/mouse, the values of mean sleeping time induced by 7, 8, 9 and 10 were 23, 35, 29 and 30 min, respectively. Although the alkyl (2-6) derivatives did not cause any hypnotic activity, some derivatives tested (3, 5, 6, 8-12) significantly prolonged the pentobarbital-induced sleeping time. When the CNS depressant effects of phenacyl substituted 1 were compared to that of other oxopyrimidine nucleosides, N3-phenacyluridine (13), N3-phenacylthymidine (14), N3-phenacyl-6-azauridine (15), compounds 12, 13 and 14 (1.0 mumol/mouse, i.c.v.) significantly decreased mouse spontaneous activity. Furthermore, 12-15 (1.0 mumol/mouse, i.c.v.) caused mouse motor incoordination. These results indicate that deoxyuridine derivatives have generally central depressant activity, and the benzyl and xylyl derivatives, but not alkyl derivatives, possess hypnotic activity.

The potent depressant effects of N3-phenacyluridine in mice

The hypnotic activity of N3-phenacyluridine in 2.0 mumol/mouse by intracerebroventricular (i.c.v.) injection was 20 times stronger than that of known N3-benzyluridine. In 0.5 mumol/mouse, i.c.v., this compound strongly potentiated both pentobarbital- and diazepam-induced sleep as compared to N3-substituted uridines, including N3-benzyluridine. Furthermore, the compound caused motor incoordination as well as decreasing spontaneous activity in the same dose. These results indicate that among the N3-substituted uridines and related compounds previously reported, N3-phenacyluridine possesses potent depressant effects.