Establishment of human intestinal organoids derived from commercially available cryopreserved intestinal epithelium and evaluation for pharmacokinetic study.

Human intestinal organoids (HIOs) have been reported to exert their functions in a way that mimics living organs, and HIOs-derived monolayers are expected to be applied to in vitro intestinal pharmacokinetic studies. However, HIOs are established from human tissue, which raises issues of availability and ethics. In the present study, to solve these problems, we have established intestinal organoids using commercially available cryopreserved human intestinal epithelial cells (C-IOs), and compared their functions with biopsy-derived human intestinal organoids (B-IOs) from a pharmacokinetic point of view. Both C-IOs and B-IOs reproduced the morphological features of the intestinal tract and were shown to be composed of epithelial cells. Monolayers generated from C-IOs and B-IOs (C-IO-2D, B-IO-2D, respectively) structurally mimic the small intestine. The C-IOs showed gene expression levels comparable to those of the B-IOs, which were close to those of adult human small intestine. Importantly, the C-IOs-2D showed levels of pharmacokinetics-related protein expression and activity-including cytochrome P450 3A4 (CYP3A4) and carboxylesterase 2 (CES2) enzymatic activities and P-glycoprotein (P-gp) transporter activities -similar to those of B-IOs-2D. This study addresses the difficulties associated with B-IOs and provides fundamental characteristics for the application of C-IOs in pharmacokinetic studies.

Quantitative Analysis of mRNA and Protein Expression Levels of Aldo-Keto Reductase and Short-Chain Dehydrogenase/Reductase Isoforms in the Human Intestine.

Enzymes catalyzing the reduction reaction of xenobiotics are mainly members of the aldo-keto reductase (AKR) and short-chain dehydrogenase/reductase (SDR) superfamilies. The intestine, together with the liver, is responsible for first-pass effects and is an organ that determines the bioavailability of orally administered drugs. In this study, we evaluated the mRNA and protein expression levels of 12 AKR isoforms (AKR1A1, AKR1B1, AKR1B10, AKR1B15, AKR1C1, AKR1C2, AKR1C3, AKR1C4, AKR1D1, AKR1E2, AKR7A2, and AKR7A3) and 7 SDR isoforms (CBR1, CBR3, CBR4, DCXR, DHRS4, HSD11B1, and HSD17B12) in each region of the human intestine using next-generation sequencing and data-independent acquisition proteomics. At both the mRNA and protein levels, most AKR isoforms were highly expressed in the upper regions of the intestine, namely the duodenum and jejunum, and then declined toward the rectum. Among the members in the SDR superfamily, CBR1 and DHRS4 were highly expressed in the upper regions, whereas the expression levels of the other isoforms were almost uniform in all regions. Significant positive correlations between mRNA and protein levels were observed in AKR1A1, AKR1B1, AKR1B10, AKR1C3, AKR7A2, AKR7A3, CBR1, and CBR3. The mRNA level of AKR1B10 was highest, followed by AKR7A3 and CBR1, each accounting for more than 10% of the sum of all AKR and SDR levels in the small intestine. This expression profile in the human intestine was greatly different from that in the human liver, where AKR1C isoforms are predominantly expressed. SIGNIFICANCE STATEMENT: In this study comprehensively determined the mRNA and protein expression profiles of aldo-keto reductase (AKR) and short-chain dehydrogenase/reductase isoforms involved in xenobiotic metabolism in the human intestine and found that most of them are highly expressed in the upper region, where AKR1B10, AKR7A3, and CBR1 are predominantly expressed. Since the intestine is significantly involved in the metabolism of orally administered drugs, the information provided here is valuable for pharmacokinetic studies in drug development.

Regional Transcriptomics and Proteomics of Pharmacokinetics-Related Genes in Human Intestine.

The intestine is an organ responsible for the absorption and metabolism of orally administered drugs. To predict pharmacokinetics behavior in the small intestine, it is necessary to examine the human intestinal expression profiles of the genes related to drug absorption, distribution, metabolism, and excretion (ADME). In this study, to obtain more accurate expression profiles in various regions of the human intestine, biopsy samples were collected from endoscopically noninflamed mucosa of the duodenum, jejunum, ileum, colon, and rectum from Japanese including Crohn's disease or ulcerative colitis patients, and both RNA-seq and quantitative proteomics analyses were performed. We also analyzed the expression of drug-metabolizing enzymes (cytochromes P450 (CYPs) and non-CYP enzymes), drug transporters, and nuclear receptors. Overall, the mRNA expression levels of these ADME-related genes correlated highly with the protein expression levels. The characteristics of the expression of ADME-related genes differed significantly between the small and large intestines, including the expression levels of CYP enzymes, which were higher and lower in the small and large intestines, respectively. Most CYPs were expressed dominantly in the small intestine, especially the jejunum, but were rarely expressed in the large intestine. On the other hand, non-CYP enzymes were expressed in the large intestine but at lower expression levels than in the small intestine. Moreover, the expression levels of drug metabolizing enzyme genes differed even between the proximal and distal small intestine. Transporters were expressed most highly in the ileum. The data in the present study will enhance understanding of the intestinal ADME of drug candidates and would be useful for drug discovery research.

Comparison of human biopsy-derived and human iPS cell-derived intestinal organoids established from a single individual.

Rodent-derived intestinal tissues or human colon cancer-derived Caco-2 cells are widely used for in vitro pharmacokinetic tests. However, both entail problems such as species differences from humans and low expression levels of specific pharmacokinetic-related factors, respectively. To solve these problems, many groups, including ours, have been focusing on human biopsy-derived intestinal organoids (b-IOs) and human iPS cell-derived intestinal organoids (i-IOs). However, no reports directly compare the two. Therefore, we established both from a single individual and conducted a comparative study. b-IOs had a shorter doubling time than i-IOs: about 59 h vs 148 h. b-IOs also had higher gene expression levels of major drug transporters and drug-metabolizing enzymes than i-IOs. To evaluate their applicability to pharmacokinetics, both organoids were two-dimensionally cultured. Although the b-IO monolayer had a lower transepithelial electrical resistance than the i-IO monolayer, it had higher gene expression levels of many drug transporters and major drug-metabolizing enzymes than the i-IO monolayer. RNA-seq analysis showed that the i-IOs monolayer had a more complex structure than the b-IOs monolayer because the former contained neuronal and vascular endothelial cells. This study provides basic information for pharmacokinetic applications of human biopsy-derived and human iPS cell-derived intestinal organoids.

Establishment of MDR1-knockout human enteroids for pharmaceutical application.

In the drug development process, it is important to assess the contributions of drug-metabolizing enzymes and/or drug transporters to the intestinal pharmacokinetics of candidate compounds. For such assessments, chemical inhibitors are often used in in vitro systems. However, this practice poses two problems: one is the low expression levels of pharmacokinetic-related genes in conventional in vitro systems, such as Caco-2 cells, and the other is the off-target and less-efficient effects of their inhibitors. Here, as a model, we have established human biopsy-derived enteroids deficient in MDR1, a key efflux transporter. The expression levels and activities of other pharmacokinetic-related genes, such as CYP3A4, in the MDR1-knockout (KO) enteroid-derived monolayers were maintained at levels as high as those in the WT enteroid-derived monolayers. The contribution of MDR1 to the cytotoxicity of vinblastine, which CYP3A4 metabolized, was accurately evaluated by using the MDR1-KO enteroid-derived monolayers. In contrast, it could not be evaluated in the WT enteroid-derived monolayers treated by verapamil, a widely used MDR1 inhibitor, due to the off-target effect of verapamil, which also inhibits CYP3A4. The combination of human enteroid-derived monolayers and genome editing technology would be a powerful tool to evaluate the contributions of specific pharmacokinetic-related molecules.

Functional coupling of organic anion transporter OAT10 (SLC22A13) and monocarboxylate transporter MCT1 (SLC16A1) influencing the transport function of OAT10.

OAT10 (SLC22A13) is a transporter highly expressed in renal tubules and transporting organic anions including nicotinate, ß-hydroxybutyrate, p-aminohippurate, and orotate. In transport assays using Xenopus oocytes and HEK293 cells, we found that apparent substrate selectivity of OAT10 was different between the expression systems, particularly less pronounced uptake of ß-hydroxybutyrate in HEK293 cells. Because functional coupling between transporters may interfere with functional properties of the transporter, we searched for endogenous transporters in HEK293 cells that could affect OAT10. By means of comprehensive approach with co-immunoprecipitation followed by LC-MS/MS analysis, we identified monocarboxylate transporter MCT1 (SLC16A1) as physically coupled with OAT10. The knockdown of MCT1 in OAT10-expressing HEK293 cells increased the uptake of ß-hydroxybutyrate and nicotinate, common substrates of OAT10 and MCT1, whereas the uptake of orotate, a substrate of only OAT10, was not affected. MCT1 is supposed to act as an escape route and mediate the efflux of nicotinate and ß-hydroxybutyrate taken up by OAT10 localized nearby MCT1, as suggested by co-immunoprecipitation. This functional coupling would explain altered apparent substrate selectivity in HEK293 cells compared with Xenopus oocytes. The findings in this study warn in transporter studies that the expression system can interfere with assessing correct transport properties due to unexpected interactions with endogenous transporters.

[Perforin gene mutation in middle-age onset hemophagocytic lymphohistiocytosis].

A 54-year-old woman was referred to our hospital for pancytopenia and liver dysfunction, and with no personal or family history of hemophagocytic lymphohistiocytosis (HLH). Although the etiology was unknown, she was diagnosed with HLH. She experienced exacerbation of HLH even after initiating systemic chemotherapy with etoposide, dexamethasone, and cyclosporine. Furthermore, flow cytometric analysis of the natural killer cells revealed a reduction in perforin expression, and DNA sequencing of the perforin gene (PRF1) revealed two known mutations, confirming the diagnosis of late-onset familial HLH type 2. She received an allogeneic stem cell transplant from an unrelated human leukocyte antigens identical donor, but developed thrombotic microangiopathy, and succumbed to septic shock shortly after the transplant. Previously, HLH in adults was believed to develop from underlying diseases. However, as in our case, several reports demonstrated that HLH gene mutations could be found even after adolescence. Adult with HLH with no underlying disorders should undergo early HLH-associated gene testing for confirmatory diagnosis.

Monolayer platform using human biopsy-derived duodenal organoids for pharmaceutical research.

The human small intestine is the key organ for absorption, metabolism, and excretion of orally administered drugs. To preclinically predict these reactions in drug discovery research, a cell model that can precisely recapitulate the in vivo human intestinal monolayer is desired. In this study, we developed a monolayer platform using human biopsy-derived duodenal organoids for application to pharmacokinetic studies. The human duodenal organoid-derived monolayer was prepared by a simple method in 3-8 days. It consisted of polarized absorptive cells and had tight junctions. It showed much higher cytochrome P450 (CYP)3A4 and carboxylesterase (CES)2 activities than did the existing models (Caco-2 cells). It also showed efflux activity of P-glycoprotein (P-gp) and inducibility of CYP3A4. Finally, its gene expression profile was closer to the adult human duodenum, compared to the profile of Caco-2 cells. Based on these findings, this monolayer assay system using biopsy-derived human intestinal organoids is likely to be widely adopted.

Comparison of culture media for human intestinal organoids from the viewpoint of pharmacokinetic studies.

Human intestinal organoids are expected to be applied in pharmaceutical research. Various culture media for human intestinal organoids have been developed, but it remains unclear which media are preferable for pharmacokinetic studies. Here, we cultured human intestinal organoids with three major culture media that are already used widely around the world: the medium of Sato et al. (S-medium; reported in 2011), Fujii et al. (F-medium; 2018), and Miyoshi et al. (M-medium; 2013). The growth of human intestinal organoids cultured in S-medium was faster than that in F- or M-medium. The gene expression levels of most pharmacokinetic-related enzymes or transporters in human intestinal organoids cultured in M-medium were higher than those in S- or F-medium, and comparable to those in the adult human small intestine. The level of cytochrome P450 (CYP) 3A4 activity was also highest in human intestinal organoids cultured in M-medium. Collectively, the results underscored the importance of selection and optimization of culture medium for various applications using human intestinal organoids, including pharmacokinetic studies.

In Vivo Gene Expression Profile of Human Intestinal Epithelial Cells: From the Viewpoint of Drug Metabolism and Pharmacokinetics.

Orally administered drugs are absorbed and metabolized in the intestine. To accurately predict pharmacokinetics in the intestine, it is essential to understand the intestinal expression profiles of the genes related to drug absorption, distribution, metabolism, and excretion (ADME). However, in many previous studies, gene expression analysis in the intestine has been carried out using specimens from patients with cancer. In this study, to obtain more accurate gene expression profiles, biopsy samples were collected under endoscopic observation from the noninflammatory regions of 14 patients with inflammatory bowel disease, and RNA-seq analysis was performed. Gene expression analysis of drug-metabolizing enzymes (cytochromes P450), non-cytochrome P450 enzymes, nuclear receptors, drug-conjugating enzymes (UDP-glucuronosyltransferases and sulfotransferases), and apical and basolateral drug transporters was performed in biopsy samples from the duodenum, ileum, colon, and rectum. The proportions of the cytochromes P450 expressed in the ileum were 25% (CYP3A4), 19% (CYP2C18), and 14% (CYP3A5). CYP3A4 and CYP2C19 were highly expressed in the duodenum and ileum, but not in the colon and rectum. In the ileum, apical transporters such as P-gp, peptide transporter 1, breast cancer resistance protein, MRP2, and ASBT were strongly expressed, and the expression levels of P-gp and ASBT in the ileum were higher than those in other regions. In the ileum, basolateral transporters such as OSTα, OSTß, and MRP3 were strongly expressed. We succeeded in obtaining gene expression profiles of ADME-related genes in human intestinal epithelial cells in vivo. We expect that this information would be useful for accurate prediction of the pharmacokinetics of oral drugs. SIGNIFICANCE STATEMENT: To obtain gene expression profiles of ADME-related genes in human intestinal epithelial cells in vivo, biopsy samples were collected under endoscopic observation from the noninflammatory regions of 14 patients with inflammatory bowel disease, and RNA-seq analysis was performed. Gene expression profiles of drug-metabolizing enzymes (cytochromes P450), non-cytochrome P450 enzymes, nuclear receptors, drug-conjugating enzymes (UDP-glucuronosyltransferases and sulfotransferases), and apical and basolateral drug transporters in biopsy samples from the duodenum, ileum, colon, and rectum were obtained in this study.

[BCR-ABL1-positive myelodysplastic syndrome with neutropenia and anemia treated successfully with imatinib mesylate].

An 81-year-old female was referred to our hospital with progressive neutropenia and anemia of unknown etiology. We performed a bone marrow biopsy which was notable for hypercellularity, multinucleated megakaryocytes and hypo-granular neutrophils with 2.6% blasts. A diagnosis of myelodysplastic syndrome with multilineage dysplasia (MDS-MLD) was made. Karyotype analysis revealed a t (9;22)(q34;q11.2) BCR-ABL1 fusion with no additional chromosomal abnormalities. BCR-ABL1 was also detected in transcripts from peripheral blood cells as well as in polynuclear leukocytes via FISH. Within one year, her peripheral blood neutrophil count had declined to 403/µl; further analysis was notable for increasing dysplasia including enlarged platelets and hypo-granular neutrophils. Platelet counts gradually increased over time and reached 100×104/µl. A second bone marrow examination revealed similar cell morphology and the BCR-ABL1 translocation. Her condition deteriorated and blood transfusions were required. Treatment with low doses of the tyrosine kinase inhibitor (TKI), imatinib mesylate (100 mg), was initiated. Thereafter, both the neutropenia and anemia resolved gradually, platelet counts returned to normal levels, and dysplasia eventually disappeared. Detection of the BCR-ABL fusion in mRNA decreased to < 0.0007% (IS%) after 16 months of treatment. Several cases of BCR-ABL1-positive myelodysplastic syndrome treated with TKIs have been reported. Our results suggest that complete hematologic recovery in response to imatinib mesylate suggests a critical role for the BCR-ABL1 fusion in the pathogenesis of this disease.

A case of AITL complicated by EBV-positive B cell and monoclonal plasma cell proliferation and effectively treated with lenalidomide.

Angioimmunoblastic T-cell lymphoma (AITL) is a common subtype of peripheral T-cell lymphoma with an aggressive clinical course and poor prognosis after conventional chemotherapy, for which there is no current standard of care. We describe here an 87-year-old woman with AITL, whose clinical diagnosis was complicated by the presence of B immunoblasts positive for Epstein-Barr virus in the lymph nodes and monoclonal plasma cells in the bone marrow at initial presentation. Rebiopsy of the lymph node led to the correct diagnosis of AITL with concurrent smoldering plasma cell myeloma. She was treated with several courses of conventional chemotherapy, resulting in progressive disease, and then switched to the immunomodulatory drug lenalidomide, which used in Japan for the treatment of multiple myeloma. Lenalidomide was effective in controlling both AITL and plasma cell myeloma.

B cells with aberrant activation of Notch1 signaling promote Treg and Th2 cell-dominant T-cell responses via IL-33.

The Notch-signaling pathway in a variety of mature B-cell neoplasms is often activated by gene alterations, but its role remains unclear. Here, we show that B cells harboring dysregulated activation of Notch1 signaling have an immunomodulatory effect on T cells by amplifying regulatory T (Treg) and T helper 2 (Th2) cell responses in an interleukin-33 (IL-33)-dependent manner. A conditional mouse model, in which constitutive expression of an active form of Notch1 is induced in B cells by Aicda gene promoter-driven Cre recombinase, revealed no obvious phenotypic changes in B cells; however, mice demonstrated an expansion of Treg and Th2 cell subsets and a decrease in cytokine production by Th1 and CD8+ T cells. The mice were susceptible to soft tissue sarcoma and defective production of CD8+ T cells specific for inoculated tumor cells, suggesting impaired antitumor T-cell activity. Gene-expression microarray revealed that altered T-cell responses were due to increased IL-33 production by Notch1-activated B cells. Knockout of IL33 or blockade of IL-33 by a receptor-blocking antibody abrogated the Treg and Th2 cell-dominant T-cell response triggered by B cells. Gene-expression data derived from human diffuse large B-cell lymphoma (DLBCL) samples showed that an activated Notch-signaling signature correlates positively with IL33 expression and Treg cell-rich gene-expression signatures. These findings indicate that B cells harboring dysregulated Notch signaling alter T-cell responses via IL-33, and suggest that aberrant activation of Notch signaling plays a role in fostering immune privilege in mature B-cell neoplasms.

Prognostic impact of activation-induced cytidine deaminase expression for patients with diffuse large B-cell lymphoma.

Activation-induced cytidine deaminase (AID) plays important roles in the development of diffuse large B-cell lymphoma (DLBCL); however, its prognostic value remains controversial. Here, we evaluated AID expression in 71 DLBCL patients treated with R-CHOP by immunohistochemistry and investigated its prognostic significance. AID expression was detected in 40.8% of DLBCL samples and associated with IRF4 expression. Notably, AID expression correlated with shorter progression-free survival and overall survival for patients with high (3-5) international prognostic index (IPI) score. Moreover, it was a strong predictor of poor overall response to salvage therapy after relapse or disease progression, which may suggest its role in promoting the evolution of tumors into highly refractory disease at relapse. Our findings indicate that AID expression effectively discriminates between IPI-high score patients with different survival outcomes, and suggest that initial disease control would be particularly important for the treatment of IPI-high score patients with AID-positive DLBCL.

Multiple Myeloma Presenting with Autoimmune Autonomic Ganglionopathy.

Autoimmune autonomic ganglionopathy is an autonomic disorder that occurs as a symptom of paraneoplastic neurological syndrome. To date, there have been no reports on multiple myeloma with autoimmune autonomic ganglionopathy. A 37-year-old Japanese woman suffered from orthostatic hypotension was diagnosed with multiple myeloma (IgG kappa type), and a serological examination revealed the presence of anti-ganglionic nicotinic acetylcholine receptor (anti-gAChR) antibodies. She was treated for multiple myeloma, as a result, the autonomic disturbance improved and her anti-gAChR antibody titer decreased to undetectable levels, despite the fact that she only achieved a partial remission of multiple myeloma. Treatment for multiple myeloma may improve autoimmune autonomic ganglionopathy.

Different Involvement of OAT in Renal Disposition of Oral Anticoagulants Rivaroxaban, Dabigatran, and Apixaban.

This study aimed to investigate the interactions of 3 anticoagulants, rivaroxaban, apixaban, and dabigatran, with 5 human solute carrier transporters, hOAT1, hOAT3, hOCT2, hOATP1B1, and hOATP1B3. Apixaban inhibited hOAT3, hOATP1B1, and hOATP1B3, and rivaroxaban inhibited hOAT3 and hOATP1B3, with IC50 values of >20 and >5 µM, respectively. The effect of dabigatran was negligible or very weak, so significant drug interactions at therapeutic doses are unlikely. Specific uptake of rivaroxaban was observed only in human and mouse OAT3-expressing cells. The Km for mouse Oat3 (mOat3) was 1.01 ± 0.70 µM. A defect in mOat3 reduced the kidney-to-plasma concentration ratio of rivaroxaban by 38% in mice. Probenecid treatment also reduced the kidney-to-plasma concentration ratio of rivaroxaban in rats by 73%. Neither mOat3 defect nor probenecid administration in rats reduced the renal clearance of rivaroxaban. The uptake of rivaroxaban by monkey kidney slices was temperature dependent and inhibited by probenecid but not by tetraethylammonium. Taken together, organic anion transporters, mainly OAT3, may mediate basolateral uptake of rivaroxaban in kidneys. hOAT3 could be an additional factor that differentiates the potential drug-drug interactions of the 3 anticoagulants in the urinary excretion process in clinical settings.

Expression of Tim-1 in primary CNS lymphoma.

Primary central nervous system lymphoma (PCNSL) is a distinct subtype of extranodal lymphoma with aggressive clinical course and poor outcome. As increased IL-10/IL-6 ratio is recognized in the cerebrospinal fluid (CSF) of PCNSL patients, we hypothesized that PCNSL might originate from a population of B cells with high IL-10-producing capacity, an equivalent of "regulatory B cells" in mice. We intended in this study to clarify whether Tim-1, a molecule known as a marker for regulatory B cells in mice, is expressed in PCNSL. By immunohistochemical analysis, Tim-1 was shown to be positive in as high as 54.2% of PCNSL (26 of 58 samples), while it was positive in 19.1% of systemic diffuse large B-cell lymphoma (DLBCL) samples (17 of 89 samples; P < 0.001). Tim-1 expression positively correlated with IL-10 expression in PCNSL (Cramer's V = 0.55, P < 0.001), and forced expression of Tim-1 in a PCNSL cell line resulted in increased IL-10 secretion, suggesting that Tim-1 is functionally linked with IL-10 production in PCNSL. Moreover, soluble Tim-1 was detectable in the CSF of PCNSL patients, and was suggested to parallel disease activity. In summary, PCNSL is characterized by frequent Tim-1 expression, and its soluble form in CSF may become a useful biomarker for PCNSL.

Dose-Modified Ifosfamide, Epirubicin, and Etoposide is a Safe and Effective Salvage Therapy with High Peripheral Blood Stem Cell Mobilization Capacity for Poorly Mobilized Hodgkin's Lymphoma and Non-Hodgkin's Lymphoma Patients.

A dose modified ifosfamide, epirubicin, and etoposide (IVE) regimen was prospectively assessed for its efficacy in mobilizing peripheral blood stem cells for autologous transplantation. Two patients with Hodgkin's lymphoma and two with non-Hodgkin's lymphoma who were undergoing stem cell therapy were studied. All patients had a history of multiple treatments with insufficient stem cell mobilization. The dose modified IVE regimen consisted of ifosfamide 3 g/m(2) intravenously (IV) administered on days 1-2 in combination with epirubicin 50 mg/m(2) IV on day 1 and etoposide 200 mg/m(2) (100 mg/m(2) in two patients with complete remission) IV on days 1-3. The ifosfamide dosage was reduced to two-thirds of the original protocol. A substantial high yield of CD34(+) cells was achieved when patients were treated with a dose-modified IVE regimen, compared with that during the previous regimen (two with the ifosfamide, carboplatin, and etoposide [ICE] regimen, one with high-dose cyclophosphamide and one with the original IVE regimen). Two patients who had refractory and residual disease received a 200 mg/m(2) dose of etoposide, which resulted in tumor reduction (one patient with complete remission and one with further reduction in tumor size). After the IVE regimen, all four patients had a sufficient yield of CD34(+) cells in total, which was available for stem cell transplantation. Hematological and non-hematological toxicities were comparable in all regimens. This single-center prospective study demonstrated that the dose-modified IVE regimen can be used as a safe treatment with high mobilizing efficacy in heavily pretreated lymphoma patients.

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.