ABSTRACT:The magnitude of P-glycoprotein [(P-gp)/multidrug resistance protein 1 (MDR1)]-mediated drug-drug interaction (DDI) at the blood-brain barrier (BBB) in rats was estimated by in vitro-in vivo correlation (IVIVC). In in vitro studies, rat Mdr1a-expressing LLC-PK1 cells were examined for the evaluation of P-gp inhibitory activity using digoxin as a P-gp probe substrate. The in vitro K i value was calculated using a modified corrected flux ratio that reflects the P-gp function. In in vivo studies, digoxin with or without P-gp inhibitors was administered to rats by constant intravenous infusion to evaluate the effect of P-gp inhibition on digoxin transport to the brain under steady-state conditions. In the presence of elacridar, the brain-to-plasma concentration ratio (K p,brain ) of digoxin was approximately 14 times the control value. However, no significant change in the K p,brain was observed

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We identified a lead series of p38 mitogen‐activated protein kinase inhibitors using a structure‐based design strategy from high‐throughput screening of hit compound 1. X‐ray crystallography of 1 with the kinase showed an infrequent flip of the peptide bond between Met109 and Gly110, which was considered to lead to high kinase selectivity. Our structure‐based design strategy was to conduct scaffold transformation of 1 with maintenance of hydrogen bond interactions with the flipped hinge backbone of the enzyme. In accordance with this strategy, we focused on scaffold transformation to identify imidazo[4,5‐b]pyridin‐2‐one derivatives as potent inhibitors of the p38 MAP kinase. Of the compounds evaluated, 21 was found to be a potent inhibitor of the p38 MAP kinase, lipopolysaccharide‐induced tumor necrosis factor‐α (TNF‐α) production in human monocytic leukemia cells, and TNF‐α‐induced production of interleukin‐8 in human whole blood cells. Herein we describe the discovery of potent and orally bioavailable imidazo[4,5‐b]pyridin‐2‐one‐based p38 MAP kinase inhibitors that suppressed cytokine production in a human whole blood cell‐based assay.

Characterizing in vivo cellular kinetics and biodistribution of chimeric antigen receptor T (CAR-T) cells is critical for toxicity assessment, nonclinical and clinical efficacy studies. To date, the standardized assay to characterize CAR-T cell distribution, expansion, contraction, and persistence profiles is not readily available. To overcome this limitation and increase comparability among studies, we have established a universal protocol for analysis. We established a duplexing ddPCR protocol for the CAR-T transgene and reference gene to normalize the genomic DNA input prepared from mouse blood and tissues. The high-throughput gDNA extraction method enabled highly reproducible gDNA extraction while eliminating labor-intensive steps. The investigational CAR-T cells were intravenously injected into immunodeficient mice bearing human colorectal cancer xenografts. The blood and tissue samples were collected to measure the cellular kinetics by ddPCR and flow cytometry. The standard curves were linear throughout the calibration range with acceptable intra- and inter-day precision and accuracy. The gDNA recovery study performed by spiking in the exo-gene plasmid DNA or CAR-T cells revealed that the recovery ranged from 60 to 100% in blood and tissue homogenates. The use of both units of copy/μg gDNA and copy/μL blood met the current regulatory requirement and allowed for a systematic understanding of CAR-T cell expansion and a direct comparison with the flow cytometry data. A standardized ddPCR assay, including automated gDNA extraction procedures, has been established for evaluating cellular kinetics and biodistribution in CAR-T cell therapies.