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Here, we report the application of a novel hepatocyte system, the cofactor-supplemented permeabilized cryopreserved human hepatocytes [MetMax human hepatocytes (MMHHs)] in a higher-throughput 384-well plate assay for the evaluation of cytochrome P450 (P450) inhibition. The assay was created to develop physiologically relevant P450 inhibition information, taking advantage of the complete organelle composition and their associated drug-metabolizing enzymes of the MMHH but with the ease of use of human liver microsomes, including storage at -80°C instead of in liquid nitrogen, and thaw and use without centrifugation and microscopic evaluation as required for intact hepatocytes. Nine key P450 isoforms for drug metabolism (CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4) were evaluated using multiple isoform-selective inhibitors. Results with MMHH were found to be comparable to those obtained with intact cryopreserved human hepatocytes (CHHs). Isoform-selective drug-metabolizing enzyme pathways evaluated were phenacetin O -deethylation (CYP1A2), coumarin 7-hydroxylation (CYP2A6), bupropion hydroxylation (CYP2B6), amodiaquine N -deethylation (CYP2C8), diclofenac 4-hydroxylation (CYP2C9), s -mephenytoin 4'-hydroxylation (CYP2C19), dextromethorphan O -demethylation (CYP2D6), chlorzoxazone 6-hydroxylation (CYP2E1), and midazolam 1'-hydroxylation and testosterone 6 β -hydroxylation (CYP3A4). The K m values obtained with MMHHs were comparable with those reported in the literature for CHHs. Using substrate concentrations at or near K m values, the IC 50 values for the standard inhibitors against the P450 activities were found to be comparable between MMHHs and CHHs, with 73% and 84% of values falling within 2-fold and 3-fold, respectively, from the line of unity. The results indicate that MMHHs can be an efficient experimental system for the evaluation of P450 inhibition in hepatocytes. SIGNIFICANCE STATEMENT: MetMax human hepatocytes (MMHHs) are cofactor-supplemented cryopreserved human hepatocytes with the complete drug-metabolizing enzyme pathways of the conventional hepatocytes but with the convenience of human liver microsomes, including storage at -80°C instead of in liquid nitrogen, and direct thaw and use without a need for centrifugation and microscopic examination. Here, we report the application of MMHH in a high-throughput assay in a 384-well plate format for the evaluation of cytochrome P450 (P450) inhibition. Our results show that data obtained with MMHH are similar to those with conventional hepatocytes, suggesting that the MMHH 384-well P450 inhibition assay can be used routinely for the evaluation of drug-drug interaction potential of new chemical entities in drug development., (Copyright © 2019 by The American Society for Pharmacology and Experimental Therapeutics.)

In this study, we report the effect of dimethyl sulfoxide (DMSO), acetonitrile, and methanol on the CYP1A2-mediated metabolism of phenacetin in human liver microsomes. Phenacetin O-deethylation is the preferred probe reaction for CYP1A2, in which the metabolite, acetaminophen, is quantified using liquid chromatography-tandem mass spectrometry. DMSO was found to inhibit CYP1A2-mediated phenacetin O-deethylation even at low concentrations (0.1%). Acetonitrile did not significantly change the phenacetin O-deethylation activity at concentrations up to 2%. There was no effect on the phenacetin O-deethylation when methanol was present at levels up to 2%. We found that the DMSO level should be kept lower than 0.05% because a concentration of 0.1% strongly affected the metabolism of phenacetin. These findings should be taken into consideration when designing in vitro metabolism studies, especially studies in which metabolism of the investigational compound needs to be evaluated, which would confound the results. The findings from this study indicate that methanol is the suitable solvent and has no significant effects on CYP1A2-mediated phenacetin O-deethylation.