A Novel In vitro Experimental System for the Evaluation of Enteric Drug Metabolism: Cofactor-Supplemented Permeabilized Cryopreserved 
Human Enterocytes (MetMax™ Cryopreserved Human Enterocytes)

BACKGROUND: We report here an evaluation of a novel experimental system- cofactor-supplemented permeabilized cryopreserved human enterocytes (MetMax™ cryopreserved human entero-cytes (MMHE), patent pending) for applications in the evaluation of enteric drug metabolism. A major advantage of MMHE over Conventional Cryopreserved Human Enterocytes (CCHE) is the simplification of the use procedures including storage at -80°C instead of in liquid nitrogen, and use of the cells imme-diately after thawing without a need for centrifugation and microscopic evaluation of cell density and via-bility and cell density adjustment. METHODS: In this study, we compared MMHE and CCHE in key phase 1 oxidation and phase 2 conjuga-tion Drug Metabolism Enzyme (DME) activities that we recently reported for cryopreserved human en-terocytes: CYP2C9 (diclofenac 4’- hydroxylation), CYP2C19 (s-mephenytoin hydroxylation), CYP3A4 (midazolam 1’-hydroxylation), CYP2J2 (astemizole O-demethylation), uridine 5'-diphospho-glucuronosyltransferase (UGT; 7-hydroxycoumarin glucuronidation), sulfotransferase (SULT; 7-hydroxycoumarin sulfation), N-acetyl transferase-1 (NAT-1; p-benzoic acid N-acetylation), and carboxy-esterase-2 (CES-2; hydrolysis of irinotecan to SN38). Both CCHE and MMHE were active in all the DME pathways evaluated, with specific activities of MMHE ranged from 142% (CYP2C9) to 1713% (UGT) of that for CCHE. β-hydroxylation and testosterone 6. RESULT AND CONCLUSION: Our results suggest that the MMHE system represents a convenient and robust in vitro experimental system for the evaluation of enteric drug metabolism