Evaluation of 23 lots of commercially available cryopreserved hepatocytes for induction assays of human cytochromes P450

Due to the importance of in vitro cytochrome P450 (P450) induction assay to assess the possible drug-drug interaction events, the recent US Food and Drug Administration draft guidance and European Medicines Agency guideline recommend to assess P450 induction using fresh or cryopreserved hepatocytes at mRNA level and/or enzyme activity level. Although cryopreserved hepatocytes are commercially available for P450 induction assays, feasibility and practicability of these hepatocytes have not been fully investigated. In this study, a total of 23 lots of human cryopreserved hepatocytes were treated with three typical inducers (omeprazole, phenobarbital, and rifampicin), and induction of CYP1A2, CYP2B6, and CYP3A4 enzyme activity was measured. In 8 of these 23 hepatocyte lots, induction of CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and CYP3A4 mRNA was also analyzed. The results revealed that CYP1A2, CYP2B6, and CYP3A4 were induced (>2.0-fold) by omeprazole, phenobarbital, and rifampicin, respectively, in all the hepatocyte lots tested at enzyme activity level (23 lots) and mRNA level (8 lots). In contrast, of the 8 hepatocyte lots treated with rifampicin, CYP2C8 and CYP2C9 mRNA were not induced in 5 and 2 hepatocyte lots, respectively, and CYP2C19 mRNA was not induced in any of the 8 hepatocyte lots tested. These results suggest that induction of CYP1A2, CYP2B6, and CYP3A4 can be readily assessed, but evaluation for CYP2C mRNA induction might not be feasible, using commercially available human cryopreserved hepatocytes.