Hepatocyte Spheroids as a Viable in vitro Model for Recapitulation of Complex in vivo Metabolism Pathways of Loratadine in Humans.

Accurate prediction of in vivo metabolic pathways in humans can be challenging because in vitro liver matrices may fail to produce certain in vivo metabolites. Rat and human spheroids, generated from cryopreserved hepatocytes in media that contained minimal amount of serum, maintained morphology, viability and cytochrome P450 (CYP) activities for at least a week without media exchange. With spheroid cultures, multiple Phase I and Phase II metabolites were observed in rat and human spheroid cultures that were incubated with loratadine (LOR) for multiple days. Consistent with in vivo observations, 3-hydroxydesloratadine, (3-OH-DL), along with its glucuronide, were observed in human spheroids, but not in rat spheroids. Interestingly, the putative intermediate metabolite leading to 3-OH-DL, DL-N-glucuronide, was observed in incubations with both rat and human spheroids. In conclusion, hepatocyte spheroid were capable of recapitulating the inter-species differences in metabolism between human and rat for LOR, therefore, it may represent a viable model for studying complex metabolic pathways.