Species differences in microsomal metabolism of hydroxychloroquine.

Hydroxychloroquine (HCQ), a medication renowned for its anti-malarial and anti-autoimmune properties, is susceptible to drug-drug interactions (DDIs), particularly those involving cytochrome P450 enzymes (CYPs). The pharmacokinetic and metabolic profiles of HCQ across species are not well-characterized. In this study, we conducted a comparative analysis of HCQ metabolism and pharmacokinetics in human liver microsomes and those from various preclinical animal models. Metabolite profiling indicated that the mono-oxidized metabolite M5 was predominantly produced in microsomes from mouse (MLM), rats (RLM), dogs (DLM), and pigs (PLM). Conversely, two other oxidative metabolites, M4 and M6, were uniquely generated in PLM. Utilizing selective inhibitors of human CYP isoforms, we identified key enzymes in HLM that differ from those in other species. Furthermore, the metabolic pathways in HLM were distinct from those observed in other species. In HLM, two metabolic pathways have been identified, each comprising a two-step reaction. CYP2D6, CYP2C8, CYP3A4, and CYP1A1 are the key enzymes involved in HCQ metabolism, with HCQ demonstrating significant substrate inhibition of CYP2D6, CYP2C8, and CYP1A1. Our work shed a new light on selection of suitable experimental animal models for accurate evaluation of HCQ's in vivo processes and its potential in multi-drug regimens.