Humanization of Drug Metabolism in the Plasmodium berghei Mouse Model for Antimalarial Drug Discovery.

Resistance to artemisinin-based combination therapies (ACTs) is steadily increasing in malaria-endemic countries, and new medicines to treat this disease are urgently needed. Drug discovery efforts are hindered by species differences in drug metabolism as new chemical entities must survive metabolism by diverse enzymes across multiple species, enabling cures in preclinical disease models before progression to the clinic. Here, we show how the use of a mouse line extensively genetically humanized for enzymes of the cytochrome P450 superfamily and their transcriptional regulators, the "8HUM" line, can circumvent this issue and improve the translational accuracy of data generated. Engraftment of human erythrocytes into 8HUM/Rag2-/-, an immunocompromised version of the 8HUM line lacking mature T and B cells, was insufficient to permit infection with Plasmodium falciparum, and depletion of natural killer cells by antibody treatment did not alter this outcome. However, infection of 8HUM with Plasmodium berghei permitted assessment of drug efficacy against this Plasmodium species. Approved antimalarials were generally more metabolically stable in 8HUM than in wild-type mice. Major species differences between humans and mice in routes of metabolic elimination for quinine derivatives were removed with 8HUM. Therefore, the 8HUM P. berghei model described here will be of value early in the critical path for antimalarial drug discovery, improving alignment of drug metabolism with the clinical situation while bypassing mouse-specific issues of metabolism to facilitate proof-of-concept in vivo demonstration of efficacy, a key requirement for validation of new drug targets and chemical series.