In vitro selection predicts malaria parasite resistance to dihydroorotate dehydrogenase inhibitors in a mouse infection model

Abstract

Resistance has developed in <i>Plasmodium</i> malaria parasites to every antimalarial drug in clinical use, prompting the need to characterize the pathways mediating resistance. Here, we report a framework for assessing development of resistance of <i>Plasmodium falciparum</i> to new antimalarial therapeutics. We investigated development of resistance by <i>P. falciparum</i> to the dihydroorotate dehydrogenase (DHODH) inhibitors DSM265 and DSM267 in tissue culture and in a mouse model of <i>P. falciparum</i> infection. We found that resistance to these drugs arose rapidly both in vitro and in vivo. We identified 13 point mutations mediating resistance in the parasite DHODH in vitro that overlapped with the DHODH mutations that arose in the mouse infection model. Mutations in DHODH conferred increased resistance (ranging from 2- to ~400-fold) to DHODH inhibitors in <i>P. falciparum</i> in vitro and in vivo. We further demonstrated that the drug-resistant parasites carrying the C276Y mutation had mitochondrial energetics comparable to the wild-type parasite and also retained their fitness in competitive growth experiments. Our data suggest that in vitro selection of drug-resistant <i>P. falciparum</i> can predict development of resistance in a mouse model of malaria infection.