Nguyen, WilliamDans, Madeline GCurrie, IainAwalt, Jon KyleBailey, Brodie LLumb, ChrisNgo, AnnaFavuzza, PaolaPalandri, JosephineRamesh, SaishyamSietsma Penington, JocelynMaier, Alexandervan Dooren, Giel2024-08-212024-08-212373-8227https://hdl.handle.net/1885/733715069The development of new antimalarials is required because of the threat of resistance to current antimalarial therapies. To discover new antimalarial chemotypes, we screened the Janssen Jumpstarter library against the P. falciparum asexual parasite and identified the 7-N-substituted-3-oxadiazole quinolone hit class. We established the structure-activity relationship and optimized the antimalarial potency. The optimized analog WJM228 (17) showed robust metabolic stability in vitro, although the aqueous solubility was limited. Forward genetic resistance studies uncovered that WJM228 targets the Qo site of cytochrome b (cyt b), an important component of the mitochondrial electron transport chain (ETC) that is essential for pyrimidine biosynthesis and an established antimalarial target. Profiling against drug-resistant parasites confirmed that WJM228 confers resistance to the Qo site but not Qi site mutations, and in a biosensor assay, it was shown to impact the ETC via inhibition of cyt b. Consistent with other cyt b targeted antimalarials, WJM228 prevented pre-erythrocytic parasite and male gamete development and reduced asexual parasitemia in a P. berghei mouse model of malaria. Correcting the limited aqueous solubility and the high susceptibility to cyt b Qo site resistant parasites found in the clinic will be major obstacles in the future development of the 3-oxadiazole quinolone antimalarial class.his work was supported by the National Health and Medical Research Council of Australia (Development Grant GNT1135421 to B.E.S. and A.F.C.; Ideas Grant GNT1182369 to G.G.v.D. and A.G.M.), Wellcome (100993/Z/13/Z to J.B.), Medicines for Malaria Venture (RD-08-2800to J.B.; RD-18-0003 to B.E.S. and A.F.C.), the AustralianCancer Research Foundation, the Victorian State GovernmentOperational Infrastructure Support, and the Australian Government NHMRC IRIISS. We thank the University of Melbourne for provision of a Research Scholarship to B.B.application/pdfen-AU© 2023 The Authors. Published by American Chemical Societyhttp://creativecommons.org/licenses/by-nc-nd/4.0/malariaPlasmodiumantimalarialmitochondriacytochrome bc1202310.1021/acsinfecdis.2c006072024-05-12CC-BY-NC-ND 4.0