3-(Oxazolo[4,5-b]pyridin-2-yl)anilides as a novel class of potent inhibitors for the kinetoplastid Trypanosoma brucei, the causative agent for human African trypanosomiasis

Abstract

A whole organism high-throughput screen of approximately 87,000 compounds against Trypanosoma brucei brucei led to the recent discovery of several novel compound classes with low micromolar activity against this organism and without appreciable cytotoxicity to mammalian cells. Herein we report a structure-activity relationship (SAR) investigation around one of these hit classes, the 3-(oxazolo[4,5-b]pyridin-2-yl)anilides. Sharp SAR is revealed, with our most active compound (5) exhibiting an IC₅₀ of 91 nM against the human pathogenic strain T.b. rhodesiense and being more than 700 times less toxic towards the L6 mammalian cell line. Physicochemical properties are attractive for many compounds in this series. For the most potent representatives, we show that solubility and metabolic stability are key parameters to target during future optimisation.

Keywords: 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide; 3-(Oxazolo[4,5-b]pyridin-2-yl)anilides; 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; BBB; DCM; DMAP; DMEM; DMF; Dulbecco's modified Eagle's medium; E(H); EDCI; FCS; HAT; HBTU; HEPES; Human African trypanosomiasis; L. donovani; Leishmania Donovani; N,N-dimethylaminopyridine; N,N-dimethylformamide; O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate; P. falciparum; Plasmodium falciparum; STPHI; Sleeping sickness; Swiss Tropical and Public Health Institute; T.b. brucei; T.b. gambiense; T.b. rhodesiense; TBAB; Trypanosoma brucei; Trypanosoma brucei brucei; Trypanosoma brucei gambiense; Trypanosoma brucei rhodesiense; Trypanosomacidal agent; WHO; World Health Organisation; blood–brain barrier; cPPB; chromatographic plasma protein binding; cytotox.; cytotoxicity; dichloromethane; foetal calf serum; hepatic extraction; human African trypanosomiasis; tetrabutylammonium bromide.