Discovery and Development of an Advanced Lead for\nthe Treatment of African Trypanosomiasis

African\ntrypanosomiasis is a widespread disease of human and veterinary\nimportance caused by various <i>Trypanosoma spp.</i> with\na globally devastating impact and a need for novel treatment options.\nWe here provide a comprehensive preclinical evaluation of nucleoside\nanalogues, 6-thioether-modified tubercidins, with curative activity\nagainst African trypanosomiasis. Promising hits were identified following <i>in vitro</i> screening against the most relevant trypanosome\nspecies. Selected hit compounds were extensively tested for <i>in vitro</i> metabolic stability, potency in <i>in vivo</i> mouse models for the various species, genotoxicity in an <i>in vitro</i> testing battery, and mode of action studies (i.e.,\ngenome-wide RNA interference library screening and metabolomics).\nAmong the nucleoside analogues, analogue <b>3</b> was curative\nin mouse models with no indication of genotoxicity and a low ecotoxicological\nfootprint. Mode-of-action studies revealed that P1-type nucleoside\ntransporters and adenosine kinase are involved in the uptake and activation,\nrespectively. Analogue <b>3</b> represents a potent, advanced\nlead fitting the preferred target product profile for a broad-spectrum\ntrypanocide regardless of the causative species.