We designed and synthesized a series of symmetric bis-6-amidino-benzothiazole derivatives with aliphatic central units and evaluated their efficacy against bloodstream forms of the African trypanosome . Of these, a dicationic benzothiazole compound () exhibited sub-nanomolar in vitro potency with remarkable selectivity over mammalian cells (>26,000-fold). Unsubstituted 5-amidine groups and a cyclohexyl spacer were the crucial determinants of trypanocidal activity. In all cases, mice treated with a single dose of 20 mg kg were cured of stage 1 trypanosomiasis. The compound displayed a favorable in vitro ADME profile, with the exception of low membrane permeability. However, we found evidence that uptake by is mediated by endocytosis, a process that results in lysosomal sequestration. The compound was also active in low nanomolar concentrations against cultured asexual forms of the malaria parasite . Therefore, has exquisite cross-species efficacy and represents a lead compound with considerable therapeutic potential.