Fexinidazole results in specific effects on DNA synthesis and DNA damage in the African trypanosome

Nitroaromatic drugs are of critical importance for the treatment of trypanosome infections in Africa and the Americas. Fexinidazole recently joined benznidazole and nifurtimox in this family when it was approved as the first oral monotherapy against Human African trypanosomiasis (HAT). Nitroaromatic prodrugs are bioactivated by the trypanosome-specific type I nitroreductase (NTR) that renders the compounds trypanocidal. The trypanocidal activity of nitroaromatic drugs has been proposed to arise from the formation of reactive oxygen species (ROS) and DNA damage. However, the specific cytotoxic effects of nitroaromatic drugs had not been thoroughly interrogated. Here we evaluate and compare the effects of clinically relevant anti-trypanosome nitroaromatic drugs using cell biology phenotypes including cell cycle progression, DNA synthesis, and DNA damage formation in the African trypanosome. We observed that fexinidazole induced cytotoxicity is distinct from related nitroaromatic drugs in its inhibition of DNA synthesis and the timing and magnitude of DNA damage formation. These findings highlight the relationship between nitroaromatic drug treatments, DNA damage formation, and ROS activation. Deconvolving the relationship between anti-parasitic drugs and the molecular basis of their cytotoxic outcomes will support future mechanistic understanding and enable improved drug design.