Drug repurposing for Chagas disease: overcoming the hit-to-preclinical candidate stage

Building upon our previous work on drug repurposing and the use of binary combinations as anti-Chagas agents, we detail our efforts to advance the most promising repositioned compounds and binary mixtures for in vitro usage beyond the hit-to-preclinical candidate stage. Accordingly, five repositioned active principles and four binary combinations of these agents that were selected for their in vitro isobolographic behaviors were evaluated in a murine model of acute Chagas disease. In the study, these nine systems were administered orally along with the negative and positive controls (benznidazole) for 15 d. The changes in the parasitemia levels and animal survival over time were evaluated together with the anti- Trypanosoma cruzi antibody levels at the end of the trials. Gabapentin was found to be the most notable repositioned drug as it decreased parasitemia and anti- T. cruzi antibody levels significantly while improving animal survival modestly. The best animal survival profile was achieved when gabapentin was combined with naftazone. Furthermore, the combination of naftazone and red clover extract, which is trademarked in Uruguay as Climodin, was another noteworthy binary mixture; this combination exhibited a consistent parasitemia reduction profile along with the best antibody reduction; however, it did not yield the best animal survival profile, which is in line with our previous in vitro findings. To advance preclinical studies, we further studied the mutagenicity of both binary combinations with and without metabolic activation, which showed that there were no observable mutagenic effects.