Ivermectin, a new old drug for Chagas disease?

MD, RUIZ; CLAUSI A; L. LAROCCA; DE PINO, V; CARRILLO C; L. FRACCAROLI,

Congreso; XXXI Molecular Parasitology Meeting; 2020

Chagas disease is an endemic parasitosis originally from Latin America, caused by the protozoan Trypanosoma cruzi (T. cruzi). The current therapies (benznidazole - BZN and nifurtimox - NFX) are limited in efficacy and show multiple side effects. Thus, there is a need to identify new effective and specific trypanocidal strategies. Ivermectin (IVM) is a broad-spectrum antiparasitic drug of human and veterinary use. It is used for both ecto- and endo-parasite treatments and presents low toxicity in humans. These factors, along with its relative low cost, make IVM an interesting drug candidate for Chagas disease treatment. In previous studies, IVM has shown an effect against T. brucei and Leishmania in animal infection models.Beginning our evaluation of IVM as a potential trypanocidal drug, the aim of this work was to characterize the effects of IVM on T. cruzi epimastigotes and other trypanosomatids.To approach this aim, we performed growth curves of epimastigotes of the Y-GFP strain in the presence of IVM (0 - 50 µM). The cultures were evaluated by cell counting in Neubauer chamber, optical density at 630 nm and MTT for 8 days. IVM dose dependently reduced the proliferation of the parasites. The relative density and the viability significantly decreased while duplication time increased, assessed at day 4 of culture. The EC50, also calculated at day 4 of culture, was 12.5 µM (10.8 - 14.5 µM). Recovery assays showed that IVM had trypanocidal or trypanostatic effects depending on the drug dose but not on the exposure time, being trypanocidal at 100 µM IVM from 30 minutes up to 4 hours of exposure. The selectivity index was 2.4 (EC50 29.9 uM of IVM on Vero cell line).To assess the interaction between IVM and BZN or NFX, epimastigotes were cultured in the presence of different combinations of those drugs according to a combination matrix and then relative density was analyzed by Combenefit and Compusyn softwares. This analysis showed mainly an additive effect with significant antagonism or synergism depending on the drug concentrations.In related trypanosomatids, IVM affected the proliferation of Phytomonas jma and Leishmania mexicana, with an estimated EC50 of 5.5 µM and 11.7 µM respectively, while it did not affect Crithidia fasciculata.These results showed that IVM affects the proliferation and viability of T. cruzi epimastigotes and other trypanosomatids suggesting that it is a good candidate drug to continue the study in the Chagas disease context.