Chagas disease is a potentially life-threatening and neglected tropical disease caused by Trypanosoma cruzi. One of the most important challenges related to Chagas disease is the search for new, safe, effective, and affordable drugs since the current therapeutic arsenal is inadequate and insufficient. Here, we report a simple and cost-effective synthesis and the biological evaluation of the second generation of Mannich base-type derivatives. Compounds 7, 9, and 10 showed improved in vitro efficiency and lower toxicity than benznidazole, in addition to no genotoxicity; thus, they were applied in in vivo assays to assess their activity in both acute and chronic phases of the disease. Compound 10 presented a similar profile to benznidazole from the parasitological perspective but also yielded encouraging data, as no toxicity was observed. Moreover, compound 9 showed lower parasitaemia and higher curative rates than benznidazole, also with lower toxicity in both acute and chronic phases. Therefore, further studies should be considered to optimize compound 9 to promote its further preclinical evaluation.

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Access to basic drugs is a major issue in developing countries. Chagas disease caused by Trypanosoma cruzi is a paradigmatic example of a chronic disease without an effective treatment. Current treatments based on benznidazole and nifurtimox are expensive, ineffective, and toxic. N,N'-Squaramides are amide-type compounds that feature both hydrogen bond donor and acceptor groups and are capable of multiple interactions with complementary sites. When combined with amine and carboxylic groups, squaramide compounds have increased solubility and therefore make suitable therapeutic agents. In this work, we introduce a group of Lipinski's rule of five compliant squaramides as candidates for treating Chagas disease. The in vivo studies confirmed the positive expectations arising from the preliminary in vitro studies, revealing compound 17 to be the most effective for both acute and chronic phases. The activity, stability, low cost of starting materials, and straightforward synthesis make amino squaramides appropriate molecules for the development of an affordable anti-Chagasic agent.

The in vivo trypanosomicidal activity of the imidazole-based benzo[g]phthalazine derivatives 1-4 and of the new related pyrazole-based compounds 5 and 6 has been studied in both the acute and chronic phases of Chagas disease. As a rule, compounds 1-6 were more active and less toxic than benznidazole in the two stages of the disease, and the monosubstituted derivatives 2, 4, and 6 were more effective than their disubstituted analogs. Feasible mechanisms of action of compounds 1-6 against the parasite have been explored by considering their inhibitory effect on the Fe-SOD enzyme, the nature of the excreted metabolites and the ultrastructural alterations produced. A complementary histopathological analysis has confirmed that the monosubstituted derivatives are less toxic than the reference drug, with the behavior of the imidazole-based compound 4 being especially noteworthy.