Imidazole derivatives as promising agents for the treatment of Chagas disease{dagger} [Experimental Therapeutics]

More than 100 years later after being firstly described, Chagas disease remains endemic in 21 Latin American countries and has spread to other continents. Indeed, this disease, caused by the protozoan parasite Trypanosoma cruzi, is no longer just a problem for the American continent but has become a global health threat. Current therapies, nifurtimox and benznidazole (Bz), are far from being adequate due to undesirable effects and their lack of efficacy in the chronic phases of the disease. In this work, we present an in-depth phenotypical evaluation in T.cruzi of a new class of imidazole compounds, discovered in a previous phenotypic screening against different trypanosomatids and designed as potential inhibitors of cAMP phosphodiesterases (PDEs). The confirmation of several activities similar or superior to Bz prompted a synthesis program of hit optimization and extended SAR, aimed at improving drug-like properties such as aqueous solubility, resulting in additional hits with IC₅₀ similar to Bz. The cellular effects of one representative hit, compound 9, on bloodstream trypomastigotes were further investigated. Transmission electron microscopy revealed cellular changes, after just 2 h of incubation with the IC₅₀ concentration, that were consistent with induced autophagy and osmotic stress - mechanisms previously linked to cAMP signaling. Compound 9 induced highly significant increases in both cellular and medium cAMP, confirming that inhibition of T.cruzi PDE(s) is part of its mechanism of action. The potent and selective activity of this imidazole-based PDE inhibitor class against T.cruzi constitutes a successful repurposing of research into inhibitors of mammalian PDEs.

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