Trypanosoma cruzi Malic Enzyme Is the Target for Sulfonamide Hits from the GSK Chagas Box.

Chagas disease, an infectious condition caused by Trypanosoma cruzi, lacks treatment with drugs with desired efficacy and safety profiles. To address this unmet medical need, a set of trypanocidal compounds were identified through a large multicenter phenotypic-screening initiative and assembled in the GSK Chagas Box. In the present work, we report the screening of the Chagas Box against T. cruzi malic enzymes (MEs) and the identification of three potent inhibitors of its cytosolic isoform (TcMEc). One of these compounds, TCMDC-143108 (1), came out as a nanomolar inhibitor of TcMEc, and 14 new derivatives were synthesized and tested for target inhibition and efficacy against the parasite. Moreover, we determined the crystallographic structures of TcMEc in complex with TCMDC-143108 (1) and six derivatives, revealing the allosteric inhibition site and the determinants of specificity. Our findings connect phenotypic hits from the Chagas Box to a relevant metabolic target in the parasite, providing data to foster new structure-activity guided hit optimization initiatives.

Development of Selective Steroid Inhibitors for the Glucose-6-phosphate Dehydrogenase from Trypanosoma cruzi.

Chagas disease is a parasitic infection affecting millions of people across Latin America, imposing a dramatic socioeconomic burden. Despite the availability of drugs, nifurtimox and benznidazole, lack of efficacy and incidence of side-effects prompt the identification of novel, efficient, and affordable drug candidates. To address this issue, one strategy could be probing the susceptibility of Trypanosoma parasites toward NADP-dependent enzyme inhibitors. Recently, steroids of the androstane group have been described as highly potent but nonselective inhibitors of parasitic glucose-6-phosphate dehydrogenase (G6PDH). In order to promote selectivity, we have synthesized and evaluated 26 steroid derivatives of epiandrosterone in enzymatic assays, whereby 17 compounds were shown to display moderate to high selectivity for T. cruzi over the human G6PDH. In addition, three compounds were effective in killing intracellular T. cruzi forms infecting rat cardiomyocytes. Altogether, this study provides new SAR data around G6PDH and further supports this target for treating Chagas disease.

Discovery of Potent N-Ethylurea Pyrazole Derivatives as Dual Inhibitors of Trypanosoma brucei and Trypanosoma cruzi.

Trypanosoma brucei (T. brucei) and Trypanosoma cruzi (T. cruzi) are causative agents of parasitic diseases known as human African trypanosomiasis and Chagas disease, respectively. Together, these diseases affect 68 million people around the world. Current treatments are unsatisfactory, frequently associated with intolerable side-effects, and generally inadequate in treating all stages of disease. In this paper, we report the discovery of N-ethylurea pyrazoles that potently and selectively inhibit the viability of T. brucei and T. cruzi. Sharp and logical SAR led to the identification of 54 as the best compound, with an in vitro IC50 of 9 nM and 16 nM against T. b. brucei and T. cruzi, respectively. Compound 54 demonstrates favorable physicochemical properties and was efficacious in a murine model of Chagas disease, leading to undetectable parasitemia within 6 days when CYP metabolism was inhibited.

In Vitro Image-Based Assay for Trypanosoma cruzi Intracellular Forms.

The advances in development and popularization of automated fluorescence microscopes and pipetting robots allowed scientists to establish high-throughput compound screening using image-based assays for Trypanosoma cruzi intracellular forms, which are associated to chronic Chagas disease. An intracellular T. cruzi image-based assay is a valuable tool to early stage drug discovery for Chagas disease, because it allows scientists to assess a compound's efficacy and safety in the same experiment. During the last 10 years, several improvements have been incorporated into intracellular T. cruzi assay protocols to make them more predictable in what happens with parasites within an infected organism. In the present chapter, a protocol will be presented for an intracellular T. cruzi assay, but at a low-throughput scale, more compatible with facilities in many academic laboratories.