In Vitro, In Silico, and In Vivo Analyses of Novel Aromatic Amidines against Trypanosoma cruzi.

Five bis-arylimidamides were assayed as anti-Trypanosoma cruzi agents by in vitro, in silico, and in vivo approaches. None were considered to be pan-assay interference compounds. They had a favorable pharmacokinetic landscape and were active against trypomastigotes and intracellular forms, and in combination with benznidazole, they gave no interaction. The most selective agent (28SMB032) tested in vivo led to a 40% reduction in parasitemia (0.1 mg/kg of body weight/5 days intraperitoneally) but without mortality protection. In silico target fishing suggested DNA as the main target, but ultrastructural data did not match.

Clinical Candidate VT-1161's Antiparasitic Effect In Vitro, Activity in a Murine Model of Chagas Disease, and Structural Characterization in Complex with the Target Enzyme CYP51 from Trypanosoma cruzi.

A novel antifungal drug candidate, the 1-tetrazole-based agent VT-1161 [(R)-2-(2,4-difluorophenyl)-1,1-difluoro-3-(1H-tetrazol-1-yl)-1-{5-[4-(2,2,2-trifluoroethoxy)phenyl]pyridin-2-yl}propan-2-ol], which is currently in two phase 2b antifungal clinical trials, was found to be a tight-binding ligand (apparent dissociation constant [Kd], 24 nM) and a potent inhibitor of cytochrome P450 sterol 14α-demethylase (CYP51) from the protozoan pathogen Trypanosoma cruzi. Moreover, VT-1161 revealed a high level of antiparasitic activity against amastigotes of the Tulahuen strain of T. cruzi in cellular experiments (50% effective concentration, 2.5 nM) and was active in vivo, causing >99.8% suppression of peak parasitemia in a mouse model of infection with the naturally drug-resistant Y strain of the parasite. The data strongly support the potential utility of VT-1161 in the treatment of Chagas disease. The structural characterization of T. cruzi CYP51 in complex with VT-1161 provides insights into the molecular basis for the compound's inhibitory potency and paves the way for the further rational development of this novel, tetrazole-based inhibitory chemotype both for antiprotozoan chemotherapy and for antifungal chemotherapy.

In vitro analyses of the effect of aromatic diamidines upon Trypanosoma cruzi.

OBJECTIVES: Aromatic diamidines (ADs) have been recognized as promising antiparasitic agents. Therefore, in the present work, the in vitro trypanocidal effect of 11 ADs upon the relevant clinical forms of Trypanosoma cruzi was evaluated, as well as determining their toxicity to mammalian cells and their subcellular localization. METHODS: The trypanocidal effect upon trypomastigotes and amastigotes was evaluated by light microscopy through the determination of the IC(50) values. The cytotoxicity was determined by the MTT colorimetric assay against mouse cardiomyocytes. For the subcellular localization, transmission electron microscopy and fluorescence approaches were used. The fluorescence intensity within the kinetoplast DNA (kDNA) and nuclear DNA (nDNA) of treated parasites was determined using the Image J program. RESULTS: Compounds 2, 5 and 7 showed the lowest IC(50) values (micromolar range) against intracellular amastigotes and trypomastigotes. In the presence of blood, all the tested ADs exhibited a reduction of their activity. The compounds did not exhibit toxicity to cardiac cells and the highest selectivity index (SI) was achieved by compound 5 with an SI of >137 for trypomastigotes and compound 7 with an SI of >107 for intracellular parasites. The subcellular effects upon bloodstream forms treated with compounds 5 and 7 were mainly on kDNA, leading to its disorganization. The higher accumulation in the kDNA observed for all tested ADs was not directly related to their efficacy. CONCLUSIONS: Our results show the high activity of this new series of ADs against both trypomastigote and amastigote forms, with excellent SIs, especially compound 7, which merits further in vivo evaluation.

Anti-Trypanosoma cruzi Activity in vitro of Phases and Isolated Compounds from Excoecaria lucida Leaves.

BACKGROUND: Chagas disease is caused by the protozoan parasite Trypanosoma cruzi. This illness is found mainly in 21 Latin American countries and an estimated 8 million people are infected worldwide. The unsatisfactory chemotherapy provokes severe toxicity and resistant strains. Medicinal plants constitute a promising source of new drugs and remedies against all kinds of disorders, mainly infectious diseases arousing interest worldwide. OBJECTIVE: The aim of this study is the isolation, structural identification and evaluation of the trypanocidal activity of samples present in the Excoecaria lucida Sw. leaves. METHODS: Total extract (TE) of E. lucida Sw. leaves was obtained by ethanol extract therefore fractionated sequentially with hexane, ethyl acetate and n-butanol, to obtain three phases: Hex, EA and But, respectively. Ellagic acid (EL1) was purified from both EA and But phases, while EL2; a 1:1 stigmasterol-3-O-ß-D-glucopyranoside plus sitosterol-3-O-ß-D-glucopyranoside mixture was obtained from the Hex phase. Activity assays were performed using bloodstream and intracellular forms of T. cruzi and cytotoxicity assays using L929 fibroblasts. RESULTS: The EL1 and EL2 samples were more active against bloodstream trypomastigote forms with EC50 of 53.0±3.6 and 58.2±29.0 µg/mL, respectively; at 100 µg/mL. These samples also showed 70% of inhibition of L929 cells infection. Toxicity assays demonstrated that after 96 h of treatment only the fractions Hex and EA presented detectable cytotoxicity. CONCLUSION: Ellagic acid, stigmasterol-3-O-ß-D-glucopyranoside and sitosterol-3-O-ß-Dglucopyranoside are reported for the first time in E. lucida Sw. leaves as well as their biological activity studies supporting further investigations for Chagas disease treatment.