Leishmaniasis is a neglected vector-born disease caused by a protozoan of the genus Leishmania and affecting more than 1.300.000 people worldwide. The couple tryparedoxin/tryparedoxin peroxidase is essential for parasite survival in the host since it neutralizes the hydrogen peroxide produced by macrophages during the infection. Herein we report a study aimed at discovering the first class of compounds able to non-covalently inhibit tryparedoxin peroxidase. We have solved the high-resolution structure of Tryparedoxin peroxidase I from Leishmania major (LmTXNPx) in the reduced state and in fully folded conformation. A first series of compounds able to inhibit LmTXNPx was identified by means of the high throughput docking technique. The inhibitory activity of these compounds was validated by a Horseradish peroxidase-based enzymatic assay and their affinity for LmTXNPx calculated by surface plasmon resonance experiments. On the basis of these results, the analysis of the enzyme-inhibitor docked models allowed us to rationally design and synthesize a series of N,N-disubstituted 3-aminomethyl quinolones. These compounds showed an inhibitory potency against LmTXNPx in the micromolar range. Among them, compound 12 represents the first non-covalent LmTXNPx inhibitor reported to date and could pave the way to the discovery of a new class of drugs against leishmaniasis.

The enzyme Zmp1 is a zinc-containing peptidase that plays a critical role in the pathogenicity of Mycobacterium tuberculosis. Herein we describe the identification of a small set of Zmp1 inhibitors based on a novel 8-hydroxyquinoline-2-hydroxamate scaffold. Among the synthesized compounds, N-(benzyloxy)-8-hydroxyquinoline-2-carboxamide (1 c) was found to be the most potent Zmp1 inhibitor known to date, and its binding mode was analyzed both by kinetics studies and molecular modeling, identifying critical interactions of 1 c with the zinc ion and residues in the active site. The effect of 1 c on intracellular Mycobacterium survival was assayed in J774 murine macrophages infected with M. tuberculosis H37Rv or M. bovis BCG and human monocyte-derived macrophages infected with M. tuberculosis H37Rv. Cytotoxicity and genotoxicity were also assessed. Overall, inhibitor 1 c displays interesting in vitro antitubercular properties worthy of further investigation.

Therapies addressing multiple stages of Plasmodium falciparum life cycle are highly desirable for implementing malaria elimination strategies. MMV019918 (1, 1-[5-(4-bromo-2-chlorophenyl)furan-2-yl]-N-[(piperidin-4-yl)methyl]methanamine) was selected from the MMV Malaria Box for its dual activity against both asexual stages and gametocytes. In-depth structure-activity relationship studies and cytotoxicity evaluation led to the selection of 25 for further biological investigation. The potential transmission blocking activity of 25 versus P. falciparum was confirmed through the standard membrane-feeding assay. Both 1 and 25 significantly prolonged atrioventricular conduction time in Langendorff-isolated rat hearts, and showed inhibitory activity of Ba current through Ca1.2 channels. An in silico target-fishing study suggested the enzyme phosphoethanolamine methyltransferase (PfPMT) as a potential target. However, compound activity against PfPMT did not track with the antiplasmodial activity, suggesting the latter activity relies on a different molecular target. Nevertheless, 25 showed interesting activity against PfPMT, which could be an important starting point for the identification of more potent inhibitors active against both sexual and asexual stages of the parasite.

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