Carlos A. Montanari
Carlos A. Montanari (USP, São Carlos/Brazil)
Non-peptidic Cruzain Inhibitors with Trypanocidal Activity Discovered by Virtual Screening and in vitro Assay
A multi-step cascade strategy using integrated ligand- and target-based virtual screening methods was developed to select a small number of compounds from the ZINC database to be evaluated for trypanocidal activity. Winnowing the database to 23 selected compounds, 12 non-covalent binding cruzain inhibitors with affinity values (Ki) in the low micromolar range (3–60 µM) acting through a competitive inhibition mechanism were identified. This mechanism has been confirmed by determining the binding mode of the cruzain inhibitor Nequimed176 through X-ray crystallographic studies. In order to select the most promising enzyme inhibitors retaining trypanocidal activity for structure-activity relationship (SAR) studies, the most potent cruzain inhibitors were assayed against T. cruzi-infected cells. Two compounds were found to have trypanocidal activity. Using compound Nequimed42 as precursor, an SAR was established in which the 2-acetamidothiophene-3-carboxamide group was identified as essential for enzyme and parasite inhibition activities. The IC50 value for compound Nequimed42 acting against the trypomastigote form of the Tulahuen lacZ strain was found to be 10.6 ± 0.1 µM, tenfold lower than that obtained for benznidazole, which was taken as positive control. In addition, by employing the strategy of molecular simplification, a smaller compound derived from Nequimed42 with a ligand efficiency (LE) of 0.33 kcal mol-1 atom-1 (compound Nequimed176) is highlighted as a novel non-peptidic, noncovalent cruzain inhibitor as a trypanocidal agent candidate for optimization. Perspectives on fragment based virtual screening for the identification of new fragments that inhibit cruzain will be shown.
Refs.: (1) Helton J. Wiggers, Josmar R. Rocha,William B. Fernandes, Renata Sesti-Costa, Zumira A. Carneiro, Juliana Cheleski, Albérico B. F. da Silva, Luiz Juliano, Maria H. S. Cezari, João S. Silva, James H. McKerrow, Carlos A. Montanari. “Non-peptidic Cruzain Inhibitors with Trypanocidal Activity Discovered by Virtual Screening and In Vitro Assay” PLoS Negl. Trop. Dis. 2013, 7(8): e2370. doi:10.1371/journal.pntd.0002370; (2) H. J. Wiggers, J. R. Rocha, J. Cheleski, and C. A. Montanari “Integration of Ligand- and Target-Based Virtual Screening for the Discovery of Cruzain Inhibitors” Mol. Inf. 2011, 30, 565 – 578 DOI: 10.1002/minf.201000146.
Acknowledgments: FAPESP, CNPq, CAPES
