The NS2B-NS3 protease has been identified as an attractive target for drug development against Zika virus (ZIKV) and combined drug repurposing and structure-based virtual screening has improved the development of antiviral drugs. In this study, we performed a structurebased virtual screening of 1861 Food and Administration (FDA) approved drugs available in DrugBank by the selection and docking validation of crystal structure of ZIKV NS2B-NS3 protease (PDB ID 5H4I) using Glide and DOCK 6 software. The antihistaminic chlorcyclizine (Grid score −24.8 kcal/ mol) exhibited the most promising interaction with NS2B-NS3 protease in comparison to crystallography ligand (Grid score −15.6 kcal/mol) by interaction to Tyr161 by hydrophobic interactions in the binding site of NS2B-NS3 which is recognized as an important amino acid in substrate molecular recognition. Cytotoxicity and global antiviral activity assay in Vero cells by MTT method showed that chlorcyclizine reduced the ZIKV induced cytopathic effect (EC 50 of 69.0 ± 7.3 μM and SI = 1.9), and explicit molecular dynamics simulations implemented on a NAMD program indicated great stability of chlorcyclizine in protease binding site, suggesting the repurposing of chlorcyclizine as a promising finding in anti-ZIKV drug development.

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