Discovery of Influenza Neuraminidase Inhibitors: Structure-Based Virtual Screening and Biological Evaluation of Novel Chemotypes

Neuraminidase (NA) decorates the surface of the influenza virus, exerting a sialidase activity that enables the viral particle to be released in the host cell. Numerous sialic-based antiviral agents competitively bind to the NA cavity and are marketed worldwide for the treatment of Influenza A infection. We designed and validated a structure-based pharmacophore model for influenza neuraminidase (NA), which guided a virtual screening campaign against an in-house library of compounds already available for testing. This fast and cost-effective in silico strategy resulted in the identification of seven candidates possessing indole or isoquinoline chemical core. In vitro assays confirmed their favorable cytotoxicity profiles and identified only one, the 1-(1<i>H</i>-indol-3-ylcarbonyl)-3-piperidinecarboxylic acid (1), with reproducible inhibitory activity toward NA at non-cytotoxic concentrations. This work suggested a validated workflow for the discovery of novel NA inhibitors and highlighted an indole-based hit compound as a starting point for further optimization.