Non-Nucleoside Inhibitors Decrease Foot-and-Mouth Disease Virus Replication by Blocking the Viral 3D pol .

Foot-and-mouth disease virus (FMDV), an economically important pathogen of cloven-hoofed livestock, is a positive-sense, single-stranded RNA virus classified in the Picornaviridae family. RNA-dependent RNA polymerase (RdRp) of RNA viruses is highly conserved. Compounds that bind to the RdRp active site can block viral replication. Herein, we combined double virtual screenings and cell-based antiviral approaches to screen and identify potential inhibitors targeting FMDV RdRp (3D ^pol ). From 5596 compounds, the blind- followed by focus-docking filtered 21 candidates fitting in the 3D ^pol active sites. Using the BHK-21 cell-based assay, we found that four compounds-NSC217697 (quinoline), NSC670283 (spiro compound), NSC292567 (nigericin), and NSC65850-demonstrated dose-dependent antiviral actions in vitro with the EC50 ranging from 0.78 to 3.49 µM. These compounds could significantly block FMDV 3D ^pol activity in the cell-based 3D ^pol inhibition assay with small IC50 values ranging from 0.8 nM to 0.22 µM without an effect on FMDV's main protease, 3C ^pro . The 3D ^pol inhibition activities of the compounds were consistent with the decreased viral load and negative-stranded RNA production in a dose-dependent manner. Conclusively, we have identified potential FMDV 3D ^pol inhibitors that bound within the enzyme active sites and blocked viral replication. These compounds might be beneficial for FMDV or other picornavirus treatment.