Influenza virus PA endonuclease: virtual screening and in-vitro validation of novel inhibitors

The influenza virus RNA-dependent RNA polymerase complex (RdRp), a heterotrimeric protein complex that is responsible for viral RNA transcription, represents an unexplored target for antiviral drug development. One particularly attractive approach is interference with the endonucleolytic "cap-snatching" reaction by the PA subunit of the RdRp, more precisely by inhibiting the metal-dependent catalytic activity which resides in the N-terminal part of PA (PA-Nter). In the last two decades, several small molecule PA inhibitors (PAIs) have been discovered. Among them, compounds belonging to the class of substituted 2,4-dioxobutanoic acids were identified as particularly potent and selective PAIs in both enzyme and cell-based assays. Here, we present a new coupled pharmacophore/docking virtual screening approach that allowed us to identify novel PAIs having interesting inhibitory activity in a PA-Nter enzymatic assay, as well as antiviral activity in a cell-based influenza virus yield assay.