Lead Optimization of Influenza Virus RNA Polymerase Inhibitors Targeting PA–PB1 Interaction

Influenza viruses are responsible for contagious respiratory illnesses in humans and cause seasonal epidemics and occasional pandemics worldwide. Previously, we identified a quinolinone derivative PA-49, which inhibited the influenza virus RNA-dependent RNA polymerase (RdRp) by targeting PA–PB1 interaction. This paper reports the structure optimization of PA-49, which resulted in the identification of 3-((dibenzylamino)­methyl)­quinolinone derivatives with more potent anti-influenza virus activity. During the optimization, the hit compound 89, which was more active than PA-49, was identified. Further optimization and scaffold hopping of 89 led to the most potent compounds 100 and a 1,8-naphthyridinone derivative 118, respectively. We conclusively determined that compounds 100 and 118 suppressed the replication of influenza virus and exhibited anti-influenza virus activity against both influenza virus types A and B in the range of 50% effective concentration (EC50) = 0.061–0.226 μM with low toxicity (50% cytotoxic concentration (CC50) >10 μM).