851331-05-0

YM-53403 is a respiratory syncytial virus (RSV) inhibitor. YM-53403 potently inhibited the replication of RSV strains belonging to both A and B subgroups, but not influenza A virus, measles virus, or herpes simplex virus type 1. A plaque reduction assay was used to determine the 50% effective concentration (EC(50)) value for YM-53403. The value, 0.20 microM, was about 100-fold more potent than ribavirin. YM-53403 is an attractive compound for the treatment of RSV infection because of its highly potent anti-RSV activity and the new mode of action, which differs from that of currently reported antiviral agents.