Therefore, development of novel anti influenza therapies is urgently needed. As one of the viral surface glycoproteins, hemagglutinin HA mediates critical virus entry steps including virus binding to host cells and virus host membrane fusion, which makes it a potential target for anti influenza drug development. In this study, we report the identification of compound CBS1116 with a 4 aminopiperidine scaffold from a chemical library screen as an entry inhibitor specifically targeting two group 1 influenza A viruses, A Puerto Rico 8 34 H1N1 and recombinant low pathogenic avian H5N1 virus A Vietnam 1203 04, VN04 Low . ...