B: High-throughput screening of a 100,000 compound library for inhibitors of influenza A virus (H3N2

Using a highly reproducible and robust cell-based high-throughput screening (HTS) assay, the authors screened a 100,000-compound library at 14- and 114-μM compound concentration against influenza strain A/Udorn/72 (H3N2). The “hit ” rates (>50 % inhibition of the viral cytopathic effect) from the 14- and 114-μM screens were 0.022 % and 0.38%, respectively. The hits were evaluated for their antiviral activity, cell toxicity, and selectivity in dose-response experiments. The screen at the lower concentration yielded 3 compounds, which displayed moderate activity (SI50 = 10-49). Intriguingly, the screen at the higher concentration revealed several additional hits. Two of these hits were highly active with an SI50> 50. Time of addi-tion experiments revealed 1 compound that inhibited early and 4 other compounds that inhibited late in the virus life cycle, suggesting they affect entry and replication, respectively. The active compounds represent several different classes of molecules such as carboxanilides, 1-benzoyl-3-arylthioureas, sulfonamides, and benzothiazinones, which have not been previously identified as having antiviral/anti-influenza activity. (Journal of Biomolecular Screening 2008:879-887