A, In vitro kinase assay analysis of the PAK1 inhibitory activities of 17 compounds compared with OSU-03012. B, Dose-response suppression of PAK1 activity by compounds 1, 3, 4, 10, 11, 15, and OSU-03012 at indicated concentrations. C and D, ATP competition assay for PAK1 kinase. The activity of PAK1 was determined in the presence of varying concentrations of ATP (5 μM–40 μM) at indicated concentrations of compounds 4 and 15. The plot shown is representative of 3 separate experiments performed in duplicate.