AT-7519 is a potent CDK inhibitor with potential antineoplastic activity. AT-7519 displays potent antiproliferative activity (40-940 nM) in a panel of human tumor cell lines, and the mechanism of action is shown to be consistent with the inhibition of CDK1 and CDK2 in solid tumor cell lines. AT-7519 causes cell cycle arrest followed by apoptosis in human tumor cells and inhibits tumor growth in human tumor xenograft models.