NG 52 (Compound 52 ) is a potent, cell-permeable, reversible, selective, and ATP-compatible inhibitor of the cell cycle-regulating kinase, Cdc28p (IC50 = 7 μM), and the related Pho85p kinase (IC50 = 2 μM). IC50 value: 7 uM [1] Target: Cdc28p Compound 52 inhibited growth in a drug-sensitized yeast strain with a GI 50 of 30 uM. In contrast, the closely related compound 52Me proved to be a significantly weaker inhibitor of yeast growth (GI50=200 uM).