666-15 is an inhibitor of gene transcription mediated by cAMP-response-element-binding protein (CREB, IC50 = 81 nM in a cell-based reporter assay). It inhibits the growth of A549, MCF-7, MDA-MB-231, and MDA-MB-468 cells (GI50s = 0.47, 0.31, 0.073, and 0.046 µM, respectively). 666-15 (10 mg/kg per day, five days per...