CBP/p300 is functionally implicated in the progression of multiple hematological malignancies. Picaud and colleagues developed a new selective and highly potent chemical probe I-CBP112 targeting the bromodomains of CBP/p300. Treatment of human acute myeloid leukemia (AML) cells growing in methylcellulose with 1, 3, and 5 μmol/L of the compound reduced the clonogenic growth of the cells in a dose-dependent manner. Cytospin preparations of I-BP112–treated primary AML blasts showed morphologic signs of differentiation. For details, see article by Picaud and colleagues on page 5106.