Among the CBP/p300-specific phenotypes, we found that I-CBP112, contrary to the BET inhibitor JQ1, did not show immediate cytotoxic effects on leukemic cell lines immortalized by the MLL-CBP fusion and other potent leukemia-associated oncogenes including the MLL-AF9, MLL-ENL or the NUP98-HOXA9, which were exposed to the compound, but instead impaired colony formation and induced cellular differentiation. This evidence concerns the gene CREBBP and leukemia.