Description: GNE-049 is a novel, highly potent and selective CBP/p300 bromodomain inhibitor with an IC50 of 1.1 nM in TR-FRET assay. GNE-049 also inhibits BRET and BRD4(1) with IC50s of 12 nM and 4200 nM, respectively. Inhibition of the bromodomain of the transcriptional regulator CBP/P300 is an especially interesting new therapeutic approach in oncology. It was discovered based on the in vivo chemical tool 1 (GNE-272) for the bromodomain of CBP that was moderately potent and selective over BRD4(1). In pursuit of a more potent and selective CBP inhibitor, we used structure-based design. Constraining the aniline of 1 into a tetrahydroquinoline motif maintained potency and increased selectivity 2-fold. Structure-activity relationship studies coupled with further structure-based design targeting the LPF shelf, BC loop, and KAc regions allowed us to significantly increase potency and selectivity, resulting in the identification of non-CNS penetrant 19 (GNE-781, TR-FRET IC50 = 0.94 nM, BRET IC50 = 6.2 nM; BRD4(1) IC50 = 5100 nΜ) that maintained good in vivo PK properties in multiple species. GNE-049 displays antitumor activity in an AML tumor model and was also shown to decrease Foxp3 transcript levels in a dose dependent manner.