Discovery of a Potent and Selective in Vivo Probe (GNE-272) for the Bromodomains of CBP/EP300

The single bromodomain of the closely related transcriptional regulators CBP/EP300 is a target of much recent interest in cancer and immune system regulation. A co-crystal structure of a ligand-efficient screening hit and the CBP bromodomain guided initial design targeting the LPF shelf, ZA loop, and acetylated lysine binding regions. Structure–activity relationship studies allowed us to identify a more potent analogue. Optimization of permeability and microsomal stability and subsequent improvement of mouse hepatocyte stability afforded <b>59</b> (GNE-272, TR-FRET IC₅₀ = 0.02 μM, BRET IC₅₀ = 0.41 μM, BRD4(1) IC₅₀ = 13 μM) that retained the best balance of cell potency, selectivity, and in vivo PK. Compound <b>59</b> showed a marked antiproliferative effect in hematologic cancer cell lines and modulates <i>MYC</i> expression in vivo that corresponds with antitumor activity in an AML tumor model