In vitro activity: Bromodomains (BD) are protein modules that bind acetylated lysine residues and are components of many epigenetic modifiers and transcription factors. The BET (Bromodomain and extra-terminal) family is composed of four members each harboring two tandem BDs. BET proteins are critical regulators of transcription through interactions with complexes including Mediator and p-TEFb at gene promoter and enhancer elements. Studies using genetic knockdown and small molecule inhibitors have demonstrated that targeting BET proteins is therapeutic in models of cancer and acute inflammation. We describe the preclinical activity of a novel BET inhibitor INCB054329 for the potential treatment of malignant diseases. INCB054329 is a novel potent and selective inhibitor of Bromodomain and extra-terminal (BET) protein. It that targets Bromodomains 1 (BD1) and BD2 of BRD2, BRD3 and BRD4. INCB054329 inhibited binding of BRD2, BRD3 and BRD4 to an acetylated histone H4 peptide with low nanomolar potency.

Kinase Assay: INCB054329 is a novel potent and selective inhibitor of Bromodomain and extra-terminal (BET) protein. It that targets Bromodomains 1 (BD1) and BD2 of BRD2, BRD3 and BRD4. INCB054329 inhibited binding of BRD2, BRD3 and BRD4 to an acetylated histone H4 peptide with low nanomolar potency.

Cell Assay: In myeloma cell lines, treatment with INCB054329 inhibited expression of c-MYC and induced HEXIM1. The majority of myeloma, AML, and lymphoma cell lines tested were growth inhibited by INCB054329 with potencies less than 200 nM. Selectivity was seen when compared with nontransformed cells as the potency for growth inhibition of IL-2 stimulated T-cells from normal donors was greater than 1300 nM. Cell cycle analysis revealed treatment-induced G1 arrest. Furthermore in both AML and lymphoma cell lines, INCB054329 induced apoptosis consistent with increased expression of pro-apoptotic regulators.