INCB057643 inhibited binding of BRD2/BRD3/BRD4 to an acetylated histone H4 peptide in the low nM range and was selective against other bromodomain-containing proteins. INCB057643 inhibited proliferation of human AML, DLBCL, and multiple myeloma cell lines, with a corresponding decrease in MYC protein levels. Cell cycle analyses indicated that G1 arrest and a concentration-dependent increase in apoptosis were seen within 48 hours of treatment with INCB057643. BRD proteins also regulate the expression of many pro-inflammatory genes. Production of several cytokines, including IL-6, IL-10 and MIP-1α, was repressed by INCB057643 in human and mouse whole blood stimulated ex vivo with LPS [1].

Oral administration of INCB057643 resulted in significant anti-tumor efficacy in xenograft models of AML, myeloma, and DLBCL. Additionally, combining INCB057643 with the standard of care agents used for the treatment of DLBCL including rituximab and bendamustine resulted in enhanced anti-tumor efficacy relative to that achieved with single-agent therapies at doses that were well tolerated [1].