GSK778 (iBET-BD1) is a potent and selective BD1 bromodomain inhibitor of the BET proteins, with IC50s of 75 nM (BRD2 BD1), 41 nM (BRD3 BD1), 41 nM (BRD4 BD1), and 143 nM (BRDT BD1), respectively. GSK778 phenocopies the effects of pan-BET inhibitors in cancer models[1].

GSK778 inhibits BRD BD2 with the IC50s of 3950 nM (BRD2 BD2), 1210 nM (BRD3 BD2), 5843 nM (BRD4 BD2), and 17451 nM (BRDT BD2), respectively[1].GSK778 (0.01-10 μM; 72 hours) inhibits the proliferative activity of human primary CD4+ T cells and the production of effector cytokines including IFNγ, IL-17A and IL-22[1].GSK778 (0.001-10 μM; 5 days) has a more pronounced effect on the growth and viability of MDA-453, MOLM-13, K562, MV4-11, THP-1, and MDA-MB-231 cells[1].GSK778 (1000 nM; 72 hours) inhibits proliferation, induces a cell cycle arrest and apoptosis in MV4-11, MOLM13, MDA-MB-231 and MB453 cells[1].GSK778 (1000 nM; 12 days) reduces the clonogenic capacity of primary human AML cells[1].

GSK778 (15 mg/kg/BID; i.p. for 30 days) offers a superior survival advantage to iBET-BD2 in the aggressive MLL-AF9 AML model[1].GSK778 (15 mg/kg/BID; s.c. for 14 days) reduces the production of anti-keyhole limpet hemocyanin (KLH) IgM and is well tolerated[1].GSK778 exhibits Cmax (85 ng/mL), Tmax (1.48 h) and AUC∞ (132 ng.h/mL) following oral administration (10 mg/kg) in mice[1].

[1]. Omer G, et, al. Selective targeting of BD1 and BD2 of the BET proteins in cancer and immunoinflammation. Science. 2020 Apr 24; 368(6489): 387-394.