I-BET151(GSK1210151A) is a BET bromodomain inhibitor. I-BET151 displays potent binding affinity to BRD2, BRD3 and BRD4 with Kd of 0.02-0.1 µM. I-BET151 (0.5 or 5 µM) inhibits the binding of BETs (BRD2, BRD3, BRD4, and BRD9) but not the binding of 23 other bromodomain proteins. I-BET151 also blocks recruitment of BET to chromatin.