with benzo [cd]indol-2(1H)-one scaffold was identified as an effective BRD4 inhibitor through the AlphaScreen-based high-throughput screening and its high-resolution crystal structure with BRD4_BD1 protein. A series of 48 compounds were designed and synthesized by structural optimization on compound 1. All the compounds have been evaluated for their BRD4 inhibitory activities. The results showed that