Design, synthesis and biological evaluation of imidazo[1,5-a] pyrazin-8(7H)-one derivatives as BRD9 inhibitors

BRD9 is the subunit of mammalian SWI/SNF chromatin remodeling complex (BAF). SWI/SNF complex mutations were found in nearly 20% of human cancers. The biological role played by BRD9 bromodomain remains poorly understood, and it is therefore imperative to identify potent and highly selective inhibitors to effectively explore the biology of individual bromodomain proteins. In this paper, we synthesized a series of imidazo[1,5-a] pyrazin-8(7H)-one derivatives as potent BRD9 inhibitors and evaluated their BRD9 inhibitory activity in vitro and anti-proliferation effects against tumor cells. Gratifyingly, compound 27 and 29 exhibited robust potency of BRD9 inhibition with IC50 values of 35 and 103 nM respectively. Docking studies were performed to explain the structure-activity relationship. Furthermore, compound 27 potently inhibited cell proliferation in cell lines A549 and EOL-1 with an IC50 value of 6.12 mu M and 1.76 mu M respectively. The chemical probe, compound 27, was identified that should prove to be useful in further exploring BRD9 bromodomain biology in both in vitro and in vivo settings.