PFI-3

PFI-3 is a selective, potent and cell-permeable SMARCA2/4 bromodomain inhibitor with a K_d of 89 nM. IC50 & Target: Kd: 89 nM (SMARCA2/4)^[1] In Vitro: PFI-3 is a potent, cell-permeable probe capable of displacing ectopically expressed, GFP-tagged SMARCA2-bromodomain from chromatin. PFI-3 binds avidly to both SMARCA2 and SMARCA4 bromodomains (BROMOScan K_d's between 55 and 110 nM) consistent with the binding constant (K_d=89 nM) measured by isothermal titration calorimetry. PFI-3 does not phenocopy the growth inhibitory effects of SMARCA2 knockdown in lung cancer^[1]. Exposure of embryonic stem cells to PFI-3 leads to deprivation of stemness and deregulates lineage specification. Furthermore, differentiation of trophoblast stem cells in the presence of PFI-3 is markedly enhanced^[2]. PFI-3 binds to certain family VIII bromodomains while displaying significant, broader bromodomain family selectivity. The high specificity of PFI-3 for family VIII is achieved through a novel bromodomain binding mode of a phenolic headgroup that leads to the unusual displacement of water molecules that are generally retained by most other bromodomain inhibitors reported to date^[3].