Design of a Chemical Probe for the Bromodomain and Plant Homeodomain Finger-Containing (BRPF) Family of Proteins

The bromodomain and plant homeodomain finger-containing (BRPF) family are scaffolding proteins important for the recruitment of histone acetyltransferases of the MYST family to chromatin. Here, we describe <b>NI-57</b> (<b>16</b>) as new pan-BRPF chemical probe of the bromodomain (BRD) of the BRPFs. Inhibitor <b>16</b> preferentially bound the BRD of BRPF1 and BRPF2 over BRPF3, whereas binding to BRD9 was weaker. Compound <b>16</b> has excellent selectivity over nonclass IV BRD proteins. Target engagement of BRPF1B and BRPF2 with <b>16</b> was demonstrated in nanoBRET and FRAP assays. The binding of <b>16</b> to BRPF1B was rationalized through an X-ray cocrystal structure determination, which showed a flipped binding orientation when compared to previous structures. We report studies that show <b>16</b> has functional activity in cellular assays by modulation of the phenotype at low micromolar concentrations in both cancer and inflammatory models. Pharmacokinetic data for <b>16</b> was generated in mouse with single dose administration showing favorable oral bioavailability