Structural Activity Relationship Study on Dual PLK1 /BRD4 Inhibitor, BI- 2536

Polo-like kinase 1 (PLK1) and BRD4 are two different therapeutic targets in cancer drug discovery. Recently it has been reported that PLK1 inhibitor, BI-2536, is also a potent inhibitor of BRD4. The simultaneous inhibition of PLK1 and BRD4 by a single drug molecule is interesting because this could lead to the development of effective therapeutic strategy for different types of disease conditions in which PLK1 and BRD4 are implicated. Structural activity relationship studies has been carried out on BI-2536 to generate analogs with enhanced dual inhibitory activity against BRD4 and PLK1 as well as to render the molecule selective to one target over the other. UMB101 and 160 have been found to exhibit enhanced dual inhibitory activity with selectivity fold of less than 30, UMB160 being the most potent dual-kinase bromodomain inhibitor (BRD4 IC50 = 28 nM, PLK1 IC50 = 40 nM). UMB131 was found to be the most selective PLK1 inhibitor over BRD4

Development of Dimethylisoxazole-Attached Imidazo[1,2‑a]pyridines as Potent and Selective CBP/P300 Inhibitors

The use of epigenetic bromodomain inhibitors as anticancer therapeutics has transitioned from targeting bromodomain extraterminal domain (BET) proteins into targeting non-BET bromodomains. The two most relevant non-BET bromodomain oncology targets are cyclic AMP response element-binding protein (CBP) and E1A binding protein P300 (EP300). To explore the growing CBP/EP300 interest, we developed a highly efficient two-step synthetic route for dimethylisoxazole-attached imidazo[1,2-a]pyridine scaffold-containing inhibitors. Our efficient two-step reactions enabled high-throughput synthesis of compounds designed by molecular modeling, which together with structure-activity relationship (SAR) studies facilitated an overarching understanding of selective targeting of CBP/EP300 over non-BET bromodomains. This led to the identification of a new potent and selective CBP/EP300 bromodomain inhibitor, UMB298 (compound 23, CBP IC50 72 nM and bromodomain 4, BRD4 IC50 5193 nM). The SAR we established is in good agreement with literature-reported CBP inhibitors, such as CBP30, and demonstrates the advantage of utilizing our two-step approach for inhibitor development of other bromodomains

Development of Dimethylisoxazole-Attached Imidazo[1,2a]pyridines as Potent and Selective CBP/P300 Inhibitors

The use of epigenetic bromodomain inhibitors as anti-cancer therapeutics has transitioned from targeting bromodomain extra terminal (BET) proteins into targeting non-BET bromodomains. The two most relevant non-BET bromodomain oncology targets are cyclic AMP response element-binding protein (CBP) and E1A binding protein P300 (EP300). To explore the growing CBP/EP300 interest, we developed a highly efficient two-step synthetic route for dimethylisoxazole-attached imidazo[1,2-a]pyridine scaffold-containing inhibitors. Our efficient two-step reactions enabled high-throughput synthesis of compounds designed by molecular modeling which together with structure activity relationship (SAR) studies facilitated overarching understanding of selective targeting of CBP/EP300 over non-BET bromodomains. This led to identification of a new potent and selective CBP/EP300 bromodomain inhibitor, UMB298 (compound 23, CBP IC(50) 72 nM and BRD4 IC(50) 5193 nM). The SAR we established is in good agreement with literature reported CBP inhibitors, such as CBP30, and demonstrates the advantage of utilizing our two-step approach for inhibitor development of other bromodomains