posted on 2022-01-10, 21:45authored byHuarui Cui, Anand Divakaran, Zachariah J. Hoell, Mikael O. Ellingson, Cole R. Scholtz, Huda Zahid, Jorden A. Johnson, Elizabeth C. Griffith, Clifford T. Gee, Amani L. Lee, Shalil Khanal, Ke Shi, Hideki Aihara, Vijay H. Shah, Richard E. Lee, Daniel A. Harki, William C. K. Pomerantz
Chemical probes for epigenetic proteins
are essential tools for
dissecting the molecular mechanisms for gene regulation and therapeutic
development. The bromodomain and extra-terminal (BET) proteins are
master transcriptional regulators. Despite promising therapeutic targets,
selective small molecule inhibitors for a single bromodomain remain
an unmet goal due to their high sequence similarity. Here, we address
this challenge via a structure–activity relationship study
using 1,4,5-trisubstituted imidazoles against the BRD4 N-terminal
bromodomain (D1). Leading compounds 26 and 30 have 15 and 18 nM affinity against BRD4 D1 and over 500-fold selectivity
against BRD2 D1 and BRD4 D2 via ITC. Broader BET selectivity was confirmed
by fluorescence anisotropy, thermal shift, and CETSA. Despite BRD4
engagement, BRD4 D1 inhibition was unable to reduce c-Myc expression
at low concentration in multiple myeloma cells. Conversely, for inflammation,
IL-8 and chemokine downregulation were observed. These results provide
new design rules for selective inhibitors of an individual BET bromodomain.