Unusual Backfolded Binding Poses of BAZ2A Bromodomain Binders

BAZ2A is a large multidomain protein overexpressed in aggressive prostate cancer, where it potentiates migration and invasion of other tissues. To counteract its metastasis-promoting role, small molecules interfering with the recognition of acetylated lysines by the BAZ2A bromodomain have been identified. However, unlike other bromodomains, BAZ2A has a shallow pocket, which significantly complicates the development of potent inhibitors. Here, we report the exploration of the acetyl-pyrrole scaffold, leading to the identification of BAZ2A-binding compounds assuming a peculiar, almost enclosed, conformation, as determined by X-ray crystallography. These molecules pose the basis for the development of potent BAZ2A macrocyclic inhibitors, as performed for other bromodomains.