10.1016/j.bmcl.2018.10.051
The study focuses on identifying a new class of azetidine compounds as selective CSF-1R Type II kinase inhibitors. CSF-1R is a receptor tyrosine kinase involved in the differentiation, proliferation, and survival of monocyte-macrophage lineage cells, and its inhibition is considered therapeutic for conditions like rheumatoid arthritis. The researchers used structure-based drug design, guided by docking models, to develop these azetidine compounds. They synthesized various azetidine analogues, such as compounds 1a-d, 2a-b, and 3a-b, to explore the optimal binding configurations. The study identified compound 4a, with a CSF-1R inhibitory activity of IC50 = 9.1 nM, as a potent inhibitor. The researchers also obtained a co-crystal structure of an azetidine compound with CSF-1R, confirming that these compounds bind to the DFG-out conformation of the protein as Type II inhibitors. This work highlights the potential of azetidine scaffolds for developing selective and potent CSF-1R inhibitors.