Colony stimulating factor 1 (CSF1) receptor (CSF1R) is a receptor protein-tyrosine kinase specifically expressed in monocyte-lineage cells, such as monocytes and macrophages. In this study, we characterized the pharmacological properties of an azetidine compound, JTE-952 ((2S)-3-{[2-({3-[4-(4-cyclopropylbenzyloxy)-3-methoxyphenyl]azetidine-1-yl}carbonyl)pyridin-4-yl]methoxy}propane-1,2-diol), which is a novel CSF1R tyrosine kinase inhibitor. JTE-952 potently inhibited human CSF1R kinase activity, with a half maximal inhibitory concentration of 11.1 nmol/L, and inhibited the phosphorylation of CSF1R in human macrophages and the CSF1-induced proliferation of human macrophages. It also inhibited human tropomyosin-related kinase A activity, but only at concentrations 200-fold higher than that required to inhibit the activity of CSF1R in inducing the proliferation of human macrophages. JTE-952 displayed no marked inhibitory activity against other kinases. JTE-952 potently inhibited lipopolysaccharide-induced proinflammatory cytokine production by human macrophages and in whole blood. JTE-952 (≥3 mg/kg given orally) also significantly attenuated the CSF1-induced priming of lipopolysaccharide-induced tumor necrosis factor-alpha production in mice and arthritis severity in a mouse model of collagen-induced arthritis. Taken together, these results indicate that JTE-952 is an orally available compound with potent and specific inhibitory activity against CSF1R, both in vitro and in vivo. JTE-952 is a potentially clinically useful agent for various human inflammatory diseases, including rheumatoid arthritis.
Keywords: JTE-952; colony stimulating factor 1 receptor; kinase inhibitor; macrophage colony-stimulating factor; rheumatoid arthritis.