Design, synthesis and structure-activity relationship studies of pyrido[2,3-d]pyrimidin-7-ones as potent Janus Kinase 3 (JAK3) covalent inhibitors.

Aberrantly activated Janus kinase 3 (JAK3) has been constantly detected in various immune disorders and hematopoietic cancers, suggesting its potential of being an attractive therapeutic target for these indications. Clinical benefits of drugs selectively targeting JAK3 versus pan-JAK inhibitors remain unclear. In this study, we report the design and synthesis of a new series of JAK3 covalent inhibitors with a pyrido[2,3-d]pyrimidin-7-one scaffold. After the extensive SAR study, compound 10f emerged to be the most potent JAK3 inhibitor with an IC value of 2.0 nM. It showed excellent selectively proliferation inhibitory activity against U937 cells harboring JAK3 M511I mutation, while remained weakly active to the other tested cancer cells. Compound 10f also dose-dependently inhibited the phosphorylation of JAK3 and its downstream signal STAT5 in U937 cells. Taken together, 10f may serve as a promising tool molecule for treating cancers with aberrantly activated JAK3.