Design, synthesis and structure-activity relationship study of aminopyridine derivatives as novel inhibitors of Janus kinase 2

Janus Kinase 2 (JAK2) is a kind of intracellular non-receptor protein tyrosine kinase and has been certified as an important target for the treatment of myeloproliferative neoplasms and rheumatoid arthritis. However, the low selectivity and potential safety issues restrict the clinical applications of JAK2 inhibitors. Here we found that crizotinib showed good inhibitory activity against JAK2 by enzymatic assays (IC ₅₀ = 27 nM). Then we carried out structure-based drug design and synthesized a series of compounds with an aminopyridine scaffold. Finally, compound 12k and 12l were identified as the promising inhibitors of JAK2, which exhibited high inhibitory activity (IC ₅₀ = 6 nM and 3 nM, respectively) and selectivity for JAK2 over JAK1 and JAK3, and showed potent antiproliferative activities toward HEL human erythroleukemia cells. Moreover, 12k suppressed symptoms of the collagen-induced arthritis (CIA) model in rats.