Xl019, a novel JAK inhibitor, suppressed osteoclasts differentiation induced by RANKL through MAPK signaling pathway.

Inbonemetabolism,osteoclastsare the only cellscapableofresorbingbone. Hyperactivity of osteoclasts may lead to osteolytic disease like osteoporosis and arthritis. Although there are several drugs for the treatment of osteolytic diseases, they have limitations and a variety of side effects. An inhibitor of Janus kinase (JAK), XL019, has shown promising results in the treatment of myelofibrosis and other cancers. But whether it can functionally impact osteoclast activity has not been proven. In this study, the effects of XL019 on osteoclastogenesis and the mechanism pathway were investigated in vitro. It was found that XL019 could impair osteoclasts formation, interfere with bone resorption ability and downregulate the osteoclast-specific genes and proteins expression. Furthermore, Western blot and molecular docking studies demonstrated that XL019 inhibited RANKL-induced osteoclastogenesis by suppressing MAPK signaling. A molecular docking analysis explained how XL019 binds to MAPK pathway factors. In addition, titanium particles induced calvarial osteolysis in mice further confirming its beneficial effect on bone homeostasis in vivo. In conclusion, this study demonstrates that Osteoclastactivity canbeeffectivelyinhibitedby XL019viaMAPK signalingpathway,making it a promising alternative pharmacologicaltreatmentfor bone metabolicdisorders.