In this study, we developed the novel multiple protein kinase inhibitor, KMU-11342, we assessed its electrophysiological safety and toxicity in vivo and ex vivo, and showcased its anti-rheumatic potential by revealing its anti-inflammtory mechanisms in vitro studies, in primary human RA fibroblast-like synoviocytes (RA-FLS) and by hindering osteoclastogenesis in RAW264.7 cells. The gene discussed is WEE1; the disease is rheumatoid arthritis.