IRAK4-IN-19 is a potent interleukin-1 receptor-associated kinase 4 ( IRAK4 ) inhibitor with an IC 50 value of 4.3 nM. IRAK4-IN-19 can inhibit LPS-induced IL23 production in THP and DC cells, and stop arthritis development in arthritis rats. IRAK4-IN-19 can be used for researching arthritis disease.