Adezmapimod hydrochloride (RWJ 64809 hydrochloride, SB 203580 hydrochloride) is an inhibitor of the MAPK family member termed as stress-activated protein kinase 2a(SAPK2a; also known as p38). It exhibits IC50 of SAPK2a/p38 and SAPK2b/p38β2 with IC50 values of 50 nM and 500 nM respectively and can be used in research of chronic inflammatory diseases, such as rheumatoid arthritis.