Water-soluble salt of SB 203580 (Cat. No. 1202). Selective inhibitor of p38 mitogen-activated protein kinase (IC50 values are 50 and 500 nM for SAPK2a/p38 and SAPK2b/p38β2 respectively). Displays 100-500-fold selectivity over LCK, GSK3β and PKBα. Shown to inhibit interleukin-2-induced T cell proliferation, cyclooxygenase-1 and -2, and thromboxane synthase. Purity 98%. MW (observed): 413.89