Potent and selective inhibitor of p38α (Ki values are 0.5, 3.6, 2600 and 4100 nM for p38α, p38β, p38γ and p38δ respectively). Displays >1000-fold selectivity against 36 other kinases; inhibits whole blood LPS-stimulated TNFα (IC50 = 3 nM). Efficacious in acute and chronic models of arthritis. Purity 98%. MW (observed): 461.56