GW 856553X is a dual inhibitor of p38α and p38β MAPK (Kis = 0.0079 and 0.025 μM, respectively, in cell-free assays). It is selective for p38α and p38β MAPK over p38γ and p38δ MAPK when used at a concentration of 10 μM. GW 856553X inhibits LPS-induced TNF-α production in isolated rat and human peripheral blood mononuclear cells (PBMCs; IC50s = 0.6 and 0.13 μM, respectively). It decreases disease severity in a mouse model of collagen-induced arthritis when administered at doses ranging from 0.8 to 20 mg/kg. GW 856553X (1.2 and 12 mg/kg) improves survival, normalizes blood pressure, and reduces increases in plasma levels of HDL, LDL, and triglycerides in spontaneously hypertensive stroke-prone rats fed a high-salt high-fat diet.
