RWJ-67657 is a potent inhibitor of the MAP kinases p38α and p38β (IC50s = 1 and 11 μM, respectively, in vitro); inactive against p38γ and p38δ, as well as several other kinases. RWJ-67657 blocks the release of TNF-α and IL-1β from peripheral blood mononuclear cells stimulated with LPS (IC50s = 3 and 11 nM, respectively) and inhibits TNF-α production in LPS-treated mice and rats. MW: 425.5. Purity ≥98% by HPLC