Tpl2 kinase inhibitor is an inhibitor of tumor progression locus 2 (Tpl2; IC50= 0.05 μM).1It is selective for Tpl2 over MEK, p38 MAPK, Src, MK2, and PKC (IC50s = >40, 180, >400, 110, and >400 μM, respectively). Tpl2 kinase inhibitor inhibits LPS-induced TNF-α production in isolated human monocytes and whole blood (IC50s = 0.7 and 8.5 μM, respectively). It enhances differentiation induced by calcitriol in HL-60 and U937 leukemia cells when used at a concentration of 5 μM.2Tpl2 kinase inhibitor (5 μM) inhibits the proliferation of KG-1a leukemia cells.3