Tyrphostins are a family of protein tyrosine kinase inhibitors originally developed to inhibit cell growth by blocking the activity of certain growth factor receptor kinases (GFRK). The tyrphostin AG-126 selectively inhibits the phosphorylation of ERK1 (p44) and ERK2 (p42) at 25-50 μM.It blocks the production of TNF-α in vitro and in vivo,attenuating signaling through NF-κB,the induced expression of COX-2 and iNOS,and the inflammatory response in diverse animal models.AG-126 is a poor inhibitor of epidermal GFRK (IC50 = 450 μM) and platelet-derived GFRK (IC50 > 100 μM).