Selective ERK inhibitor (IC50 values are 0.14 and 0.31 μM for ERK2 and ERK1 respectively). Displays 30-fold selectivity for ERK over p38α (IC50 = 10 μM); displays no activity against human recombinant MEK1, MKK4, IKKα, PKCα, Src, Syc and PDGFα at concentrations less than 30 μM. Also inhibits TGFβ-induced AP-1 activation in Mv1Lu cells (IC50 = 3.1 μM).