The extracellular signal-regulated kinase (ERK) signal transduction pathway regulates a diverse array of cellular processes. These processes include cell survival, proliferation, motility, and differentiation and are constitutively activated in cancers involving lung, colon, pancreas, kidney, and ovary. CAY10561 is a potent, ATP-competitive inhibitor of ERK2 (Ki = 2 nM). This compound is highly selective for ERK2 compared to other kinases such as PKA (Ki = 0.39 µM) and JNK3 (Ki = 4 µM). CAY10561 inhibits proliferation of COLO 205 cells with an IC50 value of 0.54 µM.