c-Jun N-terminal kinases (JNKs) phosphorylate c-Jun and regulate transcription in response to an array of inflammatory signals. JNK inhibitor V is an ATP-competitive inhibitor of JNK1, JNK2, and JNK3 (IC50s = 150, 220, and 70 nM, respectively). While initial studies demonstrated 10- to 100-fold selectivity for JNK isoforms over a panel of 25 other kinases, strong interactions of JNK inhibitor V with GSK3B, Pim-1, Pim-3, and other kinases, evaluated as a shift in thermal melting point, suggest additional targets exist. In vivo efficacy of JNK inhibitor V against JNK isoforms has been demonstrated in gerbils, mice, and rats via oral, intravenous, or intraperitoneal administration. This compound is commonly used to investigate the role of JNK signaling in cells and animals.