ATP-competitive c-Jun N-terminal kinase (JNK) inhibitor (IC50 values are 2, 4 and 52 nM for JNK1, JNK2 and JNK3 respectively). Displays > 1000 fold selectivity over other kinases, including ERK2 and p38. Inhibits c-Jun phosphorylation (EC50 = 920 nM) and prevents collagen-induced platelet aggregation in vitro.