A novel STAT inhibitor, OPB-31121, has a significant antitumor effect on leukemia with STAT-addictive onco-kinases

F Hayakawa1, K Sugimoto1,2, Y Harada2, N Hashimoto2, N Ohi2, S Kurahashi1 and T Naoe1 "Here, we demonstrated that a novel STAT3 inhibitor, OPB-31121, strongly inhibited not only STAT3 but also STAT5 phosphorylation. OPB-31121 did not inhibit activities of kinases including JFKs and SFKs and its exact mechanism of action is under investigation; however, it induced significant growth inhibition in a wide range of hematopoietic malignant cells. Investigation among various cell lines indicated that this compound was particularly effective against multiple myeloma and Burkitt lymphoma, and leukemia harboring BCR–ABL,