N-(12-Cyanindolizino[2,3-b]quinoxalin-2-yl)-2-thiophenecarboxaMide

HI TOPK 032 is an inhibitor of lymphokine-activated killer T cell-originated protein kinase (TOPK), blocking phosphorylation of the substrate histone H2AX with an IC₅₀ value of ~2 μM and providing complete inhibition at 5 μM. It also inhibits checkpoint kinase 1 (Chk1; IC₅₀ = 9.6 μM). In addition, HI TOPK 032 inhibits MEK1, achieving 40% inhibition at 5 μM, but it does not alter the activities of ERK1, JNK1, or p38 MAPK at 2 μM. HI TOPK 032 decreases the growth of colon cancer and glioma initiating cells in vitro and suppresses tumor growth in vivo.

N-(12-Cyanindolizino[2,3-b]quinoxalin-2-yl)-2-thiophenecarboxamide is a novel TOPK inhibitor that was shown to effectively suppress colon cancer growth.

HI-TOPK-032 has been used as a PDZ binding-kinase (PBK) inhibitor.

HI-TOPK-032 is a potent and specific inhibitor of TOPK. HI-TOPK-032 also reduces ERK-RSK phosphorylation, modulates the abundance of p53, cleaved caspase-7, and cleaved PARP, and induces apoptosis in cancer cells.

HI-TOPK-032 is a specific TOPK (T-LAK cell–originated protein kinase) inhibitor both in vitro and in vivo. HI-TOPK-032 suppressed tumor growth in a colon cancer xenograft model.

HI-TOPK-032 strongly suppresses TOPK kinase activity but has little effect on extracellular signal-regulated kinase 1 (ERK1), c-jun-NH2-kinase 1, or p38 kinase activities. HI-TOPK-032 occupies the ATP-binding site of TOPK and fits the binding site very well. The compound forms hydrogen bonds with GLY83 and ASP151 and has a hydrophobic interaction with LYS30. However, HI-TOPK-032 at the highest concentration (5 μM) also inhibits MEK1 activity by 40%. HI-TOPK-032 also inhibits anchorage-dependent and -independent colon cancer cell growth by reducing ERK-RSK phosphorylation as well as increasing colon cancer cell apoptosis through regulation of the abundance of p53, cleaved caspase-7, and cleaved PARP.

Treatment of mice with 1 or 10 mg/kg of HI-TOPK-032 significantly inhibits HCT-116 tumor growth by more than 60% relative to the vehicle-treated group. Mice are well tolerated with HI-TOPK-032 treatment. The expression of p53 is strongly induced, and phosphorylation of ERK and RSK, a direct downstream protein of ERK, is markedly inhibited in the HI-TOPK-032-treated group.