Novel potent HIF-1 inhibitors for the prevention of tumor metastasis: discovery and optimization of 3-aryl-5-indazole-1,2,4-oxadiazole derivatives

Hypoxia inducible factor-1 (HIF-1) is the key transcription factor of cellular response to hypoxia and plays a critical role in tumor metastasis. We describe here the discovery and a structure-activity relationship study of a series of 3-aryl-5-indazole-1,2,4-oxadiazole derivatives as novel HIF-1 inhibitors. The two most promising compounds 4g and 4h inhibit HIF-1 transcription with IC50 values of 0.62 and 0.55 mu M in vitro, respectively, and they exhibit more efficient HIF-1 inhibition in xenograft tumors than YC-1, a potential anticancer drug targeting HIF-1. In addition, they also remarkably prevent the hypoxia-driven migration of SKOV3 cells in vitro and tumor metastasis in vivo. Further investigation of the mechanism revealed that the two inhibitors could decrease HIF-1 alpha and VEGF expression. These results suggest that our newly synthesized HIF-1 inhibitors 4g and 4h are potential therapeutic agents with which to treat tumor metastasis.