A RNA antagonist of hypoxia-inducible factor-1α, EZN-2968, inhibits tumor cell growth

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that plays a critical role in angiogenesis, survival, metastasis, drug resistance, and glucose metabolism. Elevated expression of the alpha-subunit of HIF-1 (HIF-1alpha), which occurs in response to hypoxia or activation of growth factor pathways, is associated with poor prognosis in many types of cancer. Therefore, down-regulation of HIF-1alpha protein by RNA antagonists may control cancer growth. EZN-2968 is a RNA antagonist composed of third-generation oligonucleotide, locked nucleic acid, technology that specifically binds and inhibits the expression of HIF-1alpha mRNA. In vitro, in human prostate (15PC3, PC3, and DU145) and glioblastoma (U373) cells, EZN-2968 induced a potent, selective, and durable antagonism of HIF-1 mRNA and protein expression (IC(50), 1-5 nmol/L) under normoxic and hypoxic conditions associated with inhibition of tumor cell growth. Additionally, down-regulation of HIF-1alpha protein by EZN-2968 led to reduction of its transcriptional targets and of human umbilical vein endothelial cell tube formation. In vivo, administration of EZN-2968 to normal mice led to specific, dose-dependent, and highly potent down-regulation of endogenous HIF-1alpha and vascular endothelial growth factor in the liver. The effect can last for days after administration of single dose of EZN-2968 and is associated with long residence time of locked nucleic acid in certain tissues. In efficacy studies, tumor reduction was found in nude mice implanted with DU145 cells treated with EZN-2968. Ongoing phase I studies of EZN-2968 in patients with advanced malignancies will determine optimal dose and schedule for the phase II program.