Hypoxia Inducible Factor-1α Inhibitor is a novel small molecule which inhibits HIF by reducing HIF-1α accumulation and gene transcriptional activity. In a gene reporter assay using human AGS and Hep3B cell lines, hypoxia inducible factor-1α Inhibitor prevented HIF-1 transcriptional activity with IC50 values of 2.6 and 0.7 μM, respectively. Hypoxia inducible factor-1α inhibitor blocks HIF-1α accumulation in Hep3B cells in a concentration and time-dependent manner, with complete inhibition at a concentration of 30 μM within 12 hours. Hypoxia inducible factor-1α inhibitor also significantly suppresses transcription of the HIF-1 target genes VEGF and erythropoietin at 10 μM.