SYP-5 is a Hypoxia-inducible factor-1 (HIF-1) inhibitor, inhibits tumor cell migration and invasion, tumor angiogenesis; downregulates VEGF and MMP-2; suppresses hypoxia-induced HIF-1 upregulation and downstream gene expression in Hep3B/Bcap37 cells; inhibits angiogenesis in tube formation assay; retards cell migration/invasion induced by hypoxia/FBS; specifically inhibits hypoxic induction of luciferase in U251-HRE.