Hypoxia-inducible factor-l alpha (HIF-1 alpha) is a transcription factor produced by tumor cells under hypoxic conditions, and a key regulator of a number of genes important in cancer biology. Over-expression of HIF-1 alpha in human tumors is associated with poor prognosis and poor therapeutic outcomes and HIF-1 alpha has been suggested as a novel target for cancer therapy. This article provides a review of PX-478 as the first novel HIF-1 alpha inhibitor in clinical stage for the treatment of solid tumors.