Orteronel (also known as TAK-700) is a novel hormonal therapy that is currently 
in testing for the treatment of prostate cancer. Orteronel inhibits the 17,20 
lyase activity of the enzyme CYP17A1, which is important for androgen synthesis 
in the testes, adrenal glands and prostate cancer cells. Preclinical studies 
demonstrate that orteronel treatment suppresses androgen levels and causes 
shrinkage of androgen-dependent organs, such as the prostate gland. Early 
reports of clinical studies demonstrate that orteronel treatment leads to 
reduced prostate-specific antigen levels, a marker of prostate cancer tumor 
burden, and more complete suppression of androgen synthesis than conventional 
androgen deprivation therapies that act in the testes alone. Treatment with 
single-agent orteronel has been well tolerated with fatigue as the most common 
adverse event, while febrile neutropenia was the dose-limiting toxicity in a 
combination study of orteronel with docetaxel. Recently, the ELM-PC5 Phase III 
clinical trial in patients with advanced-stage prostate cancer who had received 
prior docetaxel was unblinded as the overall survival primary end point was not 
achieved. However, additional Phase III orteronel trials are ongoing in men with 
earlier stages of prostate cancer.