An orally available selective antagonist of the endothelin-A (ET-A) receptor with potential antineoplastic activity. Zibotentan binds selectively to the ET-A receptor, thereby inhibiting endothelin-mediated mechanisms that promote tumor cell proliferation. OR A substance being studied in the treatment of some types of cancer. Zibotentan may block cancer cell growth. It is a type of endothelin-A receptor antagonist.