Zibotentan (ZD4054) is an orally administered, potent and specific ETA-receptor (endothelin A receptor) antagonist (IC50 = 21 nM). IC50 value: 21 nM Target: ETA receptor Zibotentan is capable of inhibiting or reducing the multitude of effects that are evoked by ET-1 activation of the ETA receptor and which promote tumor survival, growth and progression. Zibotentan (ZD4054) treatment produced significant inhibition of tumor growth in ovarian and breast xenografts.