The purpose of the study is to to assess the effect of multiple oral doses of ZD4054 (Zibotentan) on the pharmacokinetics of a CYP450 3A Probe (midazolam) in healthy male subjects.

Inclusion Criteria:

• BMI between 18 and 30 kg/m2
• Medical and surgical history and physical examination without any clinically significant findings
• Normal resting ECG with QTcB interval <450ms

Exclusion Criteria:

• Definite or suspected personal history or family history of hypersensitivity to drugs that are endothelin antagonists; ie, ambrisentan, artrasentan, sitaxsetan and bosentan
• Healthy volunteer has a known hypersensitivity to midazolam or any of the excipients of the midazolam tablet
• Medical diagnosis of migraine with an attack during the 12 months prior to Screening