Clinical Study to Explore the Effects of Actelion's Latest Endothelin Receptor Antagonist (ERA) - at Different Dose Strengths - on the Efficacy, Safety and Tolerability in Subjects With Essential Hypertension

Inclusion Criteria:

- Signed informed consent prior to any study-mandated procedure

- Mild-to-moderate essential hypertension with or without ongoing anti-hypertensive
treatment(s)

- No contra-indication to stop (according to label) anti-hypertensive treatment(s)

- Women of childbearing potential must have a negative pregnancy test and use of
reliable methods of contraception

Exclusion Criteria:

- Severe hypertension (grade 3): mean sitting systolic/diastolic BP (SiSBP/SiDBP;
measured by OBPM) ≥ 180/110 mmHg, respectively.

- Secondary hypertension

- Known hypertensive retinopathy greater than Keith-Wagener Grade 2

- Myocardial infarction, percutaneous transluminal coronary angioplasty, or coronary
artery bypass graft within 12 months prior to randomization

- Unstable angina within 6 months prior to randomization

- Heart failure New York Heart Association class III and IV

- Valvular defects (such as severe aortic or mitral valve disease) and/or
hemodynamically relevant rhythm disturbances

- Clinical evidence of cerebrovascular insufficiency or a cerebrovascular accident
within 6 months prior to randomization.

- Subjects working night shifts

- Body mass index < 20 kg/m2 or > 40 kg/m2

- Treatment with any medication which may affect BP (e.g., treatment of psychiatric
diseases, ophthalmic preparations)

- Treatment with strong cytochrome P450 3A4 (CYP3A4) isoenzyme inhibitors or inducers

- Treatment with guanethidine and/or mineralocorticoid receptor antagonists within 1
month prior to Screening (Visit 1)

- Treatment with another investigational treatment within 1 month prior to Screening
(Visit 1)

- Any circumstances or conditions, which, in the opinion of the investigator, may affect
full participation in the study or compliance with the protocol