Multicenter, Open-label, Non-comparative, Proof-of-concept, Phase 2a Study to Evaluate the
Effect of a Single Infusion of Tezosentan on Pulmonary Vascular Resistance in Patients With
Stable, Chronic Pulmonary Arterial Hypertension, Currently Not Treated With Endothelin
Receptor Antagonists, Phosphodiesterase-5 Inhibitors or Prostacyclines