Study Providing Monotherapy (Sitaxsentan) And Combination Therapy (Sitaxsentan+Sildenafil) To Subjects With Pulmonary Arterial Hypertension (PAH) To Assess Long-Term Safety

A Phase 3, Multi-Center, Open Label Study To Evaluate The Long-Term Safety Of Monotherapy Sitaxsentan Sodium And Combination Therapy With Sitaxsentan Sodium And Sildenafil Citrate In Subjects With Pulmonary Arterial Hypertension

As sitaxsentan is the agent most highly selective for ETA (Endothelin Type A (receptor)), and does not significantly impact sildenafil pharmacokinetics the combination of most promise for pulmonary arterial hypertension (PAH) therapy is these two oral drugs administered in combination.

Inclusion Criteria:

• Previously enrolled in B1321001 for at least 4 weeks.
• Previously enrolled in B1321003, discontinued from the study.
• Completed the B1321003 study as planned.

Exclusion Criteria:

• Treated with an investigational drug (other than sitaxsentan or sildenafil in either B1321001 or B1321003) or device that has not received regulatory approval within the 30 days prior to Baseline/Day 1 or during the study.