Study to Compare Triple Therapy (Oral Treprostinil, Ambrisentan, and Tadalafil) With Dual Therapy (Ambrisentan, Tadalafil, and Placebo) in Subjects With Pulmonary Arterial Hypertension

Inclusion Criteria

• •1. Between 18 and 79 years of age, inclusive
• •2. PAH that is idiopathic / heritable, PAH associated with connective tissue disease, HIV infection, repaired congenital systemic-to-pulmonary shunts (repaired \> 1 year), or appetite suppressant / toxin use
• •3. Receiving dual therapy (ambrisentan and tadalafil)
• •4. Previous testing (e.g. right heart catheterization, echocardiography) consistent with diagnosis of PAH
• •3. Received PAH-specific drug therapy for \>2 years
• •4. History of uncontrolled sleep apnea, severe liver disease, severe renal impairment, left sided heart disease, uncontrolled systemic hypertension
• •5. Participated in an investigational drug or device study within 90 days prior to signing consent.