The primary objective of this study is to evaluate the efficacy of inhaled nebulized AIR001 administered, for 16 weeks, according to 3 treatment arms (80 mg once daily, 46 mg 4 times daily, or 80 mg 4 times daily) in subjects with World Health Organization (WHO) Group 1 Pulmonary Arterial Hypertension (PAH), as determined by change in Pulmonary Vascular Resistance (PVR) from Baseline to Week 16 measured immediately post completion of AIR001 nebulization (as soon as feasible).
Main Inclusion Criteria:
1) Age 18-75
2) WHO Group 1.1, 1.2, 1.3.1, 1.3.4, 1.3.5, (Idiopathic PAH, Heritable/Familial PAH, Drug- and toxin-induced PAH, PAH associated with collagen vascular disease, HIV infection) 1.3.2 repaired >1 year (PAH associated with congenital systemic-to-pulmonary shunts)
3) Functional class II - IV
4) mPAP >/= 25mm Hg, PVR >/= 240 dynes, PCWP or LVEDP </= 15mm Hg
5) TLC >/= 70%, FEV1 >/= 70%
6) Newly diagnosed PAH on no PAH-specific therapy or previously diagnosed PAH on stable (at least 90 days) prior to baseline study visit.
Main Exclusion Criteria:
1) History of uncontrolled systemic hypertension
2) History of obstructive sleep apnea