It is hypothesized that inhaled RT234 will provide a therapeutic benefit for "as needed" (PRN) use in patients with WHO Group 1 Pulmonary Hypertension (PH) (Pulmonary Arterial Hypertension (PAH)) to improve exercise capacity and therefore performance in activities of daily living as well as reduce exertional symptoms (e.g., dyspnea) and their deleterious impacts on quality of life (QoL). The purpose of this study is to demonstrate acute improvements in exercise capacity and exertional symptoms (i.e., dyspnea) post dosing of RT234 as assessed by cardiopulmonary exercise testing (CPET) and 6-minute walk test (6MWT). In addition, acute changes in severity of PAH symptoms before and after CPET and 6MWT will be assessed.
1. Must be between 18 and 80 years of age, inclusive.
2. Has a 6MWD of 50 or greater meters and less than 500 meters
3. Has a VE/VCO2 slope of 36 or greater during the screening and baseline CPET (as assessed by the study core laboratory)
1. Baseline systemic hypotension defined as MAP < 50 mmHg or SBP < 90 mmHg at screening/baseline.
2. Requirement of intravenous inotropes within 30 days prior to CPET procedure.
3. The use of inhaled, topical or oral nitrates within 2 weeks prior to CPET procedure.
There will be 4 study visits and a follow-up telephone call. there will be blood draws at screening and Visit 3. For screening, blood (approximately 12 mL or 2.5 teaspoons) and urine samples for routine laboratory testing will be obtained. For Visit 3, approximately 28 mL or 5.6 teaspoons of blood will be collected in total. A cardiopulmonary exercise test (CPET) will be performed at baseline and Visit 3.