Study Name: Ralinepag 302

Objective: The primary objective of this study is to evaluate the effects of ralinepag therapy on exercise capacity as assessed by change in peak VO2 derived from CPET after 28 weeks of treatment.

Inclusion criteria:

1. Has had a diagnostic RHC performed within 1 year of Screening
2. Has WHO/NYHA FC 2 to 3 symptoms.
3. Must have initiated first PAH-specific oral therapy with an ERA and/or a PDE5-I or a sGC stimulator within 9 months prior to Screening and be on a stable dose(s) defined as no change in dose or regimen for at least 30 days prior to Screening.
4.  Has a 6MWD of ≥150 meters at Screening.

Exclusion criteria:

1. Current unstable angina
2. Symptomatic coronary disease and/or myocardial infarction within past 6 months.
3. Current symptomatic aortic or mitral valve disease.
4. Current diagnosis of uncontrolled sleep apnea in the opinion of the Investigator.
5. Requires use of supplemental oxygen during CPET.