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Study ROR-PH-301, ADVANCE OUTCOMES, is designed to assess the efficacy and safety of ralinepag when added to pulmonary arterial hypertension (PAH) standard of care or PAH-specific background therapy in subjects with World Health Organization (WHO) Group 1 PAH.

Study ROR-PH-301 is a multicenter, randomized, double-blind, placebo-controlled study. Subjects who meet entry criteria will be randomly allocated 1:1 to receive ralinepag or placebo, in addition to their standard of care or PAH-specific background therapy, as applicable. The primary endpoint is the time (in days) from randomization to the first adjudicated protocol-defined clinical worsening event. All primary endpoint events will be adjudicated by an independent Clinical Event Committee (CEC) in a blinded fashion. Subjects who have a confirmed primary endpoint event adjudicated by the CEC at any time during the study and all subjects on treatment at the conclusion of the study who have completed the Week 28 Visit (after the target number of confirmed events is achieved) will have the option to enroll in an open-label extension (OLE) study. Subjects who do not choose to participate in the OLE study will discontinue study drug and should remain in the study for long-term follow-up of survival status and will receive standard of care PAH treatment, at the discretion of the treating physician.

Inclusion Criteria:

1. At least 18 years of age.

2. Evidence of a personally signed and dated informed consent form indicating that the subject has been informed of all pertinent aspects of the study prior to initiation of any study-related procedures.

3. Subjects who are willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures

4. Primary diagnosis of symptomatic PAH.

5. Has had a right heart catheterization (RHC) performed at or within 3 years prior to Screening (RHC will be performed during Screening if not available) that is consistent with the diagnosis of PAH.

6. Has WHO/ NYHA functional class II to IV symptoms.

7. If on PAH-specific background oral therapy, subject is on stable therapy with either an endothelin receptor antagonist (ERA) and/or a phosphodiesterase type 5 inhibitor (PDE5-I) or a soluble guanylate cyclase (sGC) stimulator.

8. Has a 6MWD of �150 meters.

9. If taking concomitant medications that may affect the clinical manifestations of PAH (eg, calcium channel blockers, diuretics, digoxin, or L arginine supplementation, beta blockers, angiotensin-converting enzyme inhibitors, or angiotensin II receptor blockers), must be on a stable dose for at least 30 days prior to the Baseline Visit and the dosage maintained throughout the study. The exception is that the dose of diuretics must be stable for at least the 10 days prior to Baseline.

10. Both male and female subjects agree to use a highly effective method of birth

control throughout the entire study period from informed consent through to the

30-Day Follow-up Visit, if the possibility of conception exists. Eligible male and

female subjects must also agree not to participate in a conception process during

the study and for 30 days after the last dose of IMP. Eligible male subjects must

agree not to participate in sperm donation for 90 days after the last dose of IMP.

Exclusion Criteria:

1. For subjects with known HIV-associated PAH, a cluster designation 4 (CD4+) T-cell count