A Study of Selexipag Assessing Right Ventricular Remodeling in Pulmonary Arterial Hypertension by Cardiac Magnetic Resonance Imaging

Open to people ages 18-64

• World health organization functional class (WHO FC) II or III. Enrollment will be stratified by WHO FC II or III. Proportion of participants with WHO FC II and WHO FC III are expected to be approximately 40 percent (%) and 60%, respectively
• Pulmonary arterial hypertension (PAH) etiology belonging to one of the following groups according to 6th world symposium of pulmonary hypertension (WSPH) classification: a) Idiopathic PAH, b) Heritable PAH, c) Drugs or toxins induced d) PAH associated with connective tissue disease, e) PAH associated with congenital heart disease, with simple systemic-to-pulmonary shunt at least 1 year after surgical repair
• Patients already receiving PAH-specific oral mono or dual therapy (that is, phosphodiesterase type 5 inhibitors [PDE-5i] or soluble guanylate cyclase stimulators [sGCs] and/or endothelin receptor antagonist [ERA]) or patients who are not candidates for these therapies
• N-terminal-pro-hormone brain natriuretic peptide (NT-proBNP) greater than or equal to (>=) 300 nanograms per liter (ng/L) (greater than or equal to [>=] 300 picograms per milliliter [pg/mL]; >=35.5 picomoles per liter [pmol/L]) at screening
• Women of childbearing potential must meet the following criteria: a) Have a negative serum pregnancy test during screening and a negative urine pregnancy test on Day 1, b) Agree to use acceptable methods of contraception from Day 1 to at least 30 days after study intervention discontinuation, c) If only using hormonal contraception, have used it for at least 1 month (30 days) before Day 1, and d) Agree to perform monthly pregnancy tests to at least 30 days after study intervention discontinuation
• 6-minute walking distance (6MWD) >=150 meter (m) during screening period

• Prior use of Prostacyclin (IP)-receptor agonist, prostacyclin, or prostacyclin analog. Use of such treatments for vasoreactivity testing is not exclusionary; intermittent use of such treatments for digital ulcers or Raynaud's phenomenon is not exclusionary if stopped > 6 months (180 days) prior to Day 1
• Treatment with strong inhibitors of CYP2C8 (example, gemfibrozil) within 4 weeks (28 days) prior to Day 1
• Treatment with another investigational drug planned or taken within 12 weeks (84 days) prior to Day 1
• Severe coronary heart disease or unstable angina
• Cerebrovascular events (example, transient ischemic attack, stroke) within 3 months (90 days) prior to Day 1