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

Number of Participants With Change From Baseline to Week 26 in World Health Organization (WHO) Functional Class

WHO functional classification for PAH ranged from Class I (no limitation in physical activity, ordinary physical activity does not cause undue dyspnea or fatigue, chest pain or near syncope), Class II (slight limitation of physical activity, ordinary physical activity cause undue dyspnea or fatigue, chest pain or near syncope), Class III (marked limitation of physical activity, less than ordinary activity cause undue dyspnea or fatigue, chest pain or near syncope) and Class IV (cannot perform a physical activity without any symptoms, dyspnea and/or fatigue may even be present at rest). Change from baseline in WHO functional class was classified into "Improved", "No change" and "Worsened". Improvement =reduction in functional class; worsened =increase in functional class; and no change = no change in functional class.

Time frame: Baseline, Week 26

Change From Baseline to Week 26 in N-terminal-Pro-Hormone Brain Natriuretic Peptide (NT-proBNP)

NT pro-BNP is a cardiac biomarker that is released in the blood in response to changes in the pressure inside of the heart. Levels go up when heart failure develops or gets worse, and levels go down when heart failure is stable or improves. This biomarker helps to measure the changes in the severity of heart failure over time in response to therapy.

Time frame: Baseline, Week 26

Change From Baseline to Week 26 in 6-Minute Walk Distance (6MWD)

6MWD was the distance that a participant could walk in 6 minutes. Participants were asked to perform the test at a pace that was comfortable to them, with as many breaks as they needed.

Time frame: Baseline, Week 26

Number of Participants With Treatment-Emergent Adverse Events (AEs) and Serious Adverse Events (SAEs)

An AE was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. Serious adverse event (SAE) was any untoward medical occurrence that at any dose resulted in death, was life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect, was a suspected transmission of any infectious agent via a medicinal product. Any AE occurring at or after the initial administration of study intervention up to 3 days after last dose of study intervention was considered as treatment-emergent.

Time frame: Day 1 up to 3 days after last dose of study drug (up to 52 weeks and 3 days that is 367 days)

Number of Participants With Adverse Events (AEs) Leading to Premature Discontinuation of Study Drug

Number of participants with AEs leading to premature discontinuation of study drug were reported. An AE was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship.

Time frame: Day 1 up to last dose of study drug (up to Week 52)

Number of Participants With Adverse Events of Special Interest (AESI)

Number of participants with AESI were reported. An AE was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. AESI were anaemia, bleeding events, gastrointestinal disturbances denoting intestinal intussusception (manifested as ileus or obstruction), hyperthyroidism, hypotension, light-dependent non-melanoma skin malignancies, major adverse cardiovascular events (MACE), medication errors, ophthalmological effects associated to retinal vascular system, pregnancy, pulmonary venoocclusive disease associated with pulmonary oedema, renal function impairment / acute renal failure.

Time frame: Day 1 up to 3 days after last dose of study drug (up to 52 weeks and 3 days that is 367 days)

Number of Participants With Treatment-Emergent Marked Laboratory Abnormalities

Number of participants with treatment-emergent marked laboratory abnormalities in alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total bilirubin, creatinine, sodium, potassium, hemoglobin, hematocrit; EVF; PCV (male), hematocrit; EVF; PCV (female), platelets (assuming no platelet cluster), leukocytes; white blood cells, Neutrophils (Abs), Eosinophils (Abs), lymphocytes (Abs) were reported. Abnormalities that occurred after study treatment start and up to 3 days after study treatment discontinuation, that were not present at baseline, were treatment-emergent. Treatment-emergent marked laboratory abnormalities were determined at the investigator's discretion.

Time frame: Day 1 up to 3 days after last dose of study drug (up to 52 weeks and 3 days that is 367 days)

Change From Baseline to Week 26 in Number of Non-invasive Low-risk Criteria Among the 8 Variables

The risk score is derived for each participant considering the following non-invasive low-risk criteria among the 8 variables: absence of clinical signs of right heart failure, absence of symptoms progression, absence of syncope, WHO FC I-II, 6MWD greater than (\>) 440 meter, NT-proBNP less than (\<) 300 ng/L, Right atrial (RA) area \<18 centimeter square (cm\^2) as determined by echocardiography (Echo), absence of pericardial effusion, as determined by Echo. Number of low-risk criteria at baseline and Week 26 constitutes risk score and were derived for each participant by adding '1' for each of above criteria met. Number of low-risk criteria among the 8 variables for each participant can vary from 0 (worse participants) to 8 (healthier participants). Higher score indicated healthier participants.

Time frame: Baseline, Week 26

Change From Baseline to Week 26 in Number of Non-invasive Low-risk Criteria Among the 3 Variables

The risk score is derived for each participant considering the following non-invasive low-risk criteria among the 3 variables: WHO FC I-II, 6MWD \>440 m, NT-proBNP \< 300 ng/L. Number of low-risk criteria at baseline and Week 26 constitutes risk score and were derived for each participant by adding '1' for each of above criteria met. Number of low-risk criteria among the 3 variables for each participant can vary from 0 (worse participants) to 3 (healthier participants). Higher score indicated healthier participants.

Time frame: Baseline, Week 26