Inclusion Criteria:  Pulmonary arterial hypertension (PAH) belonging to the nice 2013 updated classification group 1 PAH diagnosis confirmed by historical right heart catheterization where in the absence of pulmonary vein obstruction and/or significant lung disease pulmonary artery wedge pressure (PAWP) can be replaced by left atrium pressure (LAP) or left ventricular end diastolic pressure (LVEDP) (in absence of mitral stenosis) assessed by heart catheterization World Health Organization (WHO) functional class (FC) I to IV PAH-specific treatment-naïve participants or participants on PAH-specific treatment A female of childbearing potential must have a negative highly sensitive serum beta-human chorionic gonadotropin (beta-hCG) test at screening and a negative urine pregnancy test at the first administration of study intervention A male or female participant must not get pregnant and must agree not to donate sperm or eggs during the study and for a period of up to 4 weeks following the end of study  Exclusion Criteria:  Participants with PAH due to portal hypertension, schistosomiasis, pulmonary veno-occlusive disease, and/or pulmonary capillary hemangiomatosis, and persistent pulmonary hypertension of the newborn Participants with pulmonary vein stenosis Severe hepatic impairment, example, Child-Pugh Class C, at screening Pregnant, or breast-feeding, or planning to become pregnant while enrolled in this study or within 4 weeks after the last dose of study intervention Known allergies, hypersensitivity, or intolerance to macitentan or its excipients Participant with PAH associated with open shunts, with congenital cardiac abnormalities such as univentricular heart, with pulmonary hypertension due to lung disease, and renal dysfunction