A Clinical Study to Investigate the Long-term Safety of the Drug Macitentan in Patients With Pulmonary Hypertension Who Were Previously Treated With Macitentan in Clinical Studies.

Inclusion Criteria: 1. Signed informed consent to take part in the study before any study mandated procedure. 2. Participants from one of the parent studies and: a) the sponsor has decided to terminate the parent study in that country and b) the participant has completed the end of treatment (EOT) Visit of the parent study 3. Women of childbearing potential are able to take part in the study if the following applies: a) Urine pregnancy test is negative at Enrollment; b) Agreement to perform monthly urine or serum pregnancy tests during the study and up to at least 30 days after the study treatment discontinuation; and c) Agreement to adhere to the planned contraception scheme from Enrollment up to at least 30 days after study treatment discontinuation Exclusion Criteria: 1. Hemoglobin less than 80 gram per liter (g/L) 2. Serum Aspartate aminotransferase (AST) and/or alanine aminotransferases (ALT) more than three times the upper limit of normal range 3. Known and documented history of severe hepatic impairment that is Child-Pugh Class C. 4. Pregnant, planning to become pregnant, or breastfeeding 5. Known hypersensitivity to macitentan, its excipients, or drugs of the same class 6. Planned or current treatment with another investigational treatment up to 3 months prior to Enrollment 7. Any known factor or disease that may interfere with treatment compliance, study conduct, or interpretation of the results, such as drug or alcohol dependence or psychiatric disease 8. Treatment with a strong CYP3A4 inhibitor (e.g., ketoconazole, itraconazole, voriconazole, clarithromycin, telithromycin, nefazodone, ritonavir, and saquinavir)