A Study Providing Treatment Access in Participants With Pulmonary Hypertension Completing a Parent Study and Having no Other Option

Inclusion Criteria:

* Participant must sign an informed consent form (ICF) (or their legally designated representative must sign) indicating that participant understands the purpose of, and procedures required for, the study and is willing to participate in the study
* Participant treated with oral macitentan or selexipag or fixed dose combination (FDC) of macitentan 10 milligrams (mg) and tadalafil 40 mg at the end of a sponsor parent study and: a) the indication of the parent study is included in the intervention-specific appendices (ISA) (pulmonary arterial hypertension \[PAH\]; b) participant has completed the parent study; c) no alternative means of access to study intervention (or equivalent approved therapy) have been identified; d) participant may continue to benefit from treatment with the study intervention; e) Participant is at least 18 years old for macitentan/tadalafil FDC, and at least 2 years old for macitentan or selexipag
* A female participant of childbearing potential must: a) have a negative urine or serum pregnancy test prior to first intake of study intervention; b) agree to perform monthly urine pregnancy test up to the end of the safety follow-up period; c) If heterosexually active, agree to follow contraceptive methods until 30 days after the last intake of the study intervention. For pediatric female participants: It is the responsibility of the investigator to ensure appropriate counselling, including consultation with a specialist (if needed), to the participant and/or parent(s)/ legally designated representative (LDR)(s) on the acceptable method of contraception

Exclusion Criteria:

General:

* Participants prematurely discontinued from the study intervention in their parent study
* Female participant being pregnant, or breastfeeding, or planning to become pregnant while enrolled in this study
* Planned or current treatment with another investigational treatment

Macitentan-specific:

* Known allergies, hypersensitivity, or intolerance to macitentan or its excipients
* Hemoglobin less than (\<) 80 grams per liter (g/L)
* Serum aspartate (AST) and/or alanine aminotransferases (ALT) greater than (\>) 3\* upper limit of normal (ULN)
* Known and documented severe hepatic impairment that is, Child-Pugh Class C. For participants with hepatic impairment, Child-Pugh Class (Child-Pugh score) should be fully assessed and documented in the source documents at screening

Selexipag-specific:

* Known allergies, hypersensitivity, or intolerance to selexipag or its excipients
* Suspected or known pulmonary veno-occlusive disease (PVOD)
* Uncontrolled thyroid disease
* Severe coronary heart disease or unstable angina, myocardial infarction within the last 6 months, decompensated cardiac failure (if not under close medical supervision), severe arrhythmia, cerebrovascular events (for example, transient ischemic attack, stroke) within the last 3 months, or congenital or acquired valvular defects with clinically relevant myocardial function disorders not related to pulmonary hypertension (PH)
* Known and documented severe hepatic impairment that is, Child-Pugh Class C. For participants with hepatic impairment, Child-Pugh Class (Child-Pugh score) should be fully assessed and documented in the source documents at screening
* Children only: (a) Current suspicion of intussusception or ileus or gastrointestinal obstruction, per the investigator's judgment; (b) hemoglobin or hematocrit \<75 percent (%) of the lower limit of normal range

Macitentan/tadalafil FDC-specific:

* Known allergies, hypersensitivity, or intolerance to macitentan or tadalafil or their excipients
* Hemoglobin \<80 g/L
* Serum aspartate (AST) and/or alanine aminotransferases (ALT) \>3\* ULN range
* Known and documented severe hepatic impairment that is, Child-Pugh Class C. For participants with hepatic impairment, Child-Pugh Class should be fully assessed and documented in the source documents at screening
* Severe renal impairment (estimated glomerular filtration rate \[eGF\]/creatinine clearance \<30 milliliter per minute \[mL/min\])