ACT-064992

PVRI fold change at Week 24 was calculated as 100\*(PVRI at Week 24 divided by PVRI at baseline). PVR was determined by right heart catheterization.

Change from baseline in hematology parameters: NBF was reported. Data for each parameters was planned to be reported at specified timepoints only.

An adverse event (AE) is any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non-investigational) product. An AE does not necessarily have a causal relationship with the intervention. TEAEs are defined as a treatment-emergent AE is any AE temporally associated with the use of study treatment (from start of treatment in the PLATYPUS protocol until 30 days after study treatment discontinuation) whether or not considered by the investigator as related to study treatment.

Frequency of TEAEs leading to discontinuation of study intervention will be reported. An AE is any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non-investigational) product. An AE does not necessarily have a causal relationship with the intervention. TEAEs are defined as a treatment-emergent AE is any AE temporally associated with the use of study treatment (from start of treatment in the PLATYPUS protocol until 30 days after study treatment discontinuation) whether or not considered by the investigator as related to study treatment.

SAE is any untoward medical occurrence that at any dose results in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, is a suspected transmission of any infectious agent via a medicinal product and is medically important.

Frequency of deaths will be reported.

Time to first CEC-adjudicated M/M event on-treatment (ie.,up to 7 days after last dose of DB study intervention) is defined as time from randomization to first of following events: All-cause death, including death caused by on-treatment adverse event that occur within 4 weeks of study DB treatment discontinuation;non-planned Pulmonary Arterial Hypertension(PAH)-related hospitalization(including for worsening of PAH, atrial septostomy, lung transplantation with or without heart transplantation, or initiation of parenteral prostacyclins);PAH-related disease progression, defined as worsening of World Health Organization(WHO) Functional Class(FC) from baseline or deterioration by at least 15% in exercise capacity, as measured by 6-minute walk distance(6MWD), from baseline and confirmed by second 6MWD test performed on different day within 2 week of initial test or appearance or worsening of signs or symptoms of right-sided heart failure that require initiation of intravenous diuretics.

Change in PVR expressed as the ratio of geometric means of EDBT to baseline were reported.

An AE is any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non-investigational) product. An AE does not necessarily have a causal relationship with the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal finding), symptom, or disease temporally associated with the use of a medicinal (investigational or non-investigational) product, whether or not related to that medicinal (investigational or non-investigational) product. A treatment-emergent AE is any AE temporally associated with the use of study treatment.

Any AE will be recorded that 1) is (temporally) associated with the use of study treatment whether or not considered by the investigator as related to study treatment and 2) leads to premature discontinuation of study medication.

Any SAE as defined by the ICH guidelines will be recorded. Any hepatic AE that leads to discontinuation of study treatment will be defined as SAE.

Pregnancies with maternal exposure to macitentan will be recorded.

Observed steady-state trough (pre-dose) plasma concentration of macitentan and aprocitentan (active metabolite) at Week 12 based on body weight were reported. This outcome measure was planned to be analyzed for specified arms only.

Observed steady-state trough (pre-dose) plasma concentration of macitentan and aprocitentan (active metabolite) at Week 12 based on age group were reported. This outcome measure was planned to be analyzed for specified arms only.

Observed steady-state trough (pre-dose) plasma concentration of macitentan and aprocitentan (active metabolite) at Week 4 were reported. This outcome measure was planned to be analyzed for specified arms only.

Observed steady-state trough (pre-dose) plasma concentration of macitentan and aprocitentan (active metabolite) at Week 12 were reported.

Change from baseline in peak VO2 up to Week 16 was reported.

Change from baseline to Week 26 in PVR was expressed as the ratio of Week 26 to baseline PVR value (Week 26 divided by baseline) using re-calculated PVR. PVR was determined by right heart catheterization (RHC). A geometric least square mean ratio of Week 26 to baseline PVR less than (\<) 1 corresponds to a reduction in PVR from baseline. Missing values were imputed using a last observation carried forward (LOCF) approach.

* Treatment-emergent adverse events (AEs) * AEs leading to premature discontinuation of study drug * Treatment-emergent serious adverse events (SAEs) * Proportion of patients with treatment-emergent ALT and/or AST abnormality (\> 3, \> 5, and \> 8 x ULN) associated or not with total bilirubin \> 2 x ULN. * Proportion of patients with treatment-emergent hemoglobin abnormality (≦ 100 g/L, and ≦ 80 g/L)

The purpose of the six minute walk is to test exercise tolerance and capacity. The test measures the distance an individual is able to walk over a total of six minutes on a hard, flat surface. The goal is for the individual to walk as far as possible in six minutes.

Content validity of the PAH-SYMPACT was assessed using item performance, exploratory and confirmatory factor analysis. The final item content and domain structure of PAH-SYMPACT was determined based on these analyses from the Steering Committee (expert clinicians) and findings from the qualitative research done with patients previously.

The reliability of the PAH-SYMPACT is assessed by test-retest reliability. Intra-class correlation coefficients (ICCs) assess test-retest reliability for the symptom and impact part scores as well as domains. ICCs equal to or greater than 0.70 are considered to demonstrate good test-retest reliability for total and domain scores.

The reliability of the PAH-SYMPACT is assessed by internal consistency reliability. This was determined using Cronbach's alpha-a value on an internal level scale from 0 to 1.0 with higher scores indicating a more-reliable (precise) instrument.

DUs were assessed at each visit starting with the screening visit. Only DUs from the proximal interphalangeal joint (PIP) distally (both on the dorsal and volar surface of the hand, including the digital tip) were recorded. The location of each DU was noted. At each subsequent visit the location of each new DU was noted. DUs that occurred and healed between visits and were reported by patients were not recorded as new DUs. The evaluation was performed by an experienced physician or a trained rater with expertise in the assessment of DUs in systemic sclerosis (SSc). For a given patient, DUs were assessed by the same rater at each visit, whenever possible. Any DU that developed over a previously healed ulcer was recorded as a new DU. Incidence rate is adjusted for 16 weeks of observation, hence is calculated as the number of new DUs/total number of observation days.

An adverse event (AE) is any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. TEAE are defined as AEs with onset during the treatment period or that are a consequence of a pre-existing condition that has worsened since baseline.

Number of participants with deaths up to 28 days after study treatment discontinuation were reported.

An adverse event (AE) is any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. TEAE are defined as AEs with onset during the treatment period or that are a consequence of a pre-existing condition that has worsened since baseline. A SAE is an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly; medically significant, or requires intervention to prevent at least one of the outcomes listed above.

Number of participants with AEs leading to permanent discontinuation of study treatment were reported. An adverse event (AE) is any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship.

Number of participants with treatment-emergent abnormal liver tests: Alanine aminotransferase (ALT) greater than (\>) 3\*upper limit of normal (ULN) or aspartate aminotransferase (AST) \>3\* ULN, ALT \>5\* ULN or AST \>5\*ULN, ALT \>8\*ULN or AST \>8\*ULN, total bilirubin (TBIL) \>2\*ULN, ALT \>3\*ULN or AST \>3\*ULN and TBIL \>2\*ULN at any time were reported.

Number of participants with treatment-emergent hemoglobin (HGB) abnormality up to 28 days after study treatment discontinuation were reported. Participants assessed for different categories of HGB were \<=80 grams/Liter (g/L), \<=100g/L, decrease from baseline \>=20 g/L, and decrease from baseline \>=50 g/L.

Morbidity or mortality events were defined as: a) Death; b) Atrial septostomy; c) Lung transplantation; d) Initiation of intravenous (i.v.) or subcutaneous prostanoids, or; e) Other worsening of pulmonary arterial hypertension (PAH). Other worsening of PAH was defined by the combined occurrence of all the following 3 events: At least 15% decrease in the 6 minute walk distance from baseline, confirmed by 2 tests performed on separate days, within 2 weeks. AND worsening of PAH symptoms including at least one of the following: a) Increase in WHO Functional Class (WHO FC), or no change in patients in WHO FC IV at baseline; b) Appearance or worsening of signs of right heart failure that did not respond to optimized oral diuretic therapy AND need for new treatment(s) for PAH that included the following: a) Oral or inhaled prostanoids; b) Oral phosphodiesterase inhibitors; c) Endothelin receptor antagonists (only after discontinuation of study treatment; d) i.v. diuretics

Percent of baseline NT-proBNP assessed at Week 24 was reported. Percent of baseline is calculated as the ratio of the Week 24 NT-proBNP value over baseline value, expressed in percentage. NT-proBNP is one of the best established cardiovascular response markers among all available surrogates in heart failure (HF).

PVR ratio equals to Week 12 PVR / Baseline PVR. PVR represents the resistance against which the right ventricle needs to pump. PVR was calculated using the following formula: mean pulmonary arterial pressure (mPAP) - pulmonary artery wedge pressure (PAWP)/cardiac output (CO); where mPAP and PAWP were measured at end-expiration and CO was measured in triplicate using the thermodilution method.

An adverse event (AE) is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/ biological agent under study. TEAEs are those events that started after administration of the first dose and up to safety follow-up visit/end of study, that is, 30 days after the last dose of study medication.

Number of participants with AEs leading to study drug discontinuation was reported.

A serious adverse event (SAE) is any untoward medical occurrence that at any dose resulting in any of following outcomes: results in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, is a suspected transmission of any infectious agent via a medicinal product. Treatment-emergent SAEs were those events that started after administration of the first dose and up to safety follow-up visit/end of study, that is, 30 days after the last dose of study medication.

Number of participants with hemoglobin abnormalities were reported. It included hemoglobin less than (\<) 80 grams per liter (g/L), hemoglobin \<100 g/L, hemoglobin greater than or equal to (\>=) 80 g/L and \<100 g/L, hemoglobin \<100g/L and a decrease of \>20 g/L from baseline, decrease of \>20 g/L in hemoglobin from baseline, decrease of \>20 g/L and \<=50 g/L in hemoglobin from baseline, and decrease of \>50 g/L in hemoglobin from baseline.

Number of participants with liver tests abnormalities were reported. It included alanine aminotransferase (ALT) or aspartate aminotransferase (AST): \>=3 x Upper limit of the normal range (ULN), \>=3 and \<5 x ULN, \>=5 ULN, and \>=5 and \<8 x ULN, \>= 8 x ULN, and total bilirubin \>=2 x ULN.

Change from baseline in blood pressure at Month 6 (both systolic blood pressure \[SBP\] and diastolic blood pressure \[DBP\]) was reported.

Change from baseline in pulse rate at Month 6 was reported.

Change from baseline in body weight at Month 6 was reported.

The primary efficacy endpoint is defined as the PVR at rest at Week 16 expressed as percent of baseline PVR at rest.

The main endpoint is the number of participants who had at least one of the following: A) significant fluid retention, defined as increase in body weight at any time by ≥ 5% or ≥ 5 kg from baseline due to fluid overload and/or parenteral administration of diuretics. B) Worsening of NYHA functional class from baseline.

FVC was measured at baseline and at the end of Period 1. The same equipment and tester were used during the course of the study. The equipment was calibrated and the calibration documented prior to each patient's measurement. The person responsible for conducting the pulmonary function tests was required to comply with the study guidelines and the American Thoracic Society/European Respiratory Society joint criteria on lung function testing.