ACT-293987

Number of participants with TEAEs were reported. Adverse event (AE) was defined as any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non investigational) product. An AE did not necessarily have a causal relationship with the pharmaceutical/biological agent under study. TEAEs were defined as AEs occurring at or after the initial administration of study intervention through the day of last dose plus 3 days. Data includes all TEAEs irrespective of whether they were serious or non-serious.

Number of participants with TEAEs leading to premature discontinuation of selexipag were reported. AE was defined as any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non investigational) product. An AE did not necessarily have a causal relationship with the pharmaceutical/biological agent under study. TEAEs were defined as AEs occurring at or after the initial administration of study intervention through the day of last dose plus 3 days.

Number of participants with TESAEs were reported. AE was defined as any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non investigational) product. An AE did not necessarily have a causal relationship with the pharmaceutical/biological agent under study. A SAE was any untoward medical occurrence at any dose that: resulted in death, was life threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, or resulted in congenital anomaly/birth defect. TESAEs were defined as TSAEs occurring at or after the initial administration of study intervention through the day of last dose plus 3 days.

Number of participants with treatment-emergent deaths during the study were reported.

Number of pregnant females with maternal exposure to selexipag were reported.

Time to disease progression: time from randomization to first Clinical Event Committee (CEC)-confirmed disease progression event occurring between date of randomization until double-blind end date (DBED) + 7 days. Disease progression event as adjudicated by CEC, defined as any of the following: death (all causes); atrial septostomy or Potts' anastomosis, or registration on lung transplant list; hospitalization due to worsening pulmonary arterial hypertension (PAH); clinical worsening of PAH. Clinical worsening of PAH was defined as initiation of new PAH-specific therapy or intravenous diuretics or continuous oxygen use and at least 1 of the following: worsening in World Health Organization (WHO) functional class (FC); new occurrence or worsening: of syncope, of at least 2 PAH symptoms (shortness of breath/dyspnea, chest pain, cyanosis, dizziness/near syncope, or fatigue), of signs of right heart failure not responding to oral diuretics. Kaplan-Meier method was used for estimation.

AE is any untoward medical event that occurs in a participant during the course of the study whether or not considered by the investigator as related to the study treatment.

Prostacyclin-associated AE include headache, diarrhea, nausea, vomiting, jaw pain, myalgia, pain in the extremity, flushing and arthralgia.

This is the number of participants with at least one clinically significant reaction at the injection site (e.g., erythema/redness, tenderness, swelling, induration, hemorrhage at the injection site) occurring on the days of intravenous (iv) selexipag injection.

This is the number of subjects who discontinued the i.v. selexipag treatment due to prostacyclin-associated adverse events (headache, diarrhea, nausea, vomiting, jaw pain, myalgia, pain in the extremity, flushing and arthralgia).

This is the number of participants with at least one AE considered to be related to pulmonary arterial hypertension during the course of the study.

A sustained treatment transition is considered if the 3 following criteria are met a) being on study treatment (selexipag) at Week 16, and b) not having a study treatment interruption(s) of a total of 8 days or more prior to Week 16, and c) absence of inhaled treprostinil or any prostanoid treatment after Week 8 up to Week 16. The percentage of subjects with a sustained treatment transition is calculated with 95% confidence interval (CI) using the Clopper-Pearson method.

Percentage of subjects with treatment-emergent AEs (serious and non serious), regardless of relationship to selexipag

Number of subjects with adverse events leading to premature discontinuation of selexipag is determined from the first dose of selexipag up to the last dose of selexipag

Both systolic(SBP) and diastolic (DBP) arterial blood pressure were measured in a sitting position after at least 5 minutes of rest at scheduled time points. Median change from baseline to pre-specified post-baseline visits are calculated

Pulse rate is measured after at least 5 minutes of rest in a sitting position. Median change from baseline to pre-specified post-baseline visits are calculated.

This is the individual maximal tolerated dose (MTD) observed at Week 12 in the subjects still on selexipag at Week 16. MTD is defined as the dose of selexipag reached with the last dose change up to Week 12

Median time from baseline (Day1) to the end of down-titration of inhaled treprostinil is calculated

An adverse event (AE) is any untoward medical event that occurs in a participant administered an investigational product, and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product. A TEAE is any AE temporally associated with the use of study drug (from study drug initiation until 3 days after study drug discontinuation), whether or not considered related to the study drug.

An adverse event is any untoward medical event that occurs in a participant administered an investigational product, and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product. SAE is any AE that results in: death, persistent or significant disability/incapacity, requires inpatient hospitalization or prolongation of existing hospitalization, is life-threatening experience, is a congenital anomaly/birth defect and may jeopardize participant and/or may require medical or surgical intervention to prevent one of the outcomes listed above. Those SAEs occurring during study drug administration, that is, between study drug initiation and three days after study drug discontinuation, are defined as treatment-emergent SAEs.

An adverse event (AE) is any untoward medical event that occurs in a participant administered an investigational product, and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product. A TEAE is any AE temporally associated with the use of study drug (from study drug initiation until 3 days after study drug discontinuation), whether or not considered related to the study drug.

Time from randomization to the first occurrence of a morbidity event or death (all causes) was analyzed with the Kaplan-Meier method (event-free KM estimates at different time points). Morbidity event was defined as any of the following events confirmed by the Critical Event committee: * Hospitalization for worsening of pulmonary arterial hypertension (PAH), * Worsening of PAH resulting in need for lung transplantation or balloon atrial septostomy, * Initiation of parenteral prostanoid therapy or chronic oxygen therapy due to worsening of PAH, * Disease progression which was defined by a decrease in 6-minute walk distance from baseline (\>=15%, confirmed by a 2nd test on a different day) combined with worsening of WHO FC for patients belonging to WHO FC II/III at baseline, or combined with the need for additional PAH-specific therapy for patients belonging to WHO FC III/IV at baseline. Note: The number of patients at risk decreased over time but this cannot be captured below

AUCτ, ss, combined was defined as the area under the plasma concentration-time curve over one dosing interval at steady state. AUCτ,ss,combined was calculated as 1/38 AUCτ,ss,selexipag plus 37/38 AUCτ,ss,ACT-333679.

The number of RP attacks is determined from daily entries in electronic Diaries (eDiary).

Electrocardiograms (ECGs) will be extracted in replicate at predefined timepoints from replicated 12-lead Holter ECGs. Cardiodynamic endpoints will be assessed at steady-state for 800 μg selexipag on Day 11 and at steady-state for 1600 μg selexipag on Day 23. Based on prospective criteria, QTcI will be the primary method for heart rate (HR) correction.