The Efficacy and Safety of Initial Triple Versus Initial Dual Oral Combination Therapy in Patients With Newly Diagnosed Pulmonary Arterial Hypertension

Inclusion Criteria:

1. Signed informed consent prior to any study-mandated procedure.

2. Male or female ≥ 18 and ≤ 75 years of age at screening.

3. Initial PAH diagnosis < 6 months prior to enrollment.

4. RHC performed between Day -28 and Day 1, meeting all the following criteria:

• Mean pulmonary artery pressure (mPAP) ≥ 25 mmHg.

• Pulmonary artery wedge pressure or left ventricular end-diastolic pressure ≤ 15mmHg.

• PVR ≥ 480 dyn•sec/cm5 (≥ 6 Wood Units).

• Negative vasoreactivity test mandatory in idiopathic, heritable, and drug/toxininduced PAH (at this or a previous RHC).

5. Symptomatic PAH belonging to one of the following subgroups:

• Idiopathic.

• Heritable.

• Drug or toxin induced.

• Associated with one of the following: connective tissue disease; HIV infection;congenital heart disease.

6. 6-minute walk distance (6MWD) ≥ 50 m at screening.

7. Women of childbearing potential must not be pregnant, must perform regular pregnancytests, and use reliable contraception.

Exclusion Criteria:

1. Any PAH-specific drug therapy at any time.

2. Cardio pulmonary rehabilitation program based on exercise (planned, or started ≤ 12weeks prior to Day 1).

3. Body mass index (BMI) > 40 kg/m2 at screening.

4. Presence of three or more of the following risk factors for heart failure withpreserved ejection fraction at screening:

• BMI > 30 kg/m2.

• Diabetes mellitus of any type.

• Essential hypertension.

• Coronary artery disease, i.e., any of the following:

• History of stable angina or

• More than 50% stenosis in a coronary artery (by coronary angiography) or

• History of myocardial infarction or

• History of or planned coronary artery bypass grafting and/or coronaryartery stenting.

5. Acute myocardial infarction ≤ 12 weeks prior to screening.

6. Stroke ≤ 12 weeks prior to screening.

7. Known permanent atrial fibrillation.

8. SBP < 90 mmHg at screening or Day 1.

9. Ongoing or planned treatment with organic nitrates and/or doxazosin.

10. Presence of one or more of the following signs of relevant lung disease at any timeup to screening:

• Diffusing capacity of the lung for carbon monoxide (DLCO) < 40% of predicted (eligible only if no or mild interstitial lung disease on computed tomography).

• Forced vital capacity (FVC) < 60% of predicted.

• Forced expiratory volume in one second (FEV1) < 60% of predicted.

11. Known or suspected pulmonary veno-occlusive disease (PVOD).

12. Documented severe hepatic impairment (with or without cirrhosis) according toNational Cancer Institute organ dysfunction working group criteria, defined as totalbilirubin > 3 × upper limit of the normal range (ULN) accompanied by aspartateaminotransferase (AST) > ULN (assessed by central laboratory at screening); and/orChild-Pugh Class C.

13. Serum AST and/or alanine aminotransferase (ALT) > 3 × ULN (assessed by centrallaboratory at screening).

14. Severe renal impairment (estimated creatinine clearance ≤ 30 mL/min/1.73 m2)assessed by central laboratory at screening.

15. Ongoing or planned dialysis.

16. Hemoglobin < 100 g/L assessed by central laboratory at screening.

17. Known or suspected uncontrolled thyroid disease (hypo- or hyperthyroidism).

18. Loss of vision in one or both eyes because of non-arteritic ischemic opticneuropathy (NAION).

19. Treatment with strong inducers of cytochrome P450 3A4 (CYP3A4; e.g., carbamazepine,rifampin, rifampicin, rifabutin, rifapentin, phenobarbital, phenytoin, and St.John's wort) ≤ 28 days prior to Day 1.

20. Treatment with strong inhibitors of CYP3A4 (e.g., ketoconazole, itraconazole,voriconazole, clarithromycin, telithromycin, nefazodone, ritonavir, and saquinavir)and/or strong inhibitors of CYP2C8 (e.g., gemfibrozil) ≤ 28 days prior to Day 1.

21. Treatment with another investigational drug (planned, or taken ≤ 12 weeks prior toDay 1).

22. Hypersensitivity to any of the 3 study treatments or any excipient of theirformulations.

23. Pregnancy, breastfeeding, or intention to become pregnant during the study.

24. Concomitant life-threatening disease with a life expectancy < 12 months.

25. Alcohol abuse.

26. Any factor or condition likely to affect protocol compliance of the subject, asjudged by the investigator.