Inclusion Criteria:

• Signed informed consent prior to any study-mandated procedure.
• Male or female,  ≥ 18 and ≤ 75 years of age at screening.
• Initial PAH diagnosis < 6 months prior to Day 1.
• RHC performed between Day −28 and Day 1 (RHC data obtained at the study site within this time frame, but before the study, i.e., before signed informed consent, are acceptable), meeting all the following criteria:
  • mPAP ≥ 25 mmHg;
  • PAWP or LVEDP ≤ 15 mmHg;
  • PVR ≥ 480 dyn·sec/cm5 (≥6 WU);
  • Negative vasoreactivity test mandatory in idiopathic, heritable, and drug/toxin induced PAH (at this or a previous RHC).
• Symptomatic PAH belonging to one of the following subgroups [Simonneau 2013]:
  • Idiopathic;
  • Heritable;
  • Drug or toxin induced;
  • Associated with one of the following:
    • Connective tissue disease;
    • HIV infection;
    • Congenital heart disease with simple systemic-to-pulmonary shunt (atrial septal defect, ventricular septal defect, patent ductus arteriosus) ≥1 year after surgical repair.
• 6MWD ≥ 50 m at screening.
• Women of childbearing potential must:
  • Have a negative serum pregnancy test at the screening visit and a negative urine pregnancy test at the Day 1 visit; and
  • Agree to perform monthly pregnancy tests up to EOS; and
  • Agree to use reliable contraception from screening up to 1 month following discontinuation of the last study treatment. Reliable contraception must be started at least 11 days prior to Day 1.

Exclusion Criteria:

• Any PAH-specific drug therapy (e.g., any ERA, PDE-5i, soluble guanylate cyclase stimulator, prostacyclin, prostacyclin analog, or prostacyclin receptor agonist) at any time prior to Day 1 (administration for vasoreactivity testing is permitted; previous PAH-specific drugs used intermittently for the treatment of digital ulcers or Raynaud’s phenomenon are permitted if stopped > 6 months prior to Day 1).
• Cardio-pulmonary rehabilitation program based on exercise (planned, or started ≤ 12 weeks prior to Day 1).
• Body mass index (BMI) > 40 kg/m2 at screening.
• Presence of three or more of the following risk factors for heart failure with preserved 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 coronary artery stenting.
• Acute myocardial infarction ≤ 12 weeks prior to screening.
• Cerebrovascular events (e.g., transient ischemic attack, stroke) ≤ 12 weeks prior to screening.
• Known permanent atrial fibrillation.
• SBP < 90 mmHg at screening or Day 1.
• Ongoing or planned treatment with organic nitrates and/or doxazosin.
• Presence of one or more of the following signs of relevant lung disease at any time up to screening:
  • Diffusing capacity of the lung for carbon monoxide (DLCO) < 40% of predicted UNLESS computed tomography reveals no or mild interstitial lung disease;
  • Forced vital capacity (FVC) < 60% of predicted;
  • Forced expiratory volume in one second (FEV1) < 60% of predicted.
• Pulmonary function tests may be performed either with or without the use of bronchodilators, as per local clinical practice.
• Known or suspected pulmonary veno-occlusive disease (PVOD).
• Documented severe hepatic impairment (with or without cirrhosis) according to National Cancer Institute organ dysfunction working group criteria, defined as total bilirubin > 3 × upper limit of the normal range (ULN) accompanied by aspartate aminotransferase (AST) > ULN (assessed at screening); and/or Child-Pugh Class C.
• Serum AST and/or alanine aminotransferase (ALT) > 3 × ULN (assessed at screening).
• Severe renal impairment (estimated creatinine clearance ≤ 30 mL/min/1.73 m2) assessed at screening.
• Ongoing or planned dialysis.
• Hemoglobin < 100 g/L assessed at screening.
• Known or suspected uncontrolled thyroid disease (hypo- or hyperthyroidism).
• Loss of vision in one or both eyes because of non-arteritic ischemic optic neuropathy (NAION).
• 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.
• 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.
• Treatment with another investigational drug (planned, or taken ≤ 12 weeks prior to Day 1).
• Hypersensitivity to any of the 3 study treatments or any excipient of their formulations (lactose, magnesium stearate, microcrystalline cellulose, hydroxypropyl cellulose, povidone, corn starch, sodium starch glycolate type A, polyvinyl alcohol, polysorbate 80, titanium dioxide, talc, xanthan gum, lecithin from soya, croscarmellose sodium, hypromellose, sodium laurylsulfate, triacetin, iron oxide yellow, iron oxide red, iron oxide black, d-mannitol, propylene glycol, carnauba wax).
• Pregnancy, breastfeeding, or intention to become pregnant during the study.
• Concomitant life-threatening disease with a life expectancy < 12 months.
• Alcohol abuse.
• Any factor or condition likely to affect protocol compliance of the subject, as judged by the investigator.