The primary objective of this study is to evaluate the effect of 24-weeks of once daily treatment with TPIP compared with placebo on exercise capacity in adults with PAH.

Inclusion Criteria

• Participants must have a diagnosis of World Health Organisation (WHO) Group 1 pulmonary hypertension (PAH) in any of the following subtypes, in accordance with European Society of Cardiology European Respiratory Society (ESC/ERS) Guidelines:

  • Idiopathic PAH
  • Heritable PAH
  • Drug/toxin-induced PAH
  • Connective tissue disease (CTD)-associated PAH
  • PAH associated with congenital heart disease-related to simple systemic-to-pulmonary shunt at least 1 year following repair.

• PAH diagnosis for at least 3 months prior to Screening.

• New York Heart Association (NYHA) or World Health Organization (WHO) functional class II-IV.

• Participants must be on stable PAH therapy consisting of 1 to 3 medications from the following classes:

  • Endothelin receptor antagonists (eg, ambrisentan, bosentan, macitentan) for at least 90 days prior to Screening with the last 30 days on stable dose

  • Phosphodiesterase type 5 inhibitors (eg, sildenafil, tadalafil) for at least 90 days prior to Screening with the last 30 days on stable dose

  • Guanylate cyclase stimulator (eg, riociguat) for at least 90 days prior to Screening with the last 30 days on stable dose

  • Activin signaling inhibitor (e.g., sotatercept) for at least 6 months prior to Screening, with the last 3 months on stable dose and meeting all the following conditions:

    • no active clinically significant bleeding (eg, epistaxis and gingival bleeding requiring medical interventions) within the past 3 months.
    • no history of major bleeding events or risks (eg, gastrointestinal or intracranial bleeding) within the past 6 months.
    • platelet counts ≥100,000 per microlitre (μL) at Screening

  • For both 6-minute walk tests (6MWTs), the values of 6-minute walk distance (6MWD) should be ≥ 150 and ≤ 450 meters at Screening.

• Right heart catheterization (RHC) at Screening (or within 6 months prior to Screening, if available). Prior RHC may be used provided there has been no change in background PAH therapy and doses. The RHC must meet all of the following hemodynamic criteria:

  • Mean pulmonary arterial pressure (PAP) >20 millimetre of mercury (mmHg) at rest.
  • pulmonary capillary wedge pressure (PCWP) or left ventricular end-diastolic pressure (LVEDP) ≤15 mmHg.
  • pulmonary vascular resistance (PVR) of ≥5 wood units (WU).

Exclusion Criteria

• Diagnosis of PH WHO Groups 2, 3, 4, or 5, or subtypes of PH WHO Group 1 other than described in inclusion criterion 2 (eg, human immunodeficiency virus (HIV), complex congenital heart disease-associated PAH, portal hypertension-associated PAH, pulmonary veno-occlusive disease, Schistosomiasis associated PAH).
• Clinically significant left heart disease, including left-sided valvular disease, left ventricular systolic or diastolic dysfunction, echocardiographic findings suggestive of post-capillary pulmonary hypertension, unstable ischemic heart disease, or unstable arrhythmias.
• Evidence of airflow obstruction defined by forced expiratory volume in 1 second (FEV1) per forced vital capacity (FVC) <0.7.
• Evidence of significant restrictive lung disease as evidenced by FVC <70% predicted normal.
• Evidence of chronic thromboembolic disease or recent (within 6 months of Screening) acute pulmonary embolism.
• Known hypersensitivity or contraindication to treprostinil or TPIP or TPIP formulation excipients (e.g., mannitol, leucine).
• Any other medical or psychological condition including relevant laboratory abnormalities at Screening that, in the opinion of the Investigator, suggest a new and/or insufficiently understood disease and/or may present an unreasonable risk to the study participant as a result of his/her participation in this clinical trial, may impede their ability complete the study or the study assessments or confound the outcomes of the trial.

Note: Other protocol-defined inclusion/exclusion criteria may apply.