All subjects who received oral treprostinil in TDE-PH-311 were included in the Safety population. All AEs were captured from the time the ICF was signed. All AEs were followed until resolution (or return to normal or baseline values), until they were judged by the Investigator to no longer be clinically significant, or for up to 30 days if the AE extended beyond the final visit. All SAEs were followed until resolution, death, or the subject was lost to follow-up, even if they were ongoing more than 30 days after completion of the final visit. The overall summary of AEs includes the number of subjects with any AE, the number of subjects with any study drug-related AEs, the number of subjects with AEs leading to study drug withdrawal, the number of subjects with any serious AEs, the number of subjects with any severe AEs, and the number of subjects with any study drug-related severe/serious AEs. AEs were coded using the Medical Dictionary for Regulatory Activities.

The PK sampling occurred over a 12-hour period in subjects during BID dosing (PK Visit 1) and during TID dosing (PK Visit 2). Prior to each PK sampling day, subjects must have been receiving a stable dose for at least 5 days.

The PK sampling occurred over a 12-hour period in subjects during BID dosing (PK Visit 1) and during TID dosing (PK Visit 2). Prior to each PK sampling day, subjects must have been receiving a stable dose for at least 5 days.

The PK sampling occurred over a 12-hour period in subjects during BID dosing (PK Visit 1) and during TID dosing (PK Visit 2). Prior to each PK sampling day, subjects must have been receiving a stable dose for at least 5 days.

Successful transition was based on the number of participants that completely transitioned to oral treprostinil by the week 4 study visit and clinically maintained on oral treprostinil treatment through Week 24.

Hemodynamics (via right heart catheterization \[RHC\]) were assessed at Baseline and Week 24 or at the time of premature termination of study drug if prior to the Week 24 visit. Cardiopulmonary hemodynamic measurements included the following: mean pulmonary arterial pressure (PAPm), mean systemic arterial pressure (SAPm), mean right atrial pressure (RAPm), and mean pulmonary capillary wedge pressure (PCWPm).

Heart rate was assessed at Baseline and Week 24 or at the time of premature termination of study drug if prior to the Week 24 visit.

Hemodynamics (via right heart catheterization \[RHC\]) were assessed at Baseline and Week 24 or at the time of premature termination of study drug if prior to the Week 24 visit. Cardiopulmonary hemodynamic measurements included arterial oxygen saturation (SaO2) and mixed venous oxygen saturation (SvO2).

Hemodynamics (via right heart catheterization \[RHC\]) were assessed at Baseline and Week 24 or at the time of premature termination of study drug if prior to the Week 24 visit.

Hemodynamics (via right heart catheterization \[RHC\]) were assessed at Baseline and Week 24 or at the time of premature termination of study drug if prior to the Week 24 visit. Cardiopulmonary hemodynamic measurements included cardiac index (CI).

Hemodynamics (via right heart catheterization \[RHC\]) were assessed at Baseline and Week 24 or at the time of premature termination of study drug if prior to the Week 24 visit. Cardiopulmonary hemodynamic measurements included the following: pulmonary vascular resistance index (PVRI).