This study provided/continued to provide oral treprostinil (UT-15C SR; treprostinil diethanolamine) to eligible subjects who participated in Studies TDE-PH-202, TDE-PH-203, TDE-PH-205, TDE-PH-301, TDE-PH-302, and TDE-PH-308. The study assessed the long term safety of oral treprostinil and the effect of continued treatment with oral treprostinil on exercise capacity after 1 year of treatment.

This was an international, multicenter, open-label study designed to provide oral treprostinil for eligible subjects who participated in Studies TDE-PH-301, TDE-PH-302, TDE-PH-308, TDE-PH-202, TDE PH 203, and TDE-PH-205. Subjects randomly allocated to receive oral treprostinil in Studies TDE-PH-301, TDE-PH-302, or TDE-PH-308 and enrolled in this open-label study completed visits at Months 6, 12, 24, 36, and yearly visits thereafter. Subjects randomly allocated to receive placebo in Studies TDE-PH-301, TDE-PH-302, or TDE-PH-308 completed visits at Months 3, 6, 12, 24, 36, and yearly visits thereafter. Subjects that transitioned from Studies TDE-PH-202, TDE-PH-203, and TDE-PH-205 (that had an open-label study design) followed the regimen for subjects receiving oral treprostinil. A 6-Minute Walk Test (6MWT) and Borg dyspnea score were conducted at the visit which occurred 12 months after the subject's first exposure to oral treprostinil.

Adverse events (AEs) were reported continuously throughout the study; any AEs ongoing at the time of discharge from Studies TDE PH-301, TDE PH-302, TDE-PH-308, TDE-PH-202, TDE-PH-203, and TDE-PH-205 were recorded as AEs and marked as "ongoing from previous study" in the subject's electronic Case Report Form (eCRF). Study drug dosing and pulmonary arterial hypertension (PAH) concomitant medication usage were assessed at each scheduled study visit and recorded in the subject's eCRF.

Inclusion Criteria:

1. The subject remained on study drug and completed all assessments during the Treatment Phase of the previous study (TDE-PH-202, TDE-PH-203, TDE-PH-205, TDE-PH-301, TDE PH-302, or TDE-PH-308) OR the subject permanently discontinued study drug during the Treatment Phase of the previous study due to clinical worsening (as defined in the protocol of the previous study), completed premature termination assessments prior to discontinuing study drug, completed all remaining scheduled study visits, AND received placebo during the Treatment Phase of the previous studies OR the subject was randomized into Group 1 or Group 2 in Study TDE PH 202, permanently discontinued study drug during the 12-week Treatment Phase due to clinical worsening, completed all premature termination assessments prior to discontinuing study drug, and completed all remaining scheduled study visits and assessments (with the exception of the hemodynamic measurements) through Week 12. Such subjects should have started treatment with oral treprostinil in the open-label study at 0.25 mg twice daily (BID).
2. The subject voluntarily gave informed consent to participate in the study.
3. Women of childbearing potential includes any female who had experienced menarche and who had not undergone successful surgical sterilization (hysterectomy, bilateral tubal ligation, or bilateral oophorectomy) or was not postmenopausal (defined as amenorrhea for at least 12 consecutive months). Sexually active women of childbearing potential must have used 2 effective forms of contraception during the length of the study. Medically acceptable forms of effective contraception included: (1) approved hormonal contraceptives (such as birth control pills), (2) barrier methods (such as a condom or diaphragm) used with a spermicide, (3) an intrauterine device, (4) partner vasectomy, or (5) abstinence. Males participating in the study must have used a condom during the length of the study, and for at least 48 hours after discontinuing study medication. Protocol Amendment A.1AU included the required assessment for Austrian subjects to perform urine pregnancy tests every 4 weeks during the study.

Exclusion Criteria:

1. The subject permanently discontinued study drug during the previous study (TDE PH 202, TDE-PH-203, TDE PH 205, TDE-PH-301, TDE-PH-302, or TDE PH 308) due to treatment-related adverse events (AEs).
2. The subject permanently discontinued study drug during the Treatment Phase of the previous study (TDE-PH-202, TDE-PH-203, TDE-PH-205, TDE-PH-301, TDE-PH-302, or TDE-PH-308) due to clinical worsening (as defined in those study protocols) and did not undergo premature termination assessments prior to discontinuing study drug, and/or did not complete all remaining study visits through the final scheduled visit.
3. The subject prematurely discontinued study drug during the Treatment Phase of the previous study due to clinical worsening (as defined in those study protocols), completed premature termination assessments prior to discontinuing study drug, completed all remaining scheduled study visits AND received oral treprostinil during the Treatment Phase of the previous study (TDE PH-202, TDE-PH-203, TDE-PH-301, TDE-PH-302, or TDE PH-308). Subjects enrolled in Study TDE-PH-202 who were randomized into the individual maximum tolerated dose (iMTD) group who clinically worsened could not participate. Subjects who permanently discontinued study drug during the 12-week Treatment Phase due to treatment-related AEs were not eligible even if they completed all remaining scheduled study visits. Subjects who permanently discontinued study drug during the 12 week Treatment Phase and did not undergo premature termination assessments prior to discontinuing study drug and/or who did not complete all remaining study visits through the Week 12 visit were also not eligible.
4. The subject developed any concurrent illness or condition during the conduct of the previous study, including but not restricted to: sleep apnea, chronic renal insufficiency, anemia, uncontrolled systemic hypertension, or left sided heart disease, unless their physician felt that entry into this study would not be detrimental to their overall health.