This multi-center, open-label study will assess the tolerability and safety of transitioning
subjects with stable Pulmonary Arterial Hypertension (PAH) from continuous intravenous (IV)
or subcutaneous (SC) Remodulin infusion to oral treprostinil (UT-15C sustained release (SR)
This study will consist of an in-hospital transition phase, dose optimization/evaluation
phase, and follow up phase.