Dose-response Study of the Safety and Efficacy of Beraprost Sodium Modified Release (BPS-MR) in Patients With Pulmonary Arterial Hypertension (PAH)

This is a 12-week, international, multicenter, double-blind, three-group, dose-response study to assess the safety and efficacy of BPS-MR in patients with PAH. Eligible patients will have been previously diagnosed with PAH and will be on a stable course of an ERA and/or PDE-5 inhibitor for at least 60 days prior to Baseline. Patients will be randomized to 1 of 3 treatment groups in a 1:1:1 ratio and will be stratified by PAH background therapy (Endothelium Receptor Antagonist (ERA), Phosphodiesterase-5 (PDE-5), and both). The treatment groups consist of one Maximum Tolerated Dose (MTD) and two Fixed Dose (FD) groups. Following randomization, patients will begin taking active drug (60µg) orally twice daily. Patients will visit their investigational site at Week 6 and Week 12 for study evaluations.