Long-Term, Open Label Extension Study of Pemziviptadil (PB1046) in PAH Subjects Following Completion of Study PB1046-PT-CL-0004

Subjects entering this study will enter from the double-blind Study PB1046-PT-CL-0004. The starting dose level of pemziviptadil (PB1046) for all subjects in this parent study was a sub-therapeutic or minimally effective dose (MED) of 0.2 mg/kg, administered by SC injection. Subjects were randomized into the MED) Group or a dose-titration group. In the dose-titration group, individual subjects were titrated up to their maximum tolerated dose (MTD) in a blinded fashion, with the objective of titrating subjects up to a dose of at least 1.2 mg/kg or higher in the MTD Group, while subjects in the MED Group remained at the MED level of 0.2 mg/kg, and underwent "sham dose-titration" to maintain the blind. Subjects entering the 0006 trial prior to implementation of this protocol amendment will remain blinded until such time that open label dosing will not unblind the 0004 study.