Open-label, Clinical Study to Evaluate the Safety and Tolerability of TreT in Subjects With PAH Currently Using Tyvaso

United Therapeutics Corporation (UTC) developed a combination drug-device product comprised of a dry powder formulation of Treprostinil Inhalation Powder (TreT) and a small, portable, dry powder inhaler. In this Phase 1b safety and tolerability study, patients with PAH on a stable dose of Tyvaso (6 to 12 breaths 4 times daily \[QID\]) were evaluated after switching to a corresponding dose of TreT. Patients underwent PK assessments, safety assessments, a 6-Minute Walk Test (6MWT), and questionnaires for satisfaction/preference for inhaled devices and patient-reported PAH symptoms and impact. Following 3 weeks of treatment with TreT, patients were offered the opportunity to participate in the Optional Extension Phase until the drug/device became commercially available.