A Study of a Mean Pulmonary Artery Pressure-Targeted Approach With Early and Rapid Treprostinil Therapy to Reverse Right Ventricular Remodeling in Participants With Pulmonary Arterial Hypertension

Inclusion Criteria: * Confirmed PAH (WHO Group 1) classified by one of the following subgroups: * Idiopathic, heritable or drug/toxin induced (with the exception of amphetamine-induced PAH) * Associated with repaired congenital systemic-to-pulmonary shunts (repaired ≥1 year) * Associated with connective tissue disease * Associated with human immunodeficiency virus infection * Baseline visit right heart catheterization (RHC) must also meet the following criteria: * mPAP \>35 mmHg * Pulmonary vascular resistance (PVR) \>2 Wood units * Pulmonary artery wedge pressure (PAWP) ≤15 mmHg * On a stable dose of an endothelin receptor antagonist (ERA) and/or phosphodiesterase type 5 inhibitor (PDE-5i) or soluble guanylate cyclase stimulator (sGC) therapy or if treatment naïve, willing to take one of these medications in addition to study drug * REVEAL Lite 2 risk score ≤9 * WHO FC II or III * 6MWD \>165 meters Exclusion Criteria: PAH-related Exclusion Criteria: * Prior or current use of epoprostenol, treprostinil, iloprost, beraprost, or selexipag * Positive vasoreactivity test in idiopathic, heritable, or drug/toxin induced PAH * Amphetamine use within the past 12 months * WHO Groups 2, 3, 4, and 5 * Use of any other investigational drug, device, or therapy within 30 days of the Baseline visit * Moderate or severe hepatic impairment (Child-Pugh Class B and C) * Any other clinically significant illness or abnormal laboratory value(s) measured during screening that, in the opinion of the Investigator, might adversely affect interpretation of the study data or participant safety (for example, active infection, chronic thromboembolic pulmonary hypertension, or acute/recent deep vein thrombosis or pulmonary embolism) * Chronic atrial fibrillation, multiple premature ventricular or atrial contractions of clinical significance, or any other condition that would interfere with proper cardiac gating during cMRI * Permanent cardiac pacemaker or automatic internal cardioverter that would interfere with conduct of cMRI * Metallic implant (for example, defibrillator, neurostimulator, hearing aid, permanent infusion device, implantable pump, or body plates/screws/bolts) that would interfere with conduct of cMRI CardioMEMS-related Exclusion Criteria, if applicable: * Previously implanted with CardioMEMS pulmonary artery Sensor or unwilling/unable to permit collection and perform upload (transmission) of pulmonary artery pressure (PAP) readings * Unable to take dual antiplatelet or anticoagulation therapy for 30 days after CardioMEMS PA Sensor implantation unless the participant has an indication for warfarin or direct oral anticoagulant NOTE: Other inclusion and exclusion criteria may apply.