Efficacy and Safety of Treprostinil in Intermediate-Risk Pulmonary Arterial Hypertension

Background and Rationale: Pulmonary Arterial Hypertension (PAH) is a progressive vasculopathy leading to increased pulmonary vascular resistance, right ventricular (RV) failure, and mortality. While guidelines recommend initial combination oral therapy, a substantial number of patients, particularly those at intermediate-risk, do not achieve a low-risk status. Subclinical RV deterioration can occur even in seemingly stable patients, suggesting that more intensive therapeutic strategies may be warranted to improve long-term outcomes. Parenteral prostacyclin analogues, like Treprostinil, are potent therapies recommended for high-risk PAH. However, there is a lack of prospective data on their efficacy in inducing positive RV remodeling and improving clinical outcomes when initiated in patients with intermediate-risk PAH who are already on background oral therapies. This study aims to address this evidence gap. Study Design and Objectives: This is a prospective, single-center, single-arm, open-label, exploratory study designed to evaluate the efficacy and safety of adding subcutaneous Treprostinil to standard-of-care oral therapy for patients with intermediate-risk PAH. The primary objective is to assess the change from baseline in Right Ventricular Stroke Volume (RVSV) at 3 months, as measured by Cardiac Magnetic Resonance (CMR). The hypothesis is that the addition of Treprostinil will lead to a significant improvement in RVSV, reflecting favorable RV remodeling. Secondary objectives include evaluating changes from baseline in: WHO Functional Class (FC) 6-minute walk distance (6MWD) N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels Other CMR-derived parameters of RV structure and function (e.g., RV ejection fraction \[RVEF\], RV end-systolic volume index \[RVESVI\]) Risk stratification scores Incidence of clinical worsening events over the follow-up period. Exploratory objectives include the assessment of changes in other echocardiographic parameters, health-related quality of life, and a panel of serum biomarkers associated with inflammation and cardiac remodeling (e.g., TNF-α, IL-6, MMP2, TIMP1). Methodology: A total of 32 eligible patients with intermediate-risk PAH will be enrolled. Participants must be on a stable dose of at least one oral PAH-targeted therapy (e.g., an endothelin receptor antagonist and/or a phosphodiesterase-5 inhibitor/soluble guanylate cyclase stimulator) or be treatment-naïve and willing to start oral therapy concurrently. All participants will initiate subcutaneous Treprostinil, with the dose titrated according to tolerability and clinical response, following the product's prescribing information. Comprehensive assessments, including CMR, 6MWD, WHO FC, and laboratory tests, will be performed at baseline and at 3 months. Further follow-up assessments will occur at 1 month and continue for a total of 24 months to evaluate long-term safety and outcomes. Safety will be monitored throughout the study by recording all adverse events and laboratory abnormalities.