Relaxin mimetic in pulmonary hypertension associated with left heart disease: Design and rationale of Re-PHIRE

AIMS: Despite receiving guideline-directed medical heart failure (HF) therapy, patients with pulmonary hypertension associated with left heart disease (PH-LHD) experience higher mortality and hospitalization rates than the general HF population. AZD3427 is a functionally selective, long-acting mimetic of relaxin, a hormone that has the potential to induce vasodilation and prevent fibrosis. In a phase 1b study conducted in patients with HF, AZD3427 demonstrated a favourable safety and pharmacokinetic profile. To address the unmet medical need in patients with PH-LHD in the context of HF, AZD3427 is currently under development as a potential treatment option.

METHODS AND RESULTS: The Re-PHIRE study is a phase 2b, randomized, double-blind, placebo-controlled, multicentre, dose-ranging study to evaluate the effect of AZD3427 on a broad range of PH-LHD phenotypes. In total, 220 patients will be randomized to four treatment groups to receive a subcutaneous injection of AZD3427 or placebo every 2 weeks for 24 weeks. The primary endpoint of the study is the change in pulmonary vascular resistance in patients treated with AZD3427 versus placebo after 24 weeks of treatment. Key secondary endpoints include changes in mean pulmonary arterial pressure, pulmonary artery wedge pressure, systemic vascular resistance, 6-min walking distance, N-terminal pro B-type natriuretic peptide levels, echocardiographic parameters, and health-related quality of life (assessed by the Kansas City Cardiomyopathy Questionnaire).

CONCLUSIONS: Re-PHIRE is the first study of a relaxin mimetic in patients with PH-LHD. The insights gained from the Re-PHIRE study are expected to inform the further development of AZD3427 in the PH-LHD population, including identifying the most suitable pulmonary hypertension and HF phenotypes for treatment.