Baseline NT-proBNP correlates with change in 6-minute walk distance in patients with pulmonary arterial hypertension in the pivotal inhaled treprostinil study TRIUMPH-1

Background: N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a biomarker of disease severity in pulmonary arterial hypertension (PAH). In this study we aimed to determine whether baseline NT-proBNP levels correlate with improvement in 6-minute walk distance (6MWD) in the pivotal randomized, placebo-controlled, double-blind study of the addition of inhaled treprostinil to oral therapy for PAH. Methods: A post hoc analysis of data from the TRIUMPH-1 study was performed in patients who had assessments of NT-proBNP levels and baseline and Week 12 6MWD. Least-squares mean analysis was used to compare patients in the highest quartile of baseline NT-proBNP with those in lower quartiles with regard to change from baseline in 6MWD, stratified by treatment. Results: The NT-proBNP within-treatment median changes from baseline to Week 12 were +44 and -72 pg/ml, and the median changes in 6MWD from baseline to Week 12 were +5 and +40 m for the placebo (n = 94) and inhaled treprostinil (n = 84) groups, respectively. Baseline NT-proBNP levels demonstrated a strong interaction with treatment in predicting change from baseline for 6MWD (p < 0.01), indicating that, in the upper quartile (<1,513.5 pg/ml), patients on inhaled treprostinil had a better response (+64 vs +32 m), whereas patients on placebo fared worse (-13 vs +20 m) when compared with the lower 3 quartiles (<1,513.5 pg/ml). Furthermore, least-squares mean difference in 6MWD between active and placebo groups was +67 and +16 m for the upper and lower 3 quartiles of NT-proBNP, respectively. Conclusions: Greater improvement in 6MWD in actively treated patients with high levels of NT-proBNP enhances understanding of the robustness of clinical response to inhaled treprostinil in more advanced disease.