Inhaled Nitric Oxide in Fibrotic Lung Disease: A Randomized, Double-Blind, Placebo-controlled Trial

Rationale: Inhaled nitric oxide (iNO) has been shown to result in benefits in moderate to vigorous physical activity (MVPA) in patients with fibrotic interstitial lung disease (f-ILD) receiving supplemental oxygen in two independent trials. Objective: This phase III randomized, double-blind, placebo-controlled study sought to validate the benefit of ambulatory iNO in patients with f-ILD requiring supplemental oxygen. Methods: Patients with f-ILD receiving supplemental long-term oxygen were randomized in a 1:1 fashion to iNO at 45 μg/kg ideal body weight per hour or placebo for 16 weeks. The primary outcome was the change from baseline to Week 16 in MVPA assessed by accelerometry. Secondary outcomes included overall activity, 6-minute-walk distance and patient-reported outcomes. Results: 145 patients were enrolled; 75 were assigned to receive iNO and 70 placebo. The changes from baseline in MVPA at 16 weeks were -9.2 min/d (standard error, 3.51) in the iNO45 group and -3.7 min/d (3.76) in the placebo group (difference, 5.5; P = 0.265). No statistically significant differences between the two treatment arms were found for any of the secondary outcomes. A subgroup analysis of patients with an intermediate or high probability of pulmonary hypertension on echocardiography did not demonstrate any benefit. The most common adverse events reported were respiratory tract infections, but the therapy was generally very well tolerated. Conclusions: There was no demonstrable benefit to iNO in patients with f-ILD receiving supplemental oxygen in daily physical activity assessed by actigraphy, a potential novel clinical trial endpoint. Clinical trial registered with www.clinicaltrials.gov (NCT03267108).