Efficacy of inhaled N-acetylcysteine monotherapy in patients with early stage idiopathic pulmonary fibrosis

Background and objective:  Idiopathic pulmonary fibrosis (IPF) is a fatal disorder for which there are currently no specific or effective medical treatments. A multicentre, prospective, randomized, controlled clinical trial was conducted to assess the efficacy of inhaled N-acetylcysteine (NAC) monotherapy in Japanese patients with early stage IPF. Methods:  Eligible patients had well-defined IPF of mild-to-moderate severity, with no desaturation on exercise. Of 100 patients screened, 76 were randomly assigned to an NAC treatment group (group A; n = 38) that received 352.4 mg of NAC by inhalation twice daily or to a control group (group B; n = 38) that received no therapy. The primary endpoint was the change from baseline in forced vital capacity (FVC) at 48 weeks. Results:  There were no significant overall differences in the change in FVC between groups A and B. Post hoc exploratory analyses showed that NAC therapy was associated with stability of FVC in (i) a subset of patients with initial FVC <95% of predicted (n = 49; difference in FVC decline 0.12 L; P = 0.02) and (ii) in patients with initial diffusing capacity of carbon monoxide <55% of predicted (n = 21; difference in FVC decline 0.17 L; P = 0.009). Conclusions:  These findings indicate that NAC monotherapy may have some beneficial effect in patients with early stage IPF. Further trials in more select IPF populations with progressive disease are required to prove the efficacy of inhaled NAC.