Pirfenidone in Unclassifiable Interstitial Lung Disease: A Subgroup Analysis by Concomitant Mycophenolate Mofetil and/or Previous Corticosteroid Use

INTRODUCTION: There are currently no approved treatments solely for unclassifiable interstitial lung disease (uILD); however, a recent trial showed this population can benefit from pirfenidone. We report a subgroup analysis of this trial to assess the effects of immunomodulators (concomitant mycophenolate mofetil [MMF] and/or previous corticosteroids) with pirfenidone in patients with uILD. METHODS: This was a multicenter, international, double-blind, randomized, placebo-controlled phase II trial of patients with progressive fibrosing uILD (NCT03099187). Patients were randomized (1:1) to receive pirfenidone 2403 mg/day or placebo. This analysis assessed forced vital capacity (FVC) change from baseline measured using site spirometry (key secondary endpoint) and safety over 24 weeks by concomitant MMF use at randomization (pre-specified analysis) and/or previous corticosteroid use (post hoc analysis). RESULTS: Overall, 253 patients were randomized, including 45 (17.8%) patients (pirfenidone, n = 23; placebo, n = 22) receiving concomitant MMF with/without previous corticosteroids (MMF subgroup); 79 (31.2%) patients (pirfenidone, n = 44; placebo, n = 35) receiving previous corticosteroids without MMF (corticosteroids/no-MMF subgroup); and 129 (51.0%) patients (pirfenidone, n = 60; placebo, n = 69) not receiving concomitant MMF or previous corticosteroids (no-corticosteroids/no-MMF subgroup). At 24 weeks, difference in mean (95% confidence interval) FVC change from baseline between pirfenidone and placebo was − 55.4 mL (− 206.7, 96.0; P = 0.4645) in the MMF subgroup; 128.4 mL (− 6.4, 263.3; P = 0.0617) in the corticosteroids/no-MMF subgroup; and 115.5 mL (35.1, 195.9; P = 0.0052) in the no-corticosteroids/no-MMF subgroup. All subgroups generally exhibited a similar pattern of treatment-emergent adverse events. CONCLUSION: Although limited by design and small sample sizes, this analysis suggests pirfenidone may be less effective in patients with uILD receiving concomitant MMF, whereas a beneficial treatment effect was observed in patients not receiving concomitant MMF regardless of previous corticosteroid use. Pirfenidone was well tolerated regardless of MMF and/or corticosteroid use. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov: NCT03099187.