Tacrolimus as first-line therapy in a US cohort of idiopathic inflammatory myopathies related interstitial lung disease.

Objectives: Calcineurin inhibitors are commonly used to treat idiopathic inflammatory myopathies related interstitial lung disease (IIM-ILD) in Asia but not in the USA. Here, we evaluate the efficacy of tacrolimus (TAC) as first-line immunosuppressive therapy in a US cohort of IIM-ILD.

Methods: This retrospective, single-centre cohort study evaluated the change in absolute forced vital capacity (FVCabs) in IIM-ILD participants after 12 months of treatment with mycophenolate mofetil (MMF), azathioprine (AZA) or TAC. Participants were naïve to immunosuppressive agents other than glucocorticoids and/or intravenous immunoglobulin. Treatment with MMF, AZA or TAC was at the discretion of their primary clinician. Additional outcomes were transplant-free survival, prednisone use and supplemental oxygen use at 12 months.

Results: Thirty-one participants were included in this study. The TAC group was younger and had a shorter disease duration than the MMF/AZA group. All MDA5 patients were treated with TAC. After 12 months of therapy, the FVCabs was unchanged in the MMF/AZA group (2.4 l [95% CI 2.0, 3.2 l] vs 2.3 l [95% CI 2.0, 2.8 l]) and improved in TAC group (2.5 l [95% CI 2.0, 3.0 l] vs.1.9 l [95% CI 1.0, 2.6 l]). Transplant-free survival was 100% in both groups. All patients in the MMF/AZA group remained on supplemental oxygen at 12 months, but 4/5 patients in the TAC group resolved their oxygen requirement.

Conclusion: TAC is effective as a first-line agent in a small, non-randomized US cohort of IIM-ILD enriched for MDA5+ participants. Further work is needed to investigate the relative efficacy of calcineurin inhibitors compared with MMF/AZA in the US population.