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

Calcineurin inhibitors are commonly used to treat idiopathic inflammatory myopathies associated interstitial lung disease (IIM-ILD) in Asia but not in the U.S. Here, we evaluate the efficacy of tacrolimus (TAC) as first-line immunosuppressive therapy in a U.S cohort of IIM-ILD. 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. 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.1.9L [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. TAC is effective as a first-line agent in a small, non-randomized U.S. 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 U.S. population.