Successful treatment of refractory myositis-associated interstitial lung disease with an interleukin-6 inhibitor: four-patient case series

OBJECTIVES: Myositis-associated interstitial lung disease (ILD) is a potentially fatal disease, despite combination therapy with glucocorticoids (GC) and other immunosuppressive agents. New therapies, including biologics targeting relevant cytokines, such as interleukin (IL)-6, are warranted. We retrospectively reviewed patients with myositis-associated ILD who were treated with the IL-6 inhibitor tocilizumab (TCZ) to determine the clinical usefulness of TCZ. METHODS: Four patients with myositis-associated ILD treated with TCZ between 2019 and 2023 were identified from the records of our medical centre. RESULTS: All patients were female, aged 43-84 years. One patient was positive for the antimelanoma differentiation-associated gene 5 antibody, while the others were positive for anti-aminoacyl-tRNA synthetase antibodies. All patients met the classification criteria for rheumatoid arthritis. The initial GC dose was 1 mg/kg/day (40-60 mg/day) of prednisolone, and GC-pulse therapy was administered to all but one patient. TCZ treatment was initiated within 6 months of the initial treatment. All patients showed clinical and radiological improvements after TCZ therapy, achieving GC reduction or withdrawal. The Warrick score, which semi-quantitatively evaluates ILD, improved from a median of 14.5 (moderate) to 4 (mild). Furthermore, no relapse or serious adverse events were observed. CONCLUSION: TCZ is a potential treatment option for refractory myositis-associated ILD.