Effectiveness and safety of rituximab in patients with refractory idiopathic inflammatory myopathies: a retrospective study from a single-center cohort with a special focus on low-dose as a maintenance treatment for remission.

Objective The primary aim of this study was to evaluate the efficacy and safety of Rituximab (RTX) in patients with refractory idiopathic inflammatory myopathies (IIMs) within a monocentric cohort. Additionally, we sought to assess the effectiveness of a low-dose RTX regimen as maintenance therapy to sustain remission. Methods We conducted a retrospective analysis of a cohort of patients diagnosed with IIM, all were refractory to glucocorticoids (GC) and at least one other immunosuppressive agent. The standard RTX treatment protocol consisted of two infusions of 1 g, administered two weeks apart. For the low-dose regimen, patients received a single 1 g infusion every six months. Treatment responses, including complete and partial responses, were determined based on clinical judgment, laboratory results, and radiological findings. Results A total of 43 patients with IIM were included in the study. Of these, 23 patients (53.5%) were treated with RTX for muscular involvement, 10 (23.3%) for interstitial lung disease (ILD), and 10 (23.3%) for both lung and muscle manifestations. A complete response was observed in 30 patients (69.8%), a partial response in 10 patients (23.3%), and no response in 3 patients (6.9%), leading to an overall (complete + partial) response rate of 93.1%. Additionally, 34 (79%) patients were able to reduce their average daily GC dose. Among the 30 patients who achieved a complete response, 8 (26.7%) continued on low-dose RTX maintenance therapy, successfully retaining their remission in all cases. The most frequently observed adverse events were infections. Conclusions RTX demonstrates positive outcomes in patients with refractory IIM. Furthermore, a low-dose RTX regimen appears to be effective in maintaining remission following initial treatment with the standard dose, offering a promising approach to long-term disease management.