Effectiveness and safety of low dose Rituximab as remission-maintenance treatment for patients with refractory idiopathic inflammatory myopathies: results of a retrospective study from a monocentric cohort.

objectiveOur aim was to assess efficacy and safety of Rituximab (RTX) in patients with refractory Idiopathic inflammatory myopathies (IIM) from a monocentric cohort. Thereafter, we evaluated the efficacy of a low-dose RTX regimen as a remission-maintenance therapy.

methodsWe retrospectively evaluated a cohort of patients affected with IIM treated with RTX. All patients were refractory to glucocorticoids (GC) and at least one immunosuppressant. Two infusions of 1 g two weeks apart were considered as standard cycle of RTX, a single dose of 1 g every six months was deemed as a low-dose RTX regimen. Complete and partial response were defined according to physician's judgment, laboratory and radiological features.

resultsThirty-six patients affected with IIM were enrolled. Eighteen patients (50%) required the use of RTX for muscular involvement, 6 (16.7%) for interstitial lung disease (ILD), 12 (33.3%) for both myositis and ILD. We observed complete response to RTX in 25 patients (69.4%), partial response in 7 (19.4%) and no response in 4 (11.1%), with an overall response of 88.8% (partial and complete response). From the subgroup of twenty-five patients that achieved a complete response, six were treated with a low dose maintenance therapy maintaining a complete response to RTX. Twenty-six patients who achieved a complete or partial response were able to decrease the mean daily GC dose. Infections were the major adverse events detected in our study.

conclusionsRTX shows favorable outcomes in refractory patients with IIM. A low-dose regimen of RTX appears to be effective in maintaining remission after induction with standard dose. Key Points • The precise pathogenic mechanism of idiopathic inflammatory myopathies (IIM) remains elusive; however, a growing body of data support the autoimmune hypothesis. In this context, rituximab, a B cell-depleting agent, has emerged as a second-line therapeutic option in IIM. • Several studies have assessed It its effectiveness in refractory IIM patients. • Limited information exists on the use of Rituximab as maintenance therapy in patients who have achieved remission following induction therapy with Rituximab.