Rituximab Treatment for the Patients with Refractory Inflammatory Myopathy

Objective. To assess the efficacy and safety of rituximab (RTX) on disease activity and muscle strength in patients with inflammatory myopathies refractory to conventional therapy. Methods. Four inflammatory myopathy patients who had been refractory to glucocorticoids, one or more immunosuppressive therapies and intravenous immunoglobulin were treated on an open-label basis. Each patient received two 500 mg doses of RTX 2 weeks apart in one cycle. In one patient who did not respond after the first cycle of RTX, the infusion schedule was modified by the physician. We measured muscle enzyme including CPK, LDH and assessed muscle strength individually to evaluate RTX response. Additionally anti-CD19 antibody was measured. Results. Three patients responded to the first cycle of RTX treatment with improvements in muscle enzyme and muscle strength, and then maintained physical function over the duration of several infusion cycles. In one patient, muscle enzyme did not decrease after the first cycle of RTX, and a high dose glucocorticoid was given. After modifying the treatment schedule with monthly RTX infusion, his muscle enzyme level and muscle strength improved. Anti-CD19 antibody decreased after RTX generally, but responses were variable. Herpes zoster infection occurred in two patients. Conclusion. Rituximab may be a therapeutic choice in refractory inflammatory myopathy. However a further trial is needed to confirm the efficacy and prove the safety.