Rituximab for Refractory Polymyositis: an Open-label Prospective Study

Objective: To report the efficacy and toxicity of rituximab in the treatment of refractory polymyositis.

Methods: Adult patients with active polymyositis as evidenced by persistent proximal muscle weakness, elevated creatine kinase (CK) level, and features of active myositis on electromyography who were refractory to corticosteroids and at least 2 other immunosuppressive agents were recruited. While immunosuppressive agents were continued, rituximab (375 mg/m2) was given by intravenous infusion weekly for 4 consecutive weeks. Patients were followed up 4-weekly for serial assessment of muscle power, serum muscle enzymes, physician's and patient's global impression of disease activity, disability, and quality of life scores.

Results: Four patients (3 women, 1 man) were studied. The mean age was 53 +/- 11 years and the mean duration of polymyositis was 4.8 +/- 3.3 years. All had persistently active myositis for at least 2 years. At Week 28, significant improvement in the mean proximal muscle power scores and reduction in CK levels in comparison to baseline were observed. Two patients had return of full muscle power with significant drop in CK level. There was a trend of improvement in disability scores and both the mental and physical components of the Medical Outcomes Study Short Form-36 Health Survey scores. Rituximab was well tolerated.

Conclusion: Rituximab is an option to be considered in refractory polymyositis, but further controlled trials are necessary to confirm its efficacy.