J Korean Med Sci.  2020 Sep;35(38):e335. 10.3346/jkms.2020.35.e335.

Efficacy and Safety of Rituximab in Korean Patients with Refractory Inflammatory Myopathies

Affiliations
  • 1Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases, Seoul, Korea
  • 2Department of Rheumatology, Ajou University School of Medicine, Suwon, Korea
  • 3Division of Rheumatology, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
  • 4Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea
  • 5Division of Rheumatology, Regional Rheumatoid & Degenerative Arthritis Center, Chungnam National University Hospital, Daejeon, Korea
  • 6Division of Rheumatology, Department of Internal Medicine, Konkuk University School of Medicine, Seoul, Korea
  • 7Division of Rheumatology, Department of Internal Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea

Abstract

Background
Rituximab (RTX), a monoclonal antibody that selectively binds to CD20+ B cells, showed favorable outcomes in patients with idiopathic inflammatory myopathies (IIM) in small case series, but the evidence is still not enough. Our goal was to determine the efficacy and safety of RTX for Korean patients with refractory IIM.
Methods
We retrospectively analyzed the medical records of 16 patients with refractory IIM treated with RTX in seven tertiary rheumatology clinics in the Korea. The efficacy of RTX was evaluated with the improvement of serum creatine phosphokinase (CPK) level and physician's global assessment (PGA), and daily corticosteroid dose reduction. A > 25% decrease in CPK level, corticosteroid dose, or PGA was considered significant. A complete response (CR) was designated by meeting three efficacy criteria and a partial response (PR) by only two criteria.
Results
Sixteen patients with IIM were evaluated (13 female; median age, 51.8 years). All patients had received at least one conventional immunosuppressive agent (median, 3.6 [2.0–5.0]) and concomitant corticosteroids. The median CPK level and median dose of prednisolone was 421.0 units/L and 20.0 mg/day respectively. Eleven patients were treated with intravenous immunoglobulin. Seven patients received 2,000 mg of RTX and the others received lower dose. Twenty-four weeks after RTX treatment, 11 patients achieved a > 25% reduction in corticosteroid dose and CPK levels, and nine showed improved PGA. The overall response rate was 68.8% (11 patients). At the end of follow-up (median 24 weeks), 12 (75.0%) patients responded overall: four (25.0%) and eight (50.0%) patients achieved CR and PR, respectively. Baseline muscle enzyme levels were higher in responders than non-responders, but disease duration, RTX dose, ESR and serum CRP were not significantly different between the two groups. The rate of adverse event was 25.4/1,000 person-years.
Conclusion
RTX could be an effective and relatively safe therapeutic option in patients with refractory IIM.

Keyword

Myositis; Rituximab; Treatment Outcome; Safety
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