Comparison of rituximab efficacy in treatment-naïve and refractory inflammatory myopathies: experiences from a tertiary care centre.

Abstract

To determine whether rituximab (RTX) is effective in 'treatment-naïve' idiopathic inflammatory myopathies (IIM), and whether there could be differential treatment responses between 'treatment-naïve' and treatment 'refractory' IIM. Data were obtained from a prospectively maintained database comprising patients with IIM treated with RTX. Patient details were obtained at baseline, 3- and 6-months intervals, and at subsequent follow-up visits. Treatment response was categorized as improved, worsening or stable based on Manual Muscle Testing 8 (MMT8) scores, patient global and physician global improvement for skin and joint symptoms improvement, and spirometry at 6 months. The time to clinical improvement and remission were noted and survival analysis curves were constructed. Sixty patients with IIM (including 18 with anti-signal recognition particle myopathy) were included, of whom 33 who received RTX were treatment naïve. The remaining 27 were started on RTX for refractory myopathy. The mean age was 39 years (s.d. 12.58) in the 'treatment-naïve' group and 43 years (s.d. 12.12) in the 'refractory' group. At 6 months of follow-up, 48/55 (87%) patients showed response, 31/31 (100%) in 'treatment-naïve' and 17/24 (70%) in 'refractory' cases, P = 0.006*. In the refractory group, seven (29%) had stable disease. The mean changes in MMT8 were significantly more in the 'treatment-naïve' group [13.41 (s.d. 7.31)] compared with 'refractory' IIM [8.33 (s.d. 7.92)] (P = 0.017*). The majority of patients were able to reduce the dose to <5 mg/day before 6 months. No major adverse events were reported over the median follow-up of 24 (interquartile range 36) months. RTX is effective and safe across the spectrum of IIM. Early use in disease is associated with better outcomes.