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THU0098 Long-term effects of rituximab on B-cell counts and autoantibody production in rheumatoid arthritis: Use of high-sensitivity flow-cytometry for more sensitive assessment of B-cell depletion
  1. A. Váncsa1,
  2. L. Gergely2,
  3. Z. Szabό1,
  4. S. Szilvia1,
  5. N. Bodnár1,
  6. E. Végh1,
  7. G. Szücs1,
  8. S. Szántό1,
  9. Z. Szekanecz3
  1. 1Department of Rheumatology
  2. 2Third Department of Medicine, University of Debrecen Medical and Health Sciences Centre, Debrecen
  3. 3Department of Rheumatology, University of Debrecen Medical and Health Sciences Centre, Deb, Hungary

Abstract

Background Rituximab (RTX) is a B-cell depleting antibody widely used to treat rheumatoid arthritis (RA). Responses to RTX are in close correlation with the efficacy of B-cell depletion. Therefore the determination of residual B-cell counts is crucial for the efficacy of treatment.

Objectives Here we wished to assess the efficacy and safety of long-term RTX therapy and study correlations between B-cell depletion, clinical response and autoantibody production.

Methods Seventy-seven patients with active RA received RTX and were re-treated every six months regardless of clinical response. All patients received at least 5 cycles. We assessed DAS28, IgM rheumatoid factor (RF) and ACPA levels at baseline, after 15 days and then every 6 months for 24 months. Absolute CD19+ B-lymphocyte counts were also determined in 50 patients using high-sensitivity flow-cytometry (hsFACS).

Results After 6, 12, 18 and 24 months, 51.6%, 51.9%, 73.3% and 83.8% of patients showed good EULAR responses, respectively. Significant and sustained decreases in IgM RF and anti-CCP levels were observed as early as after 6 months and 12 months, respectively. The baseline mean absolute B-cell number was 0.234 G/l. B-cell numbers significantly dropped after the very first infusion by day 15 (0.104 G/l; p=0.007), which further decreased until 24 months (0.0013 g/l; p<0.001). One RTX infusion resulted in incomplete depletion in 76.7% of patients. B-cell numbers positively correlated with DAS28 (r=0.964; p<0.001), IgM RF (r=0.955; p<0.001) and anti-CCP (r=0.755; p<0.01). No safety issues arose.

Conclusions In RA, clinical response to RTX is associated with the extent of B-cell depletion and with autoantibody production. hsFACS may be a useful method to more accurately assess incomplete B-cell depletion and maybe, as in oncohematology, minimal residual disease.

Disclosure of Interest None Declared

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