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

• Published in: Annals of the rheumatic diseases Vol. 71; no. Suppl 3; p. 187
• Main Authors: Váncsa, A., Gergely, L., Szabό, Z., Szilvia, S., Bodnár, N., Végh, E., Szücs, G., Szántό, S., Szekanecz, Z.
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd and European League Against Rheumatism 01.06.2013; BMJ Publishing Group LTD
• ISSN: 0003-4967; 1468-2060
• DOI: 10.1136/annrheumdis-2012-eular.2063

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