AB0380IS THERE AN EFFECT OF TOCILIZUMAB IN SERUM AUTOANTIBODIES LEVELS IN RHEUMATOID ARTHRITIS?
Authors: Miguel Guerra, Sara Ganhão, Teresa Martins-Rocha, Raquel Ferreira, Bruno Miguel Fernandes, Salomé Garcia, Ana Filipa águeda, Sofia Pimenta, Alexandra Bernardo, Miguel Bernardes, Lúcia Costa
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Interleukin 6 (IL-6) plays a role on B cell differentiation and antibody production. However, few information is available considering the effect of tocilizumab (TCZ) on rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs) levels in Rheumatoid Arthritis. <h3>Objectives</h3> To compare serum levels of RF and ACPAs on RA patients at the beginning of therapy with TCZ and at 6 and 12 months under TCZ, assessing if its variations correlate with the several disease activity scores. <h3>Methods</h3> Longitudinal retrospective study of RA patients ever treated with TCZ at a Rheumatology Department. Serum levels of RF and ACPAs at 0, 6 and 12 months after starting anti-IL6 treatment were collected, as well as DAS28, DAS28 CRP, CDAI, SDAI, HAQ, ESR, CRP, patient's global assessment (PGA), physician's global assessment (PhGA), swollen joint count (SJC) and tender joint count (TJC). Demographic and clinical data were collected. SPSS statistics 22.0 was used for statistical analysis; p values under 0.05 were considered significant. <h3>Results</h3> 75 patients were included, 93.3% female (N=70), with a median (min-max) age of 58 (33-80) years and median disease duration at TCZ initiation of 10.7 years (1.0-43.3); 33.3% were on TCZ monotherapy (N=25). At baseline, forty-two (56.0%) were RF positive (&gt;=30UI/ml) and 47 (62.7%) were ACPAs positive (&gt;=10UI/ml). Median serum RF levels were 255.0 UI/mL (37.20-5560.00), 193.5 UI/mL (9.80-5270.00) and 131.0 UI/mL (9.40-6260.00) at 0, 6 and 12 months respectively; serum RF levels were only statistically different (p=0,006) between 0 and 6 months. Median serum ACPAs levels were 278.5 UI/mL (17.00-9300.00), 348.0 UI/mL (19.00-4720.00) and 277.0 UI/mL (16.00-4400.00) at 0, 6 and 12 months respectively, without any statistically significant differences. Considering the autoantibodies levels variation, ΔRF at 6 months correlated positively with ΔHAQ (r=0.482; p=0.009) and ΔCPR (r=0.413; p=0.026). After one year, ΔRF correlated positively with ESR (r=0.426; p=0.019) and DAS28 (r=0.428; p=0.018). As for ΔACPAs at 6 months, it correlated positively with PhGA (r=0.461; p=0.035). At 12 months, there was a positive correlation between ΔACPAs and ΔCDAI (r=0.385;p=0.036) and between ΔACPAs and ΔSJC (r=0.469;p=0.002). <h3>Conclusion</h3> In our RA sample, serum RF levels showed a significant titre difference past 6 months of treatment with TCZ. Moreover, a moderately strong correlation was found between ΔACPAs/ΔRF at 12 months months and the variations in several disease activity scores. Thus, this study reinforces the evidence of an impact of IL-6 inhibition on autoantibodies production in RA patients, as well as a relation between autoantibodies titre variation and clinical response. These findings need to be assessed in larger, prospective studies. <h3>References</h3> [1] Modi S, Soejima M, and Levesque MC. The effect of targeted rheumatoid arthritis therapies on anti-citrullinated protein autoantibody levels and B cell responses. Clin Exp Immunol. 2013Jul; 173(1): 8–17. [2] Maneiro RJ, Salgado E, Carmona L, Gomez-Reino JJ. Rheumatoid factor as predictor of response to abatacept, rituximab and tocilizumab in rheumatoid arthritis: Systematic review and meta-analysis. Semin Arthritis Rheum. 2013Aug;43(1):9-17. <h3>Disclosure of Interests</h3> None declared