Change of autoantibody levels in established rheumatoid arthritis patients treated by biological disease-modifying anti-rheumatic drugs -the AIRTIGHT study.

Objective: Previous studies reported that abatacept (ABT) decreased autoantibodies in early rheumatoid arthritis (RA) patients. We investigated the impact of ABT, and other biological disease-modifying anti-rheumatic drugs (bDMARDs) on autoantibody levels in established RA patients.

Methods: This prospective observational study included 50 RA patients treated with ABT and 115 RA patients treated with non-ABT bDMARDs. Serum levels of anticitrullinated peptide antibodies (ACPA), immunoglobulin (Ig) M-rheumatoid factor (IgM-RF), IgG-RF, and anti-agalactosyl IgG antibody (anti-Gal (0) IgG) were measured at baseline and after 48 weeks of treatment.

Results: After propensity score matching, 25 patients with ABT and 25 patients with non-ABT were finally analyzed. Disease activity score in 28 joints using C-reactive protein significantly decreased in both ABT group (4.5 to 3.3, p<0.01) and non-ABT group (4.4 to 2.5, p<0.01) after 48 weeks treatment. In ABT group, median titers at baseline and 48 weeks were 62.7 and 57.8 U/mL for ACPA (p=0.22), 35.0 and 39.0 IU/mL for IgM-RF (p=0.21), 0.5 and 0.5 IU/mL for IgG-RF (p=0.19), and 50.4 and 53.5 AU/mL for anti-Gal (0) IgG (p=0.22), respectively. Changes of all autoantibody titer were not significant in ABT group. Non-ABT group showed significant decreases in ACPA (baseline 143.0 to 57.8 U/mL at week 48, p=0.03), IgM-RF (50.0 to 37.0 IU/mL, p<0.01), and anti-Gal (0) IgG (93.2 to 61.8 AU/mL, p<0.01) except IgG-RF (0.6 to 0.5 IU/mL, p=0.22).

Conclusion: Autoantibody-lowering effect of ABT was not strong in established RA patients in our study.