To study whether stable treatment with DMARDs affects anti-CCP2 antibody levels in patients with rheumatoid arthritis.

In this longitudinal observational study 100 RA patients were followed for anti-CCP2 IgG antibody (U/L) and total IgG level (mg/dL) every 6 months for a total period of 2.5 years. All patients received stable DMARD treatment during this period. Five groups comprising each 20 patients were analyzed as follows: (1) methotrexate (MTX) alone, (2) tumor necrosis factor inhibitors (TNFi), (3) tocilizumab (TCZ), (4) rituximab (RTX), and (5) abatacept (ABA).

Baseline demographic and disease-specific characteristics were comparable between the 5 groups. Anti-CCP2 antibody levels did not show significant changes in patients treated with MTX (mean ± SEM: −24.1 ± 8.1%), TNFi (−14.0 ± 11.1%) or TCZ (−24.3 ± 11.3%) between baseline and the 2.5 years follow-up. In contrast, anti-CCP2 antibody levels significantly decreased during treatment with RTX (−75.6 ± 4.4%) and ABA (−82.5 ± 3.7%). With respect to total IgG levels, no significant changes were observed with MTX (−1.6 ± 3.5%), TNFi (2.5 ± 3.4%), TCZ (−4.4 ± 3.1%), or ABA (−2.4 ± 3.8%) over 2.5 years. In contrast, total IgG levels significantly decreased during treatment with RTX (−22.0 ± 3.7%).

DMARDs targeting the adaptive immune response such as ABA and RTX significantly lowered anti-CCP2 IgG levels, while cytokine inhibitors and methotrexate had no significant effects on anti-CCP2 IgG levels. RTX is the only DMARD, which also lowers total IgG level.