Background The percentage of anti-cyclic citrullinated peptide (CCP)-positive patients reported declines among early rheumatoid arthritis (RA) patients treated with abatacept (ABT).

Objectives The AIRTIGHT study (UMIN:000005570) was conducted to assess the clinical and immunological impact of ABT on established RA patients.

Methods The AIRTIGHT study included 32 patients (mean age, 60.7±13.6 years; mean duration of disease, 11.7±13.6 years; range, 0-35 years; MTX use, 81.9%; mean MTX dose, 6.1±4.6 mg/week) treated with ABT and 72 patients (mean age, 59.7±14.3 years; mean duration of disease, 9.5±10.9 years; range, 0-40 years; MTX use, 86.1%; mean MTX dose, 8.6±4.3 mg/week) treated with non-ABT biologics (adalimumab, n=20; etanercept, n=14; tocilizumab, n=19; infliximab, n=10; golimumab, n=9). Serum levels of anti-CCP, rheumatoid factor (RF), and autoantibody to galactose-deficient immunoglobulin (Ig)G (CA-RF) were measured at baseline and 48 weeks after treatment. Paired t-tests were used to compare changes in anti-CCP, RF, and CA-RF between each time point.

Results Mean DAS28 score decreased from 4.5±1.3 to 3.5±1.3 after 48 weeks on ABT. Titers of anti-CCP were 143.4±176.0 U/ml at baseline and 151.1±176.1 after 48 weeks of treatment, values for RF were 150.4±233.7 IU/ml at baseline and 137.0±191.0 IU/ml after 48 weeks of treatment, and values of CA-RF were 163.0±301.4 AU/ml at baseline and 152.8±249.3 after 48 weeks of treatment on ABT. Titers of anti-CCP (p=0.64), RF (p=0.63) and CA-RF (p=0.57) were unchanged during ABT treatment. Seven patients who achieved improvement (good DAS28 response) on ABT also did not show the decraese of those titers. Titers of anti-CCP (p=0.47), RF (p=0.12) and CA-RF (p=0.12) did not correlate significantly with changes in DAS28. Mean DAS28 decreased from 4.5±1.3 to 2.8±1.1 at 48 weeks on non-ABT. Titers of anti-CCP were 147.1±145.9 U/ml at baseline and 109.7±138.8 IU/ml after 48 weeks of treatment, levels of RF were 145.5±201.3 IU/ml at baseline and 75.4±106.0 IU/ml after 48 weeks of treatment, and levels of CA-RF were 170.1±280.7 AU/ml at baseline and 95.3±130.1 AU/ml after 48 weeks of treatment with non-ABT. Titers of anti-CCP (p<0.001), RF (p<0.001) and CA-RF (p=0.002) were reduced significantly during non-ABT treatment.

Conclusions These findings suggest that the titer of autoimmunity did not decrease during ABT treatment in established RA, regardless of disease activity. Although the titer of autoimmunity decreases during non-ABT treatment in established RA, percentage of MTX use might be involved (ABT: 71.9%, non-ABT: 86.1%; p=0.05).

Disclosure of Interest None declared