Rheumatoid factor and anti-cyclic citrullinated peptide antibody levels decline in rheumatoid arthritis patients treated with Janus kinase inhibitors or biological disease-modifying anti-rheumatic drugs.

Objective: We aimed to investigate the rate of decline in serum anti-cyclic citrullinated peptide antibody (ACPA) and rheumatoid factor (RF) levels in rheumatoid arthritis (RA) patients treated with Janus kinase inhibitors (JAKis) compared with biological disease-modifying anti-rheumatic drugs (bDMARDs) and examine factors associated with this decline.

Methods: Patients with RA who had data on ACPA and RF levels before and after JAKis or bDMARDs treatment were included in this single-center retrospective study. A reduction in ACPA and RF levels of ≥20% was defined as a decline.

Results: In total, 201 patients (mean age 53 years; 10% males) were identified. After a mean 4 years of treatment with JAKis, tumor necrosis factor inhibitors, abatacept, or tocilizumab, 43.8%, 37.5%, 14.1%, and 4.7% patients experienced ACPA decline, respectively, and 41.2%, 31.4%, 16.7%, and 10.8% experienced RF decline. The use of JAKis was not associated with a decline in ACPA and RF compared with bDMARDs. However, lower baseline ACPA level (adjusted odds ratio [aOR] 0.97, 95% confidence interval [CI] 0.95~0.99), treatment responders (aOR 2.44, 95% CI 1.23~4.87), and use of prednisone equivalent ≥7.5 mg (aOR 3.24, 95% CI 1.42~7.37) were associated with ACPA decline. Furthermore, higher baseline RF level (aOR 1.03, 95% CI 1.00~1.06) and treatment responders (aOR 3.73, 95% CI 2.01~6.93) were associated with RF decline.

Conclusion: There was no significant difference in ACPA and RF decline between groups receiving either JAKis or bDMARDs. Baseline autoantibody levels and treatment response are correlated with ACPA and RF decline after JAKis or bDMARDs administration in RA.