Rheumatoid factor titers, but not Fc fragments, may be strongly associated with drug survival of anti-TNF agents in patients with rheumatoid arthritis.

Objective: To investigate the effects of both the Fc fragment in tumor necrosis factor (TNF) inhibitors and rheumatoid factor (RF) titers on treatment survival, disease activity, and laboratory parameters in patients with rheumatoid arthritis (RA).

Methods: In this retrospective cohort study, patients with RA who had started any anti-TNF therapy between January 2017 and March 2020 and who had stayed on this treatment for at least six months were included. The data of the patients were compared separately according to continuation or discontinuation of treatment and the presence or absence of Fc portion in the structure of anti-TNFs. Patients who were taking certolizumab pegol (CZP) without the Fc fragment were placed in the "without Fc group" (wo/Fc), while patients who were taking other drugs (adalimumab, etanercept, golimumab, and infliximab) were placed in the "with Fc group" (w/Fc).

Results: Among the 221 RA patients whose data were available, 52 patients met the inclusion criteria and were included in the study. There was a significant difference in the DAS28-CRP score between wo/Fc group and w/Fc group in the third month of treatment (p=0.012). However, this difference did not persist at the sixth month of treatment (p=0.384). According to the cox-regression results, RF titers were determined to have a significant impact on the drug survival of anti-TNF agents when adjustments were made for the effects of other candidate predictors (Hazard ratio: 1.007 (1.002-1.012), p=0.009).

Conclusion: Our results suggest that compared to the Fc fragment, RF titers were the more important risk factor in survival of anti-TNF drugs.