Background and Aims: Infliximab (IFX) is a chimeric monoclonal antibody targeting tumor necrosis factor (TNF), developed to treat autoimmune diseases, including rheumatoid arthritis (RA). However, not all patients respond favorably to infliximab. The development of anti-infliximab antibodies (AIA) may contribute to treatment failure. This study aimed to investigate the association between AIA and infliximab trough levels with treatment response in patients with RA.
Materials and Methods: This cross-sectional study included 83 RA patients receiving infliximab (Remicade or Remsima) infusions at ≤ 6 months. Blood samples (3 ml) were collected prior to IFX infusion. Enzyme-linked immunosorbent assay (ELISA) kits were used to measure AIA, and infliximab trough concentration.
Results: Despite concurrent methotrexate therapy, many patients developed AIA (43.3 %). Infliximab trough concentration was higher in responders than non-responders but statistically not significant (P-value=0.114). Patients aged ≤40 years demonstrated a treatment response rate of 84.6%, compared with only 28.6% among those >60 years (P-value = 0.36). Additionally, male patients showed a higher response rate than females (P-value = 0.12).
Conclusion: The presence of AIA was associated with reduced treatment response in RA patients receiving infliximab. Higher infliximab trough levels correlated with better clinical outcomes. Age and sex may influence treatment efficacy, with younger patients and males showing better responses. Monitoring AIA and drug levels could help optimize therapeutic strategies in RA.