Long‐term follow‐up of anti‐infliximab antibodies in radiographic axial spondyloarthritis patients: a marker of drug survival and tapering

Objectives To evaluate the influence of anti‐infliximab antibodies (anti‐IFX) on 3 different points of care: response/tolerance to infliximab (IFX), tapering strategy, and in a subsequent treatment with a second tumor necrosis factor inhibitor (TNFi). Methods A prospective cohort of 60 radiographic axial spondyloarthritis (r‐axSpA) patients under IFX were evaluated retrospectively regarding clinical/laboratorial data, IFX levels and anti‐IFX, at baseline, after 6, 12‐14, 22‐24, 48‐54, 96‐102 weeks and before tapering or switching. Results Anti‐IFX were detected in 27 (45%) patients, of whom 23 (85.1%) became positive in the first year of IFX treatment. In comparison to negative anti‐IFX group, anti‐IFX positive patients demonstrated the following: less use of methotrexate (MTX) as a concomitant treatment to IFX (5 [18.5%] vs. 14 [42.4%]; p=0.048); more infusion reactions at 22‐24 weeks (p=0.020) and 48‐54 weeks (p=0.034); more treatment failures (p=0.028) at 48‐54 weeks; reduced overall IFX survival (p<0.001); and lower sustained responses (p=0.044). Of note, positive anti‐IFX patients exhibited a shorter tapering survival (9.9 months [95% CI 4.0‐15.8] vs 63.4 months [95% CI 27.9‐98.8]; p=0.004) in comparison with negative anti‐IFX patients. Conversely, for patients who failed IFX, positive anti‐IFX patients had better clinical response to the second TNFi at 3 (15 [83.3%] vs. 3 [27.3%]; p=0.005) and 6 months (15 [83.3%] vs. 4 [36.4%]; p=0.017) than the negative anti‐IFX patients after switching. Conclusions This study provided novel data that anti‐IFX is a parameter for reduced tapering survival, reinforcing its detection to guide clinical decision. Additionally, we confirmed in a long‐term cohort the anti‐IFX association with worse IFX performance and as predictor of 2 nd TNFi good clinical response.