Background/Purpose: Infliximab is a biological agent frequently used for inflammatory arthritis (IA) such as spondyloarthritis, rheumatoid arthritis, psoriatic arthritis as well as for the inflammatory bowel diseases (IBD) such as Crohn’s disease or ulcerative colitis. A major limitation to infliximab is loss of response due to the development of anti-drug antibodies (ADABs).However, It is unclear if the underlying medical condition influences antibody development. The first aim was to compare the prevalence of ADABs IA patients to IBD patients receiving treatment with infliximab. The second aim was to evaluate the correlation between ADABs and trough levels. The final objective was to determine if there were any clinical predictors of the development of ADABs.

Methods: A retrospective study was performed of all patients with IA and IBD treated with maintenance infliximab. A trough level and ADABs were obtained prior to the next infusion and drug monitoring was performed in a pro-active manner at certain. Reproducibility was confirmed in exposed and unexposed patients. Clinical data was extracted from a central database and patient medical records. Clinical predictors of ADABs development were analyzed using regression analysis. They comprised: gender, age, duration of the disease, duration of the treatment, co-medication, doses of infliximab and schedule, previous biologic exposure.

Results: A total of 166 evaluated of whom 76 were treated for IA and 90 for IBD. IBD patients were significantly younger than IA patients (mean: 37 versus 51 years) with shorter disease duration (mean: 6.9 versus 9.4 years) and a shorter duration of treatment (median: 18 versus 44 months). Overall, ADABs were detected in 35 patients (21 %) and markedly elevated (defined as >200 ug/ml) in 21 patients (12 %). There was a trend to higher prevalence of ADABs in IA patients (26%) compared to IBD patients (26% vs 15%; p= 0.08). A markedly elevated ADAB level was significantly more prevalent in IA compared to IBD (17% versus 6%; p=0.035). In both groups ADAB were highly correlated with undetectable through level.

*:ADABs+ versus ADABs- / ADAB>200 versus ADABs – In the overall cohort, no predictive factors for the development of ADABs were found (table). This was also the case when analyzing IBD or IA patients separately (table).

Conclusion: In this cohort of IA and IBD patients treated with maintenance infliximab, who received pro-active, trough level and ADABs monitoring, the prevalence of ADAB was higher in IA patients than in IBD patients. This may be explained by differences in baseline clinical characteristics. No clear predictive factors could be identified in either group.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparison-of-infliximab-immunogenicity-in-inflammatory-arthritis-versus-inflammatory-bowel-disease-patients-in-routine-clinical-practice/