High prevalence of antibodies to infliximab and their relation to clinical outcomes in inflammatory bowel disease patients

Summary Background Antibodies to infliximab (ATI) can complicate infliximab (IFX) treatment of inflammatory bowel disease (IBD) patients. Aims To identify a clinically relevant threshold for ATI using a drug‐tolerant assay and to clarify factors for ATI development and their relation to clinical outcomes. Methods A cohort study of all IBD patients receiving IFX from May 2016 to April 2017 at a tertiary referral centre. Clinical data and serial therapeutic drug monitoring (at every infusion after the first) were collected. Results Over 12 months follow‐up, 113/214 (53%) patients had positive ATI, 94/214 (44%) had negative ATI and 7/214 (3%) had transient ATI. Concomitant immunosuppression was negatively associated with ATI positivity: thiopurines OR 0.48, methotrexate OR 0.36. ATI formation was more likely to be preceded by subtherapeutic IFX levels (57%) than vice versa (9%). Positive ATI were significantly associated with infusion reactions, loss of clinical remission and a reduction in IFX levels. In patients positive for ATI at first maintenance dose, 71% were treatment failures by second maintenance dose compared to 28% in those with negative ATI (P