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P437 Anti-TNF α antibodies in patients with inflammatory bowel disease naive to anti-TNF therapy treated with biosimilar infliximab (CT-P13): a prospective single-centre real-life study


 
 
 There are several tests for detecting antibodies to infliximab. The tests differ in sensitivity and therefore the detection of antibodies varies significantly between clinical trials, and less data is available for induction compared with the maintenance therapy.
 The aim of the study was to determine the incidence of anti-drug antibodies (ADAs) in patients during induction and maintenance therapy using the Enzyme-Linked Immunosorbent Assay (ELISA) and to analyse the risk factors for their occurrence.
 
 
 
 It was a prospective single-centre study involving 84 patients with IBD during treatment with biosimilar infliximab (CT-P13) at the Tertiary IBD Center in South-eastern Poland between 2016 and 2019. All participants were naive to previous anti-TNF α therapy (80 patients). ADAs serum testing was only performed when IFX levels below 3 µg/ml were found during induction or maintenance therapy. The incidence of ADAs was analysed, and the relationship between the presence of ADAs and selected variables was assessed: gender, type of disease, immunosuppressive therapy, and undetectable drug level at week 6. The relationship between response to induction treatment and high//low ADAs titers was also compared using Fisher’s exact test.
 
 
 
 The incidence of ADAs in the study population was 10.7%, which is 20.4% of patients with non-therapeutic and 50% of patients with undetectable levels of IFX. The percentage of people with ADAs in the induction treatment group was 11.3% (n = 6) and in the maintenance group 3.9% (n = 3). There was no statistically significant difference in the frequency of finding ADAs in both groups (p = 0.158). In contrast, a statistically significant relationship between the undetectable level of IFX at week 6 and the presence of ADAs was confirmed, 88.9% of patients with ADAs vs. 16.0% patients without ADAs (p <0.001. Comparison of the relationship between response to induction treatment and high//low ADAs titers did not show a statistically significant relationship between these variables (p = 0.381).
 
 
 
 The overall incidence of ADAs in patients treated with biosimilar infliximab (CT-P13) naive to previous anti_TNF therapy was relatively low, but in the case of undetectable levels of the drug, the phenomenon of immunogenicity was detected in half of the patients. Undetectable level of infliximab at week 6 was a risk factor for the presence of ADAs. There was no significant association between response to induction therapy and ADAs titers.
