LAUSR

Abstract Introduction CT-P13 is a biosimilar drug of infliximab (IFX), effective in patients with inflammatory bowel disease (IBD). The monitoring of levels of IFX and anti-IFX antibodies is now considered part of the integral management. Objective To compare the clinical response according to a strictly clinical (CLN) or proactive (PRO) approach based on the monitoring of levels in week 14, in clinical practice. Methods We conducted a prospective study in IBD patients starting CT-P13. In the PRO group, levels of IFX and post-induction antibodies were systematically measured (week 14) and those with infraterapeutic levels ( Results We included 77 patients (23 ulcerative colitis and 54 Crohn's disease). Both PRO (n = 41) and CLN (n = 36) groups showed initial and long-term efficacy without significant differences. At week 14, 61% clinical remission (CR) (58.5% PRO, 63.9% CLN) and 80.5% at least partial response (PR) (80.5% PRO, 80.6% CLN). In week 54, 68.8% CR (61% PRO, 77.8% CLN) and 76.6% at least PR (73.2% PRO, 80.6% CLN). Of the patients in CR in week 14 (24 PRO, 23 CLN), 13 of the PRO group were intensified due to infra-therapeutic levels. In this subgroup no significant differences were observed in secondary loss of response (PRO 0%, CLN 8.7%). Conclusion Proactive management does not improve response or remission rates in the first year. The intensification of clinical remission patients with post-induction infratherapeutic levels does not seem to significantly prevent secondary loss of response in the first year.