P07 A single-centre prospective observational study comparing proactive with reactive therapeutic drug monitoring (TDM) in two cohorts of children with inflammatory bowel disease (IBD)

Background Primary non-response (PNR) and secondary loss of response (LoR) to anti-TNF therapy are a significant challenge in up to 45% of patients with IBD. Therapeutic drug monitoring (TDM) refers to the practice of measuring anti-TNF trough level and anti-drug antibody to guide clinical decisions. Reactive TDM is performed in response to a disease flare, whereas proactive TDM consists of periodic TDM to allow treatment optimization and prevention of possible flares. In the main, GI centres recommend the use of TDM as opposed to an empirical management of patients on anti-TNF. However, there are a limited number of studies that have addressed whether proactive TDM leads to improved clinical outcomes in comparison to reactive TDM. Aim The aim of this study was to investigate if proactive TDM improves patient disease management by reducing the risk of treatment failure due to LoR and/or development of anti-drug antibody. Patients and Methods We conducted a single-centre prospective observational study to accrue data on proactive TDM between June 2019 and June 2020. We compared this group to a historical cohort of patients with IBD treated at the same centre using reactive TDM between 2014 and 2017. Results 30 children with IBD (16 M, mean age at diagnosis 11.47 years ± SD 2.93, median 12, range 3–16) started on anti-TNF treatment between June 2019 and June 2020, were prospectively recruited (current follow-up duration: average 7.1 months ± SD 3, median 6.4, range 3.1–13). 10 had ulcerative colitis (UC), 19 had Crohn’s (CD) and one had IBD-U CD-like. 37 children (20 M), 6 with UC and 31 with CD, were included in the retrospective cohort managed with reactive TDM. (Table 1). More patients in the proactive TDM cohort (22/30) were managed by escalating the IFX regime (i.e. 10 mg/Kg 8 – 6 or 4 weekly) compared to the reactive TDM cohort (14/37) (chi-square 8.396, P 0.00376). In the cohort managed with reactive TDM, a higher number of patients developed high titre anti-IFX antibody (> 50 U/ml) post induction (12/37 vs 3/30) (chi-square 4.798, P 0.0285). The need for switching to different biologics was significantly higher in the reactive TDM cohort (22/37) compared to the proactive TDM cohort (1/30) (chi-square 23.15, P Conclusions The introduction of proactive TDM resulted in a significant reduction of patients requiring switch of their primary biologic and saw an increase in mean trough levels due to timely dose escalation. The results of this study are early indicators that proactive TDM offers a better method of managing children with IBD on IFX therapy compared to reactive TDM with the potential of additional clinical benefits such as reducing the risk of developing adverse drug reactions due to high antibody titres.