Proactive Therapeutic Drug Monitoring of Adalimumab Is Associated with Better Long-term Outcomes Compared with Standard of Care in Patients with Inflammatory Bowel Disease

Background and Aims: Therapeutic drug monitoring [TDM] has proven to be effective for optimising anti-tumour necrosis factor [TNF] therapy in inflammatory bowel disease [IBD]. Nevertheless, the majority of data refer to infliximab and reactive testing or association studies. We aimed to compare the long-term outcome of patients with IBD who received at least one proactive TDM of adalimumab, with standard of care, defined as empirical dose escalation and/or reactive TDM. Methods: This was a multicentre retrospective cohort study. Patients on maintenance adalimumab therapy from June 2006 to December 2015 were eligible. We analysed time to treatment failure from start of adalimumab until the end of follow-up [July 2016]. Treatment failure was defined as drug discontinuation for secondary loss of response or serious adverse event or need for IBD-related surgery. Serum adalimumab concentrations and antibodies to adalimumab were measured using the Prometheus homogeneous mobility shift assay. Results: A total of 382 patients with IBD [Crohn's disease, n = 311, 81%] were included and received either at least one proactive TDM [n = 53] or standard of care [empirical dose escalation, n = 279; reactive TDM, n = 50]. Patients were followed for a median of 3.1 years [interquartile range, 1.4-4.8 years]. Multiple Cox regression analyses showed that at least one proactive TDM was independently associated with a reduced risk for treatment failure (hazard ratio [HR]: 0.4; 95% confidence interval [CI]: 0.2-0.9; p = 0.022). Conclusions: This multicentre, retrospective cohort study reflecting real-life clinical practice provides the first evidence that proactive TDM of adalimumab may be associated with a lower risk of treatment failure compared with standard of care in patients with IBD.