Therapeutic Drug Monitoring Guides the Management of Crohn's Patients with Secondary Loss of Response to Adalimumab

Background: Managing loss of response (LOR) in Crohn's disase (CD) patients remains challenging. Compelling evidence supports therapeutic drug monitoring (TDM) to guide management in patients on infliximab, but data for other biologics are less robust. We aimed to asses if empiric dose escalation led to improved clinical outcome in addition to TDM-guided optimization in CD patients with LOR to adalimumab (ADA). Methods: Retrospective chart review of patients followed between 2014 and 2016 at McGill IBD Center with index TDM for LOR to ADA was performed. Primary outcomes were composite remission at 3, 6, and 12 months in those with empiric adjustments versus TDM-guided optimization. Results: There were 104 patients (54.8% men) who were included in the study. Of this group, 81 patients (77.9%) had serum level (SL) >= 5 mu g/ml at index TDM with a median value of 12 mu g/ml (IQR 6.1-16.5). There were 10 patients (9.6%) who had undetectable SL with high anti-ADA antibodies and 48 (46.2%) received empiric escalation. TDM led to change in treatment in 58 patients (55.8%). Among them, 28 (48.3%) had discontinued ADA, 12 (21.7%) had addition of immunomodulator or steroid, and 18 (31%) had ADA dose escalation. Empiric dose escalation before TDM-based optimization was not associated with improved outcomes at 3, 6, and 12 months, irrespective of SL levels. Clear SL cutoff associated with composite remission was not identified. Conclusions: Our data do not support empiric dose adjustment beyond that based on the result of the TDM in patients with LOR to ADA. TDM limits unnecessary dose escalation and provides appropriate treatment strategy without compromising clinical outcomes.