Abstract
Biological therapy has revolutionised the treatment of moderate to severe
inflammatory bowel disease (IBD), namely Crohn’s disease (CD) and ulcerative colitis
(UC). However, up to one-third of patients with IBD are primary non-responders, and
up to half can lose response over time.1 These unwanted outcomes can be explained
by either pharmacodynamic (mechanistic failure) or pharmacokinetic (PK) issues with
or without the development of anti-drug antibodies (ADA), so-called immunogenicity.1
Reactive therapeutic drug monitoring (TDM), defined as the measurement of drug
concentrations and anti-drug antibody (ADA) levels in the setting of primary
non-response (PNR) or secondary loss of response (SLR), can help to explain better
and manage these unwanted outcomes. However, it would make sense to try to
prevent PNR and SLR by routinely measuring drug concentrations and ADA to achieve
and maintain a targeted therapeutic drug concentration, the so-called
proactive TDM.
Here we discuss some common mistakes and significant errors to avoid when
utilising TDM of biologics in patients with IBD. The discussion is based on evidence,
whenever possible, and our clinical experience and perception of the field.