Introduction: In the last two decades, with the development of biological (anti-TNFα) therapy, the treatment paradigms for Crohn's disease and ulcerative colitis have evolved, with a continuously increasing role of biologicals. Some patients, however, experience lack- or loss of response (LOR) to treatment, and management of such patients is often empirical.
Areas covered: The available data regarding the relationship between serum anti-TNF concentrations, antibodies against anti-TNF agents, and clinical efficacy, as well as the development of adverse events and management of LOR.
Expert opinion: Monitoring drug levels and antibodies is expected to play an emerging role in the management of LOR (i.e., to confirm adherence, allow for dose adjustment, or provide a rationale for switching to another anti-TNF agent or to a different class of biological agent) in the coming years. The optimal method of detection is however not clear. In clinical practice, meticulous complex assessment of clinical symptoms, confirmation of active disease by endoscopic or radiological imaging, and exclusion of complications remains necessary.