Annual Infliximab Monitoring After Treatment Optimization.

Infliximab (IFX), a TNF-α inhibitor, remains a key treatment for inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, despite the emergence of new therapies. However, treatment failure due to primary non-response or loss of response is common and often linked to low IFX trough levels (TLs) or anti-drug antibodies. Therapeutic drug monitoring (TDM) has thus become a valuable tool in optimizing IFX therapy. Frequent TDM, while beneficial, is not always practical due to cost and burden, making appropriate interval determination essential. Lim et al. conducted a longitudinal study of 228 IBD patients receiving IFX, performing TDM approximately every two months. They found that 85% of patients with TLs > 3 µg/mL at week 14 maintained therapeutic levels for over 13 months without pharmacokinetic (PK) relapse. Annual TDM may be sufficient for stable patients. Notably, drug antibodies were mostly detected after a drop in IFX levels, emphasizing the importance of preventing TL decline. The study had limitations, including limited analysis of immunomodulator use and generalizability due to regional treatment practices and patient population (predominantly Crohn's disease). Moreover, the relationship between PK relapse and clinical outcomes remains unclear. Overall, combining IFX TDM with clinical, endoscopic, and biomarker monitoring may enhance patient outcomes. Genetic and serologic markers, such as HLA-DQA1*05 and PR3-ANCA, may help predict treatment response. Despite newer options, IFX remains central in IBD therapy, and individualized TDM strategies can support more effective and patient-centered care.