Abstract
Reliable biomarkers that enable noninvasive, longitudinal assessment of disease activity and therapeutic response remain a major unmet need in inflammatory bowel disease (IBD). While colonic biopsies are the gold standard for evaluating mucosal inflammation, their invasive nature and limited spatial and temporal resolution constrain their utility in routine monitoring and clinical trials. Blood-based biomarkers offer a complementary approach, providing minimally invasive, readily accessible measures that can be repeatedly sampled over time. Emerging blood-derived signatures, including gene expression profiles and circulating molecular inflammation scores, capture systemic immune activity and have shown promise in predicting treatment response, disease flares, and pharmacodynamic (PD) effects of therapies. Recent advances utilizing multi-omics technologies and machine learning methods have further improved the predictive performance of blood-based biomarkers, particularly in the context of biologic therapies such as anti-tumor necrosis factor agents. Despite these advances and growing promises, challenges related to validation, standardization, and clinical integration persist. This review focused on recent advances in blood-based biomarkers for IBD, with an emphasis on their use in predicting treatment response and assessing pharmacodynamic effects in clinical trials.