Microbial Metabolism of Inflammatory Bowel Disease Drugs: Current Evidence and Clinical Implementations

Immune-suppressive drugs are the most important treatment regimens for inflammatory bowel disease (IBD).1,2 However, a substantial number of IBD patients experience drug nonresponse or toxicity, leading to prolonged active inflammation and a higher risk of a worse long-term outcome, decreased quality of life, and high healthcare costs. Drug nonresponse varies among patients and between different drugs (with prevalence up to 50%) and remains largely unpredictable.3–5 Although some mechanisms, such as antibody formation against biologics,6 are well known, most cases of nonresponse remain far from understood.