[KASID Guidelines for the Medical Treatment of Crohn's Disease: 2026]

Crohn's disease (CD) is a chronic inflammatory bowel disease characterized by a heterogeneous clinical course and the potential development of irreversible bowel damage. Its therapeutic landscape has evolved substantially with the introduction of biologics and small molecules that target diverse inflammatory pathways, as well as new formulations and biosimilars of established biologics. These advances have expanded treatment options and enabled more ambitious therapeutic goals beyond symptomatic improvement, including corticosteroid-free remission, endoscopic healing, and prevention of disease progression. However, selecting and positioning therapies remain challenging because of differences in disease severity and phenotype, prior treatment exposure, safety considerations, patient preferences, and limited evidence from direct comparative studies. Additionally, important uncertainties remain regarding combination therapy with immunomodulators, treatment de-escalation, switching between originators and biosimilars, and management of perianal fistulizing disease. To provide evidence-based and clinically applicable recommendations, the Korean Association for the Study of Intestinal Diseases developed updated clinical practice guidelines for the medical management of adult patients with CD. This guideline was developed using a GRADE-ADOLOPMENT approach that combined the adaptation of high-quality existing guidelines with de novo development based on newly identified evidence. The certainty of the evidence and strength of the recommendations were assessed using the Grading of Recommendations Assessment, Development and Evaluation approach. The guideline addresses conventional therapies, immunomodulators, biologics, small molecules, biosimilars, alternative formulations, combination and de-escalation strategies, and perianal fistulizing disease. These recommendations are intended to support individualized therapeutic decision-making and improve the quality of care for adult patients with CD.