Oral Gut-Restricted Targeted Therapy for IBD: A Pipeline Review.

Oral gut-restricted therapies are being explored as a drug delivery strategy for inflammatory bowel disease (IBD), with the aim of achieving therapeutic effects within the intestinal mucosa while minimizing systemic exposure. Advances in molecular engineering and formulation technologies have enabled the development of orally administered agents intentionally designed to act locally within the gastrointestinal tract. This narrative review examines the biological, pharmacokinetic, and formulation principles underlying oral gut-restricted drug delivery in IBD, including an analysis of discontinued clinical development programs in ulcerative colitis and Crohn's disease. Across locally acting antibodies, peptides, and small molecules, the analysis of these programs reveals recurring factors contributing to discontinuation. These include limited or absent clinical efficacy despite evidence of mucosal target engagement, challenges in achieving consistent and adequate intestinal exposure, constraints related to formulation or delivery technologies, and trial-related factors such as high placebo response rates. In several cases, manufacturing variability or strategic considerations also influenced development outcomes. The review of the current clinical trial pipeline suggests an evolution in development strategies relative to earlier programs, with increasing emphasis on the confirmation of local tissue drug levels, incorporation of mucosal pharmacodynamic readouts, and selection of endpoints aligned with localized mechanisms of action, including endoscopic and histologic outcomes. These elements appear critical for interpreting early phase efficacy signals for agents designed to have minimal systemic activity. Effective translation requires alignment between mechanism of action, intestinal drug delivery, tissue-level pharmacodynamics, and clinical trial design. Incorporating these lessons may improve the likelihood of success for future oral gut-restricted therapies in IBD.