Ingestible smart capsules: from engineering innovation to GI drug delivery

Ingestible smart capsule platforms have achieved substantial engineering sophistication - integrating programmable drug release, real-time sensing, wireless telemetry, and on-demand actuation - yet their demonstrated clinical benefit in inflammatory bowel disease (IBD) remains limited, with no platform having achieved regulatory approval for therapeutic use in this indication. This disconnect constitutes a translational misalignment: a systematic gap between the assumptions embedded in device design and the biological, pharmacological, and regulatory realities of IBD management. The misalignment operates at four distinct levels. At the systems level, localization strategies calibrated on healthy-volunteer physiology fail in inflamed bowel, where pH gradients are attenuated, transit is dysregulated, and luminal anatomy is structurally altered by strictures and post-surgical remodelling. At the pharmacological level, the internal volume constraints of swallowable capsules (~ 0.3-1 mL) impose dose ceilings incompatible with the therapeutic requirements of biologics and macromolecular agents that represent the current standard of care in IBD. At the regulatory level, smart drug-delivery capsules occupy an ambiguous classification space between drug, device, and combination product, generating approval uncertainty that suppresses investment and forces conservative design choices irrespective of technical feasibility. At the patient level, capsule dimensions (up to 40 × 15 mm), active appendages, and retention risk in strictured segments impose acceptance barriers that are rarely modelled during preclinical development. This review critically examines each engineering subsystem - localization, locomotion, retention, signal transmission, drug release, power supply, reservoir design, and size - through the lens of IBD-specific translational constraints. The three most clinically advanced platforms (IntelliCap^®, InteliSite^® Companion Device, and the SOMA device) are evaluated as case studies in translational feasibility. A forward path requires not greater engineering complexity, but deliberate alignment between device architecture and the clinical, pharmacological, and regulatory realities of the disease being treated.