Small Intestine-Permeable Cyclic Peptide-Based Technology Enables Efficient Oral Delivery and Glycemic Efficacy of Zinc-Stabilized Insulin Hexamer and Its Analogs in Diabetic Mice

Oral administration of protein therapeutics, such as insulin, is hindered by enzymatic degradation and poor intestinal permeability. To overcome these barriers, we present a peptide-based delivery platform that uses a DNP peptide that is permeable in the small intestine. We engineered DNP-V, a modular carrier peptide, fused to an insulin-interacting peptide. We demonstrated that the coadministration of DNP-V with zinc-stabilized insulin hexamers in diabetic mice enables a rapid, robust, and sustained reduction in blood glucose levels to near-normal levels. This effect was reproducible across multiple diabetic models, achieving significant suppression of the initial postprandial glucose surge with once-daily oral dosing. This platform can be easily applied to long-acting insulin analogs, allowing for oral delivery without the need for complex preparation changes. Additionally, covalent conjugation of DNP peptides to insulin via click chemistry yielded stable insulin conjugates that significantly enhanced intestinal absorption and produced comparable oral glucose-lowering effects. This confirms the direct contribution of the carriers to the absorption. These findings establish DNP peptides as versatile, modular platforms for the oral delivery of macromolecular therapeutics. As long as an appropriate conjugatable partner is available, this technology can simply and effectively convert injectable biopharmaceuticals into orally administrable forms, offering a promising path to practical, patient-friendly oral therapies.