Small intestine-permeable cyclic peptide-mediated enhancement of Fc-fusion protein absorption in mice

Fragment crystallizable (Fc)-fusion proteins represent a major class of biologics with extended half-lives via neonatal Fc receptor (FcRn)-mediated recycling. However, their clinical application requires invasive intravenous or subcutaneous administration as their large molecular size prevents permeation across the small intestinal barrier. In this study, we aimed to establish a small-intestine-permeable Fc-fusion protein by using DNP peptide, a previously identified cyclic peptide that facilitates transport across small-intestinal epithelial cells. We selected dulaglutide, a GLP-1 analog fused to an IgG4 Fc moiety, as a model Fc-fusion protein. We produced dulaglutide-DNP, featuring a cyclic DNP peptide fused to the C-terminus of each Fc chain, in Chinese hamster ovary cells. Dulaglutide-DNP retained structural integrity and FcRn-binding affinity comparable to those of unmodified dulaglutide. In mice, intravenous dulaglutide-DNP lowered blood glucose levels as effectively as unmodified dulaglutide, suggesting that DNP peptide fusion did not impair the intrinsic pharmacological activity of dulaglutide. Following intraintestinal administration, pharmacokinetic analysis revealed that dulaglutide-DNP rapidly entered the portal vein within 10 min and could be subsequently detected in the systemic circulation. Consistent with this, pharmacodynamic analysis demonstrated that intraintestinal dulaglutide-DNP administration significantly reduced blood glucose levels to 39.0 % of the baseline, corresponding to a pharmacological availability of 15.7 % relative to intravenous dulaglutide-DNP administration. These results demonstrate that DNP peptide fusion permits intestinal absorption of dulaglutide while preserving its function, thereby offering a potential platform for developing orally administrable Fc-fusion therapeutics.