The role of intermolecular interactions with penetratin and its analogue on the enhancement of absorption of nasal therapeutic peptides.

We investigated the relationship between intermolecular binding and the ability of novel cell-penetrating peptides (CPPs) to enhance the nasal absorption of therapeutic peptides and proteins. The absorption-enhancing effect of a novel l-penetratin analogue, 'shuffle (R,K fix) 2' coadministered with different biotherapeutic peptides was evaluated after nasal administration in rats. Shuffle (R,K fix) 2 significantly increased the nasal absorption of insulin, glucagon-like-peptide-1 (GLP-1) and exendin-4, compared with the absorption seen with l-penetratin. Intermolecular binding was analyzed by surface plasmon resonance (SPR)-based binding assay. The binding characteristics implied that the higher the amount of CPP bound, the greater the nasal drug absorption. In addition, the calculated binding ratio between CPP and drug proved a critical aspect in enhancing the absorption of insulin and GLP-1. This difference in the enhancing effect of CPPs on nasal drug absorption is attributed to the degree of binding with the therapeutic macromolecule.