Oligomerization, albumin binding and catabolism of therapeutic peptides in the subcutaneous compartment: An investigation on lipidated GLP-1 analogs.

Lipidation, a common strategy to improve half-life of therapeutic peptides, affects their tendency to oligomerize, their interaction with plasmatic proteins, and their catabolism. In this work, we have leveraged the use of NMR and SPR spectroscopy to elucidate oligomerization propensity and albumin interaction of different analogs of the two marketed lipidated GLP-1 agonists liraglutide and semaglutide. As most lipidated therapeutic peptides are administered by subcutaneous injection, we have also assessed in vitro their catabolism in the SC tissue using the LC-HRMS-based SCiMetPep assay. We observed that oligomerization had a shielding effect against catabolism. At the same time, binding to albumin may provide only limited protection from proteolysis due to the higher unbound peptide fraction present in the subcutaneous compartment with respect to the plasma. Finally, identification of catabolites in rat plasma after SC dosing of semaglutide showed a good correlation with the in vitro data, with Tyr-Leubeing the major cleavage site. Early characterization of the complex interplay between oligomerization, albumin binding, and catabolism at the injection site is essential for the synthesis of lipidated peptides with good pharmacokinetic profiles.