Structural stability-chromatographic retention relationship on exenatide diastereomer separation

In this study, the relationship of the structural stability of peptide diastereomers in elution solvents and their retention behaviors in reversed-phase chromatography (RPC) was examined to provide guidance on the solvent selection for a better separation of peptide diastereomers. We investigated the chromatographic retention behaviors of exenatide, a peptide drug for the treatment of type II diabetes mellitus and its three diastereomers using RPC and implicit molecular dynamics (MD) simulation analysis. Three diastereomers involved in the single serine residue mutation of D-form at the 11th, 32nd, and 39th residues were investigated in this study. Results show that the order of the solution structural stability of exenatide and its diastereomers is consistent with their retention order by 36 % acetonitrile/water elution. The sample loading solvent also affects the retention behaviors of exenatide peptide diastereomers in RPC column. Furthermore, a larger solution conformation energy difference of the critical pair of exenatide and its diastereomer (D-Ser39) at the elution solvent of 32 % tetrahydrofuran/water were obtained by MD simulation, and baseline separation was proved experimentally. In summary, we demonstrated that the solution structural stability-chromatographic retention relationship could be a powerful tool for elution solvent selection in peptide chromatographic purification, especially valuable for the separation of critical pair of diastereomers.