Sustained Delivery of Liraglutide Using Multivesicular Liposome Based on Mixed Phospholipids

Background: Although peptides are widely used in the clinical treatment of various diseases due to their strong biological activity, they usually require frequent injections owing to their poor in vivo half-life. Therefore, there is a strong clinical need for sustained peptide formulations. Methods: In this study, liraglutide (Lir) and biocompatible multivesicular liposomes (MVLs) were utilized as the model drug and sustained-release carriers, respectively. The drug release rate of Lir-MVLs was controlled by changing the ratio of SPC and DEPC with different phase transition temperatures (PTT, PTT_SPC = -20 °C, PTT_DEPC = 13 °C). Results: As the SPC ratio increased, Lir-MVLs had more flexible lipid membranes, poorer structural stabilization, and fewer internal vesicles with larger particle sizes, contributing to faster release of Lir. After subcutaneous injection of Lir-MVLs, the blood glucose concentration (BGC) of db/db mice decreased to different levels. When the SPC-DEPC ratio was greater than 85:15, the drug release rate was too fast; the BGC remained below 16 mM for only 2-4 days, while when the drug release rate was too slow, was the case when the SPC-DEPC ratio was less than 50:50, the BGC also remained below 16 mM for only 2-3 days. However, when the SPC-DEPC ratio was 75:25, the BGC could be maintained below 16 mM for 8 days, indicating that the release properties of this ratio best met the pharmacological requirements of Lir. Conclusions: This study investigated the effects of phospholipids with different PTT on the release characteristics of Lir-MVLs, and provided ideas for the design of sustained-release peptide preparations.