Chemically Modified Peptide Structures And Their Formulations For Intracellular Delivery

During the past decades,peptides have got a wide range use in medicine and biological technology.And at the same time,the therapeutic peptides are also experiencing a renaissance.The peptide drugs have high safety,big tolerability,and excellent efficacy naturally.Nowdays,there are more than 80 peptide medicines approved by US Food and Drug Administration(FDA)and the number is expected to be increased significantly.More than 140 peptide drugs are in the clinical trials and more than 500 therapeutic peptides are in the pre-clinical research.The peptide medicines are mainly applied in metabolic diseases and oncology areas.The peptide drugs showed a big potential in therapeutic fields.For most peptide drugs,although their potencies may be highly significant,they may not be effective in vivo because they are impermeable through cell membrane to reach their targets inside cells.It is criticl to develop specific drug delivery systems to help the peptides to enter the target cells.In addition,after intravenous adminidation,the peptides could be highly venerable to enzymatic degradation in the blood circulation and before reach to the target organ.We therefor have to design the delivery system to maintain the peptide stability.In this study,we designed 3 different modifiedpeptidesstructures: a)a stearic acid(SA)modified peptide(A1-SA),b)SA modified cell penetrating peptide fused with A1(A1-CPP-SA)and c)l SA modified,metalloproteinases MMP substrate fused with CPP and then A1(A1-CPP-MMP-SA).They were all incorporated into liposome formulaton with different lipid compositions.There were 6different liposomes developed and then evaluated for their proliferation properties using two human hepatocarcinoma cell-lines.Based on these data and considering factors including preparation methods and encapsulation efficacy,we chose the A1-SA peptide liposomes as the candidate formulation and A1-CPP-SA liposomes as the backup.They were both evaluated for their size,size distributon,surface potential,EM morphology.Their interaction with cells and the cell uptake mechanism were all examined using confocal fluorescence microscopy.We showed that the A1-SA liposomes and A1-CPP-SA liposomes have improved safety compared to the SA peptide by itself.The MTD of A1-SA and A1-CPP-SA liposome is ≤3mg/kg,and and the NOAEL is ≤1mg/kg.PK studies in vivo indicated there was also improvement in stabilities of the peptide formulation.the half-time of A1-SAin the blood and liver are 5.02 h and 2.08 h respectively.AUC were 20492 and 7181 separately.