Peptides as functional excipients for drug delivery

Peptides have a wide variety of amino acid compositions, sequences and conformations, which allow high specificity and great functionality. Biodegradable peptides arouse less concern about toxicity and tissue accumulation, while short peptides contribute to easy design and manufacturing, high quality, and low production costs. Thanks to these advantages, peptides can be used as high-functional excipients for drug delivery systems (DDS). Recent research has demonstrated the high performance of peptide excipients, including easy drug loading and sustained release of various drugs by self-assembling peptides, efficient cellular uptake/endosomal escape and higher transmucosal permeation by cell-penetrating peptides, and effective nanoparticle DDS for targeting cells and tissues using peptide ligands. Research progress has led to the approval of some new peptide excipients for clinical use, such as PuraStat and RTP004. In addition, green synthesis of peptides at low cost is also important for the use of peptides as excipients, and recent research will enable environmentally friendly solvents and purification. Further, given the importance of regulation to ensure the safety and quality of the new peptide excipients for broad use in many drug products, this review also summarizes current regulatory information on peptides and excipients.