Thousands of naturally identified peptides have been recognized, playing important roles in human physiological processes, including as hormones, neurotransmitters, growth factors, ion channel ligands, or anti-infectives. Peptide drugs are considered to have high selectivity and efficacy, as well as relative safety and good tolerance. Therefore, interest in peptide drugs in drug research and development (R&D) is increasing, with hundreds of peptide drugs undergoing clinical trial evaluation.