BPC-157 is a pentadecapeptide that matches a partial sequence of a protein found in human gastric juice. LL-37 is the single human cathelicidin-derived antimicrobial peptide. KPV is the C-terminal tripeptide of α-MSH, and ARA290 (cibinetide) is an 11-residue peptide derived from the helix B surface of erythropoietin.
The four have little in common structurally, but they share a research use: they are applied in cell and animal models of inflammation, antimicrobial defence and tissue repair, and they are usually compared with larger endogenous proteins.