The present invention provides a peptide derivative of formula (I) or a pharmaceutically acceptable salt thereof ##STR00001## wherein X is --CH(OH)-- or --CO--; R.sup.1 is hydrogen or an amino protecting group; R.sup.2 is hydroxyl or lower alkoxy; one of R.sup.3 and R.sup.4 is the side chain (R group) of lysine the amino group of which may be protected with a protecting group and the other of R.sup.3 and R.sup.4 is the side chain (R group) of arginine the guanidino group of which may be protected with a protecting group; and R.sup.5 and R.sup.6 may be the same or different and are hydrogen, lower alkyl or aralkyl. The present invention further provides a production process and use thereof.