Structure-activity relationships of dermorphin synthetic analogues

A number of dermorphin analogues have been reviewed for antinociceptive activity after systemic administration. Analgesic peptides as potent as or more potent than dermorphin are found among the hepta- and tetrapeptide analogues, probably because of enhanced stability towards carboxyldipeptidases imparted by the Pro6 and D-Ala2 residues lying on the right and left side, respectively, of the point of cleavage. Hexapeptide analogues are practically inactive. [D-Arg2]derivatives are very potent, particularly in the tetrapeptide series. In binding studies dermorphin behaves as a pure opioid agonist, with a marked affinity and selectivity for the mu-type opioid receptors. In the heptapeptide analogues a direct correlation seems to exist between mu-selectivity and "sodium shift," and between lipophilicity and MVD/GPI potency ratio.