| abstract |
Certain peptides which exhibit high selectivity for the kappa opioid receptor (KOR) versus the mu opioid receptor and little or no CYP3A4 inhibitory activity including tetrapeptides of four D-isomer amino acid residues having a C-terminus which is an N-oxide-substituted amide such, as H-D-Phe-D-Phe-D-Nle-D-Arg-NH-4- picolyl-N-oxide. A preferred compound, which has an affinity for the KOR at least 1,000 times its affinity for the mu opioid receptor and an IC50 for CYP3 A4 of greater than about 10 micromolar, is H-D-Phe-D-Phe-D-Nle-D-Arg-NH-4-picolyl-N-oxide |