Cholecystokinin-A receptor ligands based on the kappa-opioid agonist tifluadom

Tifluadom, a kappa-opioid agonist and cholecystokinin-A (CCK-A) receptor antagonist, was utilized as a model to prepare a series of 2-(aminomethyl)- and 3-(aminomethyl)-1,4-benzodiazepines. These compounds were tested in vitro as inhibitors of the binding of [125I]CCK to rat pancreas and guinea pig brain receptors. All compounds with IC50's less than 100 microM proved to have greater affinity for the CCK-A receptor, with the most potent analogue, 6e, having an IC50 of 0.16 microM. The benzodiazepines described in this study are simultaneously CCK-A and opioid receptor ligands. The ramification of this dichotomy on current concepts of peptide hormone action are discussed. These results further demonstrate the versatility of the benzodiazepine core structure for designing nonpeptide ligands for peptide receptors and the ability to fine-tune the receptor interactions of these benzodiazepines by appropriate structure modifications.