Development of Potent and Selective CCK-A Receptor Agonists from Boc-CCK-4: Tetrapeptides Containing Lys(Nε)-Amide Residues

Article abstract of DOI:10.1021/jm00089a010

A series of Boc-CCK-4 derivatives represented by the general structure Boc-Trp-Lys(N^ε-COR)-Asp-Phe-NH2, where R is an aromatic, heterocyclic, or aliphatic group, are potent and selective CCK-A receptor agonists.These amide-bearing compounds complement the previously described urea-based tetrapeptides (Shiosaki et al.J.Med.Chem. 1991,34,2837-2842); structure-activity studies revealed parallel as well as divergent trends between these two series.A significant correlation was observed between pancreatic binding affinity and the resonance constant R of the phenyl substituent in one particular series of derivatives.Sulfation of phenolic amides appended onto the ε-amino group of the lysine did not affect affinity for the CCK-A receptor in contrast to the 500-fold increase in binding potency observed upon sulfation of CCK-8, suggesting that the lysine appendage and the sulfated tyrosine in CCK-8, both key structural elements that impart high affinity for the CCK-A receptor, are interacting differently with the receptor.The amide-bearing tetrapeptides are full agonists relative to CCK-8 in stimulating pancreatic amylase release while being partial agonists in eliciting phosphoinositide (PI) hydrolysis.Both effects were blocked by selective CCK-A receptor antagonists