New anthranilic acid based antagonists with high affinity and selectivity for the human cholecystokinin receptor 1 (hCCK1-R)

The anthranilic acid diamides represent the most recent class of nonpeptide CCK(1) receptor (CCK(1)-R) antagonists. Herein we describe the second phase of the anthranilic acid C-terminal optimization using nonproteinogenic amino acids containing a phenyl ring in their side chain. The Homo-Phe derivative 2 (VL-0797) enhanced 12-fold the affinity for the rat CCK(1)-R affinity and 15-fold for the human CCK(1)-R relative to the reference compound 12 (VL-0395). The eutomer of 2 (6) exhibited a nanomolar range affinity toward the human CCK(1)-R and was at least 400-fold selective for the CCK(1)-R over the CCK(2)-R. Molecular docking in the modeled CCK(1)-R and its validation by site-directed mutagenesis experiments showed that the 6 binding site overlaps that occupied by the C-terminal bioactive region of the natural agonist CCK. Owing to their interesting properties, new compounds provided by this study represent a solid basis for further advances aimed at synthesis of clinically valuable CCK(1)-R antagonists.