Structure-activity relationship study on artificial CXCR4 ligands possessing the cyclic pentapeptide scaffold: the exploration of amino acid residues of pentapeptides by substitutions of several aromatic amino acids.

Previously, downsizing of a 14-residue peptidic CXCR4 antagonist has led to the development of a highly potent CXCR4 antagonist [cyclo(-d-Tyr(1)-Arg(2)-Arg(3)-Nal(4)-Gly(5)-)]. In the present study, cyclic pentapeptide libraries that were designed by substitutions of several amino acids for d-Tyr(1) and Arg(2) in peptide were prepared and screened to evaluate binding activity for CXCR4. The above structure-activity relationship study led to the finding of several potent CXCR4 ligands.

Structure-activity relationship study of CXCR4 antagonists bearing the cyclic pentapeptide scaffold: identification of the new pharmacophore.

A highly potent CXCR4 antagonist 2 [cyclo (-D-Tyr1-Arg2-Arg3-Nal4-Gly5-)] has previously been identified by screening cyclic pentapeptide libraries that were designed based on pharmacophore residues of a 14-residue peptidic CXCR4 antagonist 1. In the present study, D-Tyr and Arg in peptide 2 were replaced by a bicyclic aromatic amino acid and a cationic amino acid, respectively, and their binding activity for CXCR4 was evaluated for identification of the novel pharmacophore.

Identification of novel low molecular weight CXCR4 antagonists by structural tuning of cyclic tetrapeptide scaffolds.

A highly potent CXCR4 antagonist, compound 2, was previously found by using two orthogonal cyclic pentapeptide libraries involving conformation-based and sequence-based libraries based on the pharmacophore of a 14-mer peptidic antagonist, 1. Herein, cyclic tetrapeptides derived from replacements of the dipeptide unit (Nal-Gly) with a gamma-amino acid and pseudopeptides cyclized by disulfide and olefin bridges were synthesized to find novel scaffold structures different from that of cyclic pentapeptides. These compounds contain a reduced number of peptide bonds compared to compound 2. Furthermore, several analogues with chemical modification of the side chain of Arg(4) in 2 were also prepared. From these, several new leads possessing high to moderate CXCR4-antagonistic activity were characterized.

Structure-activity relationship studies on CXCR4 antagonists having cyclic pentapeptide scaffolds.

Structure-activity relationship studies on CXCR4 antagonists, which were previously found by using cyclic pentapeptide libraries, were performed to optimize side-chain functional groups, involving conformationally constrained analogues. In addition, a new lead of cyclic pentapeptides with the introduction of a novel pharmacophore was developed.