Macrocyclization in the Design of Grb2 SH2 Domain-Binding Ligands Exhibiting High Potency in Whole-Cell Systems

• Published in: Journal of medicinal chemistry 2003-01, Vol.46 (2), p.244-254
• Main Authors: Wei, Chang-Qing, Gao, Yang, Lee, Kyeong, Guo, Ribo, Li, Bihua, Zhang, Manchao, Yang, Dajun, Burke, Terrence R
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing; Antineoplastic agents; Antineoplastic Agents - chemical synthesis; Antineoplastic Agents - chemistry; Antineoplastic Agents - pharmacology; Biological and medical sciences; Cell Line; Cyclization; Drug Design; Enzyme-Linked Immunosorbent Assay; General aspects; GRB2 Adaptor Protein; Humans; Ligands; Medical sciences; Models, Molecular; Molecular Mimicry; Peptides - chemistry; Pharmacology. Drug treatments; Phosphotyrosine - chemistry; Protein Binding; Proteins - metabolism; src Homology Domains; Structure-Activity Relationship
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/jm0203635

While most SH2 domains bind phosphotyrosyl (pTyr) containing peptides in extended fashion, the growth factor receptor-bound protein 2 (Grb2) SH2 domain preferentially binds ligands in bend conformations. Accordingly, incorporation of bend-inducing functionality into synthetic ligands could potentially enhance their affinity for this SH2 domain. A macrocyclic tripeptide mimetic that contains a simplified pTyr surrogate lacking an α-nitrogen has recently been shown to exhibit high Grb2 SH2 domain-binding affinity in extracellular ELISA-based assays. However, the same compound is largely ineffective in whole-cell assays. It is known that acidic functionality originating from the α-nitrogen of pTyr residues or from the α-position of P0 pTyr mimetics not only increases binding affinity of peptides to Grb2 SH2 domains in extracellular assays but also enhances potency in cell-based systems. Such functionality is absent from the previously reported macrocycle. Therefore, the current study was undertaken to examine the effects of introducing carboxylic functionality at the pTyr mimetic α-position of macrocyclic ligands. It was found that such a modification not only enhanced Grb2 SH2 domain binding in extracellular assays but also conferred high efficacy in whole-cell systems. The most potent compound of the current study exhibited an IC50 value of 0.002 μM in an extracellular ELISA-based assay, and in MDA-MB-453 cells, it both inhibited the association of Grb2 with p185erbB-2 and exhibited antimitogenic effects with submicromolar IC50 values.