Discovery of a Novel Nonphosphorylated Pentapeptide Motif Displaying High Affinity for Grb2-SH2 Domain by the Utilization of 3‘-Substituted Tyrosine Derivatives

• Published in: Journal of medicinal chemistry Vol. 49; no. 5; pp. 1585 - 1596
• Main Authors: Song, Yan-Li, Peach, Megan L, Roller, Peter P, Qiu, Su, Wang, Shaomeng, Long, Ya-Qiu
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 09.03.2006; Amer Chemical Soc
• Subjects: Amino Acid Motifs; Antineoplastic agents; Antineoplastic Agents - chemical synthesis; Antineoplastic Agents - pharmacology; Biological and medical sciences; Breast Neoplasms; Cell Line, Tumor; Chemistry, Medicinal; Drug Screening Assays, Antitumor; Female; General aspects; GRB2 Adaptor Protein - antagonists & inhibitors; GRB2 Adaptor Protein - metabolism; Humans; Life Sciences & Biomedicine; Medical sciences; Models, Molecular; Oligopeptides - chemical synthesis; Oligopeptides - pharmacology; Peptides, Cyclic - chemical synthesis; Peptides, Cyclic - pharmacology; Pharmacology & Pharmacy; Pharmacology. Drug treatments; Phosphorylation; Protein Binding; Receptor, ErbB-2 - metabolism; Science & Technology; src Homology Domains; Stereoisomerism; Structure-Activity Relationship; Tyrosine - analogs & derivatives; Tyrosine - chemical synthesis; Tyrosine - pharmacology; CYCLIC PEPTIDE ANTAGONISTS; L-DOPA DERIVATIVES; SH2 DOMAIN; SIGNAL-TRANSDUCTION; BREAST-CANCER; SPECIFICITY; STRUCTURAL BASIS; INHIBITORS; BINDING; STRUCTURE-BASED DESIGN; Antineoplastic agent; Peptides; Cyclic peptides; Src Homology 2 domain; Modeling; Signal transduction; Structure activity relation; Molecular model; Mammary gland; Chemical synthesis; Antimitotic; Protein-tyrosine kinase; Tumor cell; Human; Enzyme; Transferases; In vitro; Growth factor receptor; Cell line; Sulfur peptide; Sulfoxide; Affinity; Peptide synthesis; Onc gene; Pentapeptide
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/jm050910x

The growth factor receptor-bound protein 2 (Grb2) is an SH2 domain-containing docking module that represents an attractive target for anticancer therapeutic intervention. An impressive number of synthetic Grb2-SH2 domain inhibitors have been identified; however, clinical agents operating by this mechanism are lacking, due in part to the unique requirement of anionic phosphate-mimicking functionality for high SH2 domain-binding affinity or the extended peptide nature of most inhibitors. In the current study, a new binding motif was successfully developed by the incorporation of 3‘-substituted tyrosine derivatives into a simplified nonphosphorylated cyclic pentapeptide scaffold (4), which resulted in high affinity Grb2-SH2 inhibitors without any phosphotyrosine or phosphotyrosine mimetics. The new l-amino acid analogues bearing an additional nitro, amino, hydroxy, methoxy or carboxy group at the 3‘-position of the phenol ring of tyrosine were prepared in an orthogonally protected form suitable for solid-phase peptide synthesis using Fmoc protocols. The incorporation of these residues into cyclic peptides composed of a five-amino acid sequence motif, Xx-Leu-(3‘-substituted-Tyr)-Ac6c-Asn, provided a brand new class of nonphosphorylated Grb2 SH2 domain inhibitors with reduced size, charge and peptidic character. The highest binding affinity was exhibited by the 3‘-aminotyrosine (3‘-NH2-Tyr)-containing (R)-sulfoxide-cyclized pentapeptide (10b) with an IC50 = 58 nM, the first example with low-nanomolar affinity for a five-amino acid long sequence binding to Grb2-SH2 domain free of any phosphotyrosine or phosphotyrosine mimics. However, the incorporation of 3‘-NO2-Tyr, 3‘-OH-Tyr or 3‘-OCH3-Tyr surrogates in the pentapeptide scaffold is detrimental to Grb2-SH2 binding. These observations were rationalized using molecular modeling. More significantly, the best Grb2-SH2 inhibitor 10b showed excellent activity in inhibiting the growth of erbB2-dependent MDA-MB-453 tumor cell lines with an IC50 value of 19 nM. This study is the first attempt to identify novel nonphosphorylated high affinity Grb2 SH2 inhibitors by the utilization of 3‘-substituted tyrosine derivatives, providing a promising new strategy and template for the development of non-pTyr-containing Grb2-SH2 domain antagonists with potent cellular activity, which potentially may find value in chemical therapeutics for erbB2-related cancers.