Four phthalocyanine (Pc)–peptide conjugates designed to target the epidermal growth factor receptor (EGFR) were synthesized and evaluated in vitro using four cell lines: human carcinoma A431 and HEp2, human colorectal HT-29, and kidney Vero (negative control) cells. Two peptide ligands for EGFR were investigated: EGFR-L1 and -L2, bearing 6 and 13 amino acid residues, respectively. The peptides and Pc-conjugates were shown to bind to EGFR using both theoretical (Autodock) and experimental (SPR) investigations. The Pc–EGFR-L1 conjugates 5a and 5b efficiently targeted EGFR and were internalized, in part due to their cationic charge, whereas the uncharged Pc–EGFR-L2 conjugates 4b and 6a poorly targeted EGFR maybe due to their low aqueous solubility. All conjugates were nontoxic (IC50 > 100 μM) to HT-29 cells, both in the dark and upon light activation (1 J/cm2). Intravenous (iv) administration of conjugate 5b into nude mice bearing A431 and HT-29 human tumor xenografts resulted in a near-IR fluorescence signal at ca. 700 nm, 24 h after administration. Our studies show that Pc–EGFR-L1 conjugates are promising near-IR fluorescent contrast agents for CRC and potentially other EGFR overexpressing cancers.

Epidermal growth factor receptor (EGFR) kinase and the related human epidermal growth factor receptor-2 (HER2, ErbB2) are two growth factor receptors that have implications in cancer. The overexpression or activation of HER2 occurs frequently in breast, ovarian, and lung cancers, making it an important therapeutic target in the treatment of cancer. Blocking HER2-mediated signaling with antibodies or small molecules has been shown to be effective in inhibiting cell growth. After analyzing the crystal structure of the HER2-herceptin complex, several peptidomimetics (HERP5, 6 & 7) were designed to inhibit HER2-mediated signaling for cell growth. We have used an in silico screening method to investigate the chemical diversity of the designed compounds. Autodock software was used to dock the different analogs of HERP5 and HERP7 with HER2 protein extracellular domain. A total of 53 compounds were docked to HER2 protein, and their binding modes were analyzed in terms of docking energy, hydrogen bonding, and hydrophobic interactions. Compounds that exhibited low energy docked structures were chosen for chemical synthesis and biological activity. Two of the compounds (HERP5 and HERP7) exhibited antiproliferative activity, with IC 50 values of 0.396 μM and 0.143 μM, respectively, against SKBR-3 cell lines (breast cancer cell lines) that overexpress HER2 protein.Keywords breast cancer; docking; HER2; MTT assay; SKBR-3 cell line; virtual screening Human tumors express high levels of growth factors and their receptors. Epidermal growth factor receptors (EGFR) are the best-studied growth factor receptor family (1). This family consists of four homologous receptors, namely, epidermal growth factor receptor 1 (also called EGFR, ErbB1) or human epidermal growth factor receptor 1 (HER1), HER2 (ErbB2), HER3 (ErbB3), and HER4 (ErbB4) (2-7). In normal cells, activation of this receptor tyrosine kinase family triggers signaling pathways that control normal cell growth, differentiation, and motility. It is well established that binding of extracellular ligands such as epidermal growth factor (EGF) and transforming growth factor α (TGFα) to the extracellular ligand binding domain of EGFR results in receptor homo-heterodimerization, Supplementary materialThe following supplementary material is available for this article. HPLC, mass spectra, NMR data for compound HERP5 and HR-MS data for HERP5, 6 and 7. NIH Public Access Author ManuscriptChem Biol Drug Des. Author manuscript; available in PMC 2010 September 1. Results and Discussion Design strategyDomains II and IV of the HER2 extracellular region play major roles in multimerization of HERs and the downstream signaling that leads to cell growth (5). The crystal structure of HER2-herceptin complex indicates that the binding site on HER2 domain IV has a pocketlike structure homologous to that of domain II of other HERs (4). This pocket accommodates binding of small peptide/peptidomimetic molecules, which can modulate HER2-mediated signaling. Analysis of 3D structures and resultan...

Peptides and peptidomimetics can function as immunomodulating agents by either blocking the immune response or stimulating the immune response to generate tolerance. Knowledge of B- or T-cell epitopes along with conformational constraints is important in the design of peptide-based immunomodulating agents. Work on the conformational aspects of peptides, synthesis and modified amino acid side chains have contributed to the development of a new generation of therapeutic agents for autoimmune diseases and cancer. The design of peptides/peptidomimetics for immunomodulation in autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, systemic lupus and HIV infection is reviewed. In cancer therapy, peptide epitopes are used in such a way that the body is trained to recognize and fight the cancer cells locally as well as systemically.

A novel non-reversible, water-soluble lipid conjugate of sCT was successfully synthesized that showed (1) different aggregation behavior and secondary structure, (2) improved enzymatic stability and cellular uptake, and (3) comparable hypocalcemic activity in vivo compared to sCT.

Cell adhesion molecule CD2 and its ligand CD58 provide good examples of protein-protein interactions in cells that participate in the immune response. To modulate the cell adhesion interaction, peptides were designed from the discontinuous epitopes of the β-strand region of CD2 protein. The two strands were linked by a peptide bond. β-strands in the peptides were nucleated by inserting a beta-sheet-inducing (D)-Pro-Pro sequence or a dibenzofuran (DBF)-turn mimetic with key amino acid sequences from CD2 protein that binds to CD58. The solution structures of the peptides (5–10) were studied by NMR and molecular dynamics simulations. The ability of these peptides to inhibit cell adhesion interaction was studied by E-rosetting and lymphocyte epithelial assays. Peptides 6 and 7 inhibit the cell adhesion activity with an IC50 value of 7 nM and 11 nM respectively, in lymphocyte-epithelial adhesion assay. NMR and molecular modeling results indicated that peptides 6 and 7 exhibited β-hairpin structure in solution.

Protein-protein interactions (PPI) play a crucial role in many biological processes, and modulation of PPI using small molecules to target hot spots has therapeutic value. As a model system we will use PPI of human epidermal growth factor receptors (EGFRs). Among the four EGFRs, EGFR-HER2 and HER2–HER3 are well known in cancer. We have designed a small molecule that is targeted to modulate HER2-mediated signaling. Our approach is novel because the small molecule designed disrupts dimerization not only of EGFR-HER2 but also of HER2–HER3. In the present study we have shown, using surface plasmon resonance (SPR) analysis, that a peptidomimetic, compound 5, binds specifically to HER2 protein extracellular domain and disrupts the dimerization of EGFRs. To evaluate the effect of compound 5 on HER2 signaling in vitro, Western blot and PathHunter assays were used. Results indicated that compound 5 inhibits the phosphorylation of HER2 kinase domain and inhibits the heterodimerization in a dose-dependent manner. Molecular modeling methods were used to model the PPI of HER2–HER3 heterodimer.

Rapid advances in our collective understanding of biomolecular structure and, in concert, of biochemical systems, coupled with developments in computational methods, have massively impacted the field of medicinal chemistry over the past two decades, with even greater changes appearing on the horizon. In this perspective, we endeavor to profile some of the most prominent determinants of change and speculate as to further evolution that may consequently occur during the next decade. The five main angles to be addressed are: protein–protein interactions; peptides and peptidomimetics; molecular diversity and pharmacological space; molecular pharmacodynamics (significance, potential and challenges); and early-stage clinical efficacy and safety. We then consider, in light of these, the future of medicinal chemistry and the educational preparation that will be required for future medicinal chemists.

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