Engineering Stabilized Vascular Endothelial Growth Factor-A Antagonists: Synthesis, Structural Characterization, and Bioactivity of Grafted Analogues of Cyclotides

• Published in: Journal of medicinal chemistry Vol. 51; no. 24; pp. 7697 - 7704
• Main Authors: Gunasekera, Sunithi, Foley, Fiona M, Clark, Richard J, Sando, Lillian, Fabri, Louis J, Craik, David J, Daly, Norelle L
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 25.12.2008
• Subjects: Antineoplastic agents; Biological and medical sciences; Chemistry, Pharmaceutical - methods; Cyclotides - chemistry; Cystine Knot Motifs; Drug Delivery Systems; Drug Design; Epitopes - chemistry; General aspects; Hemolysis; Humans; Hydrogen-Ion Concentration; Medical sciences; Models, Chemical; Molecular Conformation; Neovascularization, Pathologic; Pharmacology. Drug treatments; Protein Structure, Tertiary; Vascular Endothelial Growth Factor A - antagonists & inhibitors; Antineoplastic agent; Hemolysis; Protein engineering; Hairpin loop; Stability; Antigenic determinant; Angiogenic factor; Molecular structure; Cyclic peptides; Toxicity; Red blood cell; Cytotoxicity; Secondary structure; In vitro; Biological activity; Vascular endothelium growth factor; Cyclization; Sulfur peptide; Polypeptide; Oxidation; Antagonist; Antiangiogenic agent; Chemical synthesis; Structural analysis
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/jm800704e

Cyclotides are plant derived mini-proteins with compact folded structures and exceptional stability. Their stability derives from a head-to-tail cyclized backbone coupled with a cystine knot arrangement of three-conserved disulfide bonds. Taking advantage of this stable framework we developed novel VEGF-A antagonists by grafting a peptide epitope involved in VEGF-A antagonism onto the stable cyclotide framework. Antagonists of this kind have potential therapeutic applications in diseases where angiogenesis is an important component of disease progression, including cancer and rheumatoid arthritis. A grafted analogue showed biological activity in an in vitro VEGF-A antagonism assay at low micromolar concentration and the in vitro stability of the target epitope was markedly increased using this approach. In general, the stabilization of bioactive peptide epitopes is a significant problem in medicinal chemistry and in the current study we have provided insight into one approach to stabilize these peptides in a biological environment.