title: High-affinity VEGF antagonists by oligomerization of a minimal sequence VEGF-binding domain.
abstract: Vascular endothelial growth factor (VEGF) neutralizing antagonists including antibodies or receptor extracellular domain Fc fusions have been applied clinically to control angiogenesis in cancer, wet age-related macular degeneration, and edema. We report here the generation of high-affinity VEGF-binding domains by chemical linkage of the second domain of the VEGF receptor Flt-1 (D2) in several configurations. Recombinant D2 was expressed with a 13 a.a. C-terminal tag, including a C-terminal cysteine to enable its dimerization by disulfide bond formation or by attachment to divalent PEGs and oligomerization by coupling to multivalent PEGs. Disulfide-linked dimers produced by Cu(2+) oxidation of the free-thiol form of the protein demonstrated picomolar affinity for VEGF in solution, comparable to that of a D2-Fc fusion (sFLT01) and ~50-fold higher than monomeric D2, suggesting the 26 a.a. tag length between the two D2 domains permits simultaneous interaction of both faces of the VEGF homodimer. Extending the separation between the D2 domains by short PEG spacers from 0.35 kD to 5 kD produced a modest ~2-fold increase in affinity over the disulfide, thus defining the optimal distance between the two D2 domains for maximum affinity. By surface plasmon resonance (SPR), a larger (~5-fold) increase in affinity was observed by conjugation of the D2 monomer to the termini of 4-arm PEG, and yielding a product with a larger hydrodynamic radius than sFLT01. The higher affinity displayed by these D2 PEG tetramers than either D2 dimer or sFLT01 was largely a consequence of a slower rate of dissociation, suggesting the simultaneous binding by these tetramers to neighboring surface-bound VEGF. Finally, disulfide-linked D2 dimers showed a greater resistance to autocatalytic fragmentation than sFLT01 under elevated temperature stress, indicating such minimum-sequence constructs may be better suited for sustained-release formulations. Therefore, these constructs represent novel Fc-independent VEGF antagonists with ultrahigh affinity, high stability, and a range of hydrodynamic radii for application to multiple therapeutic targets.
authors.affiliation: Protein Engineering, Genzyme Corporation (A Sanofi Company), Framingham, MA, USA. jstefano@genzyme.com
authors.forename: James E
authors.initials: JE
authors.lastname: Stefano
authors.forename: Julie
authors.initials: J
authors.lastname: Bird
authors.forename: Josephine
authors.initials: J
authors.lastname: Kyazike
authors.forename: Anthony Wai-Ming
authors.initials: AW
authors.lastname: Cheng
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Boudanova
authors.forename: Markryan
authors.initials: M
authors.lastname: Dwyer
authors.forename: Lihui
authors.initials: L
authors.lastname: Hou
authors.forename: Huawei
authors.initials: H
authors.lastname: Qiu
authors.forename: Gloria
authors.initials: G
authors.lastname: Matthews
authors.forename: Michael
authors.initials: M
authors.lastname: O'Callaghan
authors.forename: Clark Q
authors.initials: CQ
authors.lastname: Pan
mesh_terms: D003300:Copper / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D058990:Molecular Targeted Therapy; D008970:Molecular Weight; D010084:Oxidation-Reduction; D011092:Polyethylene Glycols / Q000737:chemistry*; D011487:Protein Conformation; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D013329:Structure-Activity Relationship; D020349:Surface Plasmon Resonance; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000737:chemistry* / Q000235:genetics
chemical_list: D004220:Disulfides; D011994:Recombinant Proteins; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D011092:Polyethylene Glycols; D003300:Copper; C501162:FLT1 protein, human; D040281:Vascular Endothelial Growth Factor Receptor-1; D003545:Cysteine