Antagonists to Human and Mouse Vascular Endothelial Growth Factor Receptor 2 Generated by Directed Protein Evolution In Vitro

SummaryUsing directed in vitro protein evolution, we generated proteins that bound and antagonized the function of vascular endothelial growth factor receptor 2 (VEGFR2). Binders to human VEGFR2 (KDR) with 10–200 nM affinities were selected by using mRNA display from a library (1013 variants) based on the tenth human fibronectin type III domain (10Fn3) scaffold. Subsequently, a single KDR binding clone (Kd = 11 nM) was subjected to affinity maturation. This yielded improved KDR binding molecules with affinities ranging from 0.06 to 2 nM. Molecules with dual binding specificities (human/mouse) were also isolated by using both KDR and Flk-1 (mouse VEGFR2) as targets in selection. Proteins encoded by the selected clones bound VEGFR2-expressing cells and inhibited their VEGF-dependent proliferation. Our results demonstrate the potential of these inhibitors in the development of anti-angiogenesis therapeutics.