Blocking angiogenesis and tumorigenesis with GFA-116, a synthetic molecule that inhibits binding of vascular endothelial growth factor to its receptor

A small synthetic library of cyclohexapeptidomimetic calixarenes was prepared to identify disrupters of vascular endothelial growth factor (VEGF) binding to its receptor that inhibits angiogenesis. From this library, we discovered GFA-116, which potently inhibits ¹²⁵I-VEGF binding to Flk-1 in Flk-1-overexpressing NIH 3T3 cells and human prostate tumor cells with an IC ₅₀ of 750 nM. This inhibition is highly selective for VEGF in that ¹²⁵I-platelet-derived growth factor binding to its receptor is not affected. GFA-116 inhibits VEGF-stimulated Flk-1 tyrosine phosphorylation and subsequent activation of Erk1/2 mitogen-activated protein kinases. Furthermore, epidermal growth factor, platelet-derived growth factor, and fibroblast growth factor-dependent stimulation of Erk1/2 phosphorylation are not affected at concentrations as high as 10 μM. In vitro, GFA-116 inhibits angiogenesis as measured by inhibition of migration and formation of capillary-like structures by human endothelial cells as well as suppression of microvessel outgrowth in rat aortic rings and rat cornea angiogenesis. In vivo, GFA-116 (50 mpk/day) inhibits tumor growth and angiogenesis as measured by CD31 staining of A-549 human lung tumors in nude mice. Furthermore, GFA-116 is also effective at inhibiting tumor growth and metastasis to the lung of B16-F10 melanoma cells injected into immunocompetent mice. Taken together, these results demonstrate that a synthetic molecule capable of disrupting the binding of VEGF to its receptor selectively inhibits VEGF-dependent signaling and suppresses angiogenesis and tumorigenesis.