Anti-tumor effect of CT-322 as an adnectin inhibitor of vascular endothelial growth factor receptor-2

Ct-322 is a new anti-angiogenic therapeutic agent based on an engineered variant of the tenth type III domain of human fibronectin, i.e., an AdnectintM, designed to inhibit vascular endothelial growth factor receptor (VeGFR)-2. this peGylated Adnectin was developed using an mRNA display technology. Ct-322 bound human VeGFR-2 with high affi nity (KD, 11 nM), but did not bind VeGFR-1 or VeGFR-3 at concentrations up to 100 nM, as determined by surface plasmon resonance studies. Western blot analysis showed that Ct-322 blocked VeGF-induced phosphorylation of VeGFR-2 and mitogenactivated protein kinase in human umbilical vascular endothelial cells. Ct-322 significantly inhibited the growth of human tumor xenograft models of colon carcinoma and glioblastoma at doses of 15-60 mg/kg administered 3 times/week. Anti-tumor effects of Ct-322 were comparable to those of sorafenib or sunitinib, which inhibit multiple kinases, in a colon carcinoma xenograft model, although Ct-322 caused less overt adverse effects than the kinase inhibitors. Ct-322 also enhanced the anti-tumor activity of the chemotherapeutic agent temsirolimus in the colon carcinoma model. the high affi nity and specificity of Ct-322 binding to VeGFR-2 and its anti-tumor activities establish Ct-322 as a promising anti-angiogenic therapeutic agent. our results further suggest that Adnectins are an important new class of targeted biologics that can be developed as potential treatments for a wide variety of diseases.