Anti-VEGFR2 and anti-IGF-1R-Adnectins inhibit Ewing's sarcoma A673-xenograft growth and normalize tumor vascular architecture.

Increasing experimental evidence suggests that IGF-1 may modulate tumor angiogenesis via activation of the expression of VEGF in Ewing sarcomas and rhabdomyosarcomas. This study investigates the effects of the PEGylated Adnectins™ CT-322, a VEGFR2-inhibitor and AT580Peg40, an IGF-1R inhibitor, as monotherapy and in combination in a murine A673 xenograft tumor model. The combination of Adnectins CT-322 and AT580Peg40 revealed a 83% reduction in tumor growth, a nearly 5 times lower vessel density, less necrotic areas and less appearance of intussusceptive angiogenesis. Monotherapy with IGF-1R or CT-322 revealed equally a significant inhibition of tumor and vessel growth. Combinatory inhibition of IGF-1R and VEGFR2 shows a downregulation of IGF-binding protein 2 and a compensatory upregulation of VEGF levels. Immunohistological analysis showed remodeling vascular effects of CT-322-treatment or combination therapy. The vascular architecture in Adnectin-treated tumors was characterized by a strong normalization of vasculature. 3D-evaluation in microvascular corrosion casts showed significantly higher intervascular and interbranching distances in Adnectin-treated tumors. CT-322-treatment and combinatory inhibition reveal a significant reduction of intussusceptive angiogenesis. These pronounced effects on tumor vasculature suggest potential therapeutic benefit of combinatorial IGF1- and VEGF-pathways inhibition in Ewing's sarcoma.

Adnectin CT-322 inhibits tumor growth and affects microvascular architecture and function in Colo205 tumor xenografts.

Antiangiogenesis has become a promising pillar in modern cancer therapy. This study investigates the antiangiogenic effects of the PEGylated Adnectin™, CT-322, in a murine Colo-205 xenograft tumor model. CT-322 specifically binds to and blocks vascular endothelial growth factor receptor (VEGFR-2). Adnectins are a novel class of targeted biologics engineered from the 10th domain of human fibronectin. CT-322 treated tumors exhibited a significant reduction in tumor growth of 69%, a 2.8 times lower tumor surface area and fewer necrotic areas. Control tumors showed a 2.36-fold higher microvessel density (MVD) and a 2.42 times higher vessel volume in corrosion casts. The vascular architecture in CT-322-treated tumors was characterized by a strong normalization of vasculature. This was quantified in corrosion casts of CT-322 treated tumors in which the intervascular distance (a reciprocal parameter indicative of vessel density) and the distance between two consecutive branchings were assessed, with these distances being 2.21 times and 2.37 times greater than in controls, respectively. Fluorescence molecular tomography (FMT) equally affirmed the inhibitory effects of CT-322 on tumor vasculature as indicated by a 60% reduction of the vascular probe, AngioSense, accumulating in tumor tissue, as a measurement of vascular permeability. Moreover, AngioSense accumulation was reduced as early as 24 h after starting treatment. The sum of these effects on tumor vasculature illustrates the anti-angiogenic mechanism underlying the antitumor activity of CT-322 and provides support for further evaluation of this Adnectin in combinatorial strategies with standard of care therapies.

A fibronectin scaffold approach to bispecific inhibitors of epidermal growth factor receptor and insulin-like growth factor-I receptor.

Engineered domains of human fibronectin (Adnectins™) were used to generate a bispecific Adnectin targeting epidermal growth factor receptor (EGFR) and insulin-like growth factor-I receptor (IGF-IR), two transmembrane receptors that mediate proliferative and survival cell signaling in cancer. Single-domain Adnectins that specifically bind EGFR or IGF-IR were generated using mRNA display with a library containing as many as 10 ( 13) Adnectin variants. mRNA display was also used to optimize lead Adnectin affinities, resulting in clones that inhibited EGFR phosphorylation at 7 to 38 nM compared to 2.6 µM for the parental clone. Individual, optimized, Adnectins specific for blocking either EGFR or IGF-IR signaling were engineered into a single protein (EI-Tandem Adnectin). The EI-Tandems inhibited phosphorylation of EGFR and IGF-IR, induced receptor degradation, and inhibited down-stream cell signaling and proliferation of human cancer cell lines (A431, H292, BxPC3 and RH41) with IC 50 values ranging from 0.1 to 113 nM. Although Adnectins bound to EGFR at a site distinct from those of anti-EGFR antibodies cetuximab, panitumumab and nimotuzumab, like the antibodies, the anti-EGFR Adnectins blocked the binding of EGF to EGFR. PEGylated EI-Tandem inhibited the growth of both EGFR and IGF-IR driven human tumor xenografts, induced degradation of EGFR, and reduced EGFR phosphorylation in tumors. These results demonstrate efficient engineering of bispecific Adnectins with high potency and desired specificity. The bispecificity may improve biological activity compared to monospecific biologics as tumor growth is driven by multiple growth factors. Our results illustrate a technological advancement for constructing multi-specific biologics in cancer therapy.

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 Adnectin™, designed to inhibit vascular endothelial growth factor receptor (VEGFR)-2. This PE Gylated Adnectin was developed using an mRNA display technology. CT-322 bound human VEGFR-2 with high affinity (K(D), 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 mitogen-activated 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 affinity 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.