The angiogenic factor Vascular Endothelial Growth Factor (VEGF) is a well-established target for cancer therapy. The humanized monoclonal antibody (mAb) bevacizumab (Avastin®), which binds and neutralizes VEGF, is widely prescribed for the treatment of colon, lung and certain other tumors, but typically provides a relatively modest survival benefit of several months. It is unknown whether the limited benefit is due to redundancy in angiogenic pathways or to the inability of bevacizumab at the doses used to fully neutralize VEGF in the tumor microenvironment. However, the exploration of higher doses of bevacizumab in the clinical setting has been very limited due to lack of incentive to perform dose-ranging studies for an already approved drug, the expense of the drug, and concern about toxicity. To determine whether more effective neutralization of VEGF would be possible and useful, we have therefore used an intensive immunization protocol to generate a new murine mAb designated VE1 that binds VEGF with very high affinity. A humanized form of this mAb, HuVE1, retains the full affinity of VE1 and binds VEGF about 5-fold better than bevacizumab. In side-by-side comparisons, HuVE1 also blocked the binding of VEGF to its receptor with an IC50 that is 5 to 10-fold lower than for bevacizumab, and it correspondingly inhibited VEGF-induced proliferation of HUVEC about 5-fold better than bevacizumab. HuVE1 almost completely blocked growth of primary human hepatocellular carcinoma (HCC) xenografts in one model, and showed a trend toward better efficacy than bevacizumab in a second HCC xenograft model. For potentially even greater anti-angiogenic efficacy, we developed a humanized mAb HuA2T that potently neutralizes angiopoietin-2 (Ang-2), a cytokine that acts through the Tie-2 receptor to promote angiogenesis, especially in combination with VEGF. The synergy between VEGF and Ang-2 provides a strong rationale to develop a bispecific mAb that neutralizes both these factors. We therefore developed such a mAb using the IgG-like bispecific antibody format Bs(scFv)4-IgG consisting of a homodimer of two monomers, each monomer having a single chain Fv from HuVE1 linked to a light chain constant region, and a single chain Fv from HuA2T linked to a heavy chain constant region. While, as is common in construction of bispecific antibodies, this bispecific HuA2T/HuVE1 mAb did lose some binding affinity for VEGF and Ang-2 relative to the original mAbs, its VEGF binding activity was still greater than that of bevacizumab, illustrating the importance of starting with an extremely high activity mAb. Based on its potency in vitro and in animal models, we believe that HuVE1, in either natural or bispecific form, has the potential for greater clinical efficacy than bevacizumab and thus merits further investigation.
Citation Format: Hangil Park, April Zhang, Yi Ding, Lihong Wang, Zhengran Wang, Maximiliano Vasquez, Cary Queen, Jin Kim. Highly potent monoclonal and bispecific anti-angiogenic antibodies to VEGF and angiopoietin-2. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3256.