Abstract 4330:In vivoevaluation of anti-tumor activity by an anti-VEGF and anti-DLL4 bispecific antibody in a humanized model of skin graft.

Both Notch/Delta-like ligand 4 (DLL4) and vascular endothelial growth factor (VEGF) pathways play a critical role in angiogenesis and tumor growth. Due to differential regulatory effects of VEGF and DLL4 on the vasculature, blockage of DLL4 or VEGF inhibits tumor growth by distinct mechanisms: anti-DLL4 treatment induces an abnormal increase of poorly perfused blood vessels, which results in a nonproductive angiogenesis unable to support tumor growth, whereas the anti-VEGF therapy significantly decreases vasculature reducing the blood supply to tumors. In our study, we have developed a bispecific monoclonal antibody that targets both human DLL4 (hDLL4) and human VEGF (hVEGF). In vitro, this antibody demonstrated nanomolar affinity to hVEGF and hDLL4, and reduced HUVEC proliferation induced by VEGF (EC50 0.86 ug/ml). To test the activity of this bispecific antibody in vivo, we developed a human skin graft model in NOD/SCID mice, and implanted human tumor specimen-derived colon cancer cells intradermally into these skin transplants. The tumor model was selected based on its sensitivity to both the anti-human DLL4 antibody, OMP-21M18, and to the human VEGF inhibitor bevacizumab. The skin graft model provides a suitable human microenvironment for evaluating anti-tumor efficacy and anti-angiogenesis of the bispecific antibody directed against the human component of DLL4 and VEGF and allows a comparison to OMP-21M18 and also to bevacizumab. Each of these treatments was administered to mice intraperitoneally at a dose of 25 mg/Kg weekly. The bispecific antibody caused a significant inhibition of tumor growth (87% TGI) compared to control antibody (p=0.00001), and this effect was superior to either OMP-21M18 (45% TGI) or bevacizumab (70%TGI). The inhibition of tumor growth by the bispecific antibody was consistently associated with increased blood vessels, up-regulated VEGFA and VEGFR2, and enhanced hypoxia and these effects were more pronounced compared to OMP-21M18. As expected, in this model bevacizumab caused a significant decrease of blood vessels, down-regulated VEGFR2, and increased hypoxia. In separate experiments with mice bearing subcutaneous human colon tumors, the bispecific antibody delayed tumor recurrence following termination of chemotherapy and impacted tumorigenicity by decreasing the frequency of tumor initiating cells. These results suggest that our bispecific anti-DLL4 and anti-VEGF antibody is a potential candidate in the treatment of tumors driven by both VEGF and Notch/DLL4 signaling pathways. Citation Format: Lucia Beviglia, Pete Yeung, Wang-Ching Yen, Belinda Cancilla, Sato Aaron, Chris Bond, Janak Raval, Fumiko Axelrod, Cecile Chartier, Shirley Ma, Austin Gurney, John Lewicki, Ann M. Kapoun, Timothy Hoey. In vivo evaluation of anti-tumor activity by an anti-VEGF and anti-DLL4 bispecific antibody in a humanized model of skin graft. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4330. doi:10.1158/1538-7445.AM2013-4330