Abstract LB-347: Ang-2/VEGF bispecific antibody reprograms macrophages and resident microglia to anti-tumor phenotype and prolongs glioblastoma survival

OBJECTIVE: We aimed to enhance the efficacy of anti-VEGF therapy in glioblastoma (GBM) through additional inhibition of Angiopoietin-2 (Ang-2), a potential mediator of resistance to antiangiogenic therapy using VEGF inhibition. INTRODUCTION: Glioblastoma (GBM) is a uniformly lethal primary brain tumor affecting more than 12.000 patients every year in the US alone. The standard therapy regimen for this highly angiogenic tumor entity comprises maximal safe resection and chemoradiation with temozolomide. The addition of antiangiogenic (anti-VEGF) therapy to the standard of care regimen improved progression-free survival, but failed to improve overall survival of GBM patients. Preclinical and clinical data suggest that resistance to anti-VEGF therapy in GBM is mediated by Ang-2, making this pathway a potential target. EXPERIMENTAL DESIGN: We tested the effect of dual Ang-2/VEGF blockade with A2V on mouse survival using a syngeneic (Gl261) model and a human xenograft (MGG8) model, compared to anti-VEGF antibody therapy (B20). In addition, we used blood-based Gaussian Luciferase (GLUC) assays, immunohistochemistry and flow cytometry to measure changes in tumor growth, microvessel density (MVD), and immune microenvironment, respectively. RESULTS: Gl261 tumors have a highly abnormal tumor vasculature. In this model, treatment with A2V reduced MVD compared to B20. The decrease in MVD was due to a reduction in pericyte-low tumor vessels, while pericyte-high vessels were unaffected. These vascular changes were accompanied by reduced tumor burden and enhanced survival. Interestingly, in the MGG8 tumors, which have a vasculature similar to the normal brain, we detected no change in MVD after A2V treatment. Nevertheless, we found a reduced tumor burden and prolonged animal survival in the MGG8 model. Since vascular normalization may impact immune cell infiltration and function in tumors, we next evaluated these cell populations. We found that A2V therapy reduced pro-tumor M2 polarization of macrophages and microglia and reprogrammed these cells toward the M1 phenotype in both the Gl261 and MGG8 models. Collectively, our data indicate that therapy-induced anti-tumor immunity is mediated by M1-type macrophages but not by T-cell infiltration or function. CONCLUSION: Dual Ang-2/VEGF therapy with A2V reprogrammed macrophages and microglia from pro-tumor M2 toward the anti-tumor M1 phenotype in two GBM models, in addition to normalizing vasculature in tumors with abnormal vessels. These data indicate that dual anti-angiogenic therapy has the potential to overcome resistance to anti-VEGF therapy and confer clinical benefits in GBM patients through vascular and immuno-modulatory effects. Citation Format: Jonas Kloepper, Lars Riedemann, Zohreh Amoozgar, Giorgio Seano, Katharina H. Susek, Veronica Yu, Nisha Dalvie, Robin L. Amelung, Meenal Datta, Jonathan W. Song, Vasileios Askoxylakis, Jennie W. Taylor, Christine Lu-Emerson, Ana Batista, Nathaniel D. Kirkpatrick, Keehoon Jung, Matija Snuderl, Alona Muzikansky, Kay G. Stubenrauch, Oliver Krieter, Hiroaki Wakimoto, Lei Xu, Lance L. Munn, Dan G. Duda, Dai Fukumura, Tracy T. Batchelor, Rakesh K. Jain. Ang-2/VEGF bispecific antibody reprograms macrophages and resident microglia to anti-tumor phenotype and prolongs glioblastoma survival. [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 LB-347.