Car-T Cell Harboring A Camelid Single Domain Antibody As A Targeting Agent To Kill Tumors Expressing Vegfr2

Modulation of the immune system is showing tremendous promise in the treatment of malignancies. In addition to checkpoint inhibitors that re-activate T cells present in the tumor microenvironment, exogenously transduced chimeric antigen receptor (CAR) T cells are providing excellent responses in clinical trials for the treatment of leukemias. In this study, we describe CAR-T cells that target VEGFR2-expressing tumors. Angiogenesis is the process of new blood vessel formation and is essential for a tumor to grow beyond a certain size. Tumors secrete the pro-angiogenic factor vascular endothelial growth factor (VEGF), which acts upon local endothelial cells by binding to vascular endothelial growth factor receptors (VEGFR). As VEGFR2 is also expressed by a variety of tumors, we investigated the utility of anti-VEGFR2 CAR-T cells as a method to treat VEGFR2-expressing tumors. Camelid antibodies are small (14 kD) single chain antibodies. To generate a camelid antibody targeting the extracellular domain of VEGFR2, a llama was immunized with recombinant VEGFR2/Fc. A phage display library was generated and screened to identify an antibody with high binding affinity to VEGFR2. The selected antibody was expressed in the E. coli. BL21 (DE3) pT7 system. The purified antibody was characterized by SEC, LC-MS peptide mapping and ELISA. CAR-T cells were engineered to express the camelid anti-VEGFR2 antibody in combination with the CD28 and 4-1BB costimulatory molecules and the CD3 zeta chain. Tumor cells were screened for expression of VEGFR2, and the HL-60 acute promyelocytic leukemia, ZR-75-30 breast ductal carcinoma and NCI-H23 non-small cell lung adenocarcinoma were identified. Co-incubation of anti-VEGFR2 CAR-T cells with the VEGFR-2-expressing cell lines resulted in dose-dependent target cell toxicity as measured by LDH release. In addition, T cell activity was confirmed, as high levels of IL-2 and IFN-γ were detected in the cell culture media. These results suggest that anti-VEGFR2 CAR-T may be useful in directly targeting VEGFR2-expressing tumors. We previously showed the utility of camelid antibodies in CAR-T constructs as anti-CEACAM6 CAR-T cells show both in vitro and in vitro efficacy against the pancreatic tumor Bx-PC3. The use of the a camelid V21 antibody to target VEGFR2-expressing tumors provides hope that camelid single domain antibodies can be developed for CAR-T therapies. Citation Format: Heman Chao, Baomin Tian, Marni Uger, Wah Wong. CAR-T cell harboring a camelid single domain antibody as a targeting agent to kill tumors expressing VEGFR2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3770. doi:10.1158/1538-7445.AM2017-3770