EXTH-13. COMBINED ANTI-ANGIOGENIC TREATMENT TO INCREASE INTRATUMORAL PERSISTENCE OF CAR T-CELLS IN LUNG CANCER BRAIN METASTASES

Abstract BACKGROUND Metastatic lung cancer, especially when it spreads to the brain, shows a devastating prognosis. Immunotherapeutic approaches including CAR T-cells show promise in hematologic malignancies. However, the presence of immunosuppressive factors within the tumor microenvironment and physical barriers like elevated interstitial pressure due to dysfunctional tumor vessels are one of the main obstacles especially in solid tumors. Evaluation of the potential synergy between anti-angiogenetic drugs and CAR T-cells in this context are an ongoing investigation. METHODS Here, we set up an immunocompetent syngeneic orthotopic cerebral metastasis model in mice by combining a chronic cranial window with repetitive intracerebral two-photon laser scanning microscopy (TPLSM). This model allows in vivo characterization of fluorescent tumor cells and CAR T-cells on a single cell level over time. Intraparenchymal injection of red fluorescent EpCAM-transduced Lewis Lung carcinoma cells (EpCAM/tdtLL/2 cells) followed by injection of EpCAM-directed or undirected CAR T-cells into the adjacent brain tissue was performed. Additionally, aVEGF-A combined with aVEGF-R2 and the respective isotype control were injected intraperitoneally. RESULTS Compared to undirected CAR T-cells, mice receiving EpCAM-directed CAR T-cells showed higher intratumoral CAR T-cell densities after intraparenchymal injection. This finding was accompanied with reduced tumor growth and eventually translates into a survival benefit. However, intratumoral CAR T-cell numbers diminish over time indicating insufficient persistence inside of the tumor microenvironment. Additional anti-VEGF-A/VEGF-R2 treatment results in reduced tumor growth after EpCAM/GFPCAR T-cell and GFPT-cell treatment, respectively. Interestingly, in vivo imaging reveals higher intratumoral CAR T-cell numbers after anti-angiogenic treatment compared to isotype controls pointing towards enhanced CAR T-cell persistence resulting in a survival benefit. CONCLUSION Collectively, our findings indicate that locally injected CAR T-cells may safely induce relevant anti-tumor effects in brain metastases from lung cancer. Additional anti-angiogenic treatment provides a mechanism to enhance intratumoral CAR T-cell persistence and reduce tumor growth.