EXTH-45. TARGETING GLIOBLASTOMA BY NOVEL INTEGRIN-SPECIFIC CAR T CELLS

Abstract

Abstract RATIONALE Innovative treatment strategies are urgently needed to improve the prognosis of glioblastoma patients. Chimeric antigen receptor (CAR) T cell therapy has shown great success in hematological malignancies. However, it remains to be shown that CAR T cells are also active against solid tumors. αv integrins are overexpressed in gliomas and have already been used as therapeutic targets for small molecule inhibitors and antibodies. While these approaches were well tolerated, they did not exert meaningful clinical activity in glioblastoma patients. We aimed at exploiting the presence of αv integrins as targets for anti-glioma CAR T cell therapy. METHODS CAR T cells targeting specific integrin heterodimers (αvβ3, αvβ5 or αvβ8) were generated and their anti-glioma activity was determined in co-culture assays with different glioma cells. The efficacy of CAR T cells to control tumor growth in vivo was assessed in clinically relevant orthotopic mouse glioma models. RESULTS All newly generated integrin-targeting CAR T cells exerted strong anti-tumor activity in vitro. The highest lytic activity against glioma cells was observed for αvβ5 and αvβ8 integrin-specific CAR T cells. CAR T cells generated from patient-derived immune cells displayed strong lytic activity when tested against autologous tumors cells. Glioma cells with a CRISPR/Cas9-mediated knockout of the target antigen were resistant to CAR T cell-mediated cytotoxicity demonstrating their specificity. The in vivo activity of integrin-specific CAR T cells was tested in 2 orthotopic glioma models. Intratumoral treatment of glioma-bearing mice with αvβ5 or αvβ8 CAR T cells significantly prolonged their survival and cured a substantial fraction of these animals. CONCLUSION αvβ5- and αvβ8-specific CAR T cells exert strong and target-specific anti-glioma activity in vitro and prolong the survival of glioma-bearing mice. These data form the basis for a clinical evaluation of integrin-specific CAR T cells against glioblastoma.