ROBO1 CAR-T CELL THERAPY FOR TREATMENT REFRACTORY BRAIN CANCER

Abstract BTFC travel award recipient Glioblastoma (GBM) is the most common malignant adult brain tumor, with a dismal prognosis. Despite the multimodal treatment regimen, tumor recurrence is inevitable, and no standardized treatment exists for recurrent glioblastoma (rGBM). Neurodevelopment signaling pathways are often hijacked during tumor progression. Roundabout guidance receptor 1 (ROBO1) protein is involved in axonal guidance during neurodevelopment. Our preliminary findings implicated aberrant ROBO1 signaling axis to be associated with higher tumorigenecity in GBM, making it a functionally relevant therapeutic target. Moreover, ROBO1 was highly expressed on the surface of malignant and treatment-refractory brain tumor initiating cells (BTICs) in rGBM, brain metastasis (BM) and medulloblastoma (MB), prompting the development of an anti-ROBO1 CAR-T cell therapy. Here we report the development and validation of second-generation CAR-T cells using a single-domain antibody targeting ROBO1 expressing BTICs across three different brain tumors. We validated anti-ROBO1 CAR-T cells in-vitro and in-vivo using our established patient derived tumor models. In-vitro studies demonstrated upregulation of activation markers, enhanced cytokine release, markedly increased proliferation, and induction of potent and specific tumor cell death with ROBO1 CAR-T cells as compared to untransduced cells (UT) in all the three cancers. These findings were further validated in-vivo using 3 different BTIC lines one each from rGBM, MB and BM. ROBO1 CAR-T showed significant reduction in tumor burden and significant increase in survival of the mice treated with ROBO1 CAR-T cells in all the three cohorts. Thus, targeting ROBO1 could be a therapeutically tractable strategy for treating rGBM as well as other brain malignancies.