Assessing resistance mechanisms in synNotch-CAR T cell-mediated glioblastoma therapy and evaluation of potential mitigation strategies

• Applicant: Dr. Marco Gallus
• Subject Area: Clinical Neurology; Neurosurgery and Neuroradiology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 516778857

Glioblastoma (GBM) is the most common primary malignant brain tumor with a median overall survival of less than 2 years and a recurrence rate of nearly 100%. Therefore, new therapeutic strategies are urgently needed. Chimeric antigen receptor T cell (CAR T) therapy is promising, but several challenges such as lack of ideal target antigens, T cell exhaustion, and tumor-induced immunosuppression must be addressed. Recently, it was discovered that chimeric forms of Notch, a type 1 transmembrane protein, can serve as a general platform for the development of new cell-cell contact signaling pathways (Synthetic Notch "synNotch"). This enables the development of T cells that exhibit customized therapeutic response programs using synthetic Notch receptors. A new generation of innovative T cell circuits that recognize glioblastoma cells based on the "prime-and-kill" strategy has been developed. In this strategy, priming antigen expressed exclusively on brain or GBM cells is recognized by the synNotch receptor, thereby inducing the expression of a CAR (synNotch-CAR=SYNC). This offers the possibility of safely targeting low-specificity GBM antigens and is also associated with excellent T cell persistence in vivo. Although this new approach appears promising, it is not yet known how efficiently SYNC T cells work in an intact immune system. Recent studies have shown that counter-active immunoregulatory molecules such as programmed death-ligand 1 (PD-L1) and transforming growth factor ß1 (TGF-β1) appear to play a key role in tumor-induced immunosuppression. Therefore, studies combining SYNC-T cell therapy with blockade of these molecules in an intact immune system are now needed. The aim of this study is to investigate potential resistance mechanisms of SYNC T cell therapy in immunocompetent C57BL/6 mice bearing EGFRvIII-expressing brain tumors of the low-immunogenic SB28 mouse glioma cell line. B-SYNC T cells developed by the Okada laboratory will be used as therapy. These cells are primed by the CNS-specific antigen Brevican and express an anti-EGFRvIII CAR upon activation. The efficacy of B-SYNC therapy alone and in combination with intravenous infusion of monoclonal antibodies directed against PD-1 or TGF-ß1 will be investigated. As a subordinate goal, I will also determine whether anti-PD-1 or TGF-ß1 expression directly by the SYNC T cell itself can overcome potential local immunosuppression and may be superior to infusion of antibodies, when integrated as an additional payload in the synNotch circuit.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Hideho Okada, Ph.D.