IL-3 NOVEL SYNNOTCH-CAR-BASED T-CELL THERAPY FOR BRAIN TUMORS

Abstract The development of safe and effective chimeric antigen receptor (CAR)T therapy for malignant gliomas, such as glioblastoma (GBM), must overcome multiple challenges, including on-target off-tumor toxicity, heterogeneity of antigen expression, and exhaustion of CART cells. To this end, we adopted a novel synthetic Notch (synNotch) receptor system and developed innovative T cell circuits that recognize tumor cells based on the “prime-and-kill” strategy. In this system, the first antigen, which is expressed exclusively on GBM cells (e.g., EGFRvIII), primes the T cells to induce expression of a CAR that recognizes IL-13Rα2 and EphA2, thereby eradicating GBM cells expressing either EphA2 or IL-13Rα2. We reported that EGFRvIII-synNotch-primed EphA2/IL-13Rα2 CAR (E-SYNC) are effectively but restrictedly activated by EGFRvIII as the GBM-specific signal, thereby leading to complete eradication of orthotopic patient-derived xenografts with heterogeneous EGFRvIII expression, without attacking EphA2/IL-13Rα2-positive cells outside of the central nervous system (CNS) (Choe J, Watchmaker PB et al. Sci. Transl. Med 2021; PMID: 33910979). To extend the utility of synNotch-CART-cells to patients whose tumors do not express EGFRvIII, such as pediatric brain tumors, we developed a new concept of priming the synNotch-CAR circuit by antigens that are restrictedly expressed on CNS cells but not on cells of non-CNS systemic organs. This should be safe because, within the CNS, EphA2 and IL-13Rα2 are expressed only on tumor cells, but not normal CNS cells. Through screening, we have found Brevican (BCAN), a proteoglycan localized to the neuronal and glial cell surface, as the most promising priming antigen. A single IV infusion of T-cells engineered with the α-BCAN synNotch → CAR (B-SYNC) circuit showed complete remission in both PDX and immunocompetent mouse models without attacking CAR antigen-positive cells outside of CNS with superior efficacy and CNS-homing compared to conventional, constitutively expressed CART-cells (Simic M., Watchmaker PB, et al. Science in press). These synNotch-CART cells were more efficacious than conventional EphA2/IL-13Rα2 CART cells, associated with excellent persistence, and more juvenile in phenotype than conventional CART cells. We recently opened the phase I study evaluating the E-SYNC T-cells in patients with GBM (NCT06186401).