DIPG-15. NOVEL CNS SENSING SYNNOTCH-CAR T CELLS FOR TARGETING DIFFUSE MIDLINE GLIOMA

Abstract

Abstract BACKGROUND Diffuse midline glioma (DMG), including Diffuse intrinsic pontine glioma (DIPG), is an aggressive brain tumor in children with limited treatment options. Recent developments of phase 1 clinical trials have shown early promise for chimeric antigen receptor (CAR) T cells in patients with DMG/DIPG. However, several barriers such as the absence of tumor-specific antigens, restricted trafficking to the tumor site, and poor persistence hinder the full therapeutic potential of CAR T cell therapy in DMG/DIPG. METHODS To safely target the glioma-associated antigens (GAAs) without attacking nomal tissues expressing the same antigens, we adopted a novel synthetic Notch (synNotch) receptor system and engineered T cell circuits employing a “prime-and-kill” strategy. In this system, a synNotch receptor recognizing the priming antigen, Brevican (BCAN), exclusively expressed on cells in the central nervous system (CNS) but not on non-CNS cells, locally induces the expression of a tandem CAR against GAAs, ephrin type A receptor (EphA2) and interleukin-13 receptor a2 (IL13Ra2), there by homogenously eliminating DMG/DIPG cells. RESULTS The α-BCAN synNotch⋄α-EphA2/IL-13Rα2 CAR (B-SYNC) T cells efficiently killed DMG/DIPG (BT-245, SF8628, SU-DIPGXIII, and SU-DIPGXVII) cells in vitro in the presence of priming cells (K562 cells expressing BCAN). Moreover, a single intravenous infusion of B-SYNC T cells significantly (P< 0.001) prolonged the survival of immunodeficient mice bearing aggressive, orthotopic SF8628 DIPG xenografts and completely eradicated the tumor in more than 50% (4/7) of mice. Strikingly, we observed excellent homing, priming, activation, and persistence of B-SYNC T cells in the brain stem of mice bearing SF8628 xenografts. In contrast, constitutively active α-EphA2/IL-13Rα2 CAR T cells or untransduced T cells demonstrated a failure to migrate to the brain stem and improve the survival of mice. CONCLUSIONS Collectively, our findings strongly support the development of clinical trials evaluating the efficacy of B-SYNC T cells in DMG/DIPG patients.