Abstract 3751: Allogeneic EGFRvIII chimeric antigen receptor T cells for treatment of glioblastoma

Abstract

Glioblastoma multiforme (GBM) is a highly aggressive form of brain tumors with a 5-year survival rate of less than 10%. Standard-of-care combining radiation therapy with temozolomide only yields a median survival of 14.6 months and more effective therapeutic options to extend patient lives are urgently needed. EGFR variant III (EGFRvIII) is a tumor specific mutant of EGFR found in 25-30% of GBM but not expressed in healthy tissues. EGFRvIII is formed by an in-frame deletion of exons 2-7 of the wild-type EGFR which leads to removal of 267 amino acids in the extracellular domain of the receptor. The truncated receptor loses its ability to bind ligands but acquires constitutive kinase activity. The lack of normal tissue expression makes EGFRvIII an ideal target for developing CAR T therapy. Most CAR T therapies in clinical development use the patients’ own T cells for CAR T manufacturing. Our approach is to develop an “off-the-shelf” CAR-T treatment for GBM using healthy donor T cells with the TCR (T-cell receptor) disrupted to prevent graft-versus-host disease. This allogeneic approach could circumvent challenges faced by some patients due to limited availability and quality of their own T cells and rapid progress of their diseases, and has the potential to reduce the high cost associated with autologous CART therapy. Using phage panning and hybridoma approaches, we generated a series of humanized and fully human EGFRvIII antibodies with a wide range of affinities. Recombinant EGFRvIII protein binding by Biacore and FACS assays using EGFRvIII and EGFR wild-type expressing cells demonstrated that these antibodies are highly specific for EGFRvIII. The antibodies were converted to ScFvs and cloned into a CAR vector. Subsequently, EGFRvIII CARs were transduced into primary human T cells for functional studies. We developed a series of assays to evaluate CAR expression, degranulation activity and target dependent cytotoxicity. Our goal is to select CAR candidate that is safe, persistent and has potent target dependent cytotoxicity. Citation Format: Oi Kwan Wong, Mathilde Dusseaux, Jing-Tyan Ma, Melinda Au, Sophie Leduc, Joyce Chou, Jessica M. Yu, Marjorie Bateman, Thomas Pertel, Kevin C. Lindquist, Julianne Smith, Barbra Sasu, Shu-Hui Liu. Allogeneic EGFRvIII chimeric antigen receptor T cells for treatment of glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3751. doi:10.1158/1538-7445.AM2017-3751