Abstract B056: Engineered T-cells, targeting overexpressed EGFR and EGFRvIII, produce complete remissions in a PDX model of human glioblastoma

Abstract Glioblastoma (GBM) is a highly aggressive brain tumor characterized by invasive growth, genetic heterogeneity and resistance to therapy. Alterations in the epithelial growth factor receptor (EGFR) are frequently detected in GBM, including gene amplifications, mutations and exon deletions, exemplified by the expression of EGFR variant III (EGFRvIII). To target both wild-type and EGFRvIII, we generated the humanized antibody A10, which reacts with the 287-302 loop that is fully exposed on the extracellular domain of EGFRvIII and conditionally exposed on cells expressing gene-amplified EGFR. However, A10 showed little or no reactivity for cells expressing normal levels of wild type EGFR. We engrafted antibody fragments derived from A10 on to ARTEMIS® Cell Receptor Platform, which introduces two separate receptors into engineered T cells to provide activation and co-stimulatory signals. Specifically, the A10 antigen-binding fragment (Fab) was fused to the N-terminus of a γδTCR-signaling domains (A10-AbTCR) while the A10 single chain variable fragment (scFv) was fused to a costimulatory signaling receptor (A10-CSR). The resulting A10 ARTEMIS® T cells were cytotoxic for tumor cell lines displaying amplified or overexpressed EGFR and EGFRvIII. Further, glioblastoma PDXs were sensitive to A10 ARTEMIS® T cell killing. This prompted an in vivo evaluation in EGFR-driven cancers. GBM39 PDX tumors (expressing amplified EGFRvIII) were implanted into the brains of NSG mice. Mice received one or two infusions. Treatment with one infusion of A10 ARTEMIS® cells resulted in prolonged survival of tumor bearing mice with 40 % of mice were long-term survivors (74 days) compared to a median survival of 32 days (control) or 52 days (mock T-cells). For mice receiving two A10 ARTEMIS® T cell infusions, there was 100% survival of mice beyond 60 days, while all control and mock treated mice were dead by 28 days. Further, treatments of EGFR-amplified MDA-MB-468 tumors resulted in complete tumor regression with one treatment of A10 ARTEMIS® cells. Thus, this new format of A10 engineered T-cells appears to be a particularly promising for treating cancers with high levels of EGFR or EGFRvIII including GBM. Citation Format: Antonella Antignani, Danielle Burgenske, Guangyan Xiong, Hongbing Zhang, Cheng Liu, Jann Sarkaria, David FitzGerald. Engineered T-cells, targeting overexpressed EGFR and EGFRvIII, produce complete remissions in a PDX model of human glioblastoma [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr B056.