Development of human B7H3/IL13Ra2 bispecific armored CAR-T for treatment of glioblastoma.

Abstract

2056 Background: Glioblastoma (GBM) remains a highly lethal malignancy driven by infiltrative growth, molecular complexity, immune evasion, and therapeutic resistance. The limited efficacy of current treatments reflects antigen heterogeneity, an immunosuppressive tumor microenvironment, and restricted delivery across the blood–brain barrier with targeted therapy. Although earlier CAR-T therapies demonstrated preliminary activity in GBM, durable efficacy remains elusive. We have developed EPC-003, a fully human bispecific B7-H3/IL13Rα2 CAR-T engineered with a multi-mechanism armor to mitigate antigen heterogeneity, modulate the tumor microenvironment, and enhance persistence via central memory T-cell enrichment. Methods: Human anti-IL13Rα2, anti-B7-H3, and anti-PD-L1 scFvs were discovered from proprietary human B-cell libraries using mRNA display platform. A multi-mechanism armor was engineered by fusing the anti-PD-L1 scFv to a fine-tuned, immune cell-type specific IL-2 variant, identified through the unique cytokine engineering platform. These binding and functional modules were systematically optimized to generate EPC-003, a bispecific tandem CAR targeting IL13Rα2 and B7-H3 and incorporating a secreted multi-mechanism armor. CAR mechanisms, anti-tumor activity, and preclinical toxicity were evaluated. A proprietary clinical manufacturing process was established to produce a central memory T cell enriched CAR-T product. Results: The secreted armor of EPC-003 suppressed regulatory T-cell activation while selectively activating central memory T-cells, with the potential to enhance CAR-T cell persistence. In a 7-day G-Rex manufacturing process, EPC-003 demonstrated promising druggability with robust and reproducible CAR expression, and the proprietary cytokine cocktail consistently enriched the product to >65% central memory CAR-T cells. In orthotopic GBM models, intracranial administration of EPC-003 (0.4 × 10⁶ and 1.2 × 10⁶ CAR-T cells) induced tumor regression and showed dose-dependent anti-tumor activity. In preclinical toxicity studies, EPC-003 exhibited a favorable safety profile, with no body weight loss, cytokine release syndrome, or systemic clinical signs. No treatment-related pathological changes were observed across 25 examined organs. Immunohistochemistry revealed no evidence of brain hemorrhage in treated groups, with minimal monocyte infiltration in the pia mater observed only at the high dose. Conclusions: EPC-003, a multi-mechanism armored bispecific CAR-T, demonstrated favorable preclinical safety, developability, robust anti-tumor activity, and potential durability. These data support its advancement into an investigator-initiated clinical trial for the treatment of glioblastoma.