Humanized bi-specific antibody shows potent activity in patient-derived xenograft models of glioblastoma

Abstract BACKGROUND Advancements in bioengineering have allowed bispecific Abs to develop with therapeutic applications in immuno-oncology. Here we describe a fully humanized bispecific t cell engager (BiTE) that binds the GBM-associated antigen interleukin 13 receptor alpha 2 (IL13Rα2) and the T Cell receptor CD3 epsilon (CD3ε) to elicit an anti-tumor immune response in patient-derived models of GBM. METHODS In vitro, BiTE-mediated activation of T Cells was assessed via flow cytometry as measurements of T cell activation markers CD25 and CD69 and cytokines IFNγ and TNFα. BiTE-directed T cell-mediated cytotoxicity was assessed in GBM 6 and GBM12patient-derived xenograft lines. In vivo, GBM6 patient-derived xenograft cells were intracranially implanted in NSG-MHC I/II DKO mice, reconstituted with HLA-matched donor peripheral blood lymphocytes (PBMC), and subsequently treated with 2.5 mg/kg BiTE via i.p. injection x 4 days/week of therapeutic BiTE for three weeks. Animals were followed for survival, and the brains of long-term survivors were analyzed for residual disease and T cell infiltration. RESULTS In vitro, BiTE potently activated T cells as determined by a high expression of CD25 and CD69 and the production of TNFα and IFNγ. BiTE also directed T cell-mediated cytotoxicity against GBM cells in a dose-dependent manner, with significant activity still seen in the low nanogram range. In vivo, BiTE significantly extended the survival of tumor-bearing animals in GBM6patient-derived xenograft models. Histological analysis of long-term surviving mice shows complete absence of tumor and robust presence of CD8+ T cells localized to the original site of tumor implantation. CONCLUSIONS Our data demonstrate the efficacy of humanized BiTE in patient-derived GBM models, and our results support the investigation of this novel therapeutic in a clinical trial setting.FUNDING: R01 NS122395-01 and R01 NS095642-01