Immunotoxin-αCD40 therapy activates innate and adaptive immunity and generates a durable antitumor response in glioblastoma models

D2C7-immunotoxin (IT), a dual-specific IT targeting wild-type epidermal growth factor receptor (EGFR) and mutant EGFR variant III (EGFRvIII) proteins, demonstrates encouraging survival outcomes in a subset of patients with glioblastoma. We hypothesized that immunosuppression in glioblastoma limits D2C7-IT efficacy. To improve the response rate and reverse immunosuppression, we combined D2C7-IT tumor cell killing with αCD40 costimulation of antigen-presenting cells. In murine glioma models, a single intratumoral injection of D2C7-IT+αCD40 treatment activated a proinflammatory phenotype in microglia and macrophages, promoted long-term tumor-specific CD8+ T cell immunity, and generated cures. D2C7-IT+αCD40 treatment increased intratumoral Slamf6+CD8+ T cells with a progenitor phenotype and decreased terminally exhausted CD8+ T cells. D2C7-IT+αCD40 treatment stimulated intratumoral CD8+ T cell proliferation and generated cures in glioma-bearing mice despite FTY720-induced peripheral T cell sequestration. Tumor transcriptome profiling established CD40 upregulation, pattern recognition receptor, cell senescence, and immune response pathway activation as the drivers of D2C7-IT+αCD40 antitumor responses. In order to determine potential translation, immunohistochemistry staining confirmed CD40 expression in human GBM tissue sections. These promising preclinical data allowed us to initiate a phase I study with D2C7-IT+αhCD40 in patients with malignant glioma (NCT04547777) to further evaluate this treatment in humans. Comparative gene expression analysis of RNA-seq data of post-treatment day 0 and day 3 of CT-2A-dmEGFRvIII-Firefly Luciferase (CT-vIII) brain tumors treated in vivo by convection-enhanced delivery with control, D2C7-IT, αCD40, and D2C7-IT+αCD40.