Abstract B013: Subcutaneous αCD40 injections near tumor-draining lymph nodes augment intratumoral antibody-toxin conjugate antitumor efficacy in glioblastoma model

Abstract Glioblastoma (GBM), the most aggressive primary brain tumor in adults, has a poor prognosis and is notoriously resistant to conventional treatments, including surgery, radiation, and chemotherapy. Given the limitations of these traditional therapies, immunotherapy, aiming to harness the body’s immune system to recognize and combat tumor cells, is being explored as an alternative approach for GBM. However, the immunosuppressive nature of the GBM microenvironment and the scarcity of intratumoral T cells pose significant challenges. A novel antibody-toxin conjugate (ATC), consisting of a truncated Pseudomonas exotoxin A and epidermal growth factor receptor (EGFR)-binding antibody fusion, selectively targets EGFR variants in GBM. In the clinic, the ATC demonstrated encouraging survival outcomes in selected patients, while in most patients, the efficacy of ATC was diminished by the immunosuppressive tumor microenvironment (TME). To counteract TME immunosuppression, we combined ATC with αCD40 costimulation of antigen-presenting cells. In glioma models, intratumoral delivery of αCD40 and ATC combination triggered durable antitumor immunity by killing tumor cells, activating microglia, reversing GAMM immune suppression, and increasing polyfunctional, tumor antigen-specific CD8 T cells. However, in the clinic, a single intratumoral dose of αCD40 may not be sufficient to overcome GBM immunosuppression, highlighting the need for subsequent systemic αCD40 administration to maintain immune activation. Recent studies have highlighted the role of the meningeal lymphatic system and deep cervical lymph nodes (DcLNs) in brain tumor immunity. Specifically, antigen-presenting cells and antigens can travel from the brain to DcLNs, activating T cells and triggering systemic antitumor responses, including the migration of activated T cells back to the brain. We hypothesized that subcutaneous cervical perilymphatic injections (CPLIs) of αCD40 near tumor-draining cervical lymph nodes (TDcLNs) could enhance the brain-lymphatic-immune axis and be administered repeatedly to counteract immunosuppression and improve ATC efficacy in clinical settings. Our findings revealed that, in a mouse glioma model, the combination of intratumoral ATC and αCD40 CPLIs resulted in a substantial increase in CD8+ T cells in the brain and along the meningeal lymphatic system (dura mater and TDcLNs). The combined treatment significantly prolonged survival in glioma-bearing mice compared to ATC monotherapy. These findings suggest that peri-lymphatic αCD40 delivery can significantly enhance the antitumor efficacy of ATC therapy, providing a promising strategy to overcome GBM immunosuppression and improve patient outcomes. This novel combination immunotherapy approach is currently being explored for GBM patients in the clinic. Citation Format: Anjali Barnwal, Hyunjung Min, Cristina Osorio, Edwige Edouard, Anthony Filiano, Annick Desjardins, Darell Bigner, Vidyalakshmi Chandramohan. Subcutaneous αCD40 injections near tumor-draining lymph nodes augment intratumoral antibody-toxin conjugate antitumor efficacy in glioblastoma model [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr B013.