Abstract CT089: Irreversible electroporation (IRE) with intratumoral CD40 antibody increases T-cell reactivity to personalized neoantigens in locally advanced pancreatic cancer

Abstract Background: Irreversible electroporation (IRE) is a form of non-thermal tumor ablation in use for locally advanced PDAC. Our published preclinical data demonstrate that combination of IRE with local CD40 agonism induces systemic anti-tumor immune effects. Mitazalimab, a second-generation CD40 agonistic IgG1 mAb, had promising clinical activity when delivered systemically in combination with chemotherapy in metastatic PDAC. Methods: We are conducting a phase I dose-escalation study of mitazalimab injected intratumorally at the time of surgical IRE in patients with locally advanced PDAC after standard of care chemotherapy (NCT06205849). Primary endpoints are the rates of dose limiting toxicities and adverse events. Secondary endpoints are progression-free and overall survival. Candidate neoantigens (NeoAg’s) are identified by profiling nucleic acids derived from tumor biopsies obtained intraoperatively prior to IRE using our Identification-Prioritization-Validation (IPV) bioinformatic pipeline. Peptides representing prioritized mutations are synthesized. Peripheral blood mononuclear cells are collected pre- and 12-weeks post-treatment to evaluate NeoAg-specific T-cell reactivity using ELISPOT for interferon-gamma. “Hits” were peptides with spots > 2 SD above negative control peptides. Results: We have enrolled eight patients since the study opened in September 2024. Pre- and post-treatment ELISPOT assays have been completed for 6 patients, and all 6 demonstrated NeoAg-specific T-cell reactivity. For most of the validated NeoAg’s, reactivity was either newly detected or increased post-treatment, but reactivity to some NeoAg’s decreased with treatment. The total number of recognized NeoAg’s was increased in post- vs pre-treatment samples for 5/6 patients assessed. Conclusions: Unbiased, personalized IPV analysis confirms the presence of NeoAg-specific responses against multiple mutations, which are diversified after treatment with IRE and CD40 agonism. The evaluation of additional patients and correlation with clinical outcomes are ongoing. Citation Format: Spencer Mirabile-Brightman, Bjoern Peters, Himangshu Sonowal, Zachary Berman, Zev Wainberg, Aaron Miller, Karen Messer, Jiayu Chen, Yago Pico de Coana, Peter Ellmark, Stephen Schoenberger, Rebekah R. White. Irreversible electroporation (IRE) with intratumoral CD40 antibody increases T-cell reactivity to personalized neoantigens in locally advanced pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr CT089.