Irreversible Electroporation + CD40 Agonism + TIGIT Blockade Improves Outcomes in Aggressive Orthotopic PDAC Model

Background Pancreatic ductal adenocarcinoma (PDAC) is an immunologically “cold” tumor with limited benefit from immune checkpoint inhibition. Irreversible electroporation (IRE) is a non-thermal local ablation therapy used in selected patients with advanced PDAC. In syngeneic orthotopic models, IRE plus intratumoral (IT) CD40 agonist antibody (CD40 Ab) showed anti-tumor immune effects and reduced liver metastases; this regimen is currently under clinical evaluation. TIGIT is an immune checkpoint that is highly co-expressed with PD-1 on infiltrating T cells in PDAC after IRE. Aims To evaluate whether systemic adjuvant TIGIT blockade (anti-TIGIT) improves outcomes after IRE+CD40 Ab in an aggressive orthotopic PDAC model. Methods Spontaneously metastasizing KPC46 PDAC organoids were implanted into the pancreatic tail of mice via laparotomy. When tumors reached approximately 7 mm, mice were randomized to sham laparotomy, IRE, IRE+CD40 Ab, sham+anti-TIGIT, IRE+anti-TIGIT, or IRE+CD40 Ab+anti-TIGIT (n=8-10/group). Immediately after IRE, CD40 Ab (50 µg) was administered IT once. Anti-TIGIT Ab (100 µg) was administered intraperitoneally every other day starting 48 hours post-IRE. Mice were euthanized on day 12 for assessment of tumor burden and immune profiling by flow cytometry. Survival cohorts included sham laparotomy, IRE, IRE+CD40 Ab, and IRE+CD40 Ab+anti-TIGIT. Results All IRE-treated groups showed smaller primary tumor volumes versus sham, with the greatest reduction after IRE+CD40 Ab+anti-TIGIT (Figure 1A). Flow cytometry demonstrated the largest reduction in regulatory T cells and the greatest increase in natural killer cells with triple therapy (not shown). These immune changes were associated with reduction in liver metastases on day 12 (Figure 1B). IRE+CD40 Ab+anti-TIGIT also improved survival over other groups with 22% complete responders (Figure 1C). Conclusion Adding systemic anti-TIGIT Ab to IRE+CD40 Ab improves local control, remodels the tumor immune microenvironment, reduces liver metastases, and prolongs survival. Ongoing experiments include rechallenging tumor-free surviving mice and comparison of anti-TIGIT to other immune checkpoint strategies.For image description, please refer to the figure legend and surrounding text.