Pressure-Enabled Drug Delivery (Pedd) of a Class C TLR9 Agonist in Combination With Checkpoint Inhibitor Therapy in a Pancreatic Cancer Murine Model

Background: Systemic immunotherapy has had limited clinical benefit in pancreatic ductal adenocarci-noma. This is thought to be due to its desmoplastic immunosuppressive tumor microenvironment in addition to high intratumoral pressures that limit drug delivery. Recent preclinical cancer models and early-phase clinical trials have demonstrated the potential of toll-like receptor 9 agonists, including the synthetic CpG oligonucleotide SD-101, to stimulate a wide range of immune cells and eliminate suppressive myeloid cells. We hypothesized that Pressure-Enabled Drug Delivery via Pancreatic Retrograde Venous Infusion of toll-like receptor 9 agonist would improve responsiveness to systemic anti-programmed death receptor-1 checkpoint inhibitor therapy in a murine orthotopic pancreatic ductal adenocarcinoma model. Methods: Murine pancreatic ductal adenocarcinoma (KPC4580P) tumors were implanted into the pancreatic tails of C57BL/6J mice and treated 8 days after implantation. Mice were assigned to one of the following treatment groups: Pancreatic Retrograde Venous Infusion delivery of saline, Pancreatic Retrograde Venous Infusion delivery of toll-like receptor 9 agonist, systemic anti-programmed death receptor-1, systemic toll-like receptor 9 agonist, or the combination of Pancreatic Retrograde Venous Infusion delivery of toll-like receptor 9 agonist and systemic anti-programmed death receptor-1 (Combo). Fluorescently labeled toll-like receptor 9 agonist (radiant efficiency) was used to measure uptake of the drug on day 1. Changes in tumor burden were evaluated by necropsy at 2 different time points, 7 and 10 days after toll-like receptor 9 agonist treatment. Blood and tumors were collected at necropsy 10 days after toll-like receptor 9 agonist treatment for flow cytometric analysis of tumor-infiltrating leukocytes and plasma cytokines. Results: All mice analyzed survived to necropsy. Site of tumor fluorescence measurements revealed 3-fold higher intensity fluorescence in Pancreatic Retrograde Venous Infusion delivery of toll-like re-ceptor 9 agonist compared to systemic toll-like receptor 9 agonist mice. Tumor weights were signifi-cantly lower in the Combo group compared to Pancreatic Retrograde Venous Infusion delivery of saline. Flow cytometry of the Combo group demonstrated significantly increased overall T-cell number, spe-cifically CD4+ T-cells, and a trend toward increased CD8+ T-cells. Cytokine analysis showed significantly decreased IL-6 and CXCL1.Conclusion: Pressure-Enabled Drug Delivery of toll-like receptor 9 agonist by Pancreatic Retrograde Venous Infusion with systemic anti-programmed death receptor-1 demonstrated improved pancreatic ductal adenocarcinoma tumor control in a murine pancreatic ductal adenocarcinoma model. These results support study of this combination therapy in pancreatic ductal adenocarcinoma patients and expansion of ongoing Pressure-Enabled Drug Delivery clinical trials.& COPY; 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).