Abstract B059: A novel pancreatic cancer mouse model with human immunity

Abstract The iRGD tumor-penetrating peptide delivers chemically linked drugs and even co-injected free drugs selectively to extravascular tumor tissue by targeting the αvβ5 integrin and neuropilin-1 (NRP1). A phase 1b clinical trial showed that iRGD appears to safely double the response rate of standard chemotherapy in patients with stage 4 pancreatic ductal adenocarcinoma (PDAC). We recently found that long-term iRGD treatment, even as a monotherapy, reduced regulatory T cells (Tregs) selectively in the PDAC tissue, which led to the expansion of CD8+ T cells and improved efficacy of immunotherapy in syngeneic PDAC mice. This finding led to the discovery of αvβ5 integrin being a novel targetable marker for tumor-resident Tregs in PDAC mice. Our recent data show that αvβ5 integrin+ Tregs are also present in human PDAC tissue. To study the significance of αvβ5 integrin+ human Tregs as a therapeutic target for iRGD, we developed a humanized PDAC (huPDAC) mouse model by transplanting human PDAC cells into human immune system (HIS) mice, which harbor fully matured human CD8+ and CD4+ T cells, natural killer T cells, B cells, and dendritic cells. The CD8+ T cells are human leukocyte antigen (HLA)-restricted and show a tumor antigen-specific response. We orthotopically implanted HLA-matched human PDAC cells into HLA-A2-positive HIS mice. Both an established human PDAC cell line (PANC-1) and patient-derived PDAC cells (0779E) successfully formed orthotopic tumors and liver metastases. The tumors were infiltrated by various human immune cells at a ratio similar to that found in patient-derived PDAC tissues. Of note, αvβ5 integrin+ human Tregs were also noted in the tumors but not in the spleen. iRGD monotherapy increased the ratio of CD8+ T cells per Tregs in the tumors, suggesting that iRGD will likely function as an immunomodulator in humans. The first patient was recently dosed in a new phase 1b/2a clinical trial (iLSTA Trial: ACTRN12623000223639), which assesses the safety and preliminary efficacy of iRGD in combination with standard-of-care chemotherapy and immunotherapy in locally advanced PDAC patients. Citation Format: Norio Miyamura, Kodai Suzuki, Richard A. Friedman, Aristidis Floratos, Yuki Kunisada, Kazuya Masuda, Andrew M. Lowy, Moriya Tsuji, Kazuki N. Sugahara. A novel pancreatic cancer mouse model with human immunity [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B059.