129P Computational approaches for enhancing the efficacy of cancer immunotherapy

Background: Pancreatic ductal adenocarcinoma (PDAC) has poor prognosis due to its late detection, high stromal content, and high relapse rate.Immunosuppressive tumor microenvironment creates a major challenge for PDAC immunotherapy requiring novel therapeutic approaches.Ad5/3-E2F-d24-vIL2 (vIL2-virus) is an engineered oncolytic adenovirus (OAd) encoding a variant IL-2 cytokine.vIL-2 expression leads to preferential stimulation of natural killer cell and effector lymphocyte expansion over T regulatory cell proliferation.We propose to combine vIL2-virus to nab-paclitaxel, gemcitabine, and anti-PD-L1 to formulate an effective immunotherapeutic treatment for the traditionally therapy-resistant PDAC.Methods: PDAC cell lines treated with vIL2-virus, normal IL-2 virus, and unarmed virus were studied in mono-and co-cultures with macrophages and fibroblasts with flow cytometry profiling.Ex vivo experiments with real time cell killing assays were performed with clinical PDAC samples with concurrent flow cytometric and cytokine analysis.In vivo antitumor efficacy and safety of the combination were tested using an immunocompetent hamster model.Results: Increasing doses of gemcitabine, paclitaxel, and virotherapies led to increased PD-L1 expression on PDAC cells.Different OAds showed lower levels of PD-L1 upregulation on cancer cells when co-cultured with macrophages or fibroblasts, while macrophages and fibroblasts expressed PD-L1 considerably more than cancer cells after IFN-gamma stimulation.Macrophages upregulated PD-L1 and PD-L2 only around virus producing normal human IL-2.Experiments with clinical PDAC samples showed efficient cancer cell killing and cytotoxic immune cell changes by the combination therapy.In vivo, the triple therapy showed significantly improved tumor growth control and survival compared to chemotherapy with anti-PD-L1 or chemotherapy alone.Moreover, animals cured by the triple treatment showed increased resistance to tumor re-challenge.Conclusions: A combination of vIL2-virus, chemotherapy, and anti-PD-L1 is a promising strategy to overcome therapeutic limitations and effectively improve outcome in patients with PDAC.