515. Oncolytic Adenovirus Armed with Cytokines Enhances CAR-T Cell Efficacy in Pancreatic Tumor Model

Background: Chimeric antigen receptor T-cell (CAR-T) therapy has shown significant efficacy in hematological malignancies, however, the efficacy against solid tumors remains limited. Immunosuppression caused by tumor microenvironment or poor infiltration of transferred T cells can restrict T cell efficacy. We propose that oncolytic Adenovirus (O-Ad) armed with cytokines improves the efficacy of adoptive T cell therapy by modulating the tumor environment. Aim: Here we aimed to study if O-Ad armed with cytokines can 1) cause direct lysis of pancreatic cancer cells, 2) enhance killing by CAR-T cells. 3) enhance infiltration and persistence of CAR-T cells in the context of solid tumors. Methods: We targeted pancreatic tumor cell lines by mesothelin specific CAR-T cells (SS1-BBz CAR-T) in combination with O-Ad; Adv-5/3-d24-IL2 or Adv-5/3-d24-TNF-IL2, which consist of an adenovirus serotype 5 nucleic acid backbone, a serotype 5/3 chimeric fiber knob, a 24-bp deletion (d24) in the Rb binding constant region 2 of E1 promoter, an E2F tumor specific promoter and cytokines (interleukin 2 or tumor necrosis factor alpha or both). Results: Pancreatic tumor cell lines used in this study; ASPC1, BXPC3, Capan2 expressed the Adv-serotype 3 receptor, DSG2. We also confirmed that O-Ad does not have adverse effects on T cell viability and proliferation even at high titer (1,000vp/cell) in an in vitro assay. To look at the efficacy of the O-Ad and CAR-T combination, we performed a killing assay. O-Ad clearly enhanced killing by CAR-T cells in luciferase based assay. We also used xCELLigence real time cell analyzer (RTCA) for kinetic analysis of killing. In combination with O-Ad, more rapid killing kinetics by CAR-T cells were observed especially in lower E:T ratio. To look at the impact of the combination in vivo, subcutaneous ASPC1-CBG-GFP in NSG mice were treated with CAR-T alone or in combination with intra-tumoral injection of O-Ad. O-Ad showed significant synergy with CAR-T in luciferase based photon assay. And higher number of T cells was observed in spleen in the O-Ad armed with IL2 combination group. Conclusions: These results suggest that combination therapy of O-Ad armed with cytokine(s) and CAR-T cells is effective against solid tumors by enhancing T cell activity.