Abstract A162: AB928, a dual antagonist of the A2aR and A2bR adenosine receptors, relieves adenosine-mediated immune suppression

Introduction: Adenosine, generated through the hydrolysis of extracellular adenosine monophosphate (AMP) by the ecto-nucleotidase CD73, is an important mechanism for immunosuppression in cancer development. Adenosine’s suppressive effects on immune cells are driven primarily through 2 of the 4 adenosine receptors, A2aR and A2bR. We have previously shown that adenosine-mediated suppression of T-cells can be blocked by the dual A2aR/A2bR antagonist, AB928. Herein, we show that AB928 is capable of relieving adenosine-mediated immune suppression using human in vitro cell cultures, advanced gene expression studies, and mouse syngeneic tumor models. Methods: The ability of AB928 to inhibit adenosine-mediated suppression of dendritic cell function in vitro was assessed using human monocyte-derived dendritic cells (moDC). Briefly, moDC were generated from freshly isolated CD14+ monocytes and differentiated with IL-4/GM-CSF for 7 days +/- adenosine/EHNA +/- AB928. Cells were then taken for NanoString analysis or placed in a mixed lymphocyte reaction (MLR) with CD4+ T-cells. Mouse syngeneic tumor studies were conducted using C57BL/6 mice inoculated with mouse mammary tumor AT3-OVA or melanoma B16-F10 cells. Tumors were subsequently treated with doxorubicin, oxaliplatin, or α-PD-1 +/- AB928. Results: Quantitative immunohistochemistry and analysis of public gene expression databases identified individual human tumor types that express high levels of adenosine processing enzymes. Most notably, non-small cell lung, renal, triple-negative breast, ovarian, colorectal, and gastroesophageal cancers were found to have the most favorable expression profiles for interventions targeting the adenosine pathway. Additionally, a high degree of correlation was found between transcript and protein measurements for CD73 (r2 = 0.87), illustrating the robust and reproducible nature of these techniques. In human in vitro cell cultures, moDC differentiated in the presence of adenosine showed a decreased ability to stimulate IFN-γ secretion from allogenic CD4+ T-cells in a MLR. This suppression was significantly reversed by addition of AB928. Next, multiplexed gene expression profiling using NanoString identified a cassette of 39 genes (>2.0 fold change, p Citation Format: Daniel DiRenzo, Dana Piovesan, Joanne Tan, Dillon H. Miles, Manmohan R. Leleti, Timothy Park, Ferdie Soriano, Bryan Handlos, Jenna L. Jeffrey, Ehesan U. Sharif, Brandon R. Rosen, Ulrike Schindler, Jay P. Powers, Matthew J. Walters. AB928, a dual antagonist of the A2aR and A2bR adenosine receptors, relieves adenosine-mediated immune suppression [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A162.