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Abstract 2718: Preclinical development of humanized CD39 and CD73 blocking antibodies targeting the ATP/adenosine immune checkpoint pathway for cancer immunotherapy

Within the tumor microenvironment, adenosine causes immune suppression and dysregulation of immune cell infiltrates resulting in tumor spreading. Adenosine accumulation results from the hydrolysis of extracellular immunoactivating ATP and ADP into AMP by the CD39 (ENTPD1) ectonucleotidase. AMP can be further hydrolyzed into immunosuppressive Adenosine (Ado) by CD73 (NT5E), a cell membrane ectonucleotidase of the NTPDase family.The immunosuppressive role of CD39 expressed on both Tregs and tumor cells has been demonstrated in several reports. Conversely, CD73 expression in the tumor environment has been associated with poor disease outcome and/or with a pro-metastatic phenotype. Blockade of CD39 and CD73 may promote anti-tumor immunity directly by accumulating immunostimulating ATP for CD39 and indirectly by reducing adenosine accumulation for both targets.In cancer tissue, using IHC and flow cytometry analyses, we observed that while CD73 is often expressed by tumor cells, CD39 is more frequently up-regulated on tumor infiltrating cells compared to PBMC or adjacent non-tumor tissue. We next describe the discovery and preclinical development of a unique anti-huCD39 blocking antibody and of an anti-human CD73 antibody for cancer immunotherapy. These anti-CD39 and anti-CD73 antibodies specifically bind with high affinity to huCD39 and huCD73 proteins, respectively. They potently inhibit enzyme activity of their respective targets under their soluble and membrane-associated forms, without inducing down-modulation of these enzymes expressed at the cell surface. Innate9s antibodies efficiently reverse Ado-mediated T cell suppression in vitro in presence of ATP and both CD39- and CD73-expressing immune cells and additionally exhibit unique features. The anti-CD39 Ab maintains high concentration of ATP in the extracellular compartment that enhances DC activation and subsequent T cell proliferation in vitro. The anti-CD73 blocking Ab exhibits a more potent ability to block soluble and membrane-associated CD73 enzyme activity than benchmark Abs currently in clinical development. Finally, in vivo blockade of ATP/Ado pathway in CD39ko mice resulted in improved anti-tumor efficacy of immunogenic cell death inducer chemotherapy and of immune checkpoint therapies, including PD1 and CTLA4.Taken together, these data support the clinical development of anti-CD39 and anti-CD73 neutralizing Abs for cancer immunotherapy, potentially in combination with chemotherapy or Immune Checkpoint therapy. The humanized anti-huCD39 and anti-huCD73 monoclonal antibodies are currently in preclinical development.The research leading to CD73 results were obtained within the TumAdoR collaborative consortium that received funding from the European Community9s Seventh Framework Program (FP7/2007-2013) under grant agreement n°602200. Citation Format: Ivan Perrot, Marc Giraudon Paoli, Severine Augier, Marilyne Royannez Blemont, Marion Gaudin, Frederic Bosco, Rachel Courtois, Stephane Delahaye, Diana Jecko, Nicolas Gourdin, Maryline Salin Agu, Cyril Perrier, Paul Ricaut, Aurelie Docquier, Stephanie Chanteux, Benjamin Rossi, Agnes Represa, Caroline Denis, Romain Remark, Cecile Bonnafous, Laurent Gauthier, Ariane Morel, Nathalie Bonnefoy, Jeremy Bastid, Yannis Morel, Carine Paturel. Preclinical development of humanized CD39 and CD73 blocking antibodies targeting the ATP/adenosine immune checkpoint pathway for cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2718.