In the tumor microenvironment, dying cells release ATP which gets converted to AMP by CD39. AMP is subsequently converted to immunosuppressive adenosine by the extracellular 5'-nucleotidase CD73. CD73 is linked to the cell surface by a GPI-anchor and can be released into the plasma as soluble CD73. In order to lower extracellular levels and reverse the immunosuppressive activity of adenosine in the tumor microenvironment, an antibody was researched and discovered that antagonizes CD73 function. INCA00186 is a humanized monoclonal antibody that binds and inhibits CD73 function. INCA00186 binds human and cynomolgus CD73 with sub-nanomolar affinity, and inhibits CD73 enzymatic activity in a manner that is non-competitive for AMP binding. In functional studies, INCA00186 restored effector T cell proliferation in the presence of high concentrations of AMP. In the human A375 melanoma tumor model in CD34+ humanized NSG mice, INCA00186 decreased levels of cell surface CD73, displayed high receptor occupancy on tumor cells, and decreased CD73 activity in ex vivo assays of tumor homogenates. In the human MDA-MB-231 breast tumor model in CD34+ humanized NSG mice, INCA00186 decreased intratumoral adenosine concentrations. In combination with the novel A2A/A2B adenosine receptor antagonist INCB106385, INCA00186 synergistically restored effector T cell activity as measured by interferon gamma (IFNγ) production in the presence of high concentrations of AMP. In the human MDA-MB-231 breast tumor model in CD34+ humanized NSG mice, combination treatment with INCA00186 and INCB106385 controlled tumor growth significantly better than monotherapies. In summary, the data presented in this study demonstrates that INCA00186 is a potent CD73 antagonist and effectively attenuates adenosine induced immunosuppression in the tumor microenvironment. INCA00186 demonstrated anti-tumor immunity alone and, to a greater extent, in combination with the A2A/A2B adenosine receptor antagonist INCB106385.

Citation Format: Shaun Stewart, Rebecca Buonpane, Jing Zhou, Michael Hansbury, Michael Smith, Hui Wang, Lu, Bin Su, Rahel Awdew, Cheng-Yen Huang, Ashwini Kulkarni, Shane Harvey, Arpita Mondal, Steve Wang, Christina Stevens, Michael Pratta, Elham Behshad, Alexandra Fanuka, Xiaodi Ren, Holly Koblish, Horacio Nastri, Patrick Mayes. Discovery and preclinical characterization of INCA00186, a humanized monoclonal antibody antagonist of CD73, as a cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB174.