An orally bioavailable antagonist of both the immunomodulatory checkpoint molecules adenosine A2A receptor (A2AR; ADORA2A) and A2B receptor (A2BR; ADORA2B), with potential immunomodulating and antineoplastic activities. Upon administration, etrumadenant competes with tumor-released adenosine for binding to A2AR and A2BR expressed on numerous intra-tumoral immune cells, such as dendritic cells (DCs), natural killer (NK) cells, macrophages and T-lymphocytes. The binding of AB928 to A2AR and A2BR inhibits A2AR/A2BR activity and prevents adenosine-A2AR/A2BR-mediated signaling. A2AR/A2BR inhibition activates and enhances the proliferation of various immune cells, abrogates the adenosine-mediated immunosuppression in the tumor microenvironment (TME) and activates the immune system to exert anti-tumor immune responses against cancer cells, which leads to tumor cell killing. A2AR and A2BR, G protein-coupled signaling receptors, are expressed on the cell surfaces of numerous immune cells. Adenosine is often overproduced by tumor cells and plays a key role in immunosuppression and tumor cell proliferation.