A small molecule immune checkpoint inhibitor of the adenosine A2A receptor (ADORA2A) with potential antineoplastic activity. Upon oral administration, adenosine-A2A receptor antagonist CPI-444 binds to adenosine A2A receptors expressed on the surface of immune cells, including T-lymphocytes, natural killer (NK) cells, macrophages and dendritic cells (DCs). This prevents tumor-released adenosine from interacting with the A2A receptors on these key immune surveillance cells, thereby abrogating adenosine-induced immunosuppression in the tumor microenvironment. This may stimulate anti-tumor immune responses, resulting in tumor regression.