A fully human monoclonal antibody directed against the cell surface receptor CD39 (cluster of differentiation 39; ectonucleoside triphosphate diphosphohydrolase-1; NTPDase1; ENTPD1), with potential immunomodulating and antineoplastic activities. Upon administration, anti-CD39 monoclonal antibody SRF617 specifically binds to the CD39 antigen, thereby preventing the conversion and degradation of adenosine triphosphate (ATP) to adenosine monophosphate (AMP). This leads to an increase in the extracellular levels of immunogenic ATP and a decrease in the levels of immunosuppressive adenosine within the tumor microenvironment (TME). A high level of ATP increases pro-inflammatory cytokine levels and promotes both T-cell proliferation and the stimulation of dendritic and other myeloid-derived cells that are necessary for innate and adaptive immunity. CD39, a cell surface ectonucleosidase, is upregulated on tumor cells as an immune evasion strategy. Blocking its action may improve anti-tumor immune responses.