A tri-specific T-cell engager and monoclonal antibody targeting CD38, a human cell surface glycoprotein and tumor-associated antigen (TAA), CD3, a T-cell surface antigen, and CD28, a T-cell specific surface glycoprotein and co-stimulatory molecule, with potential antineoplastic activity. Upon intravenous administration, anti-CD38/CD3/CD28 tri-specific monoclonal antibody SAR442257 targets and binds to CD3 and CD28 on T-cells and CD38 expressed on tumor cells. The resulting cross-linkage may trigger a potent cytotoxic T-lymphocyte (CTL) response against CD38-expressing tumor cells. In addition, SAR442257 can also directly target CD28 expressed on tumor cells, such as multiple myeloma cells, thereby enhancing the anti-tumor activity of this agent and allowing it to bind to tumor cells when CD38 is occupied by other antibodies. CD38, a type II transmembrane glycoprotein, is present on various immune cells and hematologic malignancies; its expression has been correlated with poor prognosis.