An engineered bispecific, pentameric immunoglobulin M (IgM) monoclonal antibody directed against CD3, a T-cell surface antigen, and CD38, a human cell surface glycoprotein and tumor-associated antigen (TAA), with potential antineoplastic activity. IGM-2644 consists of ten CD38 binding sites and an anti-CD3epsilon single chain variable fragment (scFv) domain fused to a joining chain. Upon intravenous administration, anti-CD3/CD38 bispecific monoclonal antibody IGM-2644 targets and binds to both CD3 on T-cells and CD38 expressed on tumor cells. The resulting cross-linkage may trigger T-cell dependent cellular cytotoxicity (TDCC) and complement-dependent cytotoxicity (CDC) against CD38-expressing tumor cells. CD38, a type II transmembrane glycoprotein, is present on various immune cells and hematologic malignancies; its expression has been correlated with poor prognosis.