A human bispecific antibody directed against the tumor-associated antigen (TAA) human B-cell maturation antigen (BCMA; tumor necrosis factor receptor superfamily member 17; TNFRSF17) and another directed against the T-cell surface antigen CD3, with potential immunostimulating and antineoplastic activities. Upon administration, anti-BCMA/anti-CD3 bispecific antibody REGN5459 binds to both CD3 on cytotoxic T-lymphocytes (CTLs) and BCMA on BCMA-expressing tumor cells. This activates and redirects CTLs to BCMA-expressing tumor cells, leading to CTL-mediated killing of BCMA-expressing tumor cells. BCMA, a member of the tumor necrosis factor receptor superfamily that is specifically overexpressed on malignant plasma cells, plays a key role in promoting plasma cell survival.