A bispecific antibody directed against both the tumor-associated antigen (TAA) Claudin 6 (CLDN6; CLDN-6) and the T-cell surface antigen CD3, with potential immunostimulating and antineoplastic activities. Upon administration, anti-CLDN6/CD3 bispecific antibody XmAb541 bivalently binds to CLDN6 expressed on tumor cells and monovalently binds to CD3 expressed on T-cells. This activates and redirects cytotoxic T-lymphocytes (CTLs) to CLDN6-expressing tumor cells, which leads to enhanced CTL-mediated killing of CLDN6-expressing tumor cells. CLDN6, a tight-junction protein and embryonic antigen, is expressed on a variety of tumor cells but is not expressed on normal, healthy adult cells. The bivalent binding to CLDN6 and monovalent binding to CD3 by XmAb541 may increase selective targeting of CLDN6-overexpressing tumor cells.