Abstract: The present inventors discovered novel multispecific antigen-binding molecules with excellent cellular cytotoxicity, which comprise a first domain comprising a first antigen variable region which binds to DLL3 and a second domain comprising a second antigen variable region which binds to T cell receptor complex. The present inventors prepared further bispecific antibodies, and assessed their T cell-dependent cell cytotoxicity (TDCC), and found that they also show strong TDCC activity. Since the molecules/antibodies of the present invention show a strong cytotoxicity against cells expressing DLL3, novel pharmaceutical compositions comprising the molecules/antibodies for treating or preventing various cancers associated with DLL3 can be provided.

Abstract: The invention relates to cytosol penetrating antigen binding molecules containing cell surface antigen binding domains, cytosolic antigen binding domains and cytosol penetrating domains; pharmaceutical compositions comprising said antigen binding molecules; methods of delivering said antigen binding molecules specifically into cytosols of target cells; methods of depleting, suppressing or activating cytosolic antigens specifically in target cells by using said antigen binding molecules; and pharmaceutical compositions for preventing or treating diseases in patients comprising said antigen binding molecules. The invention also relates to cytosol penetrating antigen binding molecules containing cytosol penetrating domains and Fc regions, wherein the Fc regions comprising one or more amino acid modifications that enhance multimerization of said cytosol penetrating antigen binding molecules.