This is a chimeric humanized IgG1 bispecific monoclonal antibody targeting delta-like ligand 3 (DLL3) and CD3. It is a first-in-class T-cell engager designed for the treatment of adults with extensive-stage small cell lung cancer (ES-SCLC) with disease progression on or after platinum-based chemotherapy. CD3 is expressed on the surface of T-cells, while DLL3 acts as an inhibitory ligand that suppresses Notch signaling and exhibits high expression levels across various SCLC disease stages and treatment statuses. The bispecificity of tarlatamab causes T-cell activation, the release of inflammatory cytokines, and lysis at DLL3-expressing cells.