Monoclonal antibodies are laboratory-produced molecules engineered to serve as substitute antibodies that can restore, enhance or mimic the immune system’s attack on cancer cells. They are designed to bind to antigens that are generally more numerous on the surface of cancer cells than healthy cells, i.e. they are an immunotherapy. Tidutamab (XmAb®18087) is a tumor-targeted bispecific antibody that contains both an SSTR2 binding domain and a T-cell binding domain (CD3). An XmAb® bispecific Fc domain serves as the scaffold for the two antigen binding domains and confers long circulating half-life, stability and ease of manufacture on tidutamab. SSTR2 (somatostatin receptor 2) is an antigen highly expressed on some solid tumors, and engagement of CD3 by tidutamab activates T cells for highly potent and targeted killing of SSTR2-expressing tumor cells. Tidutamab is being evaluated in an ongoing Phase 1 study, which is enrolling patients with neuroendocrine tumors (NETs) and gastrointestinal stromal tumors (GISTs). As this is an SSTR targeted therapy, it follows that it is designed to work with well differentiated NETs which have not yet been well served by the introduction of immunotherapy.