In cancer therapy, bispecific antibody application in radioimmunotherapy refers to the therapy in which an antibody that targets tumor-associated antigen is used to deliver cytotoxic radiation to tumor cells. BsAbs are capable of binding two or more antigens/receptors at the same time or bringing two different targets together. This character makes BsAbs widely used in payload (drugs, radiolabels, or other small molecules) delivery. BsAb-mediated payload delivery is highly specific and sensitive for targets during delivery and is rapidly developing as a pretargeting method in radioimmunodetection and radioimmunotherapy.

Pretargeting Method for Radioimmunotherapy

Though malfunctioning and uncontrolled, tumor cells are still “self” cells. How to target tumor cells over the surrounding tissues is the main obstacle for radioimmunodetection and radioimmunotherapy. High selectivity and specificity guarantee high image resolution in radioimmunodetection, and better efficacy and low toxicity in radioimmunotherapy. Previously, radioactive monoclonal antibodies or antibodies fused with radioactive materials were used for such purposes. However, disadvantages of these drugs, such as low stability, high immunogenicity, and low affinity for tumor cells, limited their efficacy. The long-term and high-dose exposure of normal cells to radiation also leads to high toxicity. An alternative way is the pretargeting method, which separates the localization of the tumor (by a specific antibody) from the subsequent delivery of the radionuclide. In this method, radiation is not applied until excess free antibodies are cleared from the body.