Bispecific monoclonal antibody
![Three types of bispecific antibodies: trifunctional antibody, chemically linked Fab and bi-specific T-cell engager (bottom row). Parts of the two different antibodies are coloured blue and green, respectively.](/Images/godic/202501/02/Engineered_monoclonal_antibodies.svg4841.png")
![The mechanism of action of a BsMAb, exemplified by catumaxomab, representing the first approved bispecific trifunctional antibody.](/Images/godic/202501/02/Catumaxomab_mechanism.svg4841.png")
A bispecific monoclonal antibody (BsMAb, BsAb) is an artificial protein that is composed of fragments of two different monoclonal antibodies and consequently binds to two different types of antigen. The most widely used application of this approach is in cancer immunotherapy, where BsMAbs are engineered that simultaneously bind to a cytotoxic cell (using a receptor like CD3) and a target like a tumour cell to be destroyed.