Catumaxomab belongs to a novel generation of engineered monoclonal antibodies termed trifunctional (or Triomab®) antibodies [1
Triomabs are hybrid antibodies that carry different antigen binding domains derived from rat IgG2b and mouse IgG2a monoclonals. One binding site (specified by the mouse IgG2a chain chain) is designed to interact with a specific tumour-associated antigen, in catumaxomab's case EpCAM. The other catumaxomab antigen binding site interacts with CD3e (specified by the rat IgG2b chain) on polyclonal T lymphocytes (effector cells). Finally, the intact Fc region of the Triomab® interacts with Fcγ receptors on accessory cells (monocytes/macrophages, natural killer cells and dendritic cells). This combination of interactions enables the formation of a tri-cell complex composed of tumour cells, T cells and accessory cells and promotes the synchronous activation of a variety of immune effector mechanisms that ultimately mediate an enhanced anti-tumour response.