Catumaxomab

Catumaxomab contains epitopes for human CD3 and human epithelial cell adehesion molecule. It also has an intact immunoglobulin gamma constant region allowing it to bind to Fcγ I, IIa, and III receptors. By binding to CD3 on killer T cells, EpCAM on cancer cells, and Fcγ receptors on accessory immune cells like macrophages and NK cells, Catumaxomab brings immune cells into close proximity to EpCAM positive cancer cells. As a functional antibody, Catumaxomab also stimulates bound NK cells to release cytotoxic mediators like granzyme or bound macrophages to phagocytose the cancer cell. Phagocytosed cancer cells can be processed and have their antigens presented on major histocompatibililty complex II to activate helper T cells and contribute to humoural immunity and activation of killer T cells against EpCAM postive cancer cells. These macrophages also release inflammatory cytokines to attract additional immune cells to EpCAM positive tissues. When antibodies reach higher concentrations, they can stimulate complement-mediated cytotoxicity against EpCAM positive cancer cells. Bound killer T cells are activated resulting in proliferation and release of cytotoxic mediators resulting in antibody-dependent cell-mediated cytotoxicity against the cancer cell.