Cetuximab is a chimeric (mouse/human) monoclonal antibody specific for EGFR, a protein expressed on a wide range of normal and neoplastic cell types. When EGFR binds to its ligand, EGF, the receptor dimerizes and signals through the MAPK pathway to induce cell division. Cetuximab blocks EGFR from binding to EGF, and is used in the treatment of a variety of cancers, including metastatic colorectal cancer and head and neck cancer.