Definition

A radioimmunoconjugate composed of ABT-806, a humanized immunoglobulin G1 (IgG1) monoclonal antibody directed against the epidermal growth factor receptor (EGFR), labeled with the radioisotope zirconium Zr 89, with potential use as an imaging agent upon positron emission tomography (PET). Upon administration of zirconium Zr 89 anti-EGFR monoclonal antibody ABT-806, the antibody moiety binds to a specific EGFR epitope of either the wild-type or the variant III mutant (EGFRvIII; de2-7 EGFR; DEGFR) on tumor cells. Upon PET imaging, EGFR-expressing tumor cells can be visualized and assessed. This may result in the quantification of EGFR-expressing tumor cells, an assessment of the expected response to treatment with ABT-806 and the selection of patients that would respond to ABT-806. ABT-806 is the humanized version of chimeric monoclonal antibody 806. EGFR, a receptor tyrosine kinase overexpressed on the cell surfaces of many tumor cell types, plays a key role in tumor cell proliferation.