Differentiation between the EGFR antibodies necitumumab, cetuximab, and panitumumab: In vitro biological and binding activities.

e13030 Background: The monoclonal antibodies cetuximab (chimeric IgG1), necitumumab (human IgG1), and panitumumab (human IgG2) competitively inhibit ligand binding to epidermal growth factor receptor (EGFR) in domain 3. These antibodies block ligand induced EGFR activation and downstream molecular signaling. Beyond protein backbone differences, further differentiation of these EGFR antibodies is an important area of investigation. Methods: The effect on the in vitro proliferation of DiFi human colorectal cancer cells was assessed by ATP luminescence. The binding of the antibodies to the soluble extracellular domain of EGFR was evaluated by ELISA and surface plasmon resonance (SPR). Inhibition of ligand induced EGFR activation and downstream signaling was evaluated utilizing electrochemiluminescence method. Finally, binding kinetics was analyzed by SPR using a capture method. Results: The necitumumab concentration producing a half-maximal anti proliferative response (IC50) in DIFI cells was comparable to t...