Both the epidermal growth factor receptor (EGFR) and the insulin-like growth factor receptor (IGFR) have been implicated in the tumorigenesis of a variety of human cancers. Effective tumor inhibition has been achieved both experimentally and clinically with a number of strategies that antagonize either receptor activity. Here we constructed and produced an IgG-like fully human tetravalent bispecific antibody (BsAb) that targets both EGFR and IGFR, using two neutralizing human antibodies originally isolated from a phage display library. The BsAb not only retained the antigen-binding capacity of each of the parent antibodies, but also was capable of binding to both targets simultaneously as demonstrated by a crosslinking ELISA. Further, the BsAb effectively blocked both ligands, EGF and IGF, from binding to their respective receptors, and inhibited tumor cell proliferation as potently as a combination of both the parent antibodies. More importantly, the BsAb was able to completely block activation of several major signal transduction molecules, including Akt and p44/p42 MAP kinases, by both EGF and IGF, whereas each individual parent antibody was only effective in inhibiting those signal molecules activated by the relevant single growth factor. The BsAb molecules retained good antigen-binding activity after incubation with mouse serum at 37°C for up to 6 days. Taken together, our results underscore the benefits of simultaneous targeting multiple growth factor receptor pathways for more efficacious cancer treatment.
[Proc Amer Assoc Cancer Res, Volume 45, 2004]