Dual Mode of Action of a Human Anti-Epidermal Growth Factor Receptor Monoclonal Antibody for Cancer Therapy

Abstract

Epidermal growth factor receptor (EGF-R) overexpression is common in a large number of solid tumors and represents a negative prognostic indicator. Overexpression of EGF-R is strongly tumor associated, and this tyrosine kinase type receptor is considered an attractive target for Ab therapy. In this study, we describe the evaluation of mAb 2F8, a high avidity human mAb (IgG1κ) directed against EGF-R, developed using human Ig transgenic mice. mAb 2F8 effectively blocked binding of EGF and TGF-α to the EGF-R. At saturating concentrations, 2F8 completely blocked EGF-R signaling and inhibited the in vitro proliferation of EGF-R-overexpressing A431 cells. At much lower concentrations, associated with low receptor occupancy, 2F8 induced efficient Ab-dependent cell-mediated cytotoxicity (ADCC) in vitro. In vivo studies showed potent antitumor effects in models with A431 tumor xenografts in athymic mice. Ex vivo analysis of the EGF-R status in tumor xenografts in 2F8-treated mice revealed that there are two therapeutic mechanisms. First, blocking of EGF-R signaling, which is most effective at complete receptor saturation and therefore requires a relatively high Ab dose. Second, at very low 2F8 receptor occupancy, we observed potent antitumor effects in mice, which are likely based on the engagement of immune effector mechanisms, in particular ADCC. Taken together, our findings indicate that ADCC represents an important effector mechanism of this Ab, which is effective at relatively low dose.

Lapatinib, a HER2 tyrosine kinase inhibitor, induces stabilization and accumulation of HER2 and potentiates trastuzumab-dependent cell cytotoxicity

“…Lapatinib-induced accumulation of inactive HER2 leads to increased ADCC in vitro Engagement of immune-effector systems is one of the main therapeutic mechanisms of anti-HER antibodies (Clynes et al, 2000;Bleeker et al, 2004;Gennari et al, 2004). Thus, we wanted to test whether the accumulation of HER2 induced by lapatinib could increase trastuzumab-dependent cell cytotoxicity in MCF-7HER2 cells by increasing the number of antibody binding sites at the cell surface.…”

High Turnover of Tissue Factor Enables Efficient Intracellular Delivery of Antibody–Drug Conjugates

“…The EGFR mAbs zalutumumab and nimotuzumab (Biacon) both inhibit ligand-binding and EGFR-driven proliferation. Zalutumumab does so with high affinity (23), whereas nimotuzumab blocks EGF binding with low affinity (24).…”

Efficient generation of stable bispecific IgG1 by controlled Fab-arm exchange

“…To find such mutations, residues L368, K370, D399, F405, and Y407, surrounding R409 in the opposite CH3 domain (Fig. 1C), were individually mutated (into all natural amino acids except C and P) and introduced as single point mutations into human IgG1 monoclonal antibody (HuMab) 2F8 (26), directed against epidermal growth factor receptor (EGFR). The resulting proteins were mixed with equimolar amounts of an IgG1-K409R version of HuMab 7D8 (27), directed against the CD20 antigen, and incubated for 90 min at 37°C in PBS supplemented with 25 mM 2-MEA.…”