Abstract 2586: Adnectins as a platform for multi-specific targeted biologics: A novel bispecific inhibitor of EGFR and IGF-IR growth factor receptors

Abstract

The epidermal growth factor receptor (EGFR) and insulin-like growth factor receptor-1 (IGFR) are transmembrane receptor tyrosine kinases that mediate proliferative and invasive cell signaling in cancer. Inhibition of either receptor reduces tumor growth in both mouse models and in human clinical studies. Blocking the EGFR pathway can induce compensatory activation of the IGFR pathway to drive tumor growth and IGFR inhibition can result in activation of EGFR signaling in preclinical models. Therefore, blocking both receptors simultaneously may achieve superior efficacy to blocking either pathway alone. We developed individual optimized Adnectins™ specific for blocking either EGFR or IGFR signaling and engineered them into a single protein that linked both Adnectins together to construct a bi-specific Adnectin targeting the EGFR and IGFR (EI-tandem). The bifunctional molecule blocked activation of EGFR and IGFR, inhibited both EGF and IGF-induced down-stream cell signaling (MAPK and AKT pathways) and was antiproliferative in human cancer cell lines. Potency of the EI-tandem was comparable to anti-EGFR and anti-IGFR antibodies. The EI-tandem demonstrated a synergistic inhibition of IGFR phosphorylation and down-stream cell signaling compared to Adnectins specific for only EGFR or IGFR alone. Although Adnectins bound to the EGFR at a site distinct from the clinically approved anti-EGFR antibodies cetuximab, panitumumab and nimotuzumab, they still blocked binding of EGF to the EGFR. PEGylated EI-tandem inhibited the growth of human tumor xenografts driven by both EGFR and IGFR signaling, degraded EGFR and IGFR, and reduced phosphorylation of EGFR in tumors. Treatment of mice with EI-tandem caused increases in levels of the circulating ligands TGFα and IGF1 resulting from blockade of their respective receptors and provided convenient soluble biomarkers of target suppression. These results show that a bifunctional Adnectin can confer improved biological activity compared to monospecific biologics in tumors where growth is driven by multiple growth factors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2586.

A fibronectin scaffold approach to bispecific inhibitors of epidermal growth factor receptor and insulin-like growth factor-I receptor

“…IGF-IR levels were not significantly reduced in the EI-Tandem treated cells, although tandems constructed from other EGFR-Adnectins were able to induce IGF-IR degradation. 33 A decrease in total EGFR was also detectable by immunocytochemical staining of DiFi cells after 48 h of treatment (Fig. 2D).…”

“…While the E#1-GS10-I-PEG EI-Tandem clone did not induce significant downregulation of IGF-IR in vitro, the I-GS10-E#4-PEG clone was a potent inducer of IGF-IR degradation in vitro and this may offer therapeutic advantages. 33 Biologic therapeutics are considered to be the new frontier for the pharmaceutical industry 48 and there is increasing interest in combining multiple biologics to treat cancer. However, combinations of biologics can be prohibitively expensive and are limited by the number of available biologics in the market.…”

Ligand-Targeted Drug Delivery

“…Thus, to achieve a high-affinity interaction with such featureless surfaces, larger ligands that can form many weak interactions covering a larger fraction of the receptor surface may be required. In an attempt to find such adaptable ligands, a variety of protein and nucleic acid scaffolds with stable 3-dimensional structures but readily mutated surfaces have been explored. − , Among the scaffolds to receive the greatest attention are nucleic acid aptamers, ,− antibody fragments, − avimers, − knottins, − affibodies, − Kunitz domains, , centyrins, − adnectins, − affilins, , anticalins, − darpins, − etc. (see Table ).…”