Abstract 4626: Application of IgDARTs™ designed for the simultaneous targeting of EGFR and IGF1R exhibit potent anti-tumor activity

Abstract

Abstract Introduction: EGFR and IGF1R are implicated in the tumorigenesis of a broad panel of human cancers. Both receptors share common downstream pathways. Blocking the signaling pathway of either receptor can lead to compensatory activation of the other receptor pathway. In consequence, dual targeting of both molecules should lead to enhanced anti-tumor activity. The generation of a bi-specific, antibody-based molecule allows targeting both receptor pathways simultaneously with a single agent. We previously described Fv-based bi-specific DART® (Dual-Affinity Re-Targeting) molecules for effector cell recruitment to specific tumor targets (Johnson et al., 2010 and Moore et al., 2011). Here we introduce the IgDART, a novel bi-specific IgG like antibody format anchored in the DART platform that supports the incorporation of two independent Fv while retaining an intact Fc region. We chose the EGFR-IGF1R pathways to demonstrate the IgDARTs potency in simultaneous targeting multiple signaling pathways in cancer cells. Methodology: Independent EGFRxIGF1R IgDART molecules comprising varying EGFR and IGF1R Fv regions were expressed in CHO cells, efficiently assembled and purified to homogeneity. IGF1R mAb specificities with different IGF1R binding and anti-cancer properties were evaluated to determine how effectively that range in properties could be supported in the IgDART structure. The binding properties of the IgDART molecules were evaluated on a cellular and protein level. The biological activity was determined across a panel of cell lines derived from human colon, lung, pancreatic, gastric, renal and breast cancer. Results: Analyses of the EGFRxIGF1R IgDART binding properties revealed they maintain those exhibited by the parental mAbs. This maintenance of binding properties was also reflected in the ability of independent EGFRxIGF1R IgDART molecules to correspondingly block growth of cancer cell lines dependent on either the EGFR or IGF1R growth pathways. A subset of colon cancer cell lines were identified that were particularly sensitive to the combined EGFR and IGFR growth inhibition by the EGFRxIGFR IgDARTs in a dose-dependent manner. Consistent with the relative activity of the parental mAbs, the EGFRxIGF1R IgDARTs display corresponding effects on ligand dependant receptor activation and degradation, as well as inhibition of downstream signaling events as determined in multiplexed assays. Conclusion: The data support the utility of the IgDART platform for targeting the EGFR and IGF1R pathways. The interchangeable nature of the IgDART architecture makes it ideal for building molecules that simultaneously interfere with two independent signaling receptors with oncogenic potential.