ABSTRACT
The EGF receptor (EGFR) HER3 is emerging as an attractive cancer therapeutic target due to its central position in the HER receptor signaling network. HER3 amplifies phosphoinositide 3-kinase (PI3K)-driven tumorigenesis and its upregulation in response to other anti-HER therapies has been implicated in resistance to them. Here, we report the development and characterization of RG7116, a novel anti-HER3 monoclonal antibody (mAb) designed to block HER3 activation, downregulate HER3, and mediate enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) via glycoengineering of the Fc moiety. Biochemical studies and X-ray crystallography revealed that RG7116 bound potently and selectively to domain 1 of human HER3. Heregulin binding was prevented by RG7116 at concentrations more than 1 nmol/L as was nearly complete inhibition of HER3 heterodimerization and phosphorylation, thereby preventing downstream AKT phosphorylation. In vivo RG7116 treatment inhibited xenograft tumor growth up to 90% relative to controls in a manner accompanied by downregulation of cell surface HER3. RG7116 efficacy was further enhanced in combination with anti-EGFR (RG7160) or anti-HER2 (pertuzumab) mAbs. Furthermore, the ADCC potency of RG7116 was enhanced compared with the nonglycoengineered parental antibody, both in vitro and in orthotopic tumor xenograft models, where an increased median survival was documented. ADCC degree achieved in vitro correlated with HER3 expression levels on tumor cells. In summary, the combination of strong signaling inhibition and enhanced ADCC capability rendered RG7116 a highly potent HER3-targeting agent suitable for clinical development.
Subject(s)
Antibodies, Monoclonal, Humanized/pharmacology , Glycoproteins/pharmacology , Receptor, ErbB-3/metabolism , Animals , Antibodies, Monoclonal, Humanized/immunology , Cell Line, Tumor , Cell Proliferation/drug effects , Crystallography, X-Ray , Down-Regulation/drug effects , Down-Regulation/immunology , Female , Glycoproteins/immunology , Humans , MCF-7 Cells , Mice , Mice, Inbred BALB C , Mice, Nude , Mice, SCID , Phosphorylation/drug effects , Proto-Oncogene Proteins c-akt/immunology , Proto-Oncogene Proteins c-akt/metabolism , Receptor, ErbB-2/immunology , Receptor, ErbB-2/metabolism , Receptor, ErbB-3/immunology , Xenograft Model Antitumor AssaysABSTRACT
In this study we present novel bispecific antibodies that simultaneously target the insulin-like growth factor receptor type I (IGF-1R) and epidermal growth factor receptor (EGFR). For this purpose disulfide stabilized scFv domains of the EGFR/ADCC antibody GA201 were fused via serine-glycine connectors to the C-terminus of the heavy (XGFR2) or light chain (XGFR4), or the N-termini of the light (XGFR5) or heavy chain (XGFR3) of the IGF-1R antibody R1507 as parental IgG1 antibody. The resulting bispecific IGF-1R-EGFR antibodies XGFR2, XGFR3 and XGFR4 were successfully generated with yields and stability comparable to conventional IgG1 antibodies. They effectively inhibited IGF-1R and EGFR phosphorylation and 3D proliferation of H322M and H460M2 tumor cells, induced strong down-modulation of IGF-1R as well as enhanced EGFR down-modulation compared to the parental EGFR antibody GA201 and were ADCC competent. The bispecific XGFR derivatives showed a strong format dependent influence of N- or C-terminal heavy and light chain scFv attachment on ADCC activity and an increase in receptor downregulation over the parental combination in vitro. XGFR2 and XGFR4 were selected for in vivo evaluation and showed potent anti-tumoral efficacy comparable to the combination of monospecific IGF-1R and EGFR antibodies in subcutaneous BxPC3 and H322M xenograft models. In summary, we have managed to overcome issues of stability and productivity of bispecific antibodies, discovered important antibody fusion protein design related differences on ADCC activity and receptor downmodulation and show that IGF-1R-EGFR antibodies represent an attractive therapeutic strategy to simultaneously target two key components de-regulated in multiple cancer types, with the ultimate goal to avoid the formation of resistance to therapy.
Subject(s)
Antibodies, Bispecific/immunology , Antibodies, Bispecific/therapeutic use , ErbB Receptors/immunology , Immunoglobulin G/immunology , Immunoglobulin G/therapeutic use , Neoplasms/therapy , Receptor, IGF Type 1/immunology , Animals , Antibodies, Bispecific/genetics , Antibody Affinity , Cell Line , Cell Line, Tumor , Cell Proliferation/drug effects , Cloning, Molecular , ErbB Receptors/metabolism , Female , Humans , Immunoglobulin G/genetics , Immunotherapy , Mice , Mice, SCID , Models, Molecular , Neoplasms/immunology , Neoplasms/metabolism , Phosphorylation/drug effects , Protein Engineering , Receptor, IGF Type 1/metabolism , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Recombinant Proteins/therapeutic use , Single-Chain Antibodies/genetics , Single-Chain Antibodies/immunology , Single-Chain Antibodies/therapeutic useABSTRACT
We have compared the transcriptional profile of large cell lung tumor cell lines NIH-H460 and H460-M making use of the Affymetrix GeneChip system. H460-M is derived from NIH-H460 and displays enhanced experimental and spontaneous metastasis in nude mice. Out of the 12,600 genes investigated, 73 (0.6%) were up-regulated and 114 (0.9%) were down-regulated on the basis of the scoring criteria. We have classified the de-regulated genes according to the following categories: immune response, enzymes, modulation of transcription, signal transduction, cytoskeleton/adhesion and extracellular matrix associated proteins, cell-cycle/apoptosis, transporters and 'others'. Among the remarkable features of this system are the up-regulation of the steady-state mRNA levels of neuroendocrine markers such as neurotensin (NTS), neuroendocrine-specific protein (NSP), neural cell adhesion molecule 1 (NCAM1) and gamma-aminobutyric acid B-type receptor (GPR51) in cell line H460-M. Semaphorin 3B (SEMA3B) was dramatically down-regulated in cell line H460-M and emerged as the most interesting gene for target validation.
