Targeting Three Distinct HER2 Domains with a Recombinant Antibody Mixture Overcomes Trastuzumab Resistance

Abstract

HER2 plays an important role in the development and maintenance of the malignant phenotype of several human cancers. As such, it is a frequently pursued therapeutic target and two antibodies targeting HER2 have been clinically approved, trastuzumab and pertuzumab. It has been suggested that optimal inhibition of HER2 is achieved when utilizing two or more antibodies targeting nonoverlapping epitopes. Superior clinical activity of the trastuzumab plus pertuzumab combination in metastatic breast cancer supports this hypothesis. Because trastuzumab and pertuzumab were not codeveloped, there may be potential for further optimizing HER2 targeting. The study herein evaluated functional activity of anti-HER2 antibody combinations identifying optimal epitope combinations that provide efficacious HER2 inhibition. High-affinity antibodies to all four extracellular domains on HER2 were identified and tested for ability to inhibit growth of different HER2-dependent tumor cell lines. An antibody mixture targeting three HER2 subdomains proved to be superior to trastuzumab, pertuzumab, or a combination in vitro and to trastuzumab in two in vivo models. Specifically, the tripartite antibody mixture induced efficient HER2 internalization and degradation demonstrating increased sensitivity in cell lines with HER2 amplification and high EGFR levels. When compared with individual and clinically approved mAbs, the synergistic tripartite antibody targeting HER2 subdomains I, II, and IV demonstrates superior anticancer activity. Mol Cancer Ther; 14(3); 669-80. Ó2015 AACR.

Pan-HER, an Antibody Mixture Simultaneously Targeting EGFR, HER2, and HER3, Effectively Overcomes Tumor Heterogeneity and Plasticity

“…As shown previously (26)(27)(28), certain combinations of two antibodies targeting nonoverlapping epitopes on EGFR or HER2 act synergistically and are superior to individual antibodies in terms of target elimination and cancer cell growth inhibition. This receptor elimination also results in superior activity versus individual antibodies (e.g., cetuximab) in the presence of EGFR ligands (27).…”

“…To generate antibodies against EGFR, HER2, and HER3, mice were immunized with soluble, recombinant antigens and/or human cancer cells overexpressing the targets as described elsewhere (28,29). The resulting antibody repertoires were cloned from single splenic B cells by the Symplex technology (30,31) and expressed as full-length mouse-human chimeric or humanized IgG1 in mammalian cells.…”

“…The anti-EGFR antibodies 1277 and 1565, anti-HER2 antibodies 4384 and 4517, and the anti-HER3 antibodies 5038 and 5082 were identified by screening for binders to soluble, recombinant antigens as well as human cancer cells as described before (29). Relative binding specificities were determined as described previously (28,29).…”

Enhanced Targeting of the EGFR Network with MM-151, an Oligoclonal Anti-EGFR Antibody Therapeutic

“…Indeed, a combination of three anti-ErbB2 antibodies is underdevelopment to achieve improved activity beyond that achievable by two-antibody combinations (58). Future development in this field must overcome the challenges of characterizing and accounting for complexities beyond simply the specificity and affinity of a monoclonal antibody to its receptor-including development of relevant in vitro and in vivo model systems that assess multiple mechanisms of action simultaneously instead of in isolation.…”

Emerging anti-cancer antibodies and combination therapies targeting HER3/ERBB3

“…Nevertheless, future mAb combinations might be identified by systematic selections of cooperating anti-HER2 antibodies that can improve efficacy relative to the trastuzumab/pertuzumab combination. 150 In analogy to anti-HER2 combinations, we noted that certain pairs of anti-EGFR antibodies could accelerate EGFR degradation 144 and they synergized in terms of inhibiting tumorigenic growth of triple negative breast cancer cells. 151 Sym004, a therapeutic antibody mixture comprising several mAbs targeting EGFR, was shown to elicit superior cancer cell inhibition and has already completed safety trials.…”