A novel anti-HER2 antibody GB235 reverses Trastuzumab resistance in HER2-expressing tumor cells in vitro and in vivo

Mengjun Shu,Zhuzi He,Chuanying Xu,Yan Wu,Qing Zhou,Hongli Wei,Hongbin Yan,Jing Xiao,Joe X Zhou,Zhaohua Chi,Weihong Nian

doi:10.1038/s41598-020-59818-2

Abstract

HER2 overexpression is frequently associated with tumor metastasis and poor prognosis of breast cancer. More evidence indicates that HER3 is involved in HER2-resistant therapies. Combination treatments with two or more different monoclonal antibodies are a promising strategy to overcome resistance to HER2 therapies. We presented a novel fully human HER2-targeted monoclonal antibody, GB235, screened from a phage-display library against the HER2 antigen. GB235 in combination with Trastuzumab overcomes resistance in HER2-positive tumors and results in more sustained inhibition of tumor growth over time. The competition binding assay showed that the epitopes of GB235 do not overlap with those of Pertuzumab and Trastuzumab on HER2. Further HER2 mutagenesis results revealed that the binding epitopes of GB235 were located in the domain III of HER2. The mechanism of action of GB235 in blocking HER2-driven tumors is different from the mechanisms of Trastuzumab or Pertuzumab. GB235 does not affect the heterodimerization of HER2 and HER3, whereas the GB235 combined treatment with Trastuzumab significantly inhibited heregulin-induced HER3 phosphorylation and downstream signaling. Moreover, GB235 in combination with Trastuzumab reversed the resistance to heregulin-induced proliferation in HER2-overexpressing cancer cell lines. GB235 combined with Trastuzumab treatment in xenograft models resulted in improved antitumor activity. Complete tumor suppression was observed in the HER2-positive NCI-N87 xenograft model treated with the combination treatment with GB235 and Trastuzumab. In a Trastuzumab-resistant patient-derived tumor xenograft model GA0060, GB235 plus Trastuzumab reversed the resistance to Trastuzumab monotherapy. Because GB235 showed a different working mechanism with Pertuzumab and Trastuzumab, these agents can be considered complementary therapy against HER2 overexpression tumors.

Highlights

HER2 overexpression is frequently associated with tumor metastasis and poor prognosis of breast cancer
The results showed that GB235 bound to human HER2 extracellular domain (ECD) in a concentration-dependent manner, without binding to other EGFR family receptors (Fig. 1A)
The cell binding assay was investigated with flow cytometry, the GB235 bound to BT-474 cells, which is consistent with the result of Trastuzumab and Pertuzumab (Fig. 1B)

Summary

Introduction

HER2 overexpression is frequently associated with tumor metastasis and poor prognosis of breast cancer. GB235 does not affect the heterodimerization of HER2 and HER3, whereas the GB235 combined treatment with Trastuzumab significantly inhibited heregulin-induced HER3 phosphorylation and downstream signaling. GB235 in combination with Trastuzumab reversed the resistance to heregulin-induced proliferation in HER2-overexpressing cancer cell lines. Pertuzumab and Trastuzumab bind to distinguishing epitopes on HER2, and the combination treatment inhibits HER2/HER3 signaling more effectively[13]. HER2-targeted bispecific antibodies in clinical development have demonstrated significant antitumor activity for the Trastuzumab-resistant malignant cancers in preclinical studies[15,16]. The combination treatment of GB235 and Trastuzumab reversed the resistance to heregulin-driven proliferation in BT-474 and NCI-N87 HER2-overexpressing tumor cells. GB235 in combination with Trastuzumab demonstrated significant tumor growth inhibition in the NCI-N87 HER2-overexpressing xenograft model. GB235 in combination with Trastuzumab might be a potential therapy against HER2-positive tumors

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Conclusion