Abstract OT3-25-02: Inetetamab combined with pyrotinib and Chemotherapy in Pretreated Patients with HER2-positive metastatic breast cancer, a single arm, multicenter phase II clinical trial

Abstract

Abstract Background: The HER2-targeted drugs selection after trastuzumab failure has become a challenging issue for HER2-positive metastatic breast cancer (MBC) patients. Inetetamab is a neotype of HER2-targeted monoclonal antibody with an engineered Fc segment that optimizes the antibody-dependent cell-mediated cytotoxicity (ADCC) effect, which was important for disease control. Moreover, HER2-targeted tyrosine kinase inhibitors, as pyrotinib, were found to further improve the ADCC effect of monoclonal antibodies in pre-clinical researches, indicating that the combination of pyrotinib and inetetamab could achieve complementarity and synergy effects in terms of short-term tumor killing effect and long-term immunotherapy benefits. Therefore, the combined treatment pattern of the two drugs has potential clinical benefits. Methods: This is a prospective, multi-center, single-arm clinical study designed to evaluate the efficacy and safety of pretreated patients with HER2-positive MBC. We recruited patients with pathologically confirmed HER2-positive MBC who had received 1-3 prior regimens for metastatic disease, which must include trastuzumab. The enrolled patients received 6 cycles of Inetetamab combined with pyrotinib and chemotherapy, subsequent maintenance therapy should be considered according to tolerability. The chemotherapy drugs were decided by physicians’ choice, and could be microtubules, anthracyclines, or antimetabolites. The primary endpoint was objective response rate (ORR) after 6 cycles of treatment, secondary endpoints included progression-free survival (PFS), overall survival (OS), and clinical benefit rate (CBR) and adverse events (AEs). Results: 57 patients were enrolled from October 2020 to July 2022. And 45 patients were available for response evaluation. The ORR and DCR were 53.5 % (24/45) and 86.7 % (39/45), respectively after 6 cycles treatment. The median PFS was 7.3 months. The incidence of grade Ⅲ-Ⅳ AEs was 15.8 %. The most common treatment-related AEs were diarrhea, anemia, neutropenia, leukopenia, hand and foot syndrome. No patient’ s left ventricle ejection fraction (LVEF) decreased to < 50% or decreased by >15%. And no significant decline in quality of life score was reported. Conclusion: Inetetamab combined with pyrotinib and chemotherapy showed a promising efficacy and a good tolerance in patients with HER2-positive metastatic breast cancer, confirming the synergistic effect between the ADCC optimized monoclonal antibodies and TKIs, which brings more treatment options for HER2-positive metastatic breast cancer. Citation Format: Jianli Zhao, Yangyang Cai, Linxiaoxiao Ding, Yaping Yang, Guorong Zou, Herui Yao, Ying Wang. Inetetamab combined with pyrotinib and Chemotherapy in Pretreated Patients with HER2-positive metastatic breast cancer, a single arm, multicenter phase II clinical trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-25-02.