Inetetamab Plus Cyclophosphamide Metronomic Chemotherapy Plus Aromatase Inhibitor in Metastatic HER2+/HR+ Breast Cancer

Trastuzumab is a humanized monoclonal antibody, and antibody-dependent cell-mediated cytotoxicity (ADCC) is one of its important mechanisms for suppressing tumors. Pre-clinical data suggest that the ADCC effect of Inetetamab, an anti-HER2 monoclonal antibody with a modified Fc segment, is 1.11 times that of trastuzumab. Previous studies indicated that enhanced ADCC effects can be transformed into clinical benefits, but the absolute benefits are still unsatisfactory. Further improvement of ADCC effects and monoclonal antibody-induced immune responses may improve the clinical benefits. Immune induction through cyclophosphamide metronomic chemotherapy may further enhance the ADCC effect of anti-HER2 monoclonal antibodies. According to previous clinical studies, for HR-positive and HER2-positive metastatic breast cancer patients, metronomic chemotherapy combined with endocrine therapy and anti-HER2 targeted therapy may be one of the treatment options. Therefore, we conducted this study to explore the efficacy and the safety of Inetetamab combined with cyclophosphamide metronomic chemotherapy and aromatase inhibitors(AI) in the treatment of metastatic HER2-positive and HR-positive breast cancer patients, and we further exploring the possible mechanisms.