ERBB2 and breast cancer: It has been reported that margetuximab showed anti-tumor activity against HER2-low expressing cell lines in an in vitro study [75], and a phase 2 clinical trial on the activity of margetuximab in relapsed or refractory advanced BC with HER2-low expression (NCT01828021) was not completed due to lack of efficacy in 17 patients (68%), adverse effect in 2 patients (20%) and withdrawal in 1 patient (4%) [76].