ERBB2 and breast carcinoma: A phase I study (NCT03255070) of ARX788 monotherapy, conducted by Frentzas et al. in 42 heavily pretreated breast cancer patients in the United States,31 reported that the median number of prior lines was six, and the ORR was 54.5% in HER2-positive patients and 23.3% in HER2-low patients.