To extend these results, we studied effects of the anti-MUC1-C ADC against the patient-derived xenograft ER-WT PDX1415 model derived from a patient with a HR+/HER2− BC refractory to treatment with aromatase inhibitor, fulvestrant, capecitabine, taxol, eribulin, and carboplatin-gemcitabine49. Here, ESR1 is linked to breast cancer.