To corroborate our findings from the BT474 xenograft model, we extended our investigation of the efficacy of Vehicle, N, T, P, N + T, or P + T regimens to BCM-3963, an ER−/HER2+ patient-derived breast cancer xenograft (PDX) model of the HER2-enriched subtype22 (Supplementary Fig. 1). Here, ESR1 is linked to breast cancer.