We confirmed by flow cytometry that this homogeneous ADC bearing a defined DAR of 2 retained its specificity and capacity to bind to the HER2 antigen in SKBR3 breast cancer cells that overexpress HER2 in comparison with triple negative breast cancer cells, MDA‐MB‐231 and non‐malignant human breast, MCF10A, which do not express HER2 receptors (Figure 3 c). This evidence concerns the gene ERBB2 and breast cancer.