Prior to freeze-drying, the IC50 of 4D5Fv-PE25 was 11.29 ng/mL for SK-BR-3, 49.66 ng/mL for BT-474, and more than 1.0 × 103 ng/mL for HER2 negative breast cancer cells (Fig. 4B). Here, ERBB2 is linked to breast carcinoma.