While in HER-2-positive cancer cells trastuzumab–cisplatin conjugates exerted a similar anticancer activity than free cisplatin (IC50 around 20 μm in both cases), in HER-2-negative cells (including MDA-MB-231 that are triple-negative breast cancer cells), the trastuzumab–cisplatin conjugate was not effective (IC50 > 50 μm), while free cisplatin exerted a similar antiproliferative effect than in HER-2-positive cells (IC50 ≈ 10–20 μm). This evidence concerns the gene ERBB2 and triple-negative breast carcinoma.