For instance, DS8201, an antibody–drug conjugate comprised of a humanized antibody against HER2, a novel enzyme-cleavable linker, and a topoisomerase I inhibitor payload also showed efficacy in pre-treated metastatic HER2-positive patients, including HER2 low expressed cancers, indicating such a “bystander” effect may even be substantial enough to induce responses in HER2 ICH 1+ tumors [22, 24]. This evidence concerns the gene ERBB2 and cancer.