T-DXd is composed of (1) an anti-HER2 humanized monoclonal immunoglobulin G1 antibody (MAAL-9001), with the same amino acid sequence as trastuzumab; (2) a cleavable maleimide tetrapeptide linker, which is selectively cleaved by cathepsins upregulated in cancer cells and in the tumor microenvironment to allow the release of the cytotoxic drug; and (3) the exatecan derivative MAAA-1181a (DXd), a DNA topoisomerase I inhibitor with a 10-fold higher inhibitory potency compared with SN-38, the active metabolite of irinotecan [17]. Here, ERBB2 is linked to cancer.