The linker-drug of T-Dxd demonstrated stability in systemic circulation and selectively targeted HER2-expressing cancer cells by facilitating the antitumor effects of trastuzumab, including ADCC, ADCP, and CDC, and was selectively cleaved by intracellular lysosomal proteases such as cathepsins in cancer cells, allowing for the payload release. The gene discussed is CTSS; the disease is cancer.