It combines a payload (topoisomerase I inhibitor) with a high DAR of up to 8, a linker cleavable selectively only within tumor cells, and potent cytotoxicity, while also possessing high cell membrane permeability to enable bystander killing effects capable of eliminating surrounding HER2-low or HER2-negative tumor cells [13]. The gene discussed is ERBB2; the disease is neoplasm.