ERBB2 and neoplasm: Especially, LCB‐ADC shows good efficacy in terms of suppressing tumor growth in a patient‐derived xenograft (PDX) model of HER2‐positive gastric cancer as well as in T‐DM1‐resistant models such as HER2 low‐expressing HER2 low expressing JIMT‐1 xenograft tumor and PDX.