Depending on the design, a BsAb could recognize a tumour‐associated antigen (TAA) such as CD19, CD20, CD123, B‐cell maturation antigen (BCMA) or human epidermal growth factor receptor 2 (HER2), on one arm and function as a T‐cell engager via CD3 or co‐stimulatory molecules on the other arm.93 Here, ERBB2 is linked to neoplasm.