CD19 and neoplasm: At present, as shown in Fig. 3, the target antigens of the approved ADC drugs are typically specific proteins overexpressed in cancer cells, including HER2, trop2, nectin4 and EGFR in solid tumors, and CD19, CD22, CD33, CD30, BCMA and CD79b in hematological malignancies.26 Driven by fundamental research in oncology and immunology, the selection of ADC target antigen has gradually extended from conventional tumor cell antigens to targets in the tumor microenvironment, e.g. in the stroma and vasculature.