Among the currently FDA-approved antibody drug conjugates (ADCs), Mylotarg and Besponsa, which comprise the pH-sensitive hydrazone linkers derived from amino groups in drugs, target relapsed CD33 + acute myeloid leukemia (AML) and CD22 + B-cell acute lymphoblastic leukemia (B-ALL), respectively [22, 23]. The gene discussed is CD33; the disease is acute myeloid leukemia.