ANPEP and neoplasm: Another novel conjugate termed poly (ethylene glycol)-poly (lysine) block copolymer-ubenimex conjugate (PEG-b-PLys (Ube)), which used the PEG as a delivery system, showed strong anti-tumor and synergistic effects with combinations of fluorouracil, cisplatin, or doxorubicin targeting CD13+ CSCs [134].