By replacing the antigen-binding domain, the present inventors discovered novel polypeptide complexes that retain BiTE's strong anti-tumor activity and excellent safety properties, as well as have long half-life in blood and can damage various different target cells.本發明發現一種新的多胜肽聯合體,其維持BiTE具有之強抗腫瘤活性、及安全性之優異性質,且具有長血中半衰期,且藉由將抗原結合域取代能以各種細胞為標的帶來細胞傷害。