The concept of using bispecific antibodies for cancer therapy by retargeting immune effector cells was developed several years ago. Initial clinical studies were rather disappointing mainly due to low efficacy, severe side effects and the immunogenicity of the bispecific antibodies. The progress in antibody engineering finally led to the generation of new classes of bispecific antibodies lacking these obstacles. In addition, new applications were established, such as pre-targeting strategies in radioimmunotherapy and dual targeting approaches in order to improve binding, selectivity and...