Transfer or induction of neo- or tumour-associated antigen specific T-cells can be a core element of successful immunotherapy. However, clinical translation of adoptive cell therapy is technically difficult, expensive, and associated with high regulatory hurdles. Therefore, we are currently investigating bispecific antibodies as a bridging tool between the patient’s immune effector cells and tumour antigens. We are presently developing strategies to increase their half-life to facilitate clinical translation by fusing them to long amino acid chains that are in silico optimized to not form secondary structures, are of low immunogenicity and are not easily filtrated from circulation in the kidney. A short half-life is a key disadvantage of currently available bispecific antibody constructs.