Bispecific antibodies (bsAbs) are increasingly being used in the treatment of cancer, inflammatory and autoimmune diseases. Various designs have been tested so far. One promising design is the one of bispecific T cell engagers (BiTEs), which are used for retargeting T cells for efficient killing of cancer cells. This design only contains two single chain fragments (scFvs) but it targets antigens on two different cells. Another interesting design is an IgG-like bispecific antibody, which can also target two molecules on one cell and increase the specificity by only targeting double positive cells in therapy, rather than single positive cells. This thesis focuses on combining the advantages of IgG-like bispecific antibodies and BiTEs in order to bind two molecules (CD59 and CD48) on the surface of one cell. These molecules are in close proximity, therefore, it is possible to target them with a small sized bispecific antibody containing only two scFvs that are connected by a rigid linker. Two different structures of antibodies were designed. For the time limitations, only one format of the bsAb was produced in the Pichia pastoris expression system and analyzed further. Additionally, it was also compared to other antibodies (monospecific mAbs and a bispecific bibody) with the same targets. The engineered bispecific antibody showed the expected characteristics and functions. It does not bind negative cells and there is a difference in binding between the single-positive and double-positive cells.