Abstract: The present invention relates to a cytokine trimer domain in which a first monomer and a second monomer linked by linker (dimer) and a third monomer are coupled by a knob-into-hole and a novel type of fusion protein in which antibody and cytokine trimer domains are linked (receptor-antibody conjugated (cell) engager, RACE) prepared by replacing a constant region (Fc) of an antibody with the cytokine trimer domain, and RACE according to the present invention exhibits superior binding ability to the target receptor than the parent antibody as well as excellent simultaneous binding ability to the antigen and the target receptor, which can be usefully utilized as a bispecific pharmaceutical composition.