A polypeptide-dimer built of two identical monomeric fragments comprising the domains 1 to 3 of the extracellular (soluble) part of glycoprotein (gp)130 and a certain polypeptide spacer are described, which are covalently linked with each other and which bear significant advantages concerning their production rate in host cells, their improved purification and their potential to bind to IL-6/soluble IL-6 receptor complexes. Furthermore, a pharmaceutical composition containing said dimeric molecule and various medical uses are described.