The invention relates to branches of biotechnology and, in particular, to mutated polypeptides of the TGFß molecule, the primary sequence of which is highly homologous with the sequence of human TGFß. These muteins lose their ability to interact with ALK5 but retain their ability to interact with the rest of the receptors that form part of the receptor complex (TßRII and TßRIII). In addition, they can antagonise the signalling of all of the natural variants of the TGFß ligands, dependent on the recruitment of ALK5 in the receptor complex, and they have an immunomodulatory effect. The invention also relates to pharmaceutical compositions comprising, as active principle, the disclosed polypeptides or fusion proteins and to the therapeutic use of the disclosed polypeptides, fusion proteins and pharmaceutical compositions owing to their immunomodulatory effect on diseases such as cancer, diseases associated with fibrosis and chronic infectious diseases.
