Peptide or pseudopeptide decoys binding to antibodies capable of being developed against endogenous proteins within the framework of autoimmune pathologies or against exogenous proteins administered to patients, in particular within the framework of pathologies due to a deficiency in these proteins, the amino acid sequence of the peptide or pseudopeptide decoys differing from that of the epitopes recognized by the antibodies, for the preparation of medicaments intended for the prevention or treatment of the autoimmune pathologies, or for the prevention or treatment of the disorders linked to the appearance of antibodies directed against the exogenous proteins.