The present invention relates to an antibody or a fragment thereof comprising at least one heterologous amino acid sequence incorporated within at least one CDR region of said antibody or fragment thereof, wherein said at least one heterologous amino acid sequence comprises an N-terminal linker sequence (Nils), an Atrial Natriuretic Peptide (ANP) and a C-terminal linker sequence (Ctls). Optionally, at least a portion of said at least one CDR region is replaced by said at least one heterologous amino acid sequence incorporated therein. The present invention further relates to such antibody or fragment thereof for use in a method for treatment, a composition comprising such antibody or fragment thereof, a nucleic acid or a mixture of nucleic acids encoding such antibody or fragment thereof, a host cell comprising such nucleic acid or such mixture of nucleic acids and to a process for producing such antibody or fragment thereof.