PEGylated Mutated Clostridium botulinum Toxin

A method of treating dystonia or for removing facial wrinkles, the method comprising treatment of a subject with a modified botulinum toxin, the modified botulinum toxin comprising a natural heavy chain and a modified light chain, characterized in that the modification of the light chain (i) comprises an extension of the chain on its N-terminus which has the structure —(C)n-(tag)m-(X)l— in the direction from the N- to the C-terminal end, wherein:

• C represents a cysteine residue,
• tag represents any tag and
• X represents the residue of any naturally occurring amino acid,
• n represents an integer from 1 to 50,
• m represents 0 or 1, and
• l represents 0 or an integer from 1 to 50,
• and in that (ii) at least one of the cysteine residues in the extension of the chain is coupled to at least one chain of PEG.