Novel recombinant botulinum neurotoxins with increased duration of effect

A method of treating a disease requiring improved chemodenervation, said method comprising the step of administering a recombinant neurotoxin to a patient in need thereof, said recombinant neurotoxin comprising:

• at least two domains wherein each domain comprises an amino acid sequence comprising at least 50 amino acid residues, wherein said amino acid sequence comprises at least one proline, at least one alanine and at least one additional amino acid residue, selected from the group consisting of serine, threonine, tyrosine and glutamine, wherein the neurotoxin further comprises at least one amino acid modification which is located at the alpha-exosite and/or at the beta-exosite of the light chain of the neurotoxin,
• wherein the said at least one amino acid modification is located at at least one position selected from D102, T109, K340, I348, N353, and K356 of the alpha-exosite, or at at least one position selected from G169, T220, P239, and S254 of the beta-exosite, and
• wherein the recombinant neurotoxin causes both (i) an increased duration of effect relative to a wildtype botulinum neurotoxin serotype A and (ii) an increased specific biological activity relative to a botulinum neurotoxin serotype A comprising two domains consisting of proline, alanine and serine residues without said modifications in the alpha-exosite and/or at the beta-exosite of the light chain of the neurotoxin.