This invention relates to novel recombinant clostridial neurotoxins exhibiting increased duration of effect and to methods for the manufacture of such recombinant clostridial neurotoxins. These novel recombinant clostridial neurotoxins comprise a random coil domain, and the methods comprise the steps of inserting a nucleic acid sequence coding for a random coil domain into a nucleic acid sequence coding for a parental clostridial neurotoxin and expression of the recombinant nucleic acid sequence comprising the random coil domain-coding sequence in a host cell. The invention further relates to novel recombinant single-chain precursor clostridial neurotoxins used in such methods, nucleic acid sequences encoding such recombinant single-chain precursor clostridial neurotoxins, and pharmaceutical compositions comprising the recombinant clostridial neurotoxin with increased duration of effect.