The present invention relates to the isolation of polypeptides derived from the Clostridium botulinum neurotoxin and the use thereof as treatment for neuronal injury such as spinal cord injury. Botulinum neurotoxin binds to neural cells and are translocated into the cytosol and therefore is useful as a target specific therapeutic delivery system. Non-toxic botulinum toxin may be created by light chain mutagenesis and/or removal of the endopeptidase domain.
