Abstract: Chimeric clostridial neurotoxins in which the activation loop has been replaced by an activation loop from a different subtype within the same serotype. Methods of producing, activating, and using such neurotoxins. Compositions comprising such neurotoxins. Polynucleotides, vectors and cells for expressing such neurotoxins.

Abstract: The invention relates to recombinant clostridial neurotoxins which have been modified to improve their activation. In particular, the present invention relates to chimeric clostridial neurotoxins in which the activation loop has been replaced by the activation loop from a different subtype within the same serotype. The present invention also relates to methods of producing such chimeric clostridial neurotoxins and methods of activating such modified clostridial neurotoxins, as well as polynucleotides, vectors and cells expressing such chimeric clostridial neurotoxins, compositions comprising such chimeric clostridial neurotoxins and uses thereof.