This invention relates to a novel method for producing di-chain proteins for use in humans from single-chain precursors, including di-chain clostridial neurotoxins. The method comprises the step of expressing a nucleic acid sequence encoding a single-chain precursor comprising a thrombin-cleavage site and the step of cleaving the single-chain precursor with a human factor Xa or a human thrombin, particularly a human thrombin drug product authorized for human therapeutic use. The invention further relates to novel di-chain clostridial neurotoxins and nucleic acid sequences encoding such novel di-chain clostridial neurotoxins.
