The activity of BiTox/DD was evaluated in rat cortical neuronal cultures and differentiated human SiMa neuroblastoma cells which were shown previously to bind BoNTs type A to C. Direct comparison of SNAP-25 cleavage by BiTox/D and BiTox/DD revealed a strong enhancement of SNAP-25 cleavage in both human and rat neurons (one hundred fold) (Fig. 3b). The gene discussed is SNAP25; the disease is neuroblastoma.