Content of Botulinum Neurotoxin in Botox®/Vistabel®, Dysport®/Azzalure®, and Xeomin®/Bocouture®

Background: Botulinum neurotoxin type A (BoNT/A) is the active substance in preparations used for the highly effective treatment of neurologic disorders such as cervical dystonia, blepharospasm, or spasticity, as well as other indications such as axillary and palmar hyperhidrosis, and urologic disorders. Objective: To determine the amount of BoNT/A protein present in pharmaceutical preparations of Botox®, Dysport®, and Xeomin®, which are identical with Vistabel®, Azzalure®, and Bocouture®, respectively. Methods: Rabbit and guinea pig antibodies raised against the 150kD BoNT/A neurotoxin purified from Clostridium botulinum type A, strain ATCC 3502 (‘Hall strain’), were used in a sensitive sandwich ELISA to determine the overall mean concentration of the 150kD neurotoxin present in four batches of Botox® (C2344C3, C2384C3, C2419, and C2385), two batches of Dysport® (678F and 689X) and three batches of Xeomin® (61111, 70604, and 81 208). The specific neurotoxin potency, defined as the potency or biologic activity (units) per mass of neurotoxin protein (ng), was calculated based on the overall mean concentration of BoNT/A neurotoxin. Results: Overall, the mean concentration of BoNT/A neurotoxin in Botox® was 0.73 ng per 100 unit vial (coefficient of variation [CV] = 3.5%), 3.24 ng per 500 unit vial of Dysport®, corresponding to 0.65 ng in 100 units (CV = 11.4%), and 0.44 ng per 100 unit vial of Xeomin® (CV = 1.9%). The specific potency of the 150kD BoNT/A neurotoxin was calculated as 137 units/ng for Botox®, 154 units/ng Dysport®, and 227 units/ng Xeomin®. Conclusions: The current study has shown that of the three products, Xeomin® contains the highest specific neurotoxin activity, followed by Dysport®, with Botox® having the lowest specific activity. This result suggests that Xeomin® contains only active neurotoxin in contrast with Botox®, which is likely to contain additional denatured/inactive neurotoxin.