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Xeomin® [Merz; 150kDa Botulinum type A toxin (BoNT/A)] and BOTOX® [Allergan; 900kDa BoNT/A complex] were compared, to assess the degree of similarity between these products in terms of potency and antigenicity. Potency was evaluated in the Digit Abduction Score (DAS) mouse assay. Full-range dose–response profiles were achieved with 3 lots of each product, with similarity between lots for a given product. Between products, however, the mean potency of Xeomin® was ~50% lower than that of BOTOX®. Subsequently, studies were conducted to investigate whether rabbit-derived, BOTOX®-neutralizing antibodies (nAbs) could also neutralize Xeomin®. Equi-efficacious, near-maximal doses (ED94) were selected for each product lot from the DAS potency profiles. Each ED94 dose for each lot was combined 1:1 with either naïve serum (control) or nAbs and then evaluated in the DAS assay. As expected, anti-BOTOX® nAbs inhibited each of the BOTOX® lots near-maximally (average DAS inhibition ~85% of matched control). Similarly, anti-BOTOX® nAbs also inhibited each lot of Xeomin® near-maximally (average DAS inhibition ∼90%). These results suggest that inhibition of the 150kDa toxin is the common basis for neutralization for both products. With lower potency and similar antigenicity, Xeomin® is not dose-equivalent to BOTOX® and would not be expected to be effective in BoNT/A-resistant subjects. [Copyright &y& Elsevier]