Replacement of the Mouse LD 50 Assay for Determination of the Potency of AbobotulinumtoxinA with a Cell-Based Method in Both Powder and Liquid Formulations.

Botulinum neurotoxins (BoNTs) are important therapeutic agents. The in vivo median lethal dose (LD50 ) assay has been commonly used to measure the potency of BoNT commercial preparations. As an alternative, we developed cell-based assays for abobotulinumtoxinA in both powder (Dysport® , Azzalure® ) and liquid (Alluzience® ) formulations using the in vitro BoCell® system. The assays demonstrated linearity over 50-130% of the expected relative potency, with a correlation coefficient of 0.98. Mean recoveries of 90-108% of the stated potency were observed over this range. The coefficients of variation for powder and liquid formulations, respectively, were 3.6% and 4.0% for repeatability and 8.3% and 5.0% for intermediate precision. A statistically powered comparability assessment of the BoCell® and LD50 assays was performed. Equivalence was demonstrated between the assays for the liquid formulation at release and end of shelf life using a paired equivalence test with predefined equivalence margins. For the powder formulation, the assays were also shown to be equivalent for release samples and when determining loss of potency following thermal degradation. The BoCell® assay was approved for establishing the potency of abobotulinumtoxinA for both powder and liquid formulations in Europe and for the powder formulation only in the USA.