To assess the potency of a formulated drug product containing 150-kd botulinum toxin type A (BoNT/A) as the active pharmaceutical ingredient.
Potencies of 3 unexpired lots of a commercially available BoNT/A drug product, reportedly devoid of complexing proteins (Xeomin), were determined using an approved in-house potency bioassay by injecting mice intraperitoneally and recording percent-mortality across dilutions. For each test session, duplicate sets of dilutions were performed for each lot alongside a 900-kd BoNT/A (BOTOX) potency reference standard. A relative potency for each 150-kd BoNT/A preparation was determined using this potency reference standard. A standard normalized potency estimate for each lot of 150-kd BoNT/A was calculated by multiplying the relative potency by the nominal value for the reference standard. The average potency for each 150-kd BoNT/A lot was calculated using a weighted combination of assay results and compared against the labeled potency of 100 U per vial. Similar follow-on testing was performed 1 year later to assess stability.
The average potencies for the 3 lots of 150-kd BoNT/A product were 69 (95% confidence interval [CI], 65-73), 75 (95% CI, 70-80), and 78 (95% CI, 70-87) U per vial. Follow-on testing produced even lower potency results for all 3 lots.
The potency of the drug product containing 150-kd BoNT/A (Xeomin) measured substantially lower than the labeled 100 U per vial when tested in a potency assay approved for release testing of an established drug product containing 900-kd BoNT/A (BOTOX).