Objective: To examine the effect of a cell-penetrating peptide (CPP) in a prototype formulation using toxin adsorption, in vivo potency, and duration analyses.

Background: Unit potencies of botulinum neurotoxin type A (BoNT/A) drugs are not interchangeable due in part to unique drug formulations and manufacturing processes. Various excipients are used to stabilize BoNT/A and prevent adsorption to surfaces.

Method: Size-exclusion chromatography compared adsorption of 150-kDa BoNT/A toxin formulated in either potassium phosphate/NaCl buffer containing polysorbate 20, 23.5 µg/mL CPP (synthesized sequence: RKKRRQRRRG-[K]15-GRKKRRQRRR) with and without polysorbate 20, human serum albumin (HSA), or in buffer alone. Digit abduction score (DAS) testing compared the potency and duration of 150-kDa BoNT/A toxin at an approximate ED₅₀ dose formulated in histidine buffer/trehalose buffer containing polysorbate 20, 0.235 µg CPP/unit BoNT/A with or without polysorbate 20, or in bovine serum albumin (BSA)/0.9% NaCl.

Results: Toxin adsorption to glass surface occurred in buffer control and CPP-only solutions at 7 hours; toxin recoveries were <64%. At 14 and 21 hours, buffer control and CPP-alone samples had decreased toxin recoveries of <42%; samples containing polysorbate 20 or HSA maintained toxin recoveries of >95%. In the mouse DAS assay, BoNT/A prepared in polysorbate formulations with or without CPP exhibited similar, predictive DAS efficacy (>ED₅₀) and duration versus formulation in BSA/0.9% NaCl. In contrast, the formulation in CPP alone demonstrated decreased potency (<<ED₂₅) and duration. Results from rat DAS assay showed similar trends.

Conclusion: CPP inclusion in a BoNT/A formulation neither prevents toxin adsorption nor increases potency or duration.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-cell-penetrating-peptide-cpp-did-not-decrease-150-kda-bont-a-toxin-adsorption-to-surfaces-or-increase-toxin-potency-or-duration-in-a-prototype-formulation/