# A Cell-Based Potency Assay for Determining the Relative Potency of Botulinum Neurotoxin A Preparations Using Manual and Semi-Automated Procedures

## TL;DR

This paper introduces a new cell-based assay for measuring the potency of botulinum toxin A using manual and semi-automated methods.

## Contribution

The study presents a qualified and sensitive cell-based potency assay for BoNT/A with improved precision and reduced operator dependency.

## Key findings

- The BoSapient CBPA can detect picomolar and sub-picomolar levels of BoNT/A.
- The semi-automated method improved intermediate precision by 39% compared to the manual method.
- The cell line maintained sensitivity and reporter expression after 30 passages.

## Abstract

Cell-based potency assays (CBPAs) are required for the potency testing and commercial release of botulinum neurotoxin (BoNT)-based drug products. These CBPAs must account for the toxin’s biological activities while meeting regulatory guidelines for precision and accuracy. Here, studies describe the characterization and qualification of the BoSapient CBPA and demonstrate that it is fit for use as a relative potency assay for BoNT/A-containing samples. The CBPA is operated in a 96-well plate format and relies upon the fluorescence emissions of a reporter that directly responds to BoNT/A activity. The BoSapient cell line expresses the BoNT/A-receptors SV2 and complex gangliosides, is responsive only to intact BoNT/A, and can robustly detect picomolar and sub-picomolar BoNT/A quantities, making the CBPA appropriate for quantifying BoNT/A-based drug products. The cell line was passaged 30 times without significant loss of reporter expression or BoNT/A sensitivity. Manual and semi-automated CBPA methods were developed and qualified according to regulatory guidelines and shown to have low bias (<4% from expected) and high precision (standard deviation < 8) across all test concentrations. Furthermore, the semi-automated method using the CBPA is demonstrated to improve intermediate precision by 39% compared to the manual method, while reducing operator dependency during method execution.