Possibility of using the imaged capillary isoelectric method as a multi‐attribute method for bispecific antibodies

An imaged capillary isoelectric focusing (icIEF)-based method was developed and validated as a multi-attribute method for a bispecific antibody (BsAb). First, as the traditional application of the icIEF method, it serves as an identity assay and purity assay for the BsAb. Second, the method can also be used as an impurity assay for the homodimer monoclonal antibodies generated during BsAb assembly. The homodimer impurity analysis for BsAb is usually done by hydrophobic interaction chromatography methods in the industry. The icIEF method has good sensitivity (down to 4 µg/mL in a limit of quantitation) when UV fluorescence detection is used, which detects the native fluorescence of proteins. This is the first report that an icIEF method has been applied as impurity assay.