Effective and robust separation of half-antibody byproduct in bispecific antibody purification by Sartobind Rapid A Protein A membrane chromatography

Half-antibody is a common byproduct associated with the production of asymmetric bispecific antibody (bsAb). We previously demonstrated that Protein A column chromatography can effectively separate this byproduct from the bsAb product, as these two species exhibit different binding valencies (half-antibody and intact bsAb contain one and two Protein A binding sites, respectively). Specifically, half-antibody, which binds weaker, can be selectively removed by an appropriate wash prior to elution of the target bsAb. However, the performance of this wash step is sensitive to the loading density, making the process unrobust to variations in harvest titer. In the current study, we demonstrate that Sartobind Rapid A Protein A membrane effectively reduces half-antibody from approximately 16.5% (in the load) to 0.1% (in the eluate). In addition, using Protein A membrane also improves process robustness by avoiding the impact of loading density variation on performance. Thus, for bsAb purification where half-antibody removal is required, Protein A membrane is a better choice than resin-based Protein A column.