Application of pH-salt dual gradient elution in purifying a WuXiBody-based bispecific antibody by MMC ImpRes mixed-mode chromatography.

WuXiBody is a novel bispecific antibody (bsAb) platform developed by WuXi Biologics. BsAbs based on WuXiBody can adopt either asymmetric or symmetric format. In general, recombinant production of asymmetric bsAbs has a more complex impurity profile than that of symmetric ones, as assembly of the former usually involves an increased number of distinct chains. Consequently, purification of asymmetric bsAb typically poses greater challenges to the downstream team. Recently while purifying a WuXiBody-based bsAb in asymmetric format, we learned that MMC ImpRes mixed-mode chromatography under linear pH or salt gradient elution can effectively remove two out of the three low-molecular-weight byproducts post Protein A chromatography but not the third one, which was eventually removed under pH-salt dual gradient elution. This finding suggests that MMC ImpRes chromatography performed under pH-salt dual gradient elution provides better resolution than that performed under pH/salt mono gradient elution.