Processing of high-salt-containing protein A eluate using mixed-mode chromatography in purifying an aggregation-prone antibody

An integrated method for IgG N-glycans enrichment and analysis: Understanding the role of IgG glycosylation in diabetic foot ulcer

Diabetic foot ulcer (DFU) is the most common and serious complication of diabetes, and its incidence, disability, and mortality rates are increasing worldwide. The pathogenesis of DFU is associated with dysregulated inflammation mediated by abnormal immunoglobulin G (IgG) glycosylation. In this study, we developed a comprehensive method for IgG N-linked glycosylation in the serum of DFU patients. Through analysis, we identified 31 IgG1 glycans, 32 IgG2 glycans, and 30 IgG4 glycans in the DFU serum. Furthermore, 13 IgG1 glycans, 12 IgG2 glycans, and 5 IgG4 glycans in the DFU groups were found to be significantly different from those of the control groups (p < 0.05). Of these, compared with the control group, one glycan was unique to DFU patients, and seven glycans were not detected in the DFU group. In terms of glycan characteristics, we observed a substantial decrease in galactosylation, sialylation and bisecting GlcNAcylation, and a significant increase in agalactosylation. Abnormal IgG N-glycosylation modifications were significantly associated with the chronic inflammation that is characteristic of DFU. Further, this is the first comprehensive analysis of subclass-specific IgG N-glycosylation in DFU patients, which not only fills the gap of DFU in terms of the pathological mechanisms related to IgG glycosylation but also may provide valuable clues for the immunotherapeutic pathway of DFU.

The beneficial impact of kosmotropic salts on the resolution and selectivity of Protein A chromatography

During the manufacturing of therapeutic antibodies, effective Protein A chromatography as initial column step is crucial to simplify the remaining purification effort for subsequent polishing steps. This is particularly relevant for molecules with high impurity content so that desired product purity can be attained. The present study demonstrates beneficial effects on impurity removal when applying kosmotropic salts, e.g., sodium sulfate or sodium chloride, in the elution phase. Initially, a screen using negative linear pH gradient elution evaluated the impact of the kosmotropic salts in comparison to no additive and chaotropic urea using three mAbs and three common resins. Retaining acceptable yield, the kosmotropic salts improved resolution of monomer and impurities and reduced the contents of process-related host cell proteins and DNA as well as of product-related low and high molecular weight forms, despite some resin- and mAb-dependent variations. Moreover, a decrease in hydrolytic activity measured by a new assay for polysorbase activity was observed. In contrast, urea was hardly effective. The findings served to establish optimized step elution conditions with 0.25 M of sodium sulfate for a challenging mAb with complex format (bispecific 2 + 1 CrossMab) displaying high relative hydrophobicity and impurity levels. With yield and purity both in the range of 90 %, the contents of all impurity components were reduced, e.g., low molecular weight forms by two-fold and polysorbase activity by four-fold. The study indicates the potential of kosmotropic salts to establish efficient and comprehensive impurity separation by Protein A for facilitated downstream processing and economic manufacturing of complex antibodies.

Mixed-Mode Chromatography and Its Role in Monoclonal Antibody Purification

As the biopharmaceutical industry matures and embraces process intensification methodologies allied to the emergence of newer personalized medicines, a key constant is the regulatory need to purify products that satisfy the criteria of safety, quality, and efficacy in each batch of released product destined for clinical use. Downstream processing operations and in particular chromatographic separations continue to play a key role in manufacturing strategies with the industry being well served by commercially available resins that provide different options to purify a particular target molecule of interest. In recent years, mixed-mode chromatography, a technique based on multimode interactions between ligands and proteins, had attracted much attention. This short review will discuss the concept and benefit of mixed-mode chromatography in purification strategies and specifically look at its application in the purification of IgG subtype monoclonal antibodies, a key product class in today's industry.

Immunoglobulin-binding protein-based affinity chromatography in bispecific antibody purification: Functions beyond product capture

In general, purification of bispecific antibody (bsAb) is more challenging than that of monospecific antibody due to the increased complexity in byproduct profile. Like in the case of monospecific antibody purification, immunoglobulin-binding protein-based affinity chromatography is an indispensable tool for bsAb purification. For example, Protein A affinity chromatography has been widely used to capture Fc-containing bsAbs whereas other affinity media such as Protein L and KappaSelect, which bind kappa light chain, are used to capture bsAbs that do not contain a Protein A-binding site. In fact, affinity chromatography also possesses the capability of removing certain product-related impurities in bsAb purification when it is conducted with suitable medium and under appropriate conditions. Fully exploring the potential of affinity chromatography in bsAb purification to achieve both product capture and byproduct removal is highly desirable, as this can greatly alleviate the purification burden on subsequent polishing steps and hence improves the overall robustness of the downstream process. This article briefly reviews the byproduct clearance potential of several commonly used affinity media under relevant bsAb purification scenarios.