Glutathione and thioredoxin systems contribute to recombinant monoclonal antibody interchain disulfide bond reduction during bioprocessing

Enhanced harvest performance predictability through advanced multivariate data analysis of mammalian cell culture particle size distribution

The industry's pursuit for higher antibody production has led to increased cell density cultures that impact the performance of subsequent product recovery steps. This increase in cell concentration has highlighted the critical role of solids concentration in centrifugation yield, while recent product degradation cases have shed light on the impact of cell lysis on product quality. Current methods for measuring solids concentration and cell lysis are not suited for early-stage high-throughput experimentation, which means that these cell culture outputs are not well characterized in early process development. This article describes a novel approach that leveraged the data from a widely-used automated cell counter (Vi-CELL™ XR) to accurately predict solids concentration and a common cell lysis indicator represented as lactate dehydrogenase (LDH) release. For this purpose, partial least squares (PLS) models were derived with k-fold cross-validation from the particle size distribution data generated by the cell counter. The PLS models showed good predictive potential for both LDH release and solids concentration. This novel approach reduced the time required for evaluating the solids concentration and LDH for a typical high-throughput cell culture system (with 48 bioreactors in parallel) from around 7 h down to a few minutes.

New high-throughput screening method for Chinese hamster ovary cell lines expressing low reduced monoclonal antibody levels: application of a system controlling the gas phase over cell lysates in miniature bioreactors and facilitating multiple sample setup

Interchain disulfide bonds in monoclonal antibodies may be reduced during large-scale mAb production using Chinese hamster ovary (CHO) cells. This reaction lowers the mAb product yield and purity; however, it may be prevented by screening cell lines that are unsusceptible to reduction and using them in mAb production. Antibody reduction susceptibility may be cell line-dependent. To the best of our knowledge, however, an efficient method of screening reduction-unsusceptible CHO cell lines has not been previously reported. Here, we report a novel screening method that can simultaneously detect and identify mAb reduction susceptibility in lysates containing ≤ 48 CHO cell lines. This evaluation system was equally effective and generated similar results at all culture scales, including 250 mL, 3 L, and 1000 L. Furthermore, we discovered that reduction-susceptible cell lines contained higher total intracellular nicotinamide adenine dinucleotide phosphate (NADPH) and NADP+ concentrations than reduction-unsusceptible cell lines, regardless of whether they expressed immunoglobulin (Ig)G4 or IgG1. NADPH or NADP+ supplementation in the lysate of reduction-unsusceptible cells resulted in mAb reduction. Application of the innovative CHO cell line screening approach could mitigate or prevent reductions in large-scale mAb generation from CHO cells.

Enzymatic basis of the Fc-selective intra-chain disulfide reduction and free thiol content variability in an antibody produced in Escherichia coli

Background

Escherichia coli (E. coli) is a promising host for production of recombinant proteins (including antibodies and antibody fragments) that don’t require complex post-translational modifications such as glycosylation. During manufacturing-scale production of a one-armed antibody in E. coli (periplasmic production), variability in the degree of reduction of the antibody’s disulfide bonds was observed. This resulted in variability in the free thiol content, a potential critical product quality attribute. This work was initiated to understand and prevent the variability in the total free thiol content during manufacturing.

Results

In this study, we found that the reduction in antibody’s disulfide bonds was observed to occur during homogenization and the ensuing homogenate hold step where in the antibody is exposed to redox enzymes and small molecule reductants present in homogenate. Variability in the downstream processing time between the start of homogenization and end of the homogenate hold step resulted in variability in the degree of antibody disulfide bond reduction and free thiol content. The disulfide bond reduction in the homogenate is catalyzed by the enzyme disulfide bond isomerase C (DsbC) and is highly site-specific and occurred predominantly in the intra-chain disulfide bonds present in the Fc CH2 region. Our results also imply that lack of glycans in E. coli produced antibodies may facilitate DsbC accessibility to the disulfide bond in the Fc CH2 region, resulting in its reduction.

Conclusions

During E. coli antibody manufacturing processes, downstream processing steps such as homogenization and subsequent processing of the homogenate can impact degree of disulfide bond reduction in the antibody and consequently product quality attributes such as total free thiol content. Duration of the homogenate hold step should be minimized as much as possible to prevent disulfide bond reduction and free thiol formation. Other approaches such as reducing homogenate temperature, adding flocculants prior to homogenization, using enzyme inhibitors, or modulating redox environments in the homogenate should be considered to prevent antibody disulfide bond reduction during homogenization and homogenate processing steps in E. coli antibody manufacturing processes.

Thiol Modifications in the Extracellular Space-Key Proteins in Inflammation and Viral Infection

Posttranslational modifications (PTMs) allow to control molecular and cellular functions in response to specific signals and changes in the microenvironment of cells. They regulate structure, localization, stability, and function of proteins in a spatial and temporal manner. Among them, specific thiol modifications of cysteine (Cys) residues facilitate rapid signal transduction. In fact, Cys is unique because it contains the highly reactive thiol group that can undergo different reversible and irreversible modifications. Upon inflammation and changes in the cellular microenvironment, many extracellular soluble and membrane proteins undergo thiol modifications, particularly dithiol-disulfide exchange, S-glutathionylation, and S-nitrosylation. Among others, these thiol switches are essential for inflammatory signaling, regulation of gene expression, cytokine release, immunoglobulin function and isoform variation, and antigen presentation. Interestingly, also the redox state of bacterial and viral proteins depends on host cell-mediated redox reactions that are critical for invasion and infection. Here, we highlight mechanistic thiol switches in inflammatory pathways and infections including cholera, diphtheria, hepatitis, human immunodeficiency virus (HIV), influenza, and coronavirus disease 2019 (COVID-19).

Switchable immune modulator for tumor-specific activation of anticancer immunity

Immune stimulatory antibodies and cytokines elicit potent antitumor immunity. However, the dose-limiting systemic toxicity greatly hinders their clinical applications. Here, we demonstrate a chemical approach, termed “switchable” immune modulator (Sw-IM), to limit the systemic exposure and therefore ameliorate their toxicities. Sw-IM is a biomacromolecular therapeutic reversibly masked by biocompatible polymers through chemical linkers that are responsive to tumor-specific stimuli, such as high reducing potential and acidic pH. Sw-IMs stay inert (switch off) in the circulation and healthy tissues but get reactivated (switch on) selectively in tumor via responsive removal of the polymer masks, thus focusing the immune boosting activities in the tumor microenvironment. Sw-IMs applied to anti–4-1BB agonistic antibody and IL-15 cytokine led to equivalent antitumor efficacy to the parental IMs with markedly reduced toxicities. Sw-IM provides a highly modular and generic approach to improve the therapeutic window and clinical applicability of potent IMs in mono- and combinational immunotherapies.

Untargeted proteomics reveals upregulation of stress response pathways during CHO-based monoclonal antibody manufacturing process leading to disulfide bond reduction

Monoclonal antibody (mAb) interchain disulfide bond reduction can cause a loss of function and negatively impact the therapeutic’s efficacy and safety. Disulfide bond reduction has been observed at various stages during the manufacturing process, including processing of the harvested material. The factors and mechanisms driving this phenomenon are not fully understood. In this study, we examined the host cell proteome as a potential factor affecting the susceptibility of a mAb to disulfide bond reduction in the harvested cell culture fluid (HCCF). We used untargeted liquid-chromatography-mass spectrometry-based proteomics experiments in conjunction with a semi-automated protein identification workflow to systematically compare Chinese hamster ovary (CHO) cell protein abundances between bioreactor conditions that result in reduction-susceptible and reduction-free HCCF. Although the growth profiles and antibody titers of these two bioreactor conditions were indistinguishable, we observed broad differences in host cell protein (HCP) expression. We found significant differences in the abundance of glycolytic enzymes, key protein reductases, and antioxidant defense enzymes. Multivariate analysis of the proteomics data determined that upregulation of stress-inducible endoplasmic reticulum (ER) and other chaperone proteins is a discriminatory characteristic of reduction-susceptible HCP profiles. Overall, these results suggest that stress response pathways activated during bioreactor culture increase the reduction-susceptibility of HCCF. Consequently, these pathways could be valuable targets for optimizing culture conditions to improve protein quality.

Optimization and kinetic modeling of interchain disulfide bond reoxidation of monoclonal antibodies in bioprocesses

Disulfide bonds play a crucial role in folding and structural stabilization of monoclonal antibodies (mAbs). Disulfide bond reduction may happen during the mAb manufacturing process, resulting in low molecular weight species and possible failure to meet product specifications. Although many mitigation strategies have been developed to prevent disulfide reduction, to the best of our knowledge, reforming disulfide bonds from the reduced antibody in manufacturing has not previously been reported. Here, we explored a novel rescue strategy in the downstream process to repair the broken disulfide bonds via in-vitro redox reactions on Protein A resin. Redox conditions including redox pair (cysteine/cystine ratio), pH, temperature, and reaction time were examined to achieve high antibody purity and a high reaction rate. Under the optimal redox condition, >90% reduced antibody could be reoxidized to form an intact antibody on Protein A resin in an hour. In addition, this study showed high flexibility on the range of the intact mAb fraction in the initial reduced mAb sample (the lower limit of intact mAb faction could be 14% based on the data reported in this study). Furthermore, a kinetic model based on elementary oxidative reactions was constructed to help optimize the reoxidation conditions and to predict product purity. Together, the deep understanding of interchain disulfide bond reoxidation, combined with the predictive kinetic model, provided a good foundation to implement a rescue strategy to generate high-purity antibodies with substantial cost savings in manufacturing processes.

Prevention of Fab-arm exchange and antibody reduction via stabilization of the IgG4 hinge region

IgG4s are dynamic molecules that undergo a process called Fab-arm exchange. Disulfide bonds between heavy chains are transiently reduced, resulting in half antibodies that reform intact antibodies with other IgG4 half antibodies. In vivo, therapeutic IgG4s can recombine with endogenous IgG4s, resulting in a heterogeneous mixture of bispecific antibodies. A related issue that can occur for any therapeutic protein during manufacturing is interchain disulfide bond reduction. For IgG4s, this primarily results in high levels of half-mAb that persist through purification processes. The S228P mutation has been used to prevent half-mAb formation. However, we demonstrated that IgG4s with the S228P mutation are subject to half-mAb formation and Fab-arm exchange in reducing environments. We identified two novel mutations that stabilize the heavy-heavy chain interaction via incorporation of additional disulfide bonds in the hinge region. Individually, these mutations increase stability toward reduction and lessen Fab-arm exchange. Combination of all three mutations, Y219C, G220C, and S228P, has an additive benefit resulting in an IgG4 with ˃7-fold increase in stability toward reduction while preventing Fab-arm exchange. Importantly, the mutations do not affect antigen binding or Fc effector function. These mutations hold great promise for solving mAb reduction during manufacturing and preventing Fab-arm exchange in vivo.

Antibody disulfide bond reduction and recovery during biopharmaceutical process development-A review

Antibody disulfide bond reduction has been a challenging issue in monoclonal antibody manufacturing. It could lead to a decrease of product purity and failure to meet the targeted product profile and/or specifications. More importantly, disulfide bond reduction could also impact drug safety and efficacy. Scientists across the industry have been examining the root causes and developing mitigation strategies to address the challenge. In recent years, with the development of high titer mammalian cell culture processes to meet the rapidly growing demand for antibody biopharmaceuticals, disulfide bond reduction has been observed more frequently. Thus, it is necessary to continue evolving the disulfide reduction mitigation strategies and developing novel approaches to maintain high product quality. Additionally, in recent years as more complex molecules (such as bispecific and trispecific antibodies) emerge, the molecular heterogeneity due to incomplete formation of the interchain disulfide bonds becomes a more imperative challenging issue. Given the disulfide reduction challenges that biotech industry is facing, in this review, we provide a comprehensive scientific summary of the root cause analysis of disulfide reduction during process development of antibody therapeutics, mitigation strategies and its potential remediated recovery based on published papers. First, this paper intends to highlight different aspects of the root cause for disulfide reduction. Secondly, to provide a broader understanding of the disulfide bond reduction in downstream process, this paper discusses disulfide bond reduction impact on product stability, associated analytical methods for disulfide bond reduction detection and characterization, process control strategies as well as their manufacturing implementation. In addition, brief perspectives on the development of future mitigation strategies are also reviewed, including platform alignment, mitigation strategy application for the emerging new modalities such as bispecific and trispecific antibodies as well as using machine learning to identify molecule susceptibility of disulfide bond reduction. The data in this review are originated from the published papers.

A novel hydrogen peroxide evolved CHO host can improve the expression of difficult to express bispecific antibodies

The manufacture of bispecific antibodies by Chinese hamster ovary (CHO) cells is often hindered by lower product yields compared to monoclonal antibodies. Recently, reactive oxygen species have been shown to negatively impact antibody production. By contrast, strategies to boost cellular antioxidant capacity appear to be beneficial for recombinant protein expression. With this in mind, we generated a novel hydrogen peroxide evolved host using directed host cell evolution. Here we demonstrate that this host has heritable resistance to hydrogen peroxide over many generations, displays enhanced antioxidant capacity through the upregulation of several, diverse antioxidant defense genes such as those involved in glutathione synthesis and turnover, and has improved glutathione content. Additionally, we show that this host has significantly improved transfection recovery times, improved growth and viability properties in a fed‐batch production process, and elevated expression of two industrially relevant difficult to express bispecific antibodies compared to unevolved CHO control host cells. These findings demonstrate that host cell evolution represents a powerful methodology for improving specific host cell characteristics that can positively impact the expression of difficult to express biotherapeutics.

Cysteine in cell culture media induces acidic IgG1 species by disrupting the disulfide bond network

A high degree of charge heterogeneity is an unfavorable phenomenon commonly observed for therapeutic monoclonal antibodies (mAbs). Removal of these impurities during manufacturing often comes at the cost of impaired step yields. A wide spectrum of posttranslational and chemical modifications is known to modify mAb charge. However, a deeper understanding of underlying mechanisms triggering charged species would be beneficial for the control of mAb charge variants during bioprocessing. In this study, a comprehensive analytical investigation was carried out to define the root causes and mechanisms inducing acidic variants of an immunoglobulin G1‐derived mAb. Characterization of differently charged species by liquid chromatography–mass spectrometry revealed the reduction of disulfide bonds in acidic variants, which is followed by cysteinylation and glutathionylation of cysteines. Importantly, biophysical stability and integrity of the mAb are not affected. By in vitro incubation of the mAb with the reducing agent cysteine, disulfide bond degradation was directly linked to an increase of numerous acidic species. Modifying the concentrations of cysteine during the fermentation of various mAbs illustrated that redox potential is a critical aspect to consider during bioprocess development with respect to charge variant control.

Toward Drug-Like Multispecific Antibodies by Design

The success of antibody therapeutics is strongly influenced by their multifunctional nature that couples antigen recognition mediated by their variable regions with effector functions and half-life extension mediated by a subset of their constant regions. Nevertheless, the monospecific IgG format is not optimal for many therapeutic applications, and this has led to the design of a vast number of unique multispecific antibody formats that enable targeting of multiple antigens or multiple epitopes on the same antigen. Despite the diversity of these formats, a common challenge in generating multispecific antibodies is that they display suboptimal physical and chemical properties relative to conventional IgGs and are more difficult to develop into therapeutics. Here we review advances in the design and engineering of multispecific antibodies with drug-like properties, including favorable stability, solubility, viscosity, specificity and pharmacokinetic properties. We also highlight emerging experimental and computational methods for improving the next generation of multispecific antibodies, as well as their constituent antibody fragments, with natural IgG-like properties. Finally, we identify several outstanding challenges that need to be addressed to increase the success of multispecific antibodies in the clinic.

Metabolic understanding of disulfide reduction during monoclonal antibody production

The disulfide reduction of intact monoclonal antibodies (mAbs) and subsequent formation of low molecular weight (LMW) species pose a direct risk to product stability, potency, and patient safety. Although enzymatic mechanisms of reduction are well established, an understanding of the cellular mechanisms during the bioreactor process leading to increased risk of disulfide reduction after harvest remains elusive. In this study, we examined bench, pilot, and manufacturing-scale batches of two mAbs expressed in Chinese hamster ovary (CHO) cells, where harvested cell culture fluid (HCCF) occasionally demonstrated disulfide reduction. Comparative proteomics highlighted a significant elevation in glyceraldehyde-3-phosphate dehydrogenase (GAPDH) levels in a highly reducing batch of HCCF, compared to a non-reducing batch. Analysis during production cell culture showed that increased GAPDH gene and protein expression correlated to disulfide reduction risk in HCCF in every case examined. Additionally, glucose 6-phosphate dehydrogenase (G6PD) activity and an increased (≥ 300%) lactate/pyruvate molar ratio (lac/pyr) during production cell culture correlated to disulfide reduction risk, suggesting a metabolic shift to the pentose phosphate pathway (PPP). In all, these results suggest that metabolic alterations during cell culture lead to changes in protein expression and enzyme activity that in turn increase the risk of disulfide reduction in HCCF. KEY POINTS: • Bioreactor conditions resulted in reduction susceptible harvest material. • GAPDH expression, G6PD activity, and lac/pyr ratio correlated with mAb reduction. • Demonstrated role for cell metabolic changes in post-harvest mAb reduction. Graphical abstract.

Investigation into the impact of tyrosine on the product formation and quality attributes of mAbs in rCHO cell cultures

Tyrosine (Tyr) is crucial to the maintenance of the monoclonal antibody (mAb) titers and quality attributes in fed-batch cultures of recombinant Chinese hamster ovary (rCHO) cells. However, the relation between tyrosine and these aspects is not yet fully defined. In order to further elucidate such a relation, two groups of fed-batch experiments with high tyrosine (H-T) or low tyrosine (L-T) additions producing an IgG1 monoclonal antibody against CD20 were implemented to investigate the intracellular and extracellular effects of tyrosine on the culture performance. It was found that the scarcity of tyrosine led to the distinctive reduction in both viable cell density and antibody specific production rate, hence the sharply reduced titer, possibly related to the impaired translation efficiency caused by the substrate limitation of tyrosine. In addition, alterations to the critical quality attributes were detected in the L-T group, compared to those in the H-T condition. Notable decrease in the contents of intact antibody was found under the L-T condition because of the elevated reductive level in the supernatant. Moreover, the aggregate content in the L-T condition was also reduced, probably resulting from the accumulation of extracellular cystine. In particular, the lysine variant content noticeably increased with tyrosine limitation owing to the downregulation of two carboxypeptidases, i.e., CpB and CpH. Overall, understanding the role of tyrosine in these aspects is fundamental to the increase of product titers and control of critical quality attributes in the monoclonal antibody production of rCHO cell fed-batch cultures. KEY POINTS: • Tyrosine is essential in the maintenance of product titers and the control of product qualities in high cell density cultivations in rCHO cell. • This study revealed the bottleneck of decreased q_mAbupon the deficiency of tyrosine. • The impact of tyrosine on the critical product qualities and the underlying mechanisms were also thoroughly assessed.

Impact of enzymatic reduction on bivalent bispecific antibody fragmentation and loss of product purity upon reoxidation

Antibody disulfide bond (DSB) reduction during manufacturing processes is a widely observed phenomenon attributed to host cell reductases present in harvest cell culture fluid. Enzyme-induced antibody reduction leads to product fragments and aggregates that increase the impurity burden on the purification process. The impact of reduction on bivalent bispecific antibodies (BisAbs), which are increasingly entering the clinic, has yet to be investigated. We focused on the reduction and reoxidation properties of a homologous library of bivalent BisAb formats that possess additional single-chain Fv (scFv) fragments with engineered DSBs. Despite all BisAbs having similar susceptibilities to enzymatic reduction, fragmentation pathways were dependent on the scFv-fusion site. Reduced molecules were allowed to reoxidize with and without low pH viral inactivation treatment. Both reoxidation studies demonstrated that multiple, complex BisAb species formed as a result of DSB mispairing. Furthermore, aggregate levels increased for all molecules when no low pH treatment was applied. Combined, our results show that complex DSB mispairing occurs during downstream processes while aggregate formation is dependent on sample treatment. These results are applicable to other novel monoclonal antibody-like formats containing engineered DSBs, thus highlighting the need to prevent reduction of novel protein therapeutics to avoid diminished product quality during manufacturing.

High-performance sono/nano-catalytic system: Fe3O4@Pd/CaCO3-DTT core/shell nanostructures, a suitable alternative for traditional reducing agents for antibodies

Herein, a novel heterogeneous nanoscale reducing agent for antibody cleavage, made of iron oxide nanoparticles, silica network, palladium on calcium carbonate (10%), and dithiothreitol (Fe₃O₄@Pd/CaCO₃-DTT), is presented as a substantial alternative for traditional homogeneous analogues. Conventionally, antibody fragmentation is accomplished using reducing agents and proteases that digest or cleave certain portions of the immunoglobulin protein structure to provide active thiol sites for drug tagging aims. Then, dialysis process is needed to separate excess chemical structures and purify the reduced antibody. In this work, we have made an effort to design a suitable heterogeneous tool for protein cleavage and skip the dialysis process for purification of the reduced antibody. In this regard, firstly, various preparation methods including microwave irradiation, reflux and ultrasonication have been precisely compared, and it has been proven that the best result is obtained through 10 min ultrasound (US) irradiation using an US bath with 50 KHz frequency and 200 W L^-1 power density. Then, all the necessary structural analyses have been done and thoroughly interpreted for the final product. Afterward, the catalytic performance of Fe₃O₄@Pd/CaCO₃-DTT nanoscale system in the presence of US waves (50 KHz, 200 W) has been monitored using some disulphide derivatives. The NPs could be conveniently separated from the mixture through their substantial paramagnetic property. Thus, dialysis process in which various types of membranes are used is practically jumped after the reduction process. In this work, this is clearly demonstrated that there is a constructive synergistic effect between US waves and prepared Fe₃O₄@Pd/CaCO₃-DTT nanoscale reducing agent. Ultimately, trastuzumab (anti HER-2) antibody has been used to test the performance of the prepared Fe₃O₄@Pd/CaCO₃-DTT NPs in a real protein reduction reaction.

On-column disulfide bond formation of monoclonal antibodies during Protein A chromatography eliminates low molecular weight species and rescues reduced antibodies

Disulfide bond reduction, which commonly occurs during monoclonal antibody (mAb) manufacturing processes, can result in a drug substance with high levels of low molecular weight (LMW) species that may fail release specifications because the drug's safety and the efficiency may be affected by the presence of this material. We previously studied disulfide reoxidation of mAbs and demonstrated that disulfide bonds could be reformed from the reduced antibody via redox reactions under an optimal redox condition on Protein A resin. The study here implements a redox system in a manufacturing setting to rescue the reduced mAb product and to further eliminate LMW issues in downstream processing. As such, we incorporate the optimized redox system as one of the wash buffers in Protein A chromatography to enable an on-column disulfide reoxidation to form intact antibody in vitro. Studies at laboratory scale (1 cm (ID) x 20 cm (Height), MabSelect SuRe LX) and pilot scale (30 cm (ID) x 20 cm (Height), MabSelect SuRe LX) were performed to demonstrate the effectiveness and robustness of disulfide formation with multiple mAbs using redox wash on Protein A columns. By applying this rescue strategy using ≤50 g/L-resin loading, the intact mAb purity was improved from <5% in the Protein A column load to >90% in the Protein A column elution with a product yield of >90%. Studies were also done to confirm that adding the redox wash has no negative impact on process yield or impurity removal or product quality. The rescued mAbs were confirmed to form complete interchain disulfide bonds, exhibiting comparable biophysical properties to the reference material. Furthermore, since the redox wash is followed by a bridging buffer wash before the final elution, no additional burden is involved in removing the redox components during the downstream steps. Due to its ease of implementation, significant product purity improvement, and minimal impact on other product quality attributes, we demonstrate that the on-column reoxidation using a redox system is a powerful, simple, and safe tool to recover reduced mAb during manufacturing. Moreover, the apparent benefits of using a high-pH redox wash may further drive the evolution of Protein A platform processes.

Using hydrogen peroxide to prevent antibody disulfide bond reduction during manufacturing process

During large-scale monoclonal antibody manufacturing, disulfide bond reduction of antibodies, which results in generation of low molecule weight species, is occasionally observed. When this happens, the drug substance does not meet specifications. Many investigations have been conducted across the biopharmaceutical industry to identify the root causes, and multiple strategies have been proposed to mitigate the problem. The reduction is correlated with the release of cellular reducing components and depletion of dissolved oxygen before, during, and after harvest. Consequently, these factors can lead to disulfide reduction over long-duration storage at room temperature prior to Protein A chromatography. Several strategies have been developed to minimize antibody reduction, including chemical inhibition of reducing components, maintaining aeration before and after harvest, and chilling clarified harvest during holding. Here, we explore the use of hydrogen peroxide in clarified harvest bulk or cell culture fluid as a strategy to prevent disulfide reduction. A lab-scale study was performed to demonstrate the effectiveness of hydrogen peroxide in preventing antibody reduction using multiple IgG molecules. Studies were done to define the optimal concentration of hydrogen peroxide needed to avoid unnecessary oxidization of the antibody products. We show that adding a controlled amount of hydrogen peroxide does not change product quality attributes of the protein. Since hydrogen peroxide is soluble in aqueous solutions and decomposes into water and oxygen, there is no additional burden involved in removing it during the downstream purification steps. Due to its ease of use and minimal product impact, we demonstrate that hydrogen peroxide treatment is a powerful, simple tool to quench reducing potential by simply mixing it with harvested cell culture fluid.