Reduction of charge variants by CHO cell culture process optimization

Assessing the Manufacturability and Critical Quality Attribute Profiles of Anti-IL-8 Immunoglobulin G Mutant Variants

Early-phase manufacturability assessment of high-concentration therapeutic monoclonal antibodies (mAbs) involves screening of process-related risks impacting their translation into the clinic. Manufacturing a mAb at scale relies on cost-effective and robust approaches to derisk manufacturability parameters, such as viscosity, conformational stability, aggregation, and process-related impurities. Using a panel of model anti-IL-8 IgG1 mutants, we investigate upstream and downstream processability, phase behavior, and process-related impurities. We correlate trends in the biophysical properties of mAbs with their cell growth, expression, filtration flux, solubility, and post-translational modifications. We find significant trends in increased relative free light chain expression with heavy chain mutants and detect a requirement for adjusted operation pH for cation exchange polishing steps with charge-altering variants. Moreover, trends between phase stability and high-concentration viscosity were observed. We also investigated unique correlations between increased glycosylation and biophysical behavior. Further in-depth analysis and modeling are required to elucidate the impact of the mAb sequence on the metabolism of the expression system, solubility limits, and alternative gelation models as future directions.

A high-titer scalable Chinese hamster ovary transient expression platform for production of biotherapeutics

Transient gene expression (TGE) in Chinese hamster ovary (CHO) cells offers a route to accelerate biologics development by delivering material weeks to months earlier than what is possible with conventional cell line development. However, low productivity, inconsistent product quality profiles, and scalability challenges have prevented its broader adoption. In this study, we develop a scalable CHO-based TGE system achieving 1.9 g/L of monoclonal antibody in an unmodified host. We integrated continuous flow-electroporation and alternate tangential flow (ATF) perfusion to enable an end-to-end closed system from N-1 perfusion to fed-batch 50-L bioreactor production. Optimization of both the ATF operation for three-in-one application-cell growth, buffer exchange, and cell mass concentration-and the flow-electroporation process, led to a platform for producing biotherapeutics using transiently transfected cells. We demonstrate scalability up to 50-L bioreactor, maintaining a titer over 1 g/L. We also show comparable quality between both transiently and stably produced material, and consistency across batches. The results confirm that purity, charge variants and N-glycan profiles are similar. Our study demonstrates the potential of CHO-based TGE platforms to accelerate biologics process development timelines and contributes evidence supporting its feasibility for manufacturing early clinical material, aiming to strengthen endorsement for TGE's wider implementation.

Enhancing recombinant antibody yield in Chinese hamster ovary cells

A range of recombinant monoclonal antibodies (rMAbs) have found application in treating diverse diseases, spanning various cancers and immune system disorders. Chinese hamster ovary (CHO) cells have emerged as the predominant choice for producing these rMAbs due to their robustness, ease of transfection, and capacity for posttranslational modifications akin to those in human cells. Transient transfection and/or stable expression could be conducted to express rMAbs in CHO cells. To bolster the yield of rMAbs in CHO cells, a multitude of approaches have been developed, encompassing vector optimization, medium formulation, cultivation parameters, and cell engineering. This review succinctly outlines these methodologies when also addressing challenges encountered in the production process, such as issues with aggregation and fucosylation.

Advancements in CHO metabolomics: techniques, current state and evolving methodologies

Background: Investigating the metabolic behaviour of different cellular phenotypes, i.e., good/bad grower and/or producer, in production culture is important to identify the key metabolite(s)/pathway(s) that regulate cell growth and/or recombinant protein production to improve the overall yield. Currently, LC-MS, GC-MS and NMR are the most used and advanced technologies for investigating the metabolome. Although contributed significantly in the domain, each technique has its own biasness towards specific metabolites or class of metabolites due to various reasons including variability in the concept of working, sample preparation, metabolite-extraction methods, metabolite identification tools, and databases. As a result, the application of appropriate analytical technique(s) is very critical. Purpose and scope: This review provides a state-of-the-art technological insights and overview of metabolic mechanisms involved in regulation of cell growth and/or recombinant protein production for improving yield from CHO cultures. Summary and conclusion: In this review, the advancements in CHO metabolomics over the last 10 years are traced based on a bibliometric analysis of previous publications and discussed. With the technical advancement in the domain of LC-MS, GC-MS and NMR, metabolites of glycolytic and nucleotide biosynthesis pathway (glucose, fructose, pyruvate and phenylalanine, threonine, tryptophan, arginine, valine, asparagine, and serine, etc.) were observed to be upregulated in exponential-phase thereby potentially associated with cell growth regulation, whereas metabolites/intermediates of TCA, oxidative phosphorylation (aspartate, glutamate, succinate, malate, fumarate and citrate), intracellular NAD+/NADH ratio, and glutathione metabolic pathways were observed to be upregulated in stationary-phase and hence potentially associated with increased cell-specific productivity in CHO bioprocess. Moreover, each of technique has its own bias towards metabolite identification, indicating their complementarity, along with a number of critical gaps in the CHO metabolomics pipeline and hence first time discussed here to identify their potential remedies. This knowledge may help in future study designs to improve the metabolomic coverage facilitating identification of the metabolites/pathways which might get missed otherwise and explore the full potential of metabolomics for improving the CHO bioprocess performances.

In-line buffer exchange in the coupling of Protein A chromatography with weak cation exchange chromatography for the determination of charge variants of immunoglobulin G derived from chinese hamster ovary cell cultures

Immunoglobulin G (IgG) is the most common monoclonal antibody (mAb) grown for therapeutic applications. While IgG is often selectively isolated from cell lines using protein A (ProA) chromatography, this is only a stepping stone for complete characterization. Further classification can be obtained from weak cation exchange chromatography (WCX) to determine IgG charge variant distributions. The charge variants of monoclonal antibodies can influence the stability and efficacy in vivo, and deviations in charge heterogeneity are often cell-specific and sensitive to upstream process variability. Current methods to characterize IgG charge variants are often performed off-line, meaning that the IgG eluate from the ProA separation is collected, diluted to adjust the pH, and then transferred to the WCX separation, adding time, complexity, and potential contamination to the sample analysis process. More recently, reports have appeared to streamline this separation using in-line two-dimensional liquid chromatography (2D-LC). Presented here is a novel, 2D-LC coupling of ProA in the first dimension (1D) and WCX in the second dimension (2D) chromatography. As anticipated, the initial direct column coupling proved to be challenging due to the pH incompatibility between the mobile phases for the two stages. To solve the solvent compatibility issue, a size exclusion column was placed in the switching valve loop of the 2D-LC instrument to act as a means for the on-line solvent exchange. The efficacy of the methodology presented was confirmed through a charge variant determination using the NIST monoclonal antibody standard (NIST mAb), yielding correct acidic, main, and basic variant compositions. The methodology was employed to determine the charge variant profile of IgG from an in-house cultured Chinese hamster ovary (CHO) cell supernatant. It is believed that this methodology can be easily implemented to provide higher-throughput assessment of IgG charge variants for process monitoring and cell line development.

An automated high inoculation density fed-batch bioreactor, enabled through N-1 perfusion, accommodates clonal diversity and doubles titers

An important consideration for biopharmaceutical processes is the cost of goods (CoGs) of biotherapeutics manufacturing. CoGs can be reduced by dramatically increasing the productivity of the bioreactor process. In this study, we demonstrate that an intensified process which couples a perfused N-1 seed reactor and a fully automated high inoculation density (HID) N stage reactor substantially increases the bioreactor productivity as compared to a low inoculation density (LID) control fed-batch process. A panel of six CHOK1SV GS-KO® CHO cell lines expressing three different monoclonal antibodies was evaluated in this intensified process, achieving an average 85% titer increase and 132% space-time yield (STY) increase was demonstrated when comparing the 12-day HID process to a 15-day LID control process. These productivity increases were enabled by automated nutrient feeding in both the N-1 and N stage bioreactors using in-line process analytical technologies (PAT) and feedback control. The N-1 bioreactor utilized in-line capacitance to automatically feed the bioreactor based on a capacitance-specific perfusion rate (CapSPR). The N-stage bioreactor utilized in-line Raman spectroscopy to estimate real-time concentrations of glucose, phenylalanine, and methionine, which are held to target set points using automatic feed additions. These automated feeding methodologies were shown to be generalizable across six cell lines with diverse feed requirements. We show this new process can accommodate clonal diversity and reproducibly achieve substantial titer uplifts compared to traditional cell culture processes, thereby establishing a baseline technology platform upon which further increases bioreactor productivity and CoGs reduction can be achieved.

From cell factories to patients: Stability challenges in biopharmaceuticals manufacturing and administration with mitigation strategies

Active ingredients of biopharmaceuticals consist of a wide array of biomolecular structures, including those of enzymes, monoclonal antibodies, nucleic acids, and recombinant proteins. Recently, these molecules have dominated the pharmaceutical industry owing to their safety and efficacy. However, their manufacturing is hindered by high cost, inadequate batch-to-batch equivalence, inherent instability, and other quality issues. This article is an up-to-date review of the challenges encountered during different stages of biopharmaceutical production and mitigation of problems arising during their development, formulation, manufacturing, and administration. It is a broad overview discussion of stability issues encountered during product life cycle i.e., upstream processing (aggregation, solubility, host cell proteins, color change), downstream bioprocessing (aggregation, fragmentation), formulation, manufacturing, and delivery to patients.

Progress in fed-batch culture for recombinant protein production in CHO cells

Nearly 80% of the approved human therapeutic antibodies are produced by Chinese Hamster Ovary (CHO) cells. To achieve better cell growth and high-yield recombinant protein, fed-batch culture is typically used for recombinant protein production in CHO cells. According to the demand of nutrients consumption, feed medium containing multiple components in cell culture can affect the characteristics of cell growth and improve the yield and quality of recombinant protein. Fed-batch optimization should have a connection with comprehensive factors such as culture environmental parameters, feed composition, and feeding strategy. At present, process intensification (PI) is explored to maintain production flexible and meet forthcoming demands of biotherapeutics process. Here, CHO cell culture, feed composition in fed-batch culture, fed-batch culture environmental parameters, feeding strategies, metabolic byproducts in fed-batch culture, chemostat cultivation, and the intensified fed-batch are reviewed. KEY POINTS: • Fed-batch culture in CHO cells is reviewed. • Fed-batch has become a common technology for recombinant protein production. • Fed batch culture promotes recombinant protein production in CHO cells.

Kinetic modeling: A tool for temperature shift and feeding optimization in cell culture process development

Mammalian cells have dominated the biopharmaceutical industry for biotherapeutic protein production and tremendous efforts have been devoted to enhancing productivity during the cell culture process development. However, determining the optimal process conditions is still a huge challenge. Constrained by the limited resources and timeline, usually it is impossible to fully explore the optimal range of all process parameters (temperature, pH, dissolved oxygen, basal and feeding medium, additives, etc.). Kinetic modeling, which finds out the global optimum by systematically screening all potential conditions for cell culture process, provides a solution to this dilemma. However, studies on optimizing temperature shift and feeding strategies simultaneously using this approach have not been reported. In this study, we built up a kinetic model of fed-batch culture process for simultaneous optimization of temperature shift and feeding strategies. The fitting results showed high accuracy and demonstrated that the kinetic model can be used to describe the mammalian cell culture performance. In addition, five more fed-batch experiments were conducted to test this model's predicting power on different temperature shift and feeding strategies. It turned out that the predicted data matched well with experimental ones on viable cell density (VCD), metabolites, and titer for the entire culture duration and allowed selecting the same best condition with the experimental results. Therefore, adopting this approach can potentially reduce the number of experiments required for culture process optimization.

Transcriptomic analysis reveals mode of action of butyric acid supplementation in an intensified CHO cell fed‐batch process

Process intensification is increasingly used in the mammalian biomanufacturing industry. The key driver of this trend is the need for more efficient and flexible production strategies to cope with the increased demand for biotherapeutics predicted in the next years. Therefore, such intensified production strategies should be designed, established, and characterized. We established a CHO cell process consisting of an intensified fed‐batch (iFB), which is inoculated by an N‐1 perfusion process that reaches high cell concentrations (100 × 10⁶ c ml⁻¹). We investigated the impact of butyric acid (BA) supplementation in this iFB process. Most prominently, higher cellular productivities of more than 33% were achieved, thus 3.5 g L⁻¹ of immunoglobulin G (IgG) was produced in 6.5 days. Impacts on critical product quality attributes were small. To understand the biological mechanisms of BA in the iFB process, we performed a detailed transcriptomic analysis. Affected gene sets reflected concurrent inhibition of cell proliferation and impact on histone modification. These translate into subsequently enhanced mechanisms of protein biosynthesis: enriched regulation of transcription, messenger RNA processing and transport, ribosomal translation, and cellular trafficking of IgG intermediates. Furthermore, we identified mutual tackling points for optimization by gene engineering. The presented strategy can contribute to meet future requirements in the continuously demanding field of biotherapeutics production.

Strategies and Considerations for Improving Recombinant Antibody Production and Quality in Chinese Hamster Ovary Cells

Recombinant antibodies are rapidly developing therapeutic agents; approximately 40 novel antibody molecules enter clinical trials each year, most of which are produced from Chinese hamster ovary (CHO) cells. However, one of the major bottlenecks restricting the development of antibody drugs is how to perform high-level expression and production of recombinant antibodies. The high-efficiency expression and quality of recombinant antibodies in CHO cells is determined by multiple factors. This review provides a comprehensive overview of several state-of-the-art approaches, such as optimization of gene sequence of antibody, construction and optimization of high-efficiency expression vector, using antibody expression system, transformation of host cell lines, and glycosylation modification. Finally, the authors discuss the potential of large-scale production of recombinant antibodies and development of culture processes for biopharmaceutical manufacturing in the future.

Chromatographic capture of cells to achieve single stage clarification in recombinant protein purification

Recent advancements in cell culture engineering have allowed drug manufacturers to achieve higher productivity by driving higher product titers through cell line engineering and high‐cell densities. However, these advancements have shifted the burden to clarification and downstream processing where the difficulties now revolve around removing higher levels of process‐ and product‐related impurities. As a result, a lot of research efforts have turned to developing new approaches and technologies or process optimization to still deliver high quality biological products while controlling cost of goods. Here, we explored the impact of a novel single use technology employing chromatographic principle‐based clarification for a process‐intensified cell line technology. In this study, a 16% economic benefit ($/g) was observed using a single‐use chromatographic clarification compared to traditional single‐use clarification technology by improving the overall product cost through decreased operational complexity, higher loading capacity, increased product recovery, and higher impurity clearance. In the end, the described novel chromatographic approach significantly simplified and enhanced the cell culture fluid harvest unit operation by combining the reduction of insoluble and key soluble contaminants of the harvest fluid into a single stage.

Chemical speciation of trace metals in mammalian cell culture media: looking under the hood to boost cellular performance and product quality

Upstream process development seeks to optimize media formulations to promote robust cell culture conditions and regulate product quality attributes such as glycosylation, aggregation, and charge variants. Transition metal ions Mn, Fe, Cu, and Zn present in cell culture media have a significant impact on cell growth, metabolism and product quality. These metals and other media components can have different chemical associations or speciation in media that are poorly characterized but may significantly impact their properties and effect on cellular performance. Computer-based equilibrium models are a good starting point for exploring metal speciation, bioavailability and conditions where precipitation may occur. However, some equilibrium constants, especially for newly introduced medium components, have not been experimentally determined. Owing to concurrent physical and biological processes, speciation may also be controlled by reaction kinetics rather than by equilibrium. These factors highlight the importance of analytically interrogating medium speciation to gain insights into the complex interconnections between media components and bioprocess performance.

Proteomic Profiling of IgG1 Producing CHO Cells Using LC/LC-SPS-MS3: The Effects of Bioprocessing Conditions on Productivity and Product Quality

The biopharmaceutical market is dominated by monoclonal antibodies, the majority of which are produced in Chinese hamster ovary (CHO) cell lines. Intense cell engineering, in combination with optimization of various process parameters results in increasing product titers. To enable further improvements in manufacturing processes, detailed information about how certain parameters affect cellular mechanisms in the production cells, and thereby also the expressed drug substance, is required. Therefore, in this study the effects of commonly applied changes in bioprocessing parameters on an anti-IL8 IgG1 producing CHO DP-12 cell line were investigated on the level of host cell proteome expression combined with product quality assessment of the expressed IgG1 monoclonal antibody. Applying shifts in temperature, pH and dissolved oxygen concentration, respectively, resulted in altered productivity and product quality. Furthermore, analysis of the cells using two-dimensional liquid chromatography-mass spectrometry employing tandem mass tag based isotopic quantitation and synchronous precursor selection-MS³ detection revealed substantial changes in the protein expression profiles of CHO cells. Pathway analysis indicated that applied bioprocessing conditions resulted in differential activation of oxidative phosphorylation. Additionally, activation of ERK5 and TNFR1 signaling suggested an affected cell cycle. Moreover, in-depth product characterization by means of charge variant analysis, peptide mapping, as well as structural and functional analysis, revealed posttranslational and structural changes in the expressed drug substance. Taken together, the present study allows the conclusion that, in anti-IL8 IgG1 producing CHO DP-12 cells, an improved energy metabolism achieved by lowering the cell culture pH is favorable when aiming towards high antibody production rates while maintaining product quality.

Use of novel cystine analogs to decrease oxidative stress and control product quality

Continuous improvements of cell culture media are required in order to ensure high yield and product quality. However, some components can be instable and lead to detrimental effects on bioprocess performances. l-cysteine is an essential amino acid commonly used in cell culture media. Despite its beneficial effect on recombinant protein production, in some cases, this component can be responsible for product microheterogeneity. In this context, alternative components have to be found in order to reduce product variants while maintaining high productivity. In this study, we have assessed the performance of different cysteine and cystine analogs : N-acetyl-cysteine, s-sulfocysteine, N,N'-diacetyl-l-cystine and the N,N'-diacetyl-l-cystine dimethylester (DACDM). Replacement of cysteine by cystine analogs, and especially DACDM, has shown positive impact on charge variants level and recombinant protein coloration level. Moreover, this molecule contributed to the increase of the intracellular glutathione pool, which suggests a close relationship with the oxidative stress regulation.