Exploring cellular behavior under transient gene expression and its impact on mAb productivity and Fc‐glycosylation

Transient gene expression (TGE) is a methodology employed in bioprocessing for the fast provision of recombinant protein material. Mild hypothermia is often introduced to overcome the low yield typically achieved with TGE and improve specific protein productivity. It is therefore of interest to examine the impact of mild hypothermic temperatures on both the yield and quality of transiently expressed proteins and the relationship to changes in cellular processes and metabolism. In this study, we focus on the ability of a Chinese hamster ovary cell line to galactosylate a recombinant monoclonal antibody (mAb) product. Through experimentation and flux balance analysis, our results show that TGE in mild hypothermic conditions led to a 76% increase in q_P compared to TGE at 36.5°C in our system. This increase is accompanied by increased consumption of nutrients and amino acids, together with increased production of intracellular nucleotide sugar species, and higher rates of mAb galactosylation, despite a reduced rate of cell growth. The reduction in biomass accumulation allowed cells to redistribute their energy and resources toward mAb synthesis and Fc‐glycosylation. Interestingly, the higher capacity of cells to galactosylate the recombinant product in TGE at 32°C appears not to have been assisted by the upregulation of galactosyltransferases (GalTs), but by the increased expression of N‐acetylglucosaminyltransferase II (GnTII) in this cell line, which facilitated the production of bi‐antennary glycan structures for further processing.     

Controlling the time evolution of mAb N‐linked glycosylation ‐ Part II: Model‐based predictions

N‐linked glycosylation is known to be a crucial factor for the therapeutic efficacy and safety of monoclonal antibodies (mAbs) and many other glycoproteins. The nontemplate process of glycosylation is influenced by external factors which have to be tightly controlled during the manufacturing process. In order to describe and predict mAb N‐linked glycosylation patterns in a CHO‐S cell fed‐batch process, an existing dynamic mathematical model has been refined and coupled to an unstructured metabolic model. High‐throughput cell culture experiments carried out in miniaturized bioreactors in combination with intracellular measurements of nucleotide sugars were used to tune the parameter configuration of the coupled models as a function of extracellular pH, manganese and galactose addition. The proposed modeling framework is able to predict the time evolution of N‐linked glycosylation patterns during a fed‐batch process as a function of time as well as the manipulated variables. A constant and varying mAb N‐linked glycosylation pattern throughout the culture were chosen to demonstrate the predictive capability of the modeling framework, which is able to quantify the interconnected influence of media components and cell culture conditions. Such a model‐based evaluation of feeding regimes using high‐throughput tools and mathematical models gives rise to a more rational way to control and design cell culture processes with defined glycosylation patterns. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1135–1148, 2016     

Controlling the time evolution of mAb N‐linked glycosylation,Part I: Microbioreactor experiments

N‐linked glycosylation is of key importance for the efficacy of many biotherapeutic proteins such as monoclonal antibodies (mAbs). Media components and cell culture conditions have been shown to significantly affect N‐linked glycosylation during the production of glycoproteins using mammalian cell fed‐batch cultures. These parameters inevitably change in modern industrial processes with concentrated feed additions and cell densities beyond 2 × 10⁷ cells/mL. In order to control the time‐dependent changes of protein glycosylation, an automated microbioreactor system was used to investigate the effects of culture pH, ammonia, galactose, and manganese chloride supplementation on nucleotide sugars as well as mAb N‐linked glycosylation in a time‐dependent way. Two different strategies comprising of a single shift of culture conditions as well as multiple media supplementations along the culture duration were applied to obtain changing and constant glycosylation profiles. The different feeding approaches enabled constant glycosylation patterns throughout the entire culture duration at different levels. By modulating the time evolution of the mAb glycan pattern, not only the endpoint but also the ratios between different glycosylation structures could be modified. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1123–1134, 2016     

N‐linked glycosylation is an important parameter for optimal selection of cell lines producing biopharmaceutical human IgG

We studied the variations in N‐linked glycosylation of human IgG molecules derived from 105 different stable cell lines each expressing one of the six different antibodies. Antibody expression was based on glutamine synthetase selection technology in suspension growing CHO‐K1SV cells. The glycans detected on the Fc fragment were mainly of the core‐fucosylated complex type containing zero or one galactose and little to no sialic acid. The glycosylation was highly consistent for the same cell line when grown multiple times, indicating the robustness of the production and glycan analysis procedure. However, a twofold to threefold difference was observed in the level of galactosylation and/or non‐core‐fucosylation between the 105 different cell lines, suggesting clone‐to‐clone variation. These differences may change the Fc‐mediated effector functions by such antibodies. Large variation was also observed in the oligomannose‐5 glycan content, which, when present, may lead to undesired rapid clearance of the antibody in vivo. Statistically significant differences were noticed between the various glycan parameters for the six different antibodies, indicating that the variable domains and/or light chain isotype influence Fc glycosylation. The glycosylation altered when batch production in shaker was changed to fed‐batch production in bioreactor, but was consistent again when the process was scaled from 400 to 5,000 L. Taken together, the observed clone‐to‐clone glycosylation variation but batch‐to‐batch consistency provides a rationale for selection of optimal production cell lines for large‐scale manufacturing of biopharmaceutical human IgG. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Rapid characterization of N‐linked glycans from secreted and gel‐purified monoclonal antibodies using MALDI‐ToF mass spectrometry

Recombinant monoclonal antibodies (MAbs) are increasingly being used for therapeutic use and correct glycosylation of these MAbs is essential for their correct function. Glycosylation profiles are host cell‐ and antibody class‐dependent and can change over culture time and environmental conditions. Therefore, rapid monitoring of glycan addition/status is of great importance for process validity. We describe two workflows of generally applicability for glycan profiling of purified and gel‐purified MAbs produced in NS0 and CHO cells, in which small‐scale antibody purification and buffer exchange is combined with PNGase F glycan cleavage and graphite HyperCarb desalting. MALDI‐ToF mass spectrometry is used for sensitive detection of glycan forms, with the ability to confirm glycan structures by selective ion fragmentation. Both workflows are rapid, technically simple and amenable to automation, and use in multi‐well formats. Biotechnol. Bioeng. 2010;107: 902–908. © 2010 Wiley Periodicals, Inc.     

Characterization and high‐yield production of non‐N‐glycosylated recombinant human BCMA‐Fc in Pichia pastoris

B‐cell maturation antigen (BCMA) fused at the C‐terminus to the Fc portion of human IgG1 (BCMA‐Fc) blocks B‐cell activating factor (BAFF) and proliferation‐inducing ligand (APRIL)‐mediated B‐cell activation, leading to immune disorders. The fusion protein has been cloned and produced by several engineering cell lines. To reduce cost and enhance production, we attempted to express recombinant human BCMA‐Fc (rhBCMA‐Fc) in Pichia pastoris under the control of the AOX1 methanol‐inducible promoter. To produce the target protein with uniform molecular weight and reduced immunogenicity, we mutated two predicted N‐linked glycosylation sites. The secretory yield was improved by codon optimization of the target gene sequence. After fed‐batch fermentation under optimized conditions, the highest yield (207 mg/L) of rhBCMA‐Fc was obtained with high productivity (3.45 mg/L/h). The purified functional rhBCMA‐Fc possessed high‐binding affinity to APRIL and dose‐dependent inhibition of APRIL‐induced proliferative activity in vitro through three‐step purification. Thus, this yeast‐derived expression method could be a low‐cost and effective alternative to the production of rhBCMA‐Fc in mammalian cell lines.     

Identification of cell culture conditions to control N‐glycosylation site‐occupancy of recombinant glycoproteins expressed in CHO cells

The effect of different cell culture conditions on N‐glycosylation site‐occupancy has been elucidated for two different recombinant glycoproteins expressed in Chinese hamster ovary (CHO) cells, recombinant human tissue plasminogen activator (t‐PA) and a recombinant enzyme (glycoprotein 2—GP2). Both molecules contain a N‐glycosylation site that is variably occupied. Different environmental factors that affect the site‐occupancy (the degree of occupied sites) of these molecules were identified. Supplementing the culture medium with additional manganese or iron increased the fraction of fully occupied t‐PA (type I t‐PA) by approximately 2.5–4%. Decreasing the cultivation temperature from 37 to 33°C or 31°C gradually increased site‐occupancy of t‐PA up to 4%. The addition of a specific productivity enhancer, butyrate, further increased site‐occupancy by an additional 1% under each cultivation temperature tested. In addition, the thyroid hormones triiodothyronine and thyroxine increased site‐occupancy of t‐PA compared to control conditions by about 2%. In contrast, the addition of relevant nucleoside precursor molecules involved in N‐glycan biosynthesis (e.g., uridine, guanosine, mannose) either had no effect or slightly reduced site‐occupancy. For the recombinant enzyme (GP2), it was discovered that culture pH and the timing of butyrate addition can be used to control N‐glycan site‐occupancy within a specific range. An increase in culture pH correlated with a decrease in site‐occupancy. Similarly, delaying the timing for butyrate addition also decreased site‐occupancy of this molecule. These results highlight the importance of understanding how cell culture conditions and media components can affect the product quality of recombinant glycoproteins expressed in mammalian cell cultures. Furthermore, the identification of relevant factors will enable one to control product quality attributes, specifically N‐glycan site‐occupancy, within a specific range when applied appropriately. Biotechnol. Bioeng. 2009;103: 1164–1175. © 2009 Wiley Periodicals, Inc.     

Expression of recombinant anti‐breast cancer immunotherapeutic monoclonal antibody in baculovirus–insect cell system

The anti‐breast cancer monoclonal antibody (mAb) BR55 was expressed in the baculovirus–insect cell expression system, which is advantageous because of its high production capacity, cell culture flexibility and glycosylation capability. The baculovirus–insect cell expression system was successfully established for production of mAb BR55 and mAb BR55 fused with the KDEL (Lys–Asp–Glu–Leu) endoplasmic reticulum (ER) retention signal (mAb BR55K). The heavy chain (HC) and light chain (LC) genes of mAb BR55 were cloned under the control of the polyhedrin (P_PH) and P₁₀ promoters, respectively, in the pFastBacDual vector. The antibody gene‐expression cassettes carrying both the HC and LC genes were transferred into a bacmid in Escherichia coli (DH10Bac). The bacmid carrying the expression cassettes was transfected into Sf9 insect cells to generate baculovirus expressing mAb BR55 and BR55K. Western blot analysis confirmed the expression of mAb BR55 and BR55K in baculovirus‐infected insect cells. Cell direct enzyme linked immunosorbent assay (ELISA) showed that both mAbs from insect cell lysates or cell culture medium bound to MCF‐7 human breast cancer cells. Both mAb BR55 and BR55K were successfully purified using a Protein A affinity column. Collectively, these results suggest that the anti‐breast cancer mAb BR55 can be expressed, properly assembled and purified from the baculovirus expression system, which can serve as an alternative system for antibody production.     

High‐efficiency affinity precipitation of multiple industrial mAbs and Fc‐fusion proteins from cell culture harvests using Z‐ELP‐E2 nanocages

Affinity precipitation using Z‐elastin‐like polypeptide‐functionalized E2 protein nanocages has been shown to be a promising alternative to Protein A chromatography for monoclonal antibody (mAb) purification. We have previously described a high‐yielding, affinity precipitation process capable of rapidly capturing mAbs from cell culture through spontaneous, multivalent crosslinking into large aggregates. To challenge the capabilities of this technology, nanocage affinity precipitation was investigated using four industrial mAbs (mAbs A–D) and one Fc fusion protein (Fc A) with diverse molecular properties. A molar binding ratio of 3:1 Z:mAb was sufficient to precipitate >95% mAb in solution for all molecules evaluated at ambient temperature without added salt. The effect of solution pH on aggregation kinetics was studied using a simplified two‐step model to investigate the protein interactions that occur during mAb–nanocage crosslinking and to determine the optimal solution pH for precipitation. After centrifugation, the pelleted mAb–nanocage complex remained insoluble and was capable of being washed at pH ≥ 5 and eluted with at pH < 4 with >90% mAb recovery for all molecules. The four mAbs and one Fc fusion were purified from cell culture using optimal process conditions, and >94% yield and >97% monomer content were obtained. mAb A–D purification resulted in a 99.9% reduction in host cell protein and >99.99% reduction in DNA from the cell culture fluids. Nanocage affinity precipitation was equivalent to or exceeded expected Protein A chromatography performance. This study highlights the benefits of nanoparticle crosslinking for enhanced affinity capture and presents a robust platform that can be applied to any target mAb or Fc‐containing proteins with minimal optimization of process parameters.     

Expression,glycosylation and function of recombinant anti‐colorectal cancer mAb CO17‐1A in SfSWT4 insect cells

Colorectal cancer is a commonly diagnosed cancer in the world. Monoclonal antibody (mAb) CO17‐1A recognizes the tumor‐associated antigen GA733, a cell surface glycoprotein highly expressed in colorectal carcinoma cell, which is considered to be applicable for diagnosis and therapeutic treatment against colorectal cancer. In addition antibodies are glycoproteins, efficiently recognize and eliminate specific pathogenic and disease antigens. We have currently established baculovirus insect cell expression system to produce anti‐colorectal cancer mAb CO17‐1A. In this study, mAb CO17‐1A was expressed in the transgenic insect cell line SfSWT4, in which glycosylation processing pathway has been humanized. Immunoblot confirmed that mAb CO17‐1A properly expressed in SfSWT4 insect cells. mAb CO17‐1A was purified using protein G affinity column. In addition, MALDI‐TOF verified that the mAb CO17‐1A fused to KDEL, endoplasmic reticulum (ER) retention signal (mAb CO17‐1AK) had high mannose type of glycan structure. Migration assay showed that insect cell‐derived mAb CO17‐1AK (mAb^I CO17‐1AK) with high mannose type of glycan structure was effective as mammalian‐derived mAb CO17‐1A (mAb^M CO17‐1A) in inhibition of metastasis. Kinetic analysis of antigen‐antibody interaction using Surface Plasmon Resonance (SPR) confirmed that mAb^I CO17‐1AK is efficient to interact with antigen GA733 as mAb^M CO17‐1A. These results suggest that the insect cell expression system with the SfSWT4 possibly can be used as a useful alternative way to produce full‐size mAb for cancer immunotherapy.     

Use of single analytic tool to quantify both absolute N-glycosylation and glycan distribution in monoclonal antibodies

Recombinant proteins represent almost half of the top selling therapeutics—with over a hundred billion dollars in global sales—and their efficacy and safety strongly depend on glycosylation. In this study, we showcase a simple method to simultaneously analyze N-glycan micro- and macroheterogeneity of an immunoglobulin G (IgG) by quantifying glycan occupancy and distribution. Our approach is linear over a wide range of glycan and glycoprotein concentrations down to 25 ng/mL. Additionally, we present a case study demonstrating the effect of small molecule metabolic regulators on glycan heterogeneity using this approach. In particular, sodium oxamate (SOD) decreased Chinese hamster ovary (CHO) glucose metabolism and reduced IgG glycosylation by 40% through upregulating reactive oxygen species (ROS) and reducing the UDP-GlcNAc pool, while maintaining a similar glycan profile to control cultures. Here, we suggest glycan macroheterogeneity as an attribute should be included in bioprocess screening to identify process parameters that optimize culture performance without compromising antibody quality.     

Effects of cell culture conditions on antibody N‐linked glycosylation—what affects high mannose 5 glycoform

The glycosylation profile of therapeutic antibodies is routinely analyzed throughout development to monitor the impact of process parameters and to ensure consistency, efficacy, and safety for clinical and commercial batches of therapeutic products. In this study, unusually high levels of the mannose‐5 (Man5) glycoform were observed during the early development of a therapeutic antibody produced from a Chinese hamster ovary (CHO) cell line, model cell line A. Follow up studies indicated that the antibody Man5 level was increased throughout the course of cell culture production as a result of increasing cell culture medium osmolality levels and extending culture duration. With model cell line A, Man5 glycosylation increased more than twofold from 12% to 28% in the fed‐batch process through a combination of high basal and feed media osmolality and increased run duration. The osmolality and culture duration effects were also observed for four other CHO antibody producing cell lines by adding NaCl in both basal and feed media and extending the culture duration of the cell culture process. Moreover, reduction of Man5 level from model cell line A was achieved by supplementing MnCl₂ at appropriate concentrations. To further understand the role of glycosyltransferases in Man5 level, N‐acetylglucosaminyltransferase I GnT‐I mRNA levels at different osmolality conditions were measured. It has been hypothesized that specific enzyme activity in the glycosylation pathway could have been altered in this fed‐batch process. Biotechnol. Bioeng. 2011;108: 2348–2358. © 2011 Wiley Periodicals, Inc.     

Production of an active anti‐CD20‐hIL‐2 immunocytokine in Nicotiana benthamiana

Anti‐CD20 murine or chimeric antibodies (Abs) have been used to treat non‐Hodgkin lymphomas (NHLs) and other diseases characterized by overactive or dysfunctional B cells. Anti‐CD20 Abs demonstrated to be effective in inducing regression of B‐cell lymphomas, although in many cases patients relapse following treatment. A promising approach to improve the outcome of mAb therapy is the use of anti‐CD20 antibodies to deliver cytokines to the tumour microenvironment. In particular, IL‐2‐based immunocytokines have shown enhanced antitumour activity in several preclinical studies. Here, we report on the engineering of an anti‐CD20‐human interleukin‐2 (hIL‐2) immunocytokine (2B8‐Fc‐hIL2) based on the C2B8 mAb (Rituximab) and the resulting ectopic expression in Nicotiana benthamiana. The scFv‐Fc‐engineered immunocytokine is fully assembled in plants with minor degradation products as assessed by SDS‐PAGE and gel filtration. Purification yields using protein‐A affinity chromatography were in the range of 15–20 mg/kg of fresh leaf weight (FW). Glycopeptide analysis confirmed the presence of a highly homogeneous plant‐type glycosylation. 2B8‐Fc‐hIL2 and the cognate 2B8‐Fc antibody, devoid of hIL‐2, were assayed by flow cytometry on Daudi cells revealing a CD20 binding activity comparable to that of Rituximab and were effective in eliciting antibody‐dependent cell‐mediated cytotoxicity of human PBMC versus Daudi cells, demonstrating their functional integrity. In 2B8‐Fc‐hIL2, IL‐2 accessibility and biological activity were verified by flow cytometry and cell proliferation assay. To our knowledge, this is the first example of a recombinant immunocytokine based on the therapeutic Rituximab antibody scaffold, whose expression in plants may be a valuable tool for NHLs treatment.     

A semi-empirical glycosylation model of a camelid monoclonal antibody under hypothermia cell culture conditions

The impact of cell culture environment on the glycan distribution of a monoclonal antibody (mAb) has been investigated through a combination of experiments and modeling. A newly developed CHO DUXB cell line was cultivated at two levels of initial Glutamine (Gln) concentrations (0, 4 mM) and incubation temperatures of (33 and 37 °C) in batch operation mode. Hypothermia was applied either through the entire culture duration or only during the post-exponential phase. Beyond reducing cell growth and increasing productivity, hypothermia significantly altered the galactosylation index profiles as compared to control conditions. A novel semi-empirical dynamic model was proposed for elucidating the connections between the extracellular cell culture conditions to galactosylation index. The developed model is based on a simplified balance of nucleotides sugars and on the correlation between sugars’ levels to the galactosylation index (GI). The model predictions were found to be in a good agreement with the experimental data. The proposed empirical model is expected to be useful for controlling the glycoprofiles by manipulating culture conditions.     

In vitro and in vivo efficacy of anti‐chikungunya virus monoclonal antibodies produced in wild‐type and glycoengineered Nicotiana benthamiana plants

Chikungunya virus (CHIKV) is a mosquito‐transmitted alphavirus, and its infection can cause long‐term debilitating arthritis in humans. Currently, there are no licensed vaccines or therapeutics for human use to combat CHIKV infections. In this study, we explored the feasibility of using an anti‐CHIKV monoclonal antibody (mAb) produced in wild‐type (WT) and glycoengineered (?XFT) Nicotiana benthamiana plants in treating CHIKV infection in a mouse model. CHIKV mAb was efficiently expressed and assembled in plant leaves and enriched to homogeneity by a simple purification scheme. While mAb produced in ?XFT carried a single N‐glycan species at the Fc domain, namely GnGn structures, WT produced mAb exhibited a mixture of N‐glycans including the typical plant GnGnXF₃ glycans, accompanied by incompletely processed and oligomannosidic structures. Both WT and ?XFT plant‐produced mAbs demonstrated potent in vitro neutralization activity against CHIKV. Notably, both mAb glycoforms showed in vivo efficacy in a mouse model, with a slight increased efficacy by the ?XFT‐produced mAbs. This is the first report of the efficacy of plant‐produced mAbs against CHIKV, which demonstrates the ability of using plants as an effective platform for production of functionally active CHIKV mAbs and implies optimization of in vivo activity by controlling Fc glycosylation.     

Short‐ and long‐term effects on mAb‐producing CHO cell lines after cryopreservation

Cryopreservation provides the foundation for research, development, and manufacturing operations in the CHO‐based biopharmaceutical industry. Despite its criticality, studies are lacking that explicitly demonstrate that the routine cell banking process and the potential stress and damage during cryopreservation and recovery from thaw have no lasting detrimental effects on CHO cells. Statistics are also scarce on the decline of cell‐specific productivity (Q_p) over time for recombinant CHO cells developed using the glutamine synthetase (GS)‐based methionine sulfoximine (MSX) selection system. To address these gaps, we evaluated the impact of freeze‐thaw on 24 recombinant CHO cell lines (generated by the GS/MSX selection system) using a series of production culture assays. Across the panel of cell lines expressing one of three monoclonal antibodies (mAbs), freeze‐thaw did not result in any significant impact beyond the initial post‐thaw passages. Production cultures sourced from cryopreserved cells and their non‐cryopreserved counterparts yielded similar performance (growth, viability, and productivity), product quality (size, charge, and glycosylation distributions), and flow cytometric profiles (intracellular mAb expression). However, many production cultures yielded lower Q_p at increased cell age: 17 of the 24 cell lines displayed ≥20% Q_p decline after ～2–3 months of passaging, irrespective of whether the cells were previously cryopreserved. The frequency of Q_p decline underscores the continued need for understanding the underlying mechanisms and for careful clone selection. Because our experiments were designed to decouple the effects of cryopreservation from those of cell age, we could conclusively rule out freeze‐thaw as a cause for Q_p decline. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:463–477, 2018     

Optimisation of the Cellular Metabolism of Glycosylation for Recombinant Proteins Produced by Mammalian Cell Systems

Many biopharmaceuticals are now produced as secreted glycoproteins from mammalian cell culture. The glycosylation profile of these proteins is essential to ensure structural stability and biological and clinical activity. However, the ability to control the glycosylation is limited by our understanding of the parameters that affect the heterogeneity of added glycan structures. It is clear that the glycosylation process is affected by a number of factors including the 3-dimensional structure of the protein, the enzyme repertoire of the host cell, the transit time in the Golgi and the availability of intracellular sugar-nucleotide donors. From a process development perspective there are many culture parameters that can be controlled to enable a consistent glycosylation profile to emerge from each batch culture. A further, but more difficult goal is to control the culture conditions to enable the enrichment of specific glycoforms identified with desirable biological activities. The purpose of this paper is to discuss the cellular metabolism associated with protein glycosylation and review the attempts to manipulate, control or engineer this metabolism to allow the expression of human glycosylation profiles in producer lines such as genetically engineered Chinese hamster ovary (CHO) cells.     

Profiling of N‐glycosylation gene expression in CHO cell fed‐batch cultures

One of the goals of recombinant glycoprotein production is to achieve consistent glycosylation. Although many studies have examined the changes in the glycosylation quality of recombinant protein with culture, very little has been done to examine the underlying changes in glycosylation gene expression as a culture progresses. In this study, the expression of 24 genes involved in N‐glycosylation were examined using quantitative RT PCR to gain a better understanding of recombinant glycoprotein glycosylation during production processes. Profiling of the N‐glycosylation genes as well as concurrent analysis of glycoprotein quality was performed across the exponential, stationary and death phases of a fed‐batch culture of a CHO cell line producing recombinant human interferon‐γ (IFN‐γ). Of the 24 N‐glycosylation genes examined, 21 showed significant up‐ or down‐regulation of gene expression as the fed‐batch culture progressed from exponential, stationary and death phase. As the fed‐batch culture progressed, there was also an increase in less sialylated IFN‐γ glycoforms, leading to a 30% decrease in the molar ratio of sialic acid to recombinant IFN‐γ. This correlated with decreased expression of genes involved with CMP sialic acid synthesis coupled with increased expression of sialidases. Compared to batch culture, a low glutamine fed‐batch strategy appears to need a 0.5 mM glutamine threshold to maintain similar N‐glycosylation genes expression levels and to achieve comparable glycoprotein quality. This study demonstrates the use of quantitative real time PCR method to identify possible “bottlenecks” or “compromised” pathways in N‐glycosylation and subsequently allow for the development of strategies to improve glycosylation quality. Biotechnol. Bioeng. 2010;107: 516–528. © 2010 Wiley Periodicals, Inc.     

Accelerating patient access to novel biologics using stable pool‐derived product for non‐clinical studies and single clone‐derived product for clinical studies

Cell cloning and subsequent process development activities are on the critical path directly impacting the timeline for advancement of next generation therapies to patients with unmet medical needs. The use of stable cell pools for early stage material generation and process development activities is an enabling technology to reduce timelines. To successfully use stable pools during development, it is important that bioprocess performance and requisite product quality attributes be comparable to those observed from clonally derived cell lines. To better understand the relationship between pool and clone derived cell lines, we compared data across recent first in human (FIH) programs at Amgen including both mAb and Fc‐fusion modalities. We compared expression and phenotypic stability, bioprocess performance, and product quality attributes between material derived from stable pools and clonally derived cells. Overall, our results indicated the feasibility of matching bioprocess performance and product quality attributes between stable pools and subsequently derived clones. These findings support the use of stable pools to accelerate the advancement of novel biologics to the clinic. © 2017 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 33:1476–1482, 2017