Development of a simple and rapid method for producing non-fucosylated oligomannose containing antibodies with increased effector function

Antibody glycan quality predicted from CHO cell culture media markers and machine learning

N-glycosylation can have a profound effect on the quality of mAb therapeutics. In biomanufacturing, one of the ways to influence N-glycosylation patterns is by altering the media used to grow mAb cell expression systems. Here, we explore the potential of machine learning (ML) to forecast the abundances of N-glycan types based on variables related to the growth media. The ML models exploit a dataset consisting of detailed glycomic characterisation of Anti-HER fed-batch bioreactor cell cultures measured daily under 12 different culture conditions, such as changes in levels of dissolved oxygen, pH, temperature, and the use of two different commercially available media. By performing spent media quantitation and subsequent calculation of pseudo cell consumption rates (termed media markers) as inputs to the ML model, we were able to demonstrate a small subset of media markers (18 selected out of 167 mass spectrometry peaks) in a Chinese Hamster Ovary (CHO) cell cultures are important to model N-glycan relative abundances (Regression - correlations between 0.80-0.92; Classification - AUC between 75.0-97.2). The performances suggest the ML models can infer N-glycan critical quality attributes from extracellular media as a proxy. Given its accuracy, we envisage its potential applications in biomaufactucuring, especially in areas of process development, downstream and upstream bioprocessing.

Maduramycin, a novel glycosylation modulator for mammalian fed-batch and steady-state perfusion processes

Controlling high-mannose (HM) content of therapeutic proteins during process intensification, reformulation for subcutaneous delivery, antibody-drug conjugate or biosimilar manufacturing represents an ongoing challenge. Even though a range of glycosylation levers to increase HM content exist, modulators specially increasing M5 glycans are still scarce. Several compounds of the polyether ionophore family were screened for their ability to selectively increase M5 glycans of mAb products and compared to the well-known α-mannosidase I inhibitor kifunensine known to increase mainly M8-M9 glycans. Maduramycin, amongst other promising polyether ionophores, showed the desired effect on different cell lines. For fed-batch processes, a double bolus addition modulator feed strategy was developed maximizing the effect on glycosylation by minimizing impact on culture performance. Further, a continuous feeding strategy for steady-state perfusion processes was successfully developed, enabling consistent product quality at elevated HM glycan levels. With kifunensine and maduramycin showing inverse effects on the relative HM distribution, a combined usage of these modulators was further evaluated to fine-tune a desired HM glycan pattern. The discovered HM modulators expand the current HM modulating toolbox for biotherapeutics. Their application not only for fed-batch processes, but also steady-state perfusion processes, make them a universal tool with regards to fully continuous manufacturing processes.

Characterization of N-glycosylation and its functional role in SIDT1-Mediated RNA uptake

The mammalian SID-1 transmembrane family members, SIDT1 and SIDT2, are multipass transmembrane proteins that mediate the cellular uptake and intracellular trafficking of nucleic acids, playing important roles in the immune response and tumorigenesis. Previous work has suggested that human SIDT1 and SIDT2 are N-glycosylated, but the precise site-specific N-glycosylation information and its functional contribution remain unclear. In this study, we use high-resolution liquid chromatography tandem mass spectrometry to comprehensively map the N-glycosites and quantify the N-glycosylation profiles of SIDT1 and SIDT2. Further molecular mechanistic probing elucidates the essential role of N-linked glycans in regulating cell surface expression, RNA binding, protein stability, and RNA uptake of SIDT1. Our results provide crucial information about the potential functional impact of N-glycosylation in the regulation of SIDT1-mediated RNA uptake and provide insights into the molecular mechanisms of this promising nucleic acid delivery system with potential implications for therapeutic applications.

Intracellular polyamine depletion induces N-linked galactosylation of the monoclonal antibody produced by CHO DP-12 cells

The heterogeneity of the N-linked glycan profile of therapeutic monoclonal antibodies (mAbs) derived from animal cells affects therapeutic efficacy and, therefore, needs to be appropriately controlled during the manufacturing process. In this study, we examined the effects of polyamines on the N-linked glycan profiles of mAbs produced by CHO DP-12 cells. Normal cell growth of CHO DP-12 cells and their growth arrest by α-difluoromethylornithine (DFMO), an inhibitor of the polyamine biosynthetic pathway, was observed when 0.5% fetal bovine serum was added to serum-free medium, despite the presence of cadaverine and aminopropylcadaverine, instead of putrescine and spermidine in cells. Polyamine depletion by DFMO increased IgG galactosylation, accompanied by β1,4-galactosyl transferase 1 (B4GAT1) mRNA elevation. Additionally, IgG production in polyamine-depleted cells was reduced by 30% compared to that in control cells. Therefore, we examined whether polyamine depletion induces an ER stress response. The results indicated increased expression levels of chaperones for glycoprotein folding in polyamine-depleted cells, suggesting that polyamine depletion causes ER stress related to glycoprotein folding. The effect of tunicamycin, an ER stress inducer that inhibits N-glycosylation, on the expression of B4GALT1 mRNA was examined. Tunicamycin treatment increased B4GALT1 mRNA expression. These results suggest that ER stress caused by polyamine depletion induces B4GALT1 mRNA expression, resulting in increased IgG galactosylation in CHO cells. Thus, introducing polyamines, particularly SPD, to serum-free CHO culture medium for CHO cells may contribute to consistent manufacturing and quality control of antibody production.

Triple Space-Time Yield in Discontinuous Antibody Biomanufacturing by Combination of Synergetic Process Intensification Strategies

Monoclonal antibodies are the workhorse of the pharmaceutical industry due to their potential to treat a variety of different diseases while providing high specificity and efficiency. As a consequence, a variety of production processes have been established within the biomanufacturing industry. However, the rapidly increasing demand for therapeutic molecules amid the recent COVID-19 pandemic demonstrated that there still is a clear need to establish novel, highly productive, and flexible production processes. Within this work, we designed a novel discontinuous process by combining two intensification strategies, thus increasing inoculation density and media exchange via a fluidized bed centrifuge, to fulfill the need for a flexible and highly productive production process for therapeutic molecules. To establish this new process, firstly, a small-scale experiment was conducted to verify synergies between both intensification strategies, followed by a process transfer towards the proof-of-concept scale. The combination of these two-process intensification measures revealed overall synergies resulting in decreased process duration (-37%) and strongly enhanced product formation (+116%) in comparison to the not-intensified standard operation. This led to an impressive threefold increase in space-time yield, while only negligible differences in product quality could be observed. Overall, this novel process not only increases the ways to react to emergency situations thanks to its flexibility and possible short development times, but also represents a possible alternative to the current established processes due to high increases in productivity, in comparison to standard fed-batch operations.

Glycosylation shapes the efficacy and safety of diverse protein, gene and cell therapies

Over recent decades, therapeutic proteins have had widespread success in treating a myriad of diseases. Glycosylation, a near universal feature of this class of drugs, is a critical quality attribute that significantly influences the physical properties, safety profile and biological activity of therapeutic proteins. Optimizing protein glycosylation, therefore, offers an important avenue to developing more efficacious therapies. In this review, we discuss specific examples of how variations in glycan structure and glycoengineering impacts the stability, safety, and clinical efficacy of protein-based drugs that are already in the market as well as those that are still in preclinical development. We also highlight the impact of glycosylation on next generation biologics such as T cell-based cancer therapy and gene therapy.

Killer to cure: Expression and production costs calculation of tobacco plant-made cancer-immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) have achieved huge clinical success. However, many still have limited response rates, and are prohibitively costly. There is a need for effective and affordable ICIs, as well as local manufacturing capacity to improve accessibility, especially to low-to-middle income countries (LMICs). Here, we have successfully expressed three key ICIs (anti-PD-1 Nivolumab, anti-NKG2A Monalizumab, and anti-LAG-3 Relatimab) transiently in Nicotiana benthamiana and Nicotiana tabacum plants. The ICIs were expressed with a combination of different Fc regions and glycosylation profiles. They were characterized in terms of protein accumulation levels, target cell binding, binding to human neonatal Fc receptors (hFcRn), human complement component C1q (hC1q) and various Fcγ receptors, as well as protein recovery during purification at 100 mg- and kg-scale. It was found that all ICIs bound to the expected target cells. Furthermore, the recovery during purification, as well as Fcγ receptor binding, can be altered depending on the Fc region used and the glycosylation profiles. This opens the possibility of using these two parameters to fine-tune the ICIs for desired effector functions. A scenario-based production cost model was also generated based on two production scenarios in hypothetical high- and low-income countries. We have shown that the product accumulation and recovery of plant production platforms were as competitive as mammalian cell-based platforms. This highlights the potential of plants to deliver ICIs that are more affordable and accessible to a widespread market, including LMICs.

Innovative Metrics for Reporting and Comparing the Glycan Structural Profile in Biotherapeutics

Glycosylation is a critical quality attribute in biotherapeutics, impacting properties such as protein stability, solubility, clearance rate, efficacy, immunogenicity, and safety. Due to the heterogenic and complex nature of protein glycosylation, comprehensive characterization is demanding. Moreover, the lack of standardized metrics for evaluating and comparing glycosylation profiles hinders comparability studies and the establishment of manufacturing control strategies. To address both challenges, we propose a standardized approach based on novel metrics for a comprehensive glycosylation fingerprint which greatly facilitates the reporting and objective comparison of glycosylation profiles. The analytical workflow is based on a liquid chromatography-mass spectrometry-based multi-attribute method. Based on the analytical data, a matrix of glycosylation-related quality attributes, both at site-specific and whole molecule level, are computed, which provide metrics for a comprehensive product glycosylation fingerprint. Two case studies illustrate the applicability of the proposed indices as a standardized and versatile approach for reporting all dimensions of the glycosylation profile. The proposed approach further facilitates the assessments of risks associated with changes in the glycosylation profile that may affect efficacy, clearance, and immunogenicity.

Altered glycosylation profiles of serum IgG in Takayasu arteritis

BACKGROUND

Takayasu arteritis (TAK) is an autoimmune inflammatory disorder with an undefined etiology. This study aimed to characterize the glycosylation profiles of serum immunoglobulin G (IgG) in patients with TAK.

METHODS

Lectin microarrays containing 56 types of lectins were used to detect the glycan levels of serum IgG in 164 patients with TAK, 128 patients with atherosclerosis used as disease controls (DCs), and 100 healthy controls (HCs). Differentially altered glycosylation patterns between TAK and control groups as well as between TAK subgroups were identified and further validated by lectin blot. The classification performance of the TAK-specific glycosylation change was measured by receiver-operating characteristic (ROC) curve analysis.

RESULTS

Lectin microarray analysis revealed significantly increased N-Acetylgalactosamine (GalNAc) levels in the TAK group compared to the DC and HC groups (all p < 0.01). For TAK subgroups, significantly decreased mannosylation was observed in patients with active TAK compared to patients with inactive disease (p < 0.01). These differences were validated by lectin blot. In addition, GalNAc levels exhibited a considerable potential for discriminating patients with TAK from patients with atherosclerosis, with an area under the curve of 0.749 (p < 0.001), a sensitivity of 71.7%, and a specificity of 73.8%.

CONCLUSIONS

Serum IgG in patients with TAK displayed disease-specific glycosylation alterations. Aberrant GalNAc glycosylation showed substantial value as a diagnostic biomarker. The potential proinflammatory properties of the abnormal glycans may provide new insights into the role of humoral immunity in the pathogenesis of TAK.

Investigation on acquired palbociclib resistance by LC-MS based multi-omics analysis

Palbociclib is a specific CDK4/6 inhibitor that has been widely applied in multiple types of tumors. Different from cytotoxic drugs, the anticancer mechanism of palbociclib mainly depends on cell cycle inhibition. Therefore, the resistance mechanism is different. For clinical cancer patients, drug resistance is inevitable for almost all cancer therapies including palbociclib. We have trained palbociclib resistant cells in vitro to simulate the clinical situation and applied LC-MS multi-omics analysis methods including proteomic, metabolomic, and glycoproteomic techniques, to deeply understand the underly mechanism behind the resistance. As a result of proteomic analysis, the resistant cells were found to rely on altered metabolic pathways to keep proliferation. Metabolic processes related to carbohydrates, lipids, DNA, cellular proteins, glucose, and amino acids were observed to be upregulated. Most dramatically, the protein expressions of COX-1 and NDUFB8 have been detected to be significantly overexpressed by proteomic analysis. When a COX-1 inhibitor was hired to combine with palbociclib, a synergistic effect could be obtained, suggesting the altered COX-1 involved metabolic pathway is an important reason for the acquired palbociclib resistance. The KEGG pathway of N-glycan biosynthesis was identified through metabolomics analysis. N-glycoproteomic analysis was therefore included and the global glycosylation was found to be elevated in the palbociclib-resistant cells. Moreover, integration analysis of glycoproteomic data allowed us to detect a lot more proteins that have been glycosylated with low abundances, these proteins were considered to be overwhelmed by those highly abundant proteins during regular proteomic LC-MS detection. These low-abundant proteins are mainly involved in the cellular biology processes of cell migration, the regulation of chemotaxis, as well as the glycoprotein metabolic process which offered us great more details on the roles played by N-glycosylation in drug resistance. Our result also verified that N-glycosylation inhibitors could enhance the cell growth inhibition of palbociclib in resistant cells. The high efficiency of the integrated multi-omics analysis workflow in discovering drug resistance mechanisms paves a new way for drug development. With a clear understanding of the resistance mechanism, new drug targets and drug combinations could be designed to resensitize the resistant tumors.

Defining the altered glycoproteomic space of the early secretory pathway by class I mannosidase pharmacological inhibition

N-glycosylation is a key process for various biological functions like protein folding, maturation and sorting for the conventional secretory compartment, cell-cell communication and immune response. This is usually accomplished by a complex system of mannosidases in which those from class I have an outstanding role, commonly involved in the early protein sorting associated to the Endoplasmic Reticulum (ER) in the N-glycan dependent quality control (ERQC) and ER-associated degradation (ERAD). Although these are vital processes in maintaining cellular homeostasis, large-scale analysis studies for this pool of molecules, further denoted as proteins from the early secretory pathway (ESP), were limited addressed. Here, using a custom workflow employing a combination of glycomics and deglycoproteomics analyses, using lectin affinity and selective Endoglycosidase H (Endo H) digestion, we scrutinize the steady-state oligomannosidic glycoprotein load and delineate ESP fraction in melanoma cells. All of these were assessed by applying our workflow for glycosite relative quantification of both the peptide chain and carbohydrate structure in cells with inhibited activity of class I mannosidases after kifunensine treatment. We found that most of the ESP are transient clients involved in cell communication via extracellular matrix, particularly integrin-mediated communication which adopt Man9 N-glycans in kifunensine-treated cells. Moreover, our results reveal that core-fucosylation is decreased subsequent inhibition of class I mannosidases and this could be explained by a general lower protein level of FUT8, the enzyme responsible for fucosylation. By comparing our data with results obtained following downregulation of a key mannosidase in misfolded protein degradation, we mapped both novel and previously suggested endogenous substrate candidates like PCDH2, HLA-B, LAMB2 or members of the integrin family of proteins such as ITGA1 and ITGA4, thus validating the findings obtained using our workflow regarding accumulation and characterization of ESP transitory members following mannosidase class I inhibition. This workflow and the associated dataset not only allowed us to investigate the oligomannosidic glycoprotein fraction but also to delineate differences mediated at glycosite-level upon kifunensine treatment and outline the potential associated cellular responses.

The Mannose in the Mirror: A Reflection on the Pharmacokinetic Impact of High Mannose Glycans of Monoclonal Antibodies in Biosimilar Development

Biosimilar development has a well-documented foundation of product quality and extensive comparative analytics providing the bulk of the "totality of the evidence" that a proposed product is biosimilar to its reference product. This work provides a retrospective evaluation of a single critical quality attribute-high mannose glycans for monoclonal antibody biosimilars. Given the well-established conclusion that high mannose glycans can impact pharmacokinetic (PK) profile, we performed a retrospective evaluation of 21 monoclonal antibody biosimilar programs (those licensed before April 2022), their levels of glycans, and the methods used to study them. We provide herein a summary of the methods used and their relative performance. We also present a subset analysis for seven biosimilar products with levels of high mannose that differ from the corresponding reference product (and where other differences in quality attributes between the two that may influence PK profile were not observed or considered minor) and compared the PK profiles. Critically, this analysis has demonstrated that the measurement of glycan profiles is highly precise, reproducible within and across programs, and can detect differences in mannose levels, even those that do not impact PK. These results provide support that analytics rather than pharmacokinetic data may be sufficient to predict whether differences within a certain magnitude of this attribute are likely to impact PK. This work enhances the Agency's understanding of this issue allowing for better understanding of challenges faced by the biotechnology industry developing biosimilars.

ADCC enhancement: A conundrum or a boon to mAb therapy?

The ability of antibodies to distinctly identify the antigens is an important feature exploited by the scientific community for the treatment of various diseases. The therapeutic action of monoclonal antibodies (mAbs) is mediated along with the cells of the immune system, such as natural killer cells, T cells and macrophages. The two major mechanisms that govern the therapeutic efficacy of mAbs are the antibody dependent cell mediated cytotoxicity (ADCC) and the complement dependent cytotoxicity (CDC). Consequently, much of the research dedicated to improving their action is focussed on enhancing either of these mechanisms. This manuscript focuses on the strategies to enhance ADCC, for providing more efficacious mAb therapeutics. These approaches essentially bring about changes in the elements of ADCC mechanism, such as the effector cell or the antibody itself and thus favour an enhanced therapeutic response. Several technologies of ADCC enhancement have been developed, based on the success of various strategies advanced by the researchers. These technologies show success with a few antibody therapeutics while they do not work with others. This review presents a detailed overview on these strategies and presents perspectives regarding the same.

Enzymatic glycan remodeling–metal free click (GlycoConnect™) provides homogenous antibody-drug conjugates with improved stability and therapeutic index without sequence engineering

Antibody-drug conjugates (ADCs) are increasingly powerful medicines for targeted cancer therapy. Inspired by the trend to further improve their therapeutic index by generation of homogenous ADCs, we report here how the clinical-stage GlycoConnect™ technology uses the globally conserved N-glycosylation site to generate stable and site-specific ADCs based on enzymatic remodeling and metal-free click chemistry. We demonstrate how an engineered endoglycosidase and a native glycosyl transferase enable highly efficient, one-pot glycan remodeling, incorporating a novel sugar substrate 6-azidoGalNAc. Metal-free click attachment of an array of cytotoxic payloads was highly optimized, in particular by inclusion of anionic surfactants. The therapeutic potential of GlycoConnect™, in combination with HydraSpace™ polar spacer technology, was compared to that of Kadcyla® (ado-trastuzumab emtansine), showing significantly improved efficacy and tolerability.

Elevated N-Glycosylation Contributes to the Cisplatin Resistance of Non-Small Cell Lung Cancer Cells Revealed by Membrane Proteomic and Glycoproteomic Analysis

Chemoresistance is the major restriction on the clinical use of cisplatin. Aberrant changes in protein glycosylation are closely associated with drug resistance. Comprehensive study on the role of protein glycosylation in the development of cisplatin resistance would contribute to precise elucidation of the complicated mechanism of resistance. However, comprehensive characterization of glycosylated proteins remains a big challenge. In this work, we integrated proteomic and N-glycoproteomic workflow to comprehensively characterize the cisplatin resistance-related membrane proteins. Using this method, we found that proteins implicated in cell adhesion, migration, response to drug, and signal transduction were significantly altered in both protein abundance and glycosylation level during the development of cisplatin resistance in the non-small cell lung cancer cell line. Accordingly, the ability of cell migration and invasion was markedly increased in cisplatin-resistant cells, hence intensifying their malignancy. In contrast, the intracellular cisplatin accumulation was significantly reduced in the resistant cells concomitant with the down-regulation of drug uptake channel protein, LRRC8A, and over-expression of drug efflux pump proteins, MRP1 and MRP4. Moreover, the global glycosylation was elevated in the cisplatin-resistant cells. Consequently, inhibition of N-glycosylation reduced cell resistance to cisplatin, whereas promoting the high-mannose or sialylated type of glycosylation enhanced the resistance, suggesting that critical glycosylation type contributes to cisplatin resistance. These results demonstrate the high efficiency of the integrated proteomic and N-glycoproteomic workflow in discovering drug resistance-related targets, and provide new insights into the mechanism of cisplatin resistance.

IgG N-glycans

Glycosylation, one of the most common post-translational modifications in mammalian cells, impacts many biological processes such as cell adhesion, proliferation and differentiation. As the most abundant glycoprotein in human serum, immunoglobulin G (IgG) plays a vital role in immune response and protection. There is a growing body of evidence suggests that IgG structure and function are modulated by attached glycans, especially N-glycans, and aberrant glycosylation is associated with disease states. In this chapter, we review IgG glycan repertoire and function, strategies for profiling IgG N-glycome and recent studies. Mass spectrometry (MS) based techniques are the most powerful tools for profiling IgG glycome. IgG glycans can be divided into high-mannose, biantennary complex and hybrid types, modified with mannosylation, core-fucosylation, galactosylation, bisecting GlcNAcylation, or sialylation. Glycosylation of IgG affects antibody half-life and their affinity and avidity for antigens, regulates crystallizable fragment (Fc) structure and Fcγ receptor signaling, as well as antibody effector function. Because of their critical roles, IgG N-glycans appear to be promising biomarkers for various disease states. Specific IgG glycosylation can convert a pro-inflammatory response to an anti-inflammatory activity. Accordingly, IgG glycoengineering provides a powerful approach to potentially develop effective drugs and treat disease. Based on the understanding of the functional role of IgG glycans, the development of vaccines with enhanced capacity and long-term protection are possible in the near future.

Comparative studies on the substrate specificity and defucosylation activity of three α-l-fucosidases using synthetic fucosylated glycopeptides and glycoproteins as substrates

Core fucosylation is the attachment of an α-1,6-fucose moiety to the innermost N-acetyl glucosamine (GlcNAc) in N-glycans in mammalian systems. It plays a pivotal role in modulating the structural and biological functions of glycoproteins including therapeutic antibodies. Yet, few α-l-fucosidases appear to be capable of removing core fucose from intact glycoproteins. This paper describes a comparative study of the substrate specificity and relative activity of the human α-l-fucosidase (FucA1) and two bacterial α-l-fucosidases, the AlfC from Lactobacillus casei and the BfFuc from Bacteroides fragilis. This study was enabled by the synthesis of an array of structurally well-defined core-fucosylated substrates, including core-fucosylated N-glycopeptides and a few antibody glycoforms. It was found that AlfC and BfFuc could not remove core fucose from intact full-length N-glycopeptides or N-glycoproteins but could hydrolyze only the truncated Fucα1,6GlcNAc-peptide substrates. In contrast, the human α-l-fucosidase (FucA1) showed low activity on truncated Fucα1,6GlcNAc substrates but was able to remove core fucose from intact and full-length core-fucosylated N-glycopeptides and N-glycoproteins. In addition, it was found that FucA1 was the only α-l-fucosidase that showed low but apparent activity to remove core fucose from intact IgG antibodies. The ability of FucA1 to defucosylate intact monoclonal antibodies reveals an opportunity to evolve the human α-l-fucosidase for direct enzymatic defucosylation of therapeutic antibodies to improve their antibody-dependent cellular cytotoxicity.

Modulation of high mannose levels in N-linked glycosylation through cell culture process conditions to increase antibody-dependent cell-mediated cytotoxicity activity for an antibody biosimilar

The regulatory approval of a biosimilar product is contingent on the favorable comparability of its safety and efficacy to that of the innovator product. As such, it is important to match the critical quality attributes of the biosimilar product to that of the innovator product. The N-glycosylation profile of a monoclonal antibody (mAb) can influence effector function activities such as antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity. In this study, we describe efforts to modulate the high-mannose (HM) levels of a biosimilar mAb produced in a Chinese hamster ovary cell fed-batch process. Because the HM level of the mAb was observed to impact ADCC activity, it was desirable to match it to the innovator mAb's levels. Several cell culture process related factors known to modulate the HM content of N-glycosylation were investigated, including osmolality, ammonium chloride (NH₄ Cl) addition, glutamine concentration, monensin addition, and the addition of alternate sugars and amino sugars to the feed medium. The process conditions evaluated varied in impact on HM levels, process performance and product quality. One condition, the addition of alternate sugars and amino sugars to feed medium, was identified as the preferred method for increasing HM levels with minimal disruptions to process performance or other product quality attributes. Interestingly, a secondary interaction between sugar and amino sugar supplemented feeds and osmolality was observed during process scale-up. These studies demonstrate sugar and amino sugar concentrations and osmolality are critical variables to evaluate to match HM content in biosimilar and their innovator mAbs.

Glycoengineering Chinese hamster ovary cells: a short history

Biotherapeutic glycoproteins have revolutionised the field of pharmaceuticals, with new discoveries and continuous improvements underpinning the rapid growth of this industry. N-glycosylation is a critical quality attribute of biotherapeutic glycoproteins that influences the efficacy, half-life and immunogenicity of these drugs. This review will focus on the advances and future directions of remodelling N-glycosylation in Chinese hamster ovary (CHO) cells, which are the workhorse of recombinant biotherapeutic production, with particular emphasis on antibody products, using strategies such as cell line and protein backbone engineering.

Glycosylation of Anti-Thyroglobulin IgG1 and IgG4 Subclasses in Thyroid Diseases

OBJECTIVE

Thyroglobulin antibodies (TgAb), principally comprising immunoglobulin G (IgG), are frequently found in healthy individuals. Previously, we showed that the glycosylation levels of TgAb IgG differed across various thyroid diseases, suggesting an important role of glycosylation on antibodies in the pathogenesis of thyroid diseases. Since IgG1 and IgG4 are the primary TgAb IgG subclasses, this study aimed to investigate the glycosylation of TgAb IgG1 and IgG4 subclasses in thyroid diseases.

METHODS

TgAb IgG was purified by affinity chromatography from the serum of patients with Hashimoto's thyroiditis (HT) (n = 16), Graves' disease (GD) (n = 8), papillary thyroid carcinoma (PTC) (n = 6), and PTC with histological lymphocytic thyroiditis (PTC-T) (n = 9) as well as healthy donors (n = 10). TgAb IgG1 and IgG4 concentrations were determined by enzyme-linked immunosorbent assay, and a lectin microassay was used to assess TgAb IgG1 and IgG4 glycosylation.

RESULTS

Significantly elevated mannose, sialic acid, and galactose levels on TgAb IgG1 were found in HT and PTC patients compared to GD patients and healthy controls (all p < 0.05). The mannose, sialic acid, and core fucose levels on TgAb IgG1 in PTC-T patients were higher than in healthy controls (all p < 0.05). Additionally, TgAb IgG1 from PTC-T patients exhibited lower sialylation than that from patients with PTC and higher fucosylation than that from patients with HT (both p < 0.05). However, TgAb IgG4 glycosylation did not differ among the five groups (p < 0.05).

CONCLUSION

Our study describes different distributions of TgAb IgG1 glycosylation in various thyroid diseases. The aberrantly increased glycosylation levels of TgAb IgG1 observed in HT, PTC, and PTC-T might be indicative of immune disorders and participate in the pathogenesis of these diseases.

Fast Afucosylation Profiling of Glycoengineered Antibody Subunits by Middle-Up Mass Spectrometry

Middle-up LC-MS antibody characterization workflows using reduction or IdeS digestion for a focused assessment of N-glycan profiling of three representative glycoengineered monoclonal antibodies (mAbs), namely, obinutuzumab (GlycomAb technology, Glycart/Roche), benralizumab (Potelligent Technology, BioWa, Kyowa Kirin) and mAb B (kifunensine) and compared to mAb A, produced in a common CHO cell line. In addition, EndoS or EndoS2 enzyme are used for quantitative determination of Fc-glycan core afucosylation and high mannose for these antibodies, as requested by health authorities for Fc-competent therapeutics mAbs critical quality attributes (CQAs).

Minor N-Glycan Mapping of Monoclonal Antibody Therapeutics Using Middle-Down NMR Spectroscopy

The N-glycosylation pattern of Asn-297 may have impacts on monoclonal antibody (mAb) drug plasma clearance, antibody-dependent cell mediated cytotoxicity (ADCC), and complement-dependent cytotoxicity (CDC). Notably, the changes in the relative abundance of certain minor glycans, like the afucosylation, high-mannose, or galactosylation are known to change mAb properties and functions. Here, a middle-down NMR spectroscopy based analytical procedure was applied to assess the composition and structure of glycans on adalimumab and trastuzumab without glycan cleavage from the mAbs. The anomeric 2D ¹H-¹³C spectra showed distinct patterns that could be used to profile and differentiate mAb glycan compositions. Specifically, the anomeric C1/H1 resonances from N-acetylglucosamine (GlcNAc2 and -5) and mannose (Man4) were identified as characteristic peaks for key glycan anomeric linkages and branching states. They were also utilized for measuring the relative abundance of minor glycans of total afucosylation (aFuc%), high mannose (HM%), and branch specific galactosylation (Gal_1-3% and Gal_1-6%). The obtained total aFuc% value of 11-12% was similar between the two mAbs; however, trastuzumab had significantly lower level of high mannose and a higher level of galactosylation than adalimumab. Overall, the 2D-NMR measurements provided functionally relevant mAb glycan composition and structure information. The method was deemed fit-for-purpose for assessment of these mAb quality attributes and involved fewer chemical preparation steps than the classical approaches that cleave glycans prior to making measurements.

A class of low-cost alternatives to kifunensine for increasing high mannose N-linked glycosylation for monoclonal antibody production in Chinese hamster ovary cells

N-linked glycosylation of therapeutic monoclonal antibodies is an important product quality attribute for drug safety and efficacy. An increase in the percent of high mannose N-linked glycosylation may be required for drug efficacy or to match the glycosylation profile of the innovator drug during the development of a biosimilar. In this study, the addition of several chemical additives to a cell culture process resulted in high mannose N-glycans on monoclonal antibodies produced by Chinese hamster ovary (CHO) cells without impacting cell culture performance. The additives, which include known mannosidase inhibitors (kifunensine and deoxymannojirimycin) as well as novel inhibitors (tris, bis-tris, and 1-amino-1-methyl-1,3-propanediol), contain one similar molecular structure: 2-amino-1,3-propanediol, commonly referred to as serinol. The shared chemical structure provides insight into the binding and inhibition of mannosidase in CHO cells. One of the novel inhibitors, tris, is safer compared to kifunensine, 35x as cost-effective, and stable at room temperature. In addition, tris and bis-tris provide multiple low-cost alternatives to kifunensine for manipulating glycosylation in monoclonal antibody production in a cell culture process with minimal impact to productivity or cell health.

Glycosylation-dependent opsonophagocytic activity of staphylococcal protein A antibodies

All currently licensed antibodies against bacteria target exotoxins. For most pathogens, neutralization of toxin(s) is not sufficient to prevent bacterial replication. Antibodies against surface determinants represent better candidates to enhance opsonophagocytic killing, but the mechanisms of action of such antibodies have not been systematically studied. Staphylococcal protein A is a conserved surface protein of Staphylococcus aureus and a crucial virulence determinant that manipulates B-cell responses and blocks deposition of opsonin. Monoclonal antibodies directed against SpA represent potential therapeutic agents as well as a formidable tool to identify and optimize effector functions of antibodies that can promote bacterial clearance.

Antibodies may bind to bacterial pathogens or their toxins to control infections, and their effector activity is mediated through the recruitment of complement component C1q or the engagement with Fcγ receptors (FcγRs). For bacterial pathogens that rely on a single toxin to cause disease, immunity correlates with toxin neutralization. Most other bacterial pathogens, including Staphylococcus aureus, secrete numerous toxins and evolved multiple mechanisms to escape opsonization and complement killing. Several vaccine candidates targeting defined surface antigens of S. aureus have failed to meet clinical endpoints. It is unclear that such failures can be solely attributed to the poor selection of antibody targets. Thus far, studies to delineate antibody-mediated uptake and killing of Gram-positive pathogens remain extremely limited. Here, we exploit 3F6-hIgG1, a human monoclonal antibody that binds and neutralizes the abundant surface-exposed Staphylococcal protein A (SpA). We find that galactosylation of 3F6-hIgG1 that favors C1q recruitment is indispensable for opsonophagocytic killing of staphylococci and for protection against bloodstream infection in animals. However, the simple removal of fucosyl residues, which results in reduced C1q binding and increased engagement with FcγR, maintains the opsonophagocytic killing and protective attributes of the antibody. We confirm these results by engineering 3F6-hIgG1 variants with biased binding toward C1q or FcγRs. While the therapeutic benefit of monoclonal antibodies against infectious disease agents may be debatable, the functional characterization of such antibodies represents a powerful tool for the development of correlates of protection that may guide future vaccine trials.

Glycan engineering reveals interrelated effects of terminal galactose and core fucose on antibody-dependent cell-mediated cytotoxicity

Antibody-dependent cell-mediated cytotoxicity (ADCC) has been identified as one of the potentially critical effector functions underlying the clinical efficacy of some therapeutic immunoglobin G1 (IgG1) antibodies. It has been well established that higher levels of afucosylated N-linked glycan structures on the Fc region enhance the IgG binding affinity to the FcγIIIa receptor and lead to increased ADCC activity. However, whether terminal galactosylation of an IgG1 impacts its ADCC activity is less understood. Here, we used a new strategy for glycan enrichment and remodeling to study the impact of terminal galactose on ADCC activity for therapeutic IgG1s. Our results indicate that the degree of influence of terminal galactose on in vitro ADCC activity depends on the presence or absence of the core fucose, which is typically linked to the first N-acetyl glucosamine residue of an N-linked glycosylation core structure. Specifically, terminal galactose on afucosylated IgG1 mAbs enhanced ADCC activity with impact coefficients (ADCC%/Gal%) more than 20, but had minimal influence on ADCC activity on fucosylated structures with impact coefficient in the range of 0.1-0.2. Knowledge gained here can be used to guide product and process development activities for biotherapeutic antibodies that require effector function for efficacy, and also highlight the complexity in modulating the immune response through N-linked glycosylation of antibodies.

Biolayer Interferometry-based FcγRIIa binding assay for a therapeutic antibody with strong effector function

FcγRIIa receptor binding is part of the mechanism of action for many therapeutic antibodies. AlphaScreen® technology and Biolayer Interferometry (BLI) are often used to assess protein-protein interactions. Recently we demonstrated that the presence of aggregates in samples significantly increased binding potency values in AlphaScreen®-based FcRn binding assays, sometimes masking the loss of potency. Even bigger effect of aggregates was observed in an AlphaScreen®-based FcγRIIa binding assay for a monoclonal antibody with strong effector function. To resolve this issue a novel BLI-based FcγRIIa binding assay was developed and qualified. The assay measures association binding responses and calculates the binding potency of the samples relative to the standard using Parallel Line Analysis. The method overcomes interference of aggregates present in the samples, distinguishes different Fc glycosylation patterns, and is stability-indicating. It can be used for sample characterization, drug product release and stability testing.

Principles of N-Linked Glycosylation Variations of IgG-Based Therapeutics: Pharmacokinetic and Functional Considerations

The development of recombinant therapeutic proteins has been a major revolution in modern medicine. Therapeutic-based monoclonal antibodies (mAbs) are growing rapidly, providing a potential class of human pharmaceuticals that can improve the management of cancer, autoimmune diseases, and other conditions. Most mAbs are typically of the immunoglobulin G (IgG) subclass, and they are glycosylated at the conserved asparagine position 297 (Asn-297) in the CH2 domain of the Fc region. Post-translational modifications here account for the observed high heterogeneity of glycoforms that may or not impact the stability, pharmacokinetics (PK), efficacy, and immunogenicity of mAbs. These modifications are also critical for the Fc receptor binding, and consequently, key antibody effector functions including antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). Moreover, mAbs produced in non-human cells express oligosaccharides that are not normally found in serum IgGs might lead to immunogenicity issues when administered to patients. This review summarizes our understanding of the terminal sugar residues, such as mannose, sialic acids, fucose, or galactose, which influence therapeutic mAbs either positively or negatively in this regard. This review also discusses mannosylation, which has significant undesirable effects on the PK of glycoproteins, causing a decreased mAbs’ half-life. Moreover, terminal galactose residues can enhance CDC activities and Fc–C1q interactions, and core fucose can decrease ADCC and Fc–FcγRs binding. To optimize the therapeutic use of mAbs, glycoengineering strategies are used to reduce glyco-heterogeneity of mAbs, increase their safety profile, and improve the therapeutic efficacy of these important reagents.

N-Glycosylation of IgG and IgG-Like Recombinant Therapeutic Proteins: Why Is It Important and How Can We Control It?

Regulatory bodies worldwide consider N-glycosylation to be a critical quality attribute for immunoglobulin G (IgG) and IgG-like therapeutics. This consideration is due to the importance of posttranslational modifications in determining the efficacy, safety, and pharmacokinetic properties of biologics. Given its critical role in protein therapeutic production, we review N-glycosylation beginning with an overview of the myriad interactions of N-glycans with other biological factors. We examine the mechanism and drivers for N-glycosylation during biotherapeutic production and the several competing factors that impact glycan formation, including the abundance of precursor nucleotide sugars, transporters, glycosidases, glycosyltransferases, and process conditions. We explore the role of these factors with a focus on the analytical approaches used to characterize glycosylation and associated processes, followed by the current state of advanced glycosylation modeling techniques. This combination of disciplines allows for a deeper understanding of N-glycosylation and will lead to more rational glycan control.

Blocking PD-1/PD-L1 by an ADCC enhanced anti-B7-H3/PD-1 fusion protein engages immune activation and cytotoxicity

Antibody therapy based on PD-1/PD-L1 blocking or ADCC effector has produced significant clinical benefit for cancer patients. We generated a novel anti-B7-H3 antibody (07B) and engineered the Fc fragment to enhance ADCC. To improve efficacy and tumor selectivity, we developed anti-B7-H3/PD-1 bispecific fusion proteins that simultaneously engaged tumor associate marker B7-H3 and immune suppressing ligand PD-L1 as well as enhanced ADCC to promote potent and highly selective tumor killing. Fusion proteins were designed by fusing human PD-1 extra domain to 07B in four different formats and showed good binding capacity to both targets. Indeed, the affinity of fusion proteins to B7-H3 is over 10,000 fold higher compared to that of the analogous PD-L1 and the blocking of fusion proteins to PD-L1 was worse but it greatly enhanced when bound to B7-H3, thus achieving directly PD-L1-blockade to B7-H3-expressing tumor cells. Importantly, IL-2 production was enhanced by fusion proteins from staphylococcal enterotoxin B (SEB) stimulated PBMC. Similarly, cytokines induced by fusion proteins was enhanced when co-cultured with stimulated CD8⁺ T cells and B7-H3/PD-L1 transfected raji cells. Additionally, fusion proteins improved activation to CD16a by Fc modification and delivered selective cytotoxicity to B7-H3 expressing tumor cells. In conclusion, fusion proteins blocked the PD-1/PD-L1 signal pathway and significantly increased potency of ADCC in a B7-H3-directed manner, thereby selectively activating CD8⁺ T cells and enhancing natural killing towards tumor. This novel fusion protein with its unique targeting preference may be useful to enhance efficacy and safety of immunotherapy for B7-H3-overexpressing malignancies.

Quality by Design-Based Assessment for Analytical Similarity of Adalimumab Biosimilar HLX03 to Humira®

Quality by design (QbD) is an efficient but challenging approach for the development of biosimilar due to the complex relationship among process, quality, and efficacy. Here, the analytical similarity of adalimumab biosimilar HLX03 to Humira® was successfully established following a QbD quality study. Quality target product profile (QTPP) of HLX03 was first generated according to the public available information and initial characterization of 3 batches of Humira®. The critical quality attributes (CQAs) were then identified through risk assessment according to impact of each quality attribute on efficacy and safety. The anticipated range for each CQA was derived from similarity acceptance range and/or the corresponding regulatory guidelines. Finally, a panel of advanced and orthogonal physicochemical and functional tests and comparison of 6 batches of HLX03 and 10 batches of the reference standard demonstrated high similarity of HLX03 to Humira®, except for slightly lower percentage of high mannosylated glycans (%HM) in HLX03 which had no effect on FcγRIII binding and antibody-dependent cell-mediated cytotoxicity (ADCC) activity in human peripheral blood mononuclear cell (PBMC). All above demonstrated the feasibility and efficiency of QbD-based similarity assessment of a biosimilar monoclonal antibody (mAb).

Perspectives for Glyco-Engineering of Recombinant Biopharmaceuticals from Microalgae

Microalgae exhibit great potential for recombinant therapeutic protein production, due to lower production costs, immunity to human pathogens, and advanced genetic toolkits. However, a fundamental aspect to consider for recombinant biopharmaceutical production is the presence of correct post-translational modifications. Multiple recent studies focusing on glycosylation in microalgae have revealed unique species-specific patterns absent in humans. Glycosylation is particularly important for protein function and is directly responsible for recombinant biopharmaceutical immunogenicity. Therefore, it is necessary to fully characterise this key feature in microalgae before these organisms can be established as industrially relevant microbial biofactories. Here, we review the work done to date on production of recombinant biopharmaceuticals in microalgae, experimental and computational evidence for N- and O-glycosylation in diverse microalgal groups, established approaches for glyco-engineering, and perspectives for their application in microalgal systems. The insights from this review may be applied to future glyco-engineering attempts to humanize recombinant therapeutic proteins and to potentially obtain cheaper, fully functional biopharmaceuticals from microalgae.

Evaluation of Antibody Properties and Clinically Relevant Immunogenicity, Anaphylaxis, and Hypersensitivity Reactions in Two Phase III Trials of Tralokinumab in Severe, Uncontrolled Asthma

Introduction

Tralokinumab is a monoclonal antibody (mAb) that neutralizes interleukin (IL)-13, a cytokine involved in the pathogenesis of asthma.

Objective

The objectives of this study were to characterize the potential immunogenic properties of tralokinumab and report data for anti-drug antibodies (ADAs) and hypersensitivity reactions from two phase III clinical trials.

Methods

The oligosaccharide structure of tralokinumab, Fab-arm exchange, and ADAs were characterized by standard techniques. Hypersensitivity adverse events (AEs) were evaluated in two pivotal clinical trials of tralokinumab in severe, uncontrolled asthma: STRATOS 1 and 2 (NCT02161757 and NCT02194699).

Results

No galactose-α-1,3-galactose (α-Gal) epitopes were found in the Fab region of tralokinumab and only 4.5% of glycoforms contained α-Gal in the Fc region. Under non-reducing conditions, Fab-arm exchange did not take place with another immunoglobulin (Ig) G₄ mAb (mavrilimumab). However, following glutathione reduction, a hybrid antibody with monovalent bioactivity was detected. ADA incidences (titers) were as follows: STRATOS 1—every 2 weeks (Q2 W) 0.8% (26.0), every 4 weeks (Q4 W) 0.5% (26.0), placebo 0.8% (52.0); STRATOS 2—Q2 W 1.2% (39.0), placebo 0.8% (13.0). Participant-reported hypersensitivity AE rates were as follows: STRATOS 1—Q2 W 25.9%, Q4 W 25.0%, placebo 25.5%; STRATOS 2—Q2 W 13.2%, placebo 9.0%. External evaluation for anaphylaxis by Sampson criteria found no tralokinumab-related severe hypersensitivity or anaphylaxis reactions.

Conclusion

Preclinical assessments suggested a low likelihood of immunogenicity for tralokinumab. In STRATOS 1 and 2, ADA incidence was low, no differences were found between tralokinumab-treated and placebo groups in reporting of hypersensitivity reactions, and there were no Sampson criteria-evaluated anaphylaxis events with tralokinumab treatment. Together, the results suggest that tralokinumab treatment would not increase the risk for severe hypersensitivity or anaphylactic reactions.

Electronic supplementary material

The online version of this article (10.1007/s40264-018-00788-w) contains supplementary material, which is available to authorized users.

IgG Glycosylation Profile and the Glycan Score Are Associated with Type 2 Diabetes in Independent Chinese Populations: A Case-Control Study

BACKGROUND

The relationship between the IgG glycan panel and type 2 diabetes remains unclear in Chinese population. We aimed to investigate the association of the IgG glycan profile and glycan score with type 2 diabetes.

METHODS

In the discovery population, 162 individuals diagnosed with type 2 diabetes and 162 matched controls from Beijing health management cohort were included. We analyzed the IgG glycan profile and composed a glycan score for type 2 diabetes. Findings were validated in the replication population from Beijing Xuanwu community cohort (280 cases and 508 controls). Area under curve (AUC) using 10-fold and bootstrap validation, net reclassification index (NRI), and integrated discrimination index (IDI) were calculated for the glycan score.

RESULTS

In the discovery population, 5 initial IgG glycans and 7 derived traits were significantly associated with type 2 diabetes after Bonferroni correction and Lasso selection, which were validated in the replication population subsequently. The glycan score composed of these IgG glycans and traits showed a strong association with type 2 diabetes (combined odds ratio (OR): 3.78) and its risk factors. In the replication population, AUC of the model involving clinical traits improved from 0.74 to above 0.90, and the values of NRI and IDI were 0.35 and 0.42, respectively, with the glycan score added.

CONCLUSIONS

IgG glycosylation profiles were associated with type 2 diabetes and the glycan score may be a novel indicator for diabetes which reflected a proinflammatory status.

Antibody Structure and Function: The Basis for Engineering Therapeutics

Antibodies and antibody-derived macromolecules have established themselves as the mainstay in protein-based therapeutic molecules (biologics). Our knowledge of the structure–function relationships of antibodies provides a platform for protein engineering that has been exploited to generate a wide range of biologics for a host of therapeutic indications. In this review, our basic understanding of the antibody structure is described along with how that knowledge has leveraged the engineering of antibody and antibody-related therapeutics having the appropriate antigen affinity, effector function, and biophysical properties. The platforms examined include the development of antibodies, antibody fragments, bispecific antibody, and antibody fusion products, whose efficacy and manufacturability can be improved via humanization, affinity modulation, and stability enhancement. We also review the design and selection of binding arms, and avidity modulation. Different strategies of preparing bispecific and multispecific molecules for an array of therapeutic applications are included.

Glycoengineering of Antibodies for Modulating Functions

Antibodies are immunoglobulins that play essential roles in immune systems. All antibodies are glycoproteins that carry at least one or more conserved N-linked oligosaccharides (N-glycans) at the Fc domain. Many studies have demonstrated that both the presence and fine structures of the attached glycans can exert a profound impact on the biological functions and therapeutic efficacy of antibodies. However, antibodies usually exist as mixtures of heterogeneous glycoforms that are difficult to separate in pure glycoforms. Recent progress in glycoengineering has provided useful methods that enable production of glycan-defined and site-selectively modified antibodies for functional studies and for improved therapeutic efficacy. This review highlights major approaches in glycoengineering of antibodies with a focus on recent advances in three areas: glycoengineering through glycan biosynthetic pathway manipulation, glycoengineering through in vitro chemoenzymatic glycan remodeling, and glycoengineering of antibodies for site-specific antibody-drug conjugation.

Generation of site-distinct N-glycan variants for in vitro bioactivity testing

Glycosylation, a critical product quality attribute, may affect the efficacy and safety of therapeutic proteins in vivo. Chinese hamster ovary fed-batch cell culture batches yielded consistent glycoprofiles of a Fc-fusion antibody comprizing three different N-glycosylation sites. By adding media supplements at specific concentrations in cell culture and applying enzymatic glycoengineering, a diverse N-glycan variant population was generated, including high mannose, afucosylated, fucosylated, agalactosylated, galactosylated, asialylated, and sialylated forms. Site-specific glycosylation profiles were elucidated by glycopeptide mapping and the effect of the glycosylation variants on the FcγRIIIa receptor binding affinity and the biological activity (cell-based and surface plasmon resonance) was assessed. The two fusion body glycosylation sites were characterized by a high degree of sialic acid, more complex N-glycan structures, a higher degree of antennarity, and a site-specific behavior in the presence of a media supplement. On the other hand, the media supplements affected the Fc-site glycosylation heterogeneity similarly to the various studies described in the literature with classical monoclonal antibodies. Enzymatic glycoengineering solely managed to generate high levels of galactosylation at the fusion body sites. Variants with low core fucosylation, and to a lower extent, high mannose glycans exhibited increased FcγRIIIa receptor binding affinity. All N-glycan variants exhibited weak effects on the biological activity of the fusion body. Both media supplementation and enzymatic glycoengineering are suitable to generate sufficient diversity to assess the effect of glycostructures on the biological activity.

Macro- and Micro-Heterogeneity of Natural and Recombinant IgG Antibodies

Recombinant monoclonal antibodies (mAbs) intended for therapeutic usage are required to be thoroughly characterized, which has promoted an extensive effort towards the understanding of the structures and heterogeneity of this major class of molecules. Batch consistency and comparability are highly relevant to the successful pharmaceutical development of mAbs and related products. Small structural modifications that contribute to molecule variants (or proteoforms) differing in size, charge or hydrophobicity have been identified. These modifications may impact (or not) the stability, pharmacokinetics, and efficacy of mAbs. The presence of the same type of modifications as found in endogenous immunoglobulin G (IgG) can substantially lower the safety risks of mAbs. The knowledge of modifications is also critical to the ranking of critical quality attributes (CQAs) of the drug and define the Quality Target Product Profile (QTPP). This review provides a summary of the current understanding of post-translational and physico-chemical modifications identified in recombinant mAbs and endogenous IgGs at physiological conditions.

In Vivo Glycan Engineering via the Mannosidase I Inhibitor (Kifunensine) Improves Efficacy of Rituximab Manufactured in Nicotiana benthamiana Plants

N-glycosylation has been shown to affect the pharmacokinetic properties of several classes of biologics, including monoclonal antibodies, blood factors, and lysosomal enzymes. In the last two decades, N-glycan engineering has been employed to achieve a N-glycosylation profile that is either more consistent or aligned with a specific improved activity (i.e., effector function or serum half-life). In particular, attention has focused on engineering processes in vivo or in vitro to alter the structure of the N-glycosylation of the Fc region of anti-cancer monoclonal antibodies in order to increase antibody-dependent cell-mediated cytotoxicity (ADCC). Here, we applied the mannosidase I inhibitor kifunensine to the Nicotiana benthamiana transient expression platform to produce an afucosylated anti-CD20 antibody (rituximab). We determined the optimal concentration of kifunensine used in the infiltration solution, 0.375 µM, which was sufficient to produce exclusively oligomannose glycoforms, at a concentration 14 times lower than previously published levels. The resulting afucosylated rituximab revealed a 14-fold increase in ADCC activity targeting the lymphoma cell line Wil2-S when compared with rituximab produced in the absence of kifunensine. When applied to the cost-effective and scalable N. benthamiana transient expression platform, the use of kifunensine allows simple in-process glycan engineering without the need for transgenic hosts.

Pharmacokinetic and Pharmacodynamic Considerations in the Design of Therapeutic Antibodies

The design and development of therapeutic monoclonal antibodies (mAbs) through optimizing their pharmacokinetic (PK) and pharmacodynamic (PD) properties is crucial to improve efficacy while minimizing adverse events. Many of these properties are interdependent, which highlights the inherent challenges in therapeutic antibody design, where improving one antibody property can sometimes lead to changes in others. Here, we discuss optimization approaches for PK/PD properties of therapeutic mAbs.

Structure, heterogeneity and developability assessment of therapeutic antibodies

Increasing attention has been paid to developability assessment with the understanding that thorough evaluation of monoclonal antibody lead candidates at an early stage can avoid delays during late-stage development. The concept of developability is based on the knowledge gained from the successful development of approximately 80 marketed antibody and Fc-fusion protein drug products and from the lessons learned from many failed development programs over the last three decades. Here, we reviewed antibody quality attributes that are critical to development and traditional and state-of-the-art analytical methods to monitor those attributes. Based on our collective experiences, a practical workflow is proposed as a best practice for developability assessment including in silico evaluation, extended characterization and forced degradation using appropriate analytical methods that allow characterization with limited material consumption and fast turnaround time.

Influence of N-glycosylation on effector functions and thermal stability of glycoengineered IgG1 monoclonal antibody with homogeneous glycoforms

Glycosylation of the conserved asparagine residue in each heavy chain of IgG in the CH2 domain is known as N-glycosylation. It is one of the most common post-translational modifications and important critical quality attributes of monoclonal antibody (mAb) therapeutics. Various studies have demonstrated the effects of the Fc N-glycosylation on safety, Fc effector functions, and pharmacokinetics, both dependent and independent of neonatal Fc receptor (FcRn) pathway. However, separation of various glycoforms to investigate the biological and functional relevance of glycosylation is a major challenge, and existing studies often discuss the overall impact of N-glycans, without considering the individual contributions of each glycoform when evaluating mAbs with highly heterogeneous distributions. In this study, chemoenzymatic glycoengineering incorporating an endo-β-N-acetylglucosaminidase (ENGase) EndoS2 and its mutant with transglycosylation activity was used to generate mAb glycoforms with highly homogeneous and well-defined N-glycans to better understand and precisely evaluate the effect of each N-glycan structure on Fc effector functions and protein stability. We demonstrated that the core fucosylation, non-reducing terminal galactosylation, sialylation, and mannosylation of IgG1 mAb N-glycans impact not only on FcγRIIIa binding, antibody-dependent cell-mediated cytotoxicity, and C1q binding, but also FcRn binding, thermal stability and propensity for protein aggregation.

A polymeric immunoglobulin-antigen fusion protein strategy for enhancing vaccine immunogenicity

In this study, a strategy based on polymeric immunoglobulin G scaffolds (PIGS) was used to produce a vaccine candidate for Mycobacterium tuberculosis. A genetic fusion construct comprising genes encoding the mycobacterial Ag85B antigen, an immunoglobulin γ-chain fragment and the tailpiece from immunoglobulin μ chain was engineered. Expression was attempted in Chinese Hamster Ovary (CHO) cells and in Nicotiana benthamiana. The recombinant protein assembled into polymeric structures (TB-PIGS) in N. benthamiana, similar in size to polymeric IgM. These complexes were subsequently shown to bind to the complement protein C1q and FcγRs with increased affinity. Modification of the N-glycans linked to TB-PIGS by removal of xylose and fucose residues that are normally found in plant glycosylated proteins also resulted in increased affinity for low-affinity FcγRs. Immunization studies in mice indicated that TB-PIGS are highly immunogenic with and without adjuvant. However, they did not improve protective efficacy in mice against challenge with M. tuberculosis compared to conventional vaccination with BCG, suggesting that additional or alternative antigens may be needed to protect against this disease. Nevertheless, these results establish a novel platform for producing polymeric antigen-IgG γ-chain molecules with inherent functional characteristics that are desirable in vaccines.

The Mechanistic Impact of N-Glycosylation on Stability, Pharmacokinetics, and Immunogenicity of Therapeutic Proteins

N-glycosylation is one of major post-translational modifications in nature, and it is essential for protein structure and function. As hydrophilic moieties of glycoproteins, N-glycans play important roles in protein stability. They protect the proteins against proteolytic degradation, aggregation, and thermal denaturation through maintaining optimal conformations. There are extensive evidences showing the involvement of N-glycans in the pharmacodynamics and pharmacokinetics of recombinant therapeutic proteins and antibodies. Highly sialylated complex-type glycans enable the longer serum half-lives of proteins against uptake through hepatic asialoglycoprotein receptor and mannose receptor for degradation in lysosomes. Moreover, the presence of nonhuman glycans results in clearance through pre-existing antibodies from serum and induces IgE-mediated anaphylaxis. N-glycans also facilitate or reduce the adverse immune responses of the proteins through interacting with multiple glycan-binding proteins, including those specific for mannose or mannose 6-phosphate. Due to the glycan impacts, a few therapeutic proteins were glycoengineered to improve the pharmacokinetics and stability. Thus, N-glycosylation should be extensively investigated and optimized for each individual protein for better efficacy and safety.

Chemoenzymatic Methods for the Synthesis of Glycoproteins

Glycosylation is one of the most prevalent posttranslational modifications that profoundly affects the structure and functions of proteins in a wide variety of biological recognition events. However, the structural complexity and heterogeneity of glycoproteins, usually resulting from the variations of glycan components and/or the sites of glycosylation, often complicates detailed structure-function relationship studies and hampers the therapeutic applications of glycoproteins. To address these challenges, various chemical and biological strategies have been developed for producing glycan-defined homogeneous glycoproteins. This review highlights recent advances in the development of chemoenzymatic methods for synthesizing homogeneous glycoproteins, including the generation of various glycosynthases for synthetic purposes, endoglycosidase-catalyzed glycoprotein synthesis and glycan remodeling, and direct enzymatic glycosylation of polypeptides and proteins. The scope, limitation, and future directions of each method are discussed.

Biosimilar Drugs for Psoriasis: Principles, Present, and Near Future

Psoriasis is a chronic, inflammatory, lifelong disease with a high prevalence (afflicting approximately 1-5% of the population worldwide) and is associated with significant morbidity. The introduction of biologic therapies has improved the management of this disease. Multiple biologic medicines that block cytokine signaling, including tumor necrosis factor (TNF) antagonists (adalimumab, etanercept, and infliximab) and inhibitors of interleukin (IL)-17 (brodalumab, ixekizumab, and secukinumab), IL-23 (guselkumab), or IL-12/23 (ustekinumab), are approved for the treatment of psoriasis. Despite the clinical benefits associated with use of biologics in psoriasis, many patients are not treated with biologic therapy, and access to treatment may be limited for various reasons, such as high treatment costs. Patents for many biologics have expired or will soon expire, and biosimilar versions of these agents are available or in development. A biosimilar is a biological product that is highly similar to an approved biologic (i.e., originator or reference) product, and has no clinically meaningful differences in safety, purity, or potency when compared with the reference product. Biosimilars may offer less expensive treatment options for patients with psoriasis; they also may increase access to and address problems with underutilization of biologic therapy. Biosimilar development and approval follows a well-regulated process in many countries, with guidelines developed by the European Medicines Agency, US Food and Drug Administration, and World Health Organization. Currently, several anti-TNF biosimilars are available for use in patients with psoriasis, and other monoclonal antibodies are in development. This review provides dermatologists and those who treat and/or manage psoriasis with a working knowledge of the scientific principles of biosimilar development and approval. It also examines real-world experience with biosimilars available for or used in dermatology that will enable physicians to make informed treatment decisions for their patients with psoriasis.

FUNDING

Pfizer Inc.

CD83 Antibody Inhibits Human B Cell Responses to Antigen as well as Dendritic Cell-Mediated CD4 T Cell Responses

Anti-CD83 Ab capable of Ab-dependent cellular cytotoxicity can deplete activated CD83+ human dendritic cells, thereby inhibiting CD4 T cell-mediated acute graft-versus-host disease. As CD83 is also expressed on the surface of activated B lymphocytes, we hypothesized that anti-CD83 would also inhibit B cell responses to stimulation. We found that anti-CD83 inhibited total IgM and IgG production in vitro by allostimulated human PBMC. Also, Ag-specific Ab responses to immunization of SCID mice xenografted with human PBMC were inhibited by anti-CD83 treatment. This inhibition occurred without depletion of all human B cells because anti-CD83 lysed activated CD83+ B cells by Ab-dependent cellular cytotoxicity and spared resting (CD83-) B cells. In cultured human PBMC, anti-CD83 inhibited tetanus toxoid-stimulated B cell proliferation and concomitant dendritic cell-mediated CD4 T cell proliferation and expression of IFN-γ and IL-17A, with minimal losses of B cells (<20%). In contrast, the anti-CD20 mAb rituximab depleted >80% of B cells but had no effect on CD4 T cell proliferation and cytokine expression. By virtue of the ability of anti-CD83 to selectively deplete activated, but not resting, B cells and dendritic cells, with the latter reducing CD4 T cell responses, anti-CD83 may be clinically useful in autoimmunity and transplantation. Advantages might include inhibited expansion of autoantigen- or alloantigen-specific B cells and CD4 T cells, thus preventing further production of pathogenic Abs and inflammatory cytokines while preserving protective memory and regulatory cells.

Impact of Glycosylation on the Local Backbone Flexibility of Well-Defined IgG1-Fc Glycoforms Using Hydrogen Exchange-Mass Spectrometry

We have used hydrogen exchange-mass spectrometry to characterize local backbone flexibility of 4 well-defined IgG1-Fc glycoforms expressed and purified from Pichia pastoris, 2 of which were prepared using subsequent in vitro enzymatic treatments. Progressively decreasing the size of the N-linked N297 oligosaccharide from high mannose (Man8-Man12), to Man5, to GlcNAc, to nonglycosylated N297Q resulted in progressive increases in backbone flexibility. Comparison of these results with recently published physicochemical stability and Fcγ receptor binding data with the same set of glycoproteins provide improved insights into correlations between glycan structure and these pharmaceutical properties. Flexibility significantly increased upon glycan truncation in 2 potential aggregation-prone regions. In addition, a correlation was established between increased local backbone flexibility and increased deamidation at asparagine 315. Interestingly, the opposite trend was observed for oxidation of tryptophan 277 where faster oxidation correlated with decreased local backbone flexibility. Finally, a trend of increasing C'E glycopeptide loop flexibility with decreasing glycan size was observed that correlates with their FcγRIIIa receptor binding properties. These well-defined IgG1-Fc glycoforms serve as a useful model system to identify physicochemical stability and local backbone flexibility data sets potentially discriminating between various IgG glycoforms for potential applicability to future comparability or biosimilarity assessments.