Increased serum clearance of oligomannose species present on a human IgG1 molecule

Strategic approaches for designing yeast strains as protein secretion and display platforms

Yeast has been established as a versatile platform for expressing functional molecules, owing to its well-characterized biology and extensive genetic modification tools. Compared to prokaryotic systems, yeast possesses advanced cellular mechanisms that ensure accurate protein folding and post-translational modifications. These capabilities are particularly advantageous for the expression of human-derived functional proteins. However, designing yeast strains as an expression platform for proteins requires the integration of molecular and cellular functions. By delving into the complexities of yeast-based expression systems, this review aims to empower researchers with the knowledge to fully exploit yeast as a functional platform to produce a diverse range of proteins. This review includes an exploration of the host strains, gene cassette structures, as well as considerations for maximizing the efficiency of the expression system. Through this in-depth analysis, the review anticipates stimulating further innovation in the field of yeast biotechnology and protein engineering.

Role of Antibody Glycosylation in Health, Disease, and Therapy

Immunoglobulin G (IgG) antibodies are an essential component of humoral immunity protecting the host from recurrent infections. Among all antibody isotypes, IgG antibodies have a uniquely long half-life, can basically reach any tissue in the body, and have the ability to kill opsonized target cells, which has made them the molecule of choice for therapeutic interventions in cancer and autoimmunity. Moreover, IgG antibodies in the form of pooled serum IgG preparations from healthy donors are used to treat chronic inflammatory and autoimmune diseases, providing evidence that serum IgG antibodies can have an active immunomodulatory activity. Research over the last two decades has established that the single sugar moiety attached to each IgG heavy chain plays a very important role in modulating the pro- and anti-inflammatory activities of IgG. Moreover, specific sugar moieties such as sialic acid and galactose residues can serve as highly specific biomarkers for ongoing inflammatory processes. This chapter will summarize how different sugar residues in the IgG sugar moiety change upon inflammation and how such changes may translate to altered IgG function and hence maybe useful for optimizing or modulating the function of therapeutic antibodies.

Escherichia coli and Pichia pastoris: microbial cell-factory platform for -full-length IgG production

Owing to the unmet demand, the pharmaceutical industry is investigating an alternative host to mammalian cells to produce antibodies for a variety of therapeutic and research applications. Regardless of some disadvantages, Escherichia coli and Pichia pastoris are the preferred microbial hosts for antibody production. Despite the fact that the production of full-length antibodies has been successfully demonstrated in E. coli, which has mostly been used to produce antibody fragments, such as: antigen-binding fragments (Fab), single-chain fragment variable (scFv), and nanobodies. In contrast, Pichia, a eukaryotic microbial host, is mostly used to produce glycosylated full-length antibodies, though hypermannosylated glycan is a major challenge. Advanced strategies, such as the introduction of human-like glycosylation in endotoxin-edited E. coli and cell-free system-based glycosylation, are making progress in creating human-like glycosylation profiles of antibodies in these microbes. This review begins by explaining the structural and functional requirements of antibodies and continues by describing and analyzing the potential of E. coli and P. pastoris as hosts for providing a favorable environment to create a fully functional antibody. In addition, authors compare these microbes on certain features and predict their future in antibody production. Briefly, this review analyzes, compares, and highlights E. coli and P. pastoris as potential hosts for antibody production.

"Small is beautiful" - Examining reliable determination of low-abundant therapeutic antibody glycovariants

Glycans associated with biopharmaceutical drugs play crucial roles in drug safety and efficacy, and therefore, their reliable detection and quantification is essential. Our study introduces a multi-level quantification approach for glycosylation analysis in monoclonal antibodies (mAbs), focusing on minor abundant glycovariants. Mass spectrometric data is evaluated mainly employing open-source software tools. Released N-glycan and glycopeptide data form the basis for integrating information across different structural levels up to intact glycoproteins. Comprehensive comparison showed that indeed, variations across structural levels were observed especially for minor abundant species. Utilizing modification finder (MoFi), a tool for annotating mass spectra of intact proteins, we quantify isobaric glycosylation variants at the intact protein level. Our workflow's utility is demonstrated on NISTmAb, rituximab and adalimumab, profiling their minor abundant variants for the first time across diverse structural levels. This study enhances understanding and accessibility in glycosylation analysis, spotlighting minor abundant glycovariants in therapeutic antibodies.

Enhanced N-Glycan Profiling of Therapeutic Monoclonal Antibodies through the Application of Upper-Hinge Middle-Up Level LC-HRMS Analysis

Therapeutic monoclonal antibodies (mAbs) are crucial in modern medicine due to their effectiveness in treating various diseases. However, the structural complexity of mAbs, particularly their glycosylation patterns, presents challenges for quality control and biosimilarity assessment. This study explores the use of upper-hinge middle-up (UHMU)-level ultra-high-performance liquid chromatography-high-resolution mass spectrometry (LC-HRMS) analysis to improve N-glycan profiling of mAbs. Two specific enzymes, known as IgG degradation enzymes (IGDEs), were used to selectively cleave therapeutic mAbs above the hinge region to separate antibody subunits for further Fc glycan analysis by means of the UHMU/LC-HRMS workflow. The complexity of the mass spectra of IGDEs-digested mAbs was significantly reduced compared to the intact MS level, enabling reliable assignment and relative quantitation of paired Fc glycoforms. The results of the UHMU/LC-HRMS analysis of nine approved therapeutics highlight the significance of this approach for in-depth glycoform profiling.

Comprehensive analysis and characterization of glycan pairing in therapeutic antibodies and Fc-containing biotherapeutics: Addressing current limitations and implications for N-glycan impact

N-glycosylation of the Fc part is a (critical) quality attribute of therapeutic antibodies and Fc-containing biotherapeutics, that impacts their stability, immunogenicity, pharmacokinetics, and effector functions. Current glycosylation analysis methods focus on the absolute amounts of glycans, neglecting the apparent glycan distribution over the entirety of proteins. The combination of the two Fc N-glycans, herein referred to as glyco-pair, therefore remains unknown, which is a major drawback for N-glycan impact assessment. This study presents a comprehensive workflow for the analysis and characterization of Fc N-glycan pairing in biotherapeutics, addressing the limitations of current glycosylation analysis methods. The applicability of the method across various biotherapeutic proteins including antibodies, bispecific antibody formats, and a Fc-Fusion protein is demonstrated, and the impact of method conditions on glycan pairing analysis is highlighted. Moreover, the influence of the molecular format, Fc backbone, production process, and cell line on glycan pairing pattern was investigated. The results underscore the significance of comprehensive glycan pairing analysis to accurately assess the impact of N-glycans on important product quality attributes of therapeutic antibodies and Fc-containing biotherapeutics.

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.

Decoding the mannose receptor-mAb interaction: the importance of high-mannose N-glycans and glycan-pairing

During the development process of therapeutic monoclonal antibodies (mAbs), it is crucial to control (critical) quality attributes such as N-glycosylation influencing pharmacokinetics (PK) and Fc effector functions. Previous reports have shown that mAbs containing high-mannose N-glycans are cleared faster from blood circulation, leading to reduced half-lives. The high-mannose N-glycan content of mAbs can be influenced during the cell culture process by factors such as cell lines, process conditions, and media. Furthermore, mAbs have either one high mannose N-glycan (asymmetrical high-mannose glyco-pair) or two high mannose N-glycans (symmetrical high-mannose glyco-pair). The hypothesis that the mannose receptor (MR, CD206) accelerates clearance by facilitating their internalization and subsequent lysosomal degradation is widespread. However, the interaction between MR and mAbs has not been explicitly demonstrated. This study aimed to investigate this interaction, providing the first systematic demonstration of MR binding to the Fc region of mAbs with high-mannose N-glycans. Two novel analytical methods, MR surface plasmon resonance and MR affinity chromatography, were developed and applied to investigate the MR-mAb interaction. The interaction is found to be dependent on high-mannose content, but is independent of the mAb format or sequence. However, different glyco-pairs exhibited varying binding affinities to the MR, with the symmetrical high-mannose glyco-pair showing the strongest binding properties. These findings strengthen the hypothesis for the MR-mediated mAb interaction and contribute to a deeper understanding of the MR-mAb interaction, which could affect the criticality of high-mannose containing mAbs development strategies of IgG-based molecules and improve their PK profiles.

Benchmark Glycan Profile of Therapeutic Monoclonal Antibodies Produced by Mammalian Cell Expression Systems

PURPOSE

This study aims to establish a benchmark glycan profile for commercial therapeutic monoclonal antibodies (mAbs) approved by the US Food and Drug Administration (FDA).

METHODS

We conducted a rigorous comparison of glycosylation data from the regulatory submissions for FDA-approved therapeutic antibodies up to May 2023. This analysis includes over 150 mAbs produced by various mammalian cell expression systems.

RESULTS

The study identified nine prevalent glycan epitopes across all FDA-approved monoclonal antibodies produced by different expression systems. These epitopes include terminal N-acetylglucosamine, core fucose, terminal galactose, high mannose, α-galactose, terminal α2,3-linked N-acetylneuraminic acid, terminal α2,6-linked N-glycolylneuraminic acid, triantennary structure, and bisecting N-acetylglucosamine, thus establishing a benchmark glycan profile.

CONCLUSIONS

The findings of this study have significant implications for therapeutic antibody development, quality control, and regulatory compliance. The benchmark glycan profile enables the assessment of glycosylation consistency and comparability across a diverse range of antibody products, ensuring improved product quality within the biopharmaceutical industry.

Plant-based biopharmaceutical engineering

Plants can be engineered to recombinantly produce high-quality proteins such as therapeutic proteins and vaccines, also known as molecular farming. Molecular farming can be established in various settings with minimal cold-chain requirements and could thus ensure rapid and global-scale deployment of biopharmaceuticals, promoting equitable access to pharmaceuticals. State of the art plant-based engineering relies on rationally assembled genetic circuits, engineered to enable the high-throughput and rapid expression of multimeric proteins with complex post-translational modifications. In this Review, we discuss the design of expression hosts and vectors, including Nicotiana benthamiana, viral elements and transient expression vectors, for the production of biopharmaceuticals in plants. We examine engineering of post-translational modifications and highlight the plant-based expression of monoclonal antibodies and nanoparticles, such as virus-like particles and protein bodies. Techno-economic analyses suggest a cost advantage of molecular farming compared with mammalian cell-based protein production systems. However, regulatory challenges remain to be addressed to enable the widespread translation of plant-based biopharmaceuticals.

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.

Risk-Based Control Strategies of Recombinant Monoclonal Antibody Charge Variants

Since the first approval of the anti-CD3 recombinant monoclonal antibody (mAb), muromonab-CD3, a mouse antibody for the prevention of transplant rejection, by the US Food and Drug Administration (FDA) in 1986, mAb therapeutics have become increasingly important to medical care. A wealth of information about mAbs regarding their structure, stability, post-translation modifications, and the relationship between modification and function has been reported. Yet, substantial resources are still required throughout development and commercialization to have appropriate control strategies to maintain consistent product quality, safety, and efficacy. A typical feature of mAbs is charge heterogeneity, which stems from a variety of modifications, including modifications that are common to many mAbs or unique to a specific molecule or process. Charge heterogeneity is highly sensitive to process changes and thus a good indicator of a robust process. It is a high-risk quality attribute that could potentially fail the specification and comparability required for batch disposition. Failure to meet product specifications or comparability can substantially affect clinical development timelines. To mitigate these risks, the general rule is to maintain a comparable charge profile when process changes are inevitably introduced during development and even after commercialization. Otherwise, new peaks or varied levels of acidic and basic species must be justified based on scientific knowledge and clinical experience for a specific molecule. Here, we summarize the current understanding of mAb charge variants and outline risk-based control strategies to support process development and ultimately commercialization.

Quantitative clinical glycomics strategies: A guide for selecting the best analysis approach

Glycans introduce complexity to the proteins to which they are attached. These modifications vary during the progression of many diseases; thus, they serve as potential biomarkers for disease diagnosis and prognosis. The immense structural diversity of glycans makes glycosylation analysis and quantitation difficult. Fortunately, recent advances in analytical techniques provide the opportunity to quantify even low-abundant glycopeptides and glycans derived from complex biological mixtures, allowing for the identification of glycosylation differences between healthy samples and those derived from disease states. Understanding the strengths and weaknesses of different quantitative glycomics analysis methods is important for selecting the best strategy to analyze glycosylation changes in any given set of clinical samples. To provide guidance towards selecting the proper approach, we discuss four widely used quantitative glycomics analysis platforms, including fluorescence-based analysis of released N-linked glycans and three different varieties of MS-based analysis: liquid chromatography (LC)-mass spectrometry (MS) analysis of glycopeptides, matrix-assisted laser desorption ionization-time of flight MS, and LC-ESI-MS analysis of released N-linked glycans. These methods' strengths and weaknesses are compared, particularly associated with the figures of merit that are important for clinical biomarker studies, including: the initial sample requirements, the methods' throughput, sample preparation time, the number of species identified, the methods' utility for isomer separation and structural characterization, method-related challenges associated with quantitation, repeatability, the expertise required, and the cost for each analysis. This review, therefore, provides unique guidance to researchers who endeavor to undertake a clinical glycomics analysis by offering insights on the available analysis technologies.

Highly sensitive characterization of non-human glycan structures of monoclonal antibody drugs utilizing tandem mass spectrometry

Glycosylation is an important attribute of monoclonal antibodies (mAbs) for assessing manufacturing quality. Analysis of non-human glycans containing terminal galactose-α1,3-galactose and N-glycolylneuraminic acid is essential due to the potential immunogenicity and insufficient efficacy caused by mAb expression in non-human mammalian cells. Using parallel sequencing of isobaric glycopeptides and isomeric glycans that were separated by reversed-phase and porous graphitic carbon LC, we report a highly sensitive LC MS/MS method for the comprehensive characterization of low-abundance non-human glycans and their closely related structural isomers. We demonstrate that the straightforward use of high-abundance diagnostic ions and complementary fragments under the positive ionization low-energy collision-induced dissociation is a universal approach to rapidly discriminate branch-linkage structures of biantennary glycans. Our findings reveal the structural diversity of non-human glycans and sulfation of α-galactosylated glycans, providing both an analytical method and candidate structures that could potentially be used in the crucial quality control of therapeutic mAb products.

Analytical and functional similarity of biosimilar Elizaria® with eculizumab reference product

A recombinant humanized monoclonal antibody (mAb) Eculizumab, C5-complement cascade inhibitor, is an important treatment of complement-based diseases recommended by international guidelines. Elizaria® Drug Product (DP), developed by IBC Generium, Russia, is the world's first registered biosimilar of eculizumab (Soliris®, Alexion Pharmaceuticals). Using sensitive state-of-the-art analytical techniques extensive similarity assessment has been conducted to demonstrate the structural and functional similarity of original Soliris® (Eculizumab Reference Product, RP) and the biosimilar Elizaria®, focusing on the physicochemical and biological quality attributes, including those known to affect the mechanisms of action. A multitude of analyses revealed that amino acid sequence is identical, the higher order structures, post-translational modifications, purity, and product variants are highly similar between Elizaria® DP and Eculizumab RP, except for minor differences in the relative abundance of the charge variants and glycan moieties considered not clinically significant. The results demonstrate that Elizaria® is highly analytically similar to Eculizumab RP in terms of physicochemical properties and biological activities.

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

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

Differential N- and O-glycosylation signatures of HIV-1 Gag virus-like particles and coproduced extracellular vesicles

HIV-1 virus-like particles (VLPs) are nanostructures derived from the self-assembly and cell budding of Gag polyprotein. Mimicking the native structure of the virus and being non-infectious, they represent promising candidates for the development of new vaccines as they elicit a strong immune response. In addition to this, the bounding membrane can be functionalized with exogenous antigens to target different diseases. Protein glycosylation depends strictly on the production platform and expression system used and the displayed glycosylation patterns may influence down-stream processing as well as the immune response. One of the main challenges for the development of Gag VLP production bioprocess is the separation of VLPs and coproduced extracellular vesicles (EVs). In this work, porous graphitized carbon separation method coupled with mass spectrometry was used to characterize the N- and O- glycosylation profiles of Gag VLPs produced in HEK293 cells. We identified differential glycan signatures between VLPs and EVs that could pave the way for further separation and purification strategies in order to optimize downstream processing and move forward in VLP-based vaccine production technology. This article is protected by copyright. All rights reserved.

Rapid monitoring of high-mannose glycans during cell culture process of therapeutic monoclonal antibodies using lectin affinity chromatography

We developed a simple high‐performance liquid chromatography assay to monitor high‐mannose glycans in monoclonal antibodies by monitoring terminal alpha‐mannose as a surrogate marker. Analysis of glycan data of therapeutic monoclonal antibodies by 2‐aminobenzamide assay showed a linear relationship between high mannose and terminal mannose of Fc glycans. Concanavalin A has a strong affinity to alpha‐mannose in glycans of typical therapeutic monoclonal antibodies. To show that terminal mannose binds specifically to Concanavalin A column, exoglycosidase‐treated monoclonal antibodies were serially blended with untreated monoclonal antibodies. Linear responses of terminal‐mannose binding to the column and comparable data trending with high mannose levels by 2‐aminobenzamide assay confirmed that terminal‐mannose levels measured by the Concanavalin A column can be used as a surrogate for the prediction of high‐mannose levels in monoclonal antibodies. The assay offers a simple, fast, and specific capability for the prediction of high‐mannose content in samples compared with traditional glycan profiling by 2‐aminobenzamide or mass spectrometry‐based methods. When the Concanavalin A column was coupled with protein A column for purification of antibodies from cell culture samples in a fully automated two‐dimensional analysis, high‐mannose data could be relayed to the manufacturing team in less than 30 min, allowing near‐real‐time monitoring of high‐mannose levels in the cell culture process.

HDX-MS and MD Simulations Provide Evidence for Stabilization of the IgG1-FcγRIa (CD64a) Immune Complex Through Intermolecular Glycoprotein Bonds

Previous reports present different models for the stabilization of the Fc-FcγRI immune complex. Although accord exists on the importance of L235 in IgG1 and some hydrophobic contacts for complex stabilization, discord exists regarding the existence of stabilizing glycoprotein contacts between glycans of IgG1 and a conserved FG-loop (¹⁷¹MGKHRY¹⁷⁶) of FcγRIa. Complexes formed from the FcγRIa receptor and IgG1s containing biantennary glycans with N-acetylglucosamine, galactose, and α2,6-N-acetylneuraminic terminations were measured by hydrogen-deuterium exchange mass spectrometry (HDX-MS), classified for dissimilarity with Welch's ANOVA and Games-Howell post hoc procedures, and modeled with molecular dynamics (MD) simulations. For each glycoform of the IgG1-FcγRIa complex peptic peptides of Fab, Fc and FcγRIa report distinct H/D exchange rates. MD simulations corroborate the differences in the peptide deuterium content through calculation of the percent of time that transient glycan-peptide bonds exist. These results indicate that stability of IgG1-FcγRIa complexes correlate with the presence of intermolecular glycoprotein interactions between the IgG1 glycans and the ¹⁷³KHR¹⁷⁵ motif within the FG-loop of FcγRIa. The results also indicate that intramolecular glycan-protein bonds stabilize the Fc region in isolated and complexed IgG1. Moreover, HDX-MS data evince that the Fab domain has glycan-protein binding contacts within the IgG1-FcγRI complex.

Need for a risk-based control strategy for managing glycosylation profile for biosimilar products

INTRODUCTION

Monoclonal antibodies, though a popular class of therapeutics, are complex molecules that are manufactured using complex processes, making it nontrivial to maintain high level of batch-to-batch consistency in product quality. Glycosylation is a posttranslation modification that is widely considered a critical quality attribute (CQA) as its variations are known to impact the Fc effector functions of mAbs. With continuing rise of biosimilars, comparability of these products to the reference product with respect to glycosylation is a topic of immense interest.

AREAS COVERED

In this article, we focus on the various aspects related to this topic including criticality of the various glycosylated forms, as well as comparability of biosimilars with respect to glycosylation.

EXPERT OPINION

We propose that manufacturers should focus on those glycoforms that are present in larger amounts and are known to be critical with respect to the biotherapeutic's safety and efficacy. Such risk-based evaluation of glycoforms and their control would offer an optimal route to biosimilar manufacturers for a cost-effective approach toward product development without compromising on the safety and efficacy characteristics of the therapeutic. For mAbs lacking Fc effector function, devising stringent glycosylation control strategies can be bypassed, thereby simplifying process and product development.

Profiling the glycome of Cardicola forsteri, a blood fluke parasitic to bluefin tuna

Infections by blood flukes (Cardicola spp.) are considered the most significant health issue for ranched bluefin tuna, a major aquaculture industry in Japan and Australia. The host-parasite interfaces of trematodes, namely their teguments, are particularly rich in carbohydrates, which function both in evasion and modulation of the host immune system, while some are primary antigenic targets. In this study, histochemistry and mass spectrometry techniques were used to profile the glycans of Cardicola forsteri. Fluorescent lectin staining of adult flukes indicates the presence of oligomannose (Concanavalin A-reactive) and fucosylated (Pisum sativum agglutinin-reactive) N-glycans. Additionally, reactivity of succinylated wheat germ agglutinin (s-WGA) was localised to several internal organs of the digestive and monoecious reproductive systems. Glycan structures were further investigated with tandem mass spectrometry, which revealed structures indicated by lectin reactivity. While O-glycans from these adult specimens were not detectable by mass spectrometry, several oligomannose, paucimannosidic, and complex-type N-glycans were identified, including some carrying hexuronic acid and many carrying core xylose. This is, to our knowledge, the first glycomic characterisation of a marine platyhelminth, with broader implications for research into other trematodes.

Creation of monoclonal antibody expressing CHO cell lines grown with sodium butyrate and characterization of resulting antibody glycosylation

Chinese hamster ovary (CHO) cells are the primary mammalian cell lines utilized to produce monoclonal antibodies (mAbs). The upsurge in biosimilar development and the proven health benefits of mAb treatments reinforces the need for innovative methods to generate robust CHO clones and enhance production, while maintaining desired product quality attributes. Among various product titer-enhancing approaches, the use of histone deacetylase inhibitors (HDACis) such as sodium butyrate (NaBu) has yielded promising results. The titer-enhancing effect of HDACi treatment has generally been observed in lower producer cell lines but those studies are typically done on individual clones. Here, we describe a cell line development (CLD) platform approach for creating clones with varying productivities. We then describe a method for selecting an optimal NaBu concentration to evaluate potential titer-enhancing capabilities in a fed-batch study. Finally, a method for purifying the mAb using protein A chromatography, followed by glycosylation analysis using mass spectrometry, is described. The proposed workflow can be applied for a robust CLD process optimization to generate robust clones, enhance product expression, and improve product quality attributes.

Current status and future prospects for ion-mobility mass spectrometry in the biopharmaceutical industry

Detailed characterization of protein reagents and biopharmaceuticals is key in defining successful drug discovery campaigns, aimed at bringing molecules through different discovery stages up to development and commercialization. There are many challenges in this process, with complex and detailed analyses playing paramount roles in modern industry. Mass spectrometry (MS) has become an essential tool for characterization of proteins ever since the onset of soft ionization techniques and has taken the lead in quality assessment of biopharmaceutical molecules, and protein reagents, used in the drug discovery pipeline. MS use spans from identification of correct sequences, to intact molecule analyses, protein complexes and more recently epitope and paratope identification. MS toolkits could be incredibly diverse and with ever evolving instrumentation, increasingly novel MS-based techniques are becoming indispensable tools in the biopharmaceutical industry. Here we discuss application of Ion Mobility MS (IMMS) in an industrial setting, and what the current applications and outlook are for making IMMS more mainstream.

Customized yeast cell factories for biopharmaceuticals: from cell engineering to process scale up

The manufacture of recombinant therapeutics is a fastest-developing section of therapeutic pharmaceuticals and presently plays a significant role in disease management. Yeasts are established eukaryotic host for heterologous protein production and offer distinctive benefits in synthesising pharmaceutical recombinants. Yeasts are proficient of vigorous growth on inexpensive media, easy for gene manipulations, and are capable of adding post translational changes of eukaryotes. Saccharomyces cerevisiae is model yeast that has been applied as a main host for the manufacture of pharmaceuticals and is the major tool box for genetic studies; nevertheless, numerous other yeasts comprising Pichia pastoris, Kluyveromyces lactis, Hansenula polymorpha, and Yarrowia lipolytica have attained huge attention as non-conventional partners intended for the industrial manufacture of heterologous proteins. Here we review the advances in yeast gene manipulation tools and techniques for heterologous pharmaceutical protein synthesis. Application of secretory pathway engineering, glycosylation engineering strategies and fermentation scale-up strategies in customizing yeast cells for the synthesis of therapeutic proteins has been meticulously described.

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.

Structure and Functional Characterization of a Humanized Anti-CCL20 Antibody following Exposure to Serum Reveals the Formation of Immune Complex That Leads to Toxicity

mAbs have revolutionized the treatment of autoimmune disorders. Even though mAbs have shown impressive efficacy in blocking T cell or B cell activation and/or recruitment to sites of inflammation, this group of biologicals are not devoid of adverse effects. The most serious adverse effects include infusion reactions, including the activation of the complement pathway. In this study, we present a detailed structure-function study of an anti-CCL20 humanized IgG1 mAb that neutralizes CCL20 chemokine and prevents the recruitment of Th17 cells to sites of inflammation. We demonstrate that the anti-CCL20 Ab changes significantly following administration to humans and monkeys and exposure to human serum. Analysis of the drug product revealed that the anti-CCL20 Ab has unexpectedly high C1q binding. This high binding was linked to immune complex formation in vivo but not during in vitro serum incubation. The immune complex contained multiple complement components. Anti-CCL20 Ab-mediated, complement-dependent cytotoxicity occurred when the Ab bound to CCL20 tethered to the cell membrane of target cells. Taken together, these results provide a likely cause for the animal toxicity observed. In addition, anti-CCL20 revealed progressive acidification because of N100 (located in CDR) deamidation over time, which did not directly impact Ag binding. Our study demonstrates that the safety profiling of mAbs should include the evaluation of effector functions in addition to typical stressed conditions.

Glycosylation is required for the neutralizing activity of human IgG1 antibodies against human rabies induced by pre-exposure prophylaxis

Rabies lyssavirus (RABV) neutralizing IgG antibodies confer protection after rabies vaccination, although how the RABV-specific antibodies neutralize the virus is still unknown. As changes in the antibody's carbohydrate chain can interfere with its effector functions, we compared the glycosylation patterns of both neutralizing and non-neutralizing IgG1 induced by pre-exposure prophylaxis to human rabies and analyzed their influence on in vitro antibody neutralizing activities. Specific IgG1 were purified from human serum using affinity chromatography. Purity and avidity were analyzed by SDS-PAGE and indirect ELISA using NH₄SCN respectively. The N-linked oligosaccharide chain of the purified IgG antibody was evaluated using a lectin-based ELISA assay with a panel of seven lectins. The activity of purified IgG1 and neutralizing IgG1 deglycosylated by PNGase F enzyme were analyzed using the rapid fluorescent focus inhibition test. The purified IgG1 showed an electrophoretic pattern compatible with human IgG. All of the antibodies recognized RABV, although neutralizing IgG1 had a higher avidity (RAI = 80%) than non-neutralizing IgG1 (RAI = 30%). The neutralizing IgG1 also showed higher binding to WFA, ECA, WGA, and ConA lectins, indicating possible different N-acetylgalactosamine, galactose, N-acetylglucosamine, and mannose contents. Non-neutralizing IgG1, on the other hand, showed strong binding at UEA-1 and SNA, which bind to fucose and sialic acid residues respectively. Different glycosylation profiles were also observed in Fab and Fc fragments from neutralizing and non-neutralizing IgG1, although the deglycosylated IgG1 lost its neutralizing activity. Our results suggest that antibody glycosylation is important for neutralizing RABV in vitro, since neutralizing IgG1 has a different glycosylation profile than non-neutralizing IgG1. Further research will be needed to better evaluate the differential glycosylation patterns between IgG1 antibodies following vaccination.

Glycoform-resolved pharmacokinetic studies in a rat model employing glycoengineered variants of a therapeutic monoclonal antibody

Good pharmacokinetic (PK) behavior is a key prerequisite for sufficient efficacy of therapeutic monoclonal antibodies (mAbs). Fc glycosylation is a critical quality attribute (CQA) of mAbs, due to its impact on stability and effector functions. However, the effects of various IgG Fc glycoforms on antibody PK remain unclear. We used a combination of glycoengineering and glycoform-resolved PK measurements by mass spectrometry (MS) to assess glycoform effects on PK. Four differently glycoengineered mAbs, each still containing multiple glycoforms, were separately injected into rats. Rat models have been shown to be predictive of human PK. At different time points, blood was taken, from which the mAbs were purified and analyzed with a liquid chromatography-MS-based bottom-up glycoproteomics approach. This allowed us to follow changes in the glycosylation profiles of each glycoengineered mAb over time. Enzyme-linked immunosorbent assay measurements provided an absolute concentration in the form of a sum value for all glycoforms. Information from both readouts was then combined to calculate PK parameters per glycoform. Thereby, multiple glycoform kinetics were resolved within one mAb preparation. We confirmed increased clearance of high-mannose (Man5) and hybrid-type (Man5G0) glycoforms. Specifically, Man5 showed a 1.8 to 2.6-fold higher clearance than agalactosylated, complex glycans (G0F). Unexpectedly, clearance was even higher (4.7-fold) for the hybrid-type glycan Man5G0. In contrast, clearance of agalactosylated, monoantennary glycoforms (G0F-N) was only slightly increased over G0F (1.2 to 1.4-fold). Thus, monoantennary, hybrid-type and high-mannose glycoforms should be distinguished in CQA assessments. Strikingly, α2,3-linked sialylation did not affect clearance, contradicting the involvement of the asialoglycoprotein receptor in mAb clearance.

Importance and Monitoring of Therapeutic Immunoglobulin G Glycosylation

The complex diantennary-type oligosaccharides at Asn297 residues of the IgG heavy chains have a profound impact on the safety and efficacy of therapeutic IgG monoclonal antibodies (mAbs). Fc glycosylation of a mAb is an established critical quality attribute (CQA), and its oligosaccharide profile is required to be thoroughly characterized by state-of-the-art analytical methods. The Fc oligosaccharides are highly heterogeneous, and the differentially glycosylated species (glycoforms) of IgG express unique biological activities. Glycoengineering is a promising approach for the production of selected mAb glycoforms with improved effector functions, and non- and low-fucosylated mAbs exhibiting enhanced antibody-dependent cellular cytotoxicity activity have been approved or are under clinical evaluation for treatment of cancers, autoimmune/chronic inflammatory diseases, and infection. Recently, the chemoenzymatic glycoengineering method that allows for the transfer of structurally defined oligosaccharides to Asn-linked GlcNAc residues with glycosynthase has been developed for remodeling of IgG-Fc oligosaccharides with high efficiency and flexibility. Additionally, various glycoengineering methods have been developed that utilize the Fc oligosaccharides of IgG as reaction handles to conjugate cytotoxic agents by "click chemistry", providing new routes to the design of antibody-drug conjugates (ADCs) with tightly controlled drug-antibody ratios (DARs) and homogeneity. This review focuses on current understanding of the biological relevance of individual IgG glycoforms and advances in the development of next-generation antibody therapeutics with improved efficacy and safety through glycoengineering.

Fc γ receptor IIIa/CD16a processing correlates with the expression of glycan-related genes in human natural killer cells

Many therapeutic monoclonal antibodies require binding to Fc γ receptors (FcγRs) for full effect and increasing the binding affinity increases efficacy. Preeminent among the five activating human FcγRs is FcγRIIIa/CD16a expressed by natural killer (NK) cells. CD16a is heavily processed, and recent reports indicate that the composition of the five CD16a asparagine(N)-linked carbohydrates (glycans) impacts affinity. These observations indicate that specific manipulation of CD16a N-glycan composition in CD16a-expressing effector cells including NK cells may improve treatment efficacy. However, it is unclear if modifying the expression of select genes that encode processing enzymes in CD16a-expressing effector cells is sufficient to affect N-glycan composition. We identified substantial processing differences using a glycoproteomics approach by comparing CD16a isolated from two NK cell lines, NK92 and YTS, with CD16a expressed by HEK293F cells and previous reports of CD16a from primary NK cells. Gene expression profiling by RNA-Seq and qRT-PCR revealed expression levels for glycan-modifying genes that correlated with CD16a glycan composition. These results identified a high degree of variability between the processing of the same human protein by different human cell types. N-glycan processing correlated with the expression of glycan-modifying genes and thus explained the substantial differences in CD16a processing by NK cells of different origins.

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.

Impact of Fc N-linked glycans on in vivo clearance of an immunoglobulin G1 antibody produced by NS0 cell line

The heterogeneity of glycosylation on therapeutic monoclonal antibodies (mAbs) may affect the safety and efficacy of these agents. In particular, glycans of nonhuman origin, such as galactose-alpha-1,3-galactose (gal-α-gal) and N-glycolylneuraminic acid (NGNA), in the Fc region of therapeutic mAbs produced from murine cell lines carry a risk of immunogenicity. Immunogenic glycan structures can have immune-mediated clearance, resulting in faster clearance from in vivo circulation than non-immunogenic structures. To demonstrate the impact of these Fc nonhuman glycans on in vivo clearance, we purified and analyzed the glycan profile of a monoclonal antibody (mAb1) from human serum samples collected from clinical study participants. We purified mAb1 in a three-step chromatographic separation process (protein A, immobilized anti-mAb1 antibody affinity, and weak cation exchange chromatography) and extracted and labeled its N-linked oligosaccharide structures with 2-aminobenzamide acid for analysis on ultrahigh-performance hydrophilic interaction liquid chromatography. A comparison of the glycan profile of mAb1 recovered from human serum on the same day and 4 weeks after dosing revealed no significant differences, indicating similar clearance of mAb1 with nonhuman gal-α-gal or NGNA glycan in the Fc region compared with the human glycans. The relative proportions of the glycans remained similar, and all patients who had already received multiple doses of mAb1 over the course of a year were negative for antidrug antibodies, suggesting that none of the glycans induced an immune response. Therefore, we concluded that mAb1 gal-α-gal and NGNA glycoforms represent a low risk of conferring immunogenicity.

Functional analysis of glycosylation in Etanercept: Effects over potency and stability

Etanercept is a biotechnological product that has a complex glycosylation profile. To elucidate Etanercept glycosylation effect over biological activity and stability, we deglycosylated sequentially this molecule. Sequential deglycosylation was performed to understand which glycans are critical for Etanercept folding and activity. Extended study showed that gross glycosylation differences, affect thermal stability, hydrodynamic radius, pI, CDC, ADCC, protection against oxidation and charge surface exposition with any effect (within biological assay dispersion) over TNFα neutralization, indicating which glycoforms have a critical effect over Etanercept ADCC, CDC and stability. In this regard, complete remotion of sialic acids have a predominant importance over pI, ADCC, CDC and surface charge while N and O glycosylation over thermal stability, hydrophobicity, aggregation and protection against oxidation. Our research suggest that gross differences in the glycosylation profile are relevant for the stability and biological main activities of Etanercept, and that significant differences that affect the activities related to this fusion protein could be detected with proper analytical methods and stability studies.

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.

More comprehensive standards for monitoring glycosylation

Biologics manufacturers must continually monitor the attachment of carbohydrates, called glycans, to their products, because any variability can impact safety and efficacy. To help the industry meet this challenge, the United States Pharmacopeial Convention (USP) offers glycan reference standards and validated methods for glycoprofiling using high-performance liquid chromatography (HPLC). The industry has recently adopted more advanced technologies for glycan analysis, including ultra-high performance liquid chromatography (UHPLC) and mass spectrometry. In this study, we confirm that USP's glycan reference standards are compatible with UHPLC by demonstrating comparable peak separation and glycan identification to HPLC methods. The improved resolving power and shorter run-times of UHPLC also allowed us to identify many of the minor glycan components present in USP's glycan reference standards. These more comprehensively characterized glycan reference standards will enable manufacturers to assess the micro-heterogeneity that can negatively impact the safety and efficacy of biological products.

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.

Mass spectrometry for the identification and analysis of highly complex glycosylation of therapeutic or pathogenic proteins

INTRODUCTION

Protein glycosylation influences characteristics such as folding, stability, protein interactions, and solubility. Therefore, glycan moieties of therapeutic proteins and proteins that are likely associated with disease pathogenesis should be analyzed in-depth, including glycan heterogeneity and modification sites. Recent advances in analytical methods and instrumentation have enabled comprehensive characterization of highly complex glycosylated proteins.

AREA COVERED

The following aspects should be considered when analyzing glycosylated proteins: sample preparation, chromatographic separation, mass spectrometry (MS) and fragmentation methods, and bioinformatics, such as software solutions for data analyses. Notably, analysis of glycoproteins with heavily sialylated glycans or multiple glycosylation sites requires special considerations. Here, we discuss recent methodological advances in MS that provide detailed characterization of heterogeneous glycoproteins.

EXPERT OPINION

As characterization of complex glycosylated proteins is still analytically challenging, the function or pathophysiological significance of these proteins is not fully understood. To reproducibly produce desired forms of therapeutic glycoproteins or to fully elucidate disease-specific patterns of protein glycosylation, a highly reproducible and robust analytical platform(s) should be established. In addition to advances in MS instrumentation, optimization of analytical and bioinformatics methods and utilization of glycoprotein/glycopeptide standards is desirable. Ultimately, we envision that an automated high-throughput MS analysis will provide additional power to clinical studies and precision medicine.

High-Throughput Quantification and Glycosylation Analysis of Antibodies Using Bead-Based Assays

A novel version of bead -based assays with fluorescence detection enables the high-throughput analysis of antibodies and proteins. The protocols are carried out in special 384-well plates, require very few manual interventions, and are easy to automate. Here we describe how the technology can be used to determine antibody titers and screen for product glycosylation, a critical quality attribute, early in cell line and bioprocess development.

Are Biotransformation Studies of Therapeutic Proteins Needed? Scientific Considerations and Technical Challenges

For therapeutic proteins, the currently established standard development path generally does not foresee biotransformation studies by default because it is well known that the clearance of therapeutic proteins proceeds via degradation to small peptides and individual amino acids. In contrast to small molecules, there is no general need to identify enzymes involved in biotransformation because this information is not relevant for drug-drug interaction assessment and for understanding the clearance of a therapeutic protein. Nevertheless, there are good reasons to embark on biotransformation studies, especially for complex therapeutic proteins. Typical triggers are unexpected rapid clearance, species differences in clearance not following the typical allometric relationship, a mismatch in the pharmacokinetics/pharmacodynamics (PK/PD) relationship, and the need to understand observed differences between the results of multiple bioanalytical methods (e.g., total vs. target-binding competent antibody concentrations). Early on during compound optimization, knowledge on protein biotransformation may help to design more stable drug candidates with favorable in vivo PK properties. Understanding the biotransformation of a therapeutic protein may also support designing and understanding the bioanalytical assay and ultimately the PK/PD assessment. Especially in cases where biotransformation products are pharmacologically active, quantification and assessment of their contribution to the overall pharmacological effect can be important for establishing a PK/PD relationship and extrapolation to humans. With the increasing number of complex therapeutic protein formats, the need for understanding the biotransformation of therapeutic proteins becomes more urgent. This article provides an overview on biotransformation processes, proteases involved, strategic considerations, regulatory guidelines, literature examples for in vitro and in vivo biotransformation, and technical approaches to study protein biotransformation. SIGNIFICANCE STATEMENT: Understanding the biotransformation of complex therapeutic proteins can be crucial for establishing a pharmacokinetic/pharmacodynamic relationship. This article will highlight scientific, strategic, regulatory, and technological features of protein biotransformation.

Quantitation and modeling of post-translational modifications in a therapeutic monoclonal antibody from single- and multiple-dose monkey pharmacokinetic studies using mass spectrometry

Post-translational modifications (PTMs) of therapeutic monoclonal antibodies (mAbs) are important product quality attributes (PQAs) that can potentially impact drug stability, safety, and efficacy. The PTMs of a mAb may change remarkably in the bloodstream after drug administration compared to in vitro conditions. Thus, monitoring in vivo PTM changes of mAbs helps evaluate the criticality of PQAs during the product risk assessment. In addition, quantitation of the subject exposures to PTM variants helps assess the impact of PTMs on the safety and efficacy of therapeutic mAbs. Here, we developed an immunocapture-liquid chromatography/mass spectrometry (LC/MS) method to quantify in vivo PTM changes a therapeutic mAb overtime in single- and multiple-dose monkey pharmacokinetic (PK) studies. We also built mathematical models to predict the in vivo serum concentrations of PQAs, the subject exposures to PQAs, and the relative abundance of PQAs in single- and multiple-dose regimens. The model predictions are in good agreement with the experimental results. The immunocapture-LC/MS method and mathematical models enable bioanalytical chemists to quantitatively assess the criticality of PQAs during drug development.

Impact of Fc N-glycan sialylation on IgG structure

Human IgG antibodies containing terminal alpha 2,6-linked sialic acid on their Fc N-glycans have been shown to reduce antibody-dependent cell-mediated cytotoxicity and possess anti-inflammatory properties. Although terminal sialylation on complex N-glycans can happen via either an alpha 2,3-linkage or an alpha 2,6-linkage, sialic acids on human serum IgG Fc are almost exclusively alpha 2,6-linked. Recombinant IgGs expressed in Chinese hamster ovary (CHO) cells, however, have sialic acids through alpha 2,3-linkages because of the lack of the alpha 2,6-sialyltransferase gene. The impact of different sialylation linkages to the structure of IgG has not been determined. In this work, we investigated the impact of different types of sialylation to the conformational stability of IgG through hydrogen/deuterium exchange (HDX) and limited proteolysis experiments. When human-derived and CHO-expressed IgG1 were analyzed by HDX, sialic acid-containing glycans were found to destabilize the CH2 domain in CHO-expressed IgG, but not human-derived IgG. When structural isomers of sialylated glycans were chromatographically resolved and identified in the limited proteolysis experiment, we found that only alpha 2,3-linked sialic acid on the 6-arm (the major sialylated glycans in CHO-expressed IgG1) destabilizes the CH2 domain, presumably because of the steric effect that decreases the glycan-CH2 domain interaction. The alpha 2,6-linked sialic acid on the 3-arm (the major sialylated glycan in human-derived IgG), and the alpha 2,3-linked sialic acid on the 3-arm, do not have this destabilizing effect.

Two-pore physiologically based pharmacokinetic model with de novo derived parameters for predicting plasma PK of different size protein therapeutics

Two-pore PBPK models have been used for characterizing the PK of protein therapeutics since 1990s. However, widespread utilization of these models is hampered by the lack of a priori parameter values, which are typically estimated using the observed data. To overcome this hurdle, here we have presented the development of a two-pore PBPK model using de novo derived parameters. The PBPK model was validated using plasma PK data for different size proteins in mice. Using the "two pore theory" we were able to establish the relationship between protein size and key model parameters, such as: permeability-surface area product (PS), vascular reflection coefficient (σ), peclet number (Pe), and glomerular sieving coefficient (θ). The model accounted for size dependent changes in tissue extravasation and glomerular filtration. The model was able to a priori predict the PK of 8 different proteins: IgG (150 kDa), scFv-Fc (105 kDa), F(ab)₂ (100 kDa, minibody (80 kDa), scFv₂ (55 kDa), Fab (50 kDa), diabody (50 kDa), scFv (27 kDa), and nanobody (13 kDa). In addition, the model was able to provide unprecedented quantitative insight into the relative contribution of convective and diffusive pathway towards trans-capillary mass transportation of different size proteins. The two-pore PBPK model was also able to predict systemic clearance (CL) versus Molecular Weight relationship for different size proteins reasonably well. As such, the PBPK model proposed here represents a bottom-up systems PK model for protein therapeutics, which can serve as a generalized platform for the development of truly translational PBPK model for protein therapeutics.

Development of a filter-aided extraction method coupled with glycosylamine labeling to simplify and enhance high performance liquid chromatography-based N-glycan analysis

Efficient sample pretreatment of N-glycans from glycoproteins is essential but challenging due to the limitations of existing tedious and laborious methods in N-glycomics. This study aimed to establish a filter-aided extraction method coupled with glycosylamine AQC labeling for a simple and rapid direct HPLC-FLD-based analysis of N-glycans. The developed method was demonstrated to be simpler and more sensitive compared to previous HILIC SPE purification method coupled with glycosylamine labeling. It has been validated with wild-type N-glycans from human transferrin and RNase B and then was successfully applied to investigate N-glycan profiles of the transferrin in human serum and a monoclonal antibody (mAb). Results showed good applicability of the method for complex samples. Additionally, this method is compatible with the replicate determination of N-glycan samples to assess the high-throughput analysis of glycan variability in mAb sample.

Concentration and Glycoform of Rituximab in Plasma of Patients with B Cell Non-Hodgkin's Lymphoma

PURPOSE

Therapeutic antibodies have heterogeneities in their structures, although its structural alteration in the body is unclear. Here, we analyzed the change of amino acid modifications and carbohydrate chains of rituximab after administration to patients.

METHODS

Twenty B cell non-Hodgkin's lymphoma patients who were treated with rituximab for the first time or after more than one year's abstinence were recruited. Structural analysis of rituximab was carried out at 1 h after administration and at the trough by using liquid chromatography/time-of-flight-mass spectrometry. Plasma rituximab concentration and pharmacodynamic markers were also determined.

RESULTS

Of recruited twenty, 3 patients exhibited rapid rituximab clearance. Nine types of carbohydrate chains were detected in rituximab isolated from the blood. The composition ratios in some glycoforms were significantly different between at 1 h after administration and at the trough, although consisted amino acids remained unchanged. The patients with high clearance showed extensive alterations of glycoform composition ratios. However, pharmacodynamics makers were not different.

CONCLUSION

Inter-individual variations in plasma concentrations of rituximab were found in some B-NHL patients. We could analyze a change in glycoforms of rituximab in the patients, and this finding may affect the pharmacokinetics of rituximab.

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.

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.