Glycosylation of Recombinant Antibody Therapeutics

Discovery and Characterization of Unusual O-Linked Glycosylation of IgG4 Antibody Using LC-MS

BACKGROUND

Consensus is that immunoglobulin IgG4 contains only N-linked glycosylation. The analysis of several batches of commercial biopharmaceutical product Dupixent using top-down intact mass spectrometry revealed that this IgG4 features a small amount of O-linked glycosylation in the Fab region. This is the first report of an O-linked glycosylation in an IgG4 antibody.

METHODS

Monoclonal antibody solutions were subjected to cation exchange (CEX) and reverse phase (RP) chromatography and/or additional preconcentration/fractionation methods to prepare samples for subsequent analysis. Advanced MS analysis and fragmentation techniques (HCD, ETD, and EThcD) were employed to localize the O-linked glycosylation as well as elucidate the structure of the glycan(s).

RESULTS

O-linked glycosylation in the IgG4 dupilumab was discovered by intact-MS. The probable location was narrowed down to four sites in the CH1 domain, and the structure of the O-linked glycan was determined to be of Core 1 type. The relative quantities of the modifications were low, but the glycosylation was consistently detected in several batches of Dupixent.

CONCLUSIONS

We discovered a rare glycosylation modification on dupilumab, an IgG4 antibody. The O-linked glycosylation was characterized and localized in the Fab region.

A multimodal digital microfluidic testing platform for antibody-producing cell lines

In recent years, monoclonal antibodies (mAbs) have become a powerful tool in the treatment of human diseases. Currently, over 100 mAbs have received approval for therapeutic use in the US, with wide-ranging applications from cancer to infectious diseases. The predominant method of producing antibodies for therapeutics involves expression in mammalian cell lines. In the mAb production process, significant optimization is typically done to maximize antibody titres from cells grown in bioreactors. Therefore, systems that can miniaturize and automate cell line testing (e.g., viability and antibody production assays) are valuable in reducing therapeutic mAb development costs. Here we present a novel platform for cell line optimization for mAb production using digital microfluidics. The platform enables testing of cell culture samples in 6-8 μL droplets with semi-automated viability, media pH, and antibody production assays. This system provides a unique bridge between cell growth and productivity metrics, while minimizing culture volume requirements for daily testing. We propose that this technology and its future iterations has the potential to help reduce the time-to-market and development costs of antibody-producing cell lines.

Systematic Preparation of a 66-IgG Library with Symmetric and Asymmetric Homogeneous Glycans and Their Functional Evaluation

Immunoglobulin G (IgG) antibodies possess a conserved N-glycosylation site in the Fc domain. In FcγRIIIa affinity column chromatography, unglycosylated, hemiglycosylated, and fully glycosylated IgG retention times differ considerably. Using retention-time differences, 66 different trastuzumab antibodies with symmetric and asymmetric homogeneous glycans were prepared systematically, substantially expanding the scope of IgGs with homogeneous glycans. Using the prepared trastuzumab with homogeneous glycans, thermal stability and antibody-dependent cellular cytotoxicity were investigated. In some glycan series, a directly proportional relationship was observed between the thermal unfolding temperature (Tm) and the calorimetric unfolding heat (ΔHcal). Antibody function could be deduced from the combination of a pair of glycans in an intact form. Controlling glycan structure through the combination of a pair of glycans permits the precise tuning of stability and effector functions of IgG. Overall, our technology can be used to investigate the effects of glycans on antibody functions.

Rapid Mass Spectrometry-Based Multiattribute Method for Glycation Analysis with Integrated Afucosylation Detection Capability

The multiattribute method (MAM) has emerged as a powerful tool for simultaneously screening multiple product quality attributes of therapeutic antibodies. One such potential critical quality attribute (CQA) is glycation, a common modification that can impact the heterogeneity, functional activity, and immunogenicity of therapeutic antibodies. However, current methods for monitoring glycation levels in MAM are rare and not sufficiently rapid and accurate. In this study, an improved mass spectrometry (MS)-based MAM was developed to simultaneously monitor glycation and other quality attributes including afucosylation. The method was evaluated using two therapeutic antibodies with different glycosylation site numbers. Treatment with IdeS, Endo F2, and dithiothreitol generated three distinct subunits, and the glycation results obtained were similar to those treated with PNGase F, which is routinely used to release glycans; the sample processing time was greatly reduced while providing additional quality attribute information. The MS-based MAM was also employed to assess the glycation progression following forced glycation in various buffer solutions. A significant increase in oxidation was observed when forced glycation was conducted in an ammonium bicarbonate buffer solution, and a total of 23 potential glycation sites and 4 significantly oxidized sites were identified. Notably, we found that ammonium bicarbonate was found to specifically stimulate oxidation, while glycation had a synergistic effect on oxidation. These findings establish this study as a novel methodology for achieving a technologically advanced platform and concept that enhances the efficacy of product development and quality control, characterized by its broad-spectrum, rapid, and accurate nature.

Structure-Based High-Efficiency Homogeneous Antibody Platform by Endoglycosidase Sz Provides Insights into Its Transglycosylation Mechanism

Monoclonal antibodies (mAbs) have gradually dominated the drug markets for various diseases. Improvement of the therapeutic activities of mAbs has become a critical issue in the pharmaceutical industry. A novel endo-β-N-acetylglucosaminidase, EndoSz, from Streptococcus equisubsp. zooepidemicus Sz105 is discovered and applied to enhance the activities of mAbs. Our studies demonstrate that the mutant EndoSz-D234M possesses an excellent transglycosylation activity to generate diverse glycoconjugates on mAbs. We prove that EndoSz-D234M can be applied to various marketed therapeutic antibodies and those in development for antibody remodeling. The remodeled homogeneous antibodies (mAb-G2S2) produced by EndoSz-D234M increase the relative ADCC activities by 3-26-fold. We further report the high-resolution crystal structures of EndoSz-D234M in the apo-form at 2.15 Å and the complex form with a bound G2S2-oxazoline intermediate at 2.25 Å. A novel pH-jump method was utilized to obtain the complex structure with a high resolution. The detailed interactions of EndoSz-D234M and the carried G2S2-oxazoline are hence delineated. The oxazoline sits in a hole, named the oxa-hole, which stabilizes the G2S2-oxazoline in transit and catalyzes the further transglycosylation reaction while targeting Asn-GlcNAc (+1) of Fc. In the oxa-hole, the H-bonding network involved with oxazoline dominates the transglycosylation activity. A mobile loop2 (a.a. 152-159) of EndoSz-D234M reshapes the binding grooves for the accommodation of G2S2-oxazoline upon binding, at which Trp154 forms a hydrogen bond with Man (-2). The long loop4 (a.a. 236-248) followed by helix3 is capable of dominating the substrate selectivity of EndoSz-D234M. In addition, the stepwise transglycosylation behavior of EndoSz-D234M is elucidated. Based on the high-resolution structures of the apo-form and the bound form with G2S2-oxazoline as well as a systematic mutagenesis study of the relative transglycosylation activity, the transglycosylation mechanism of EndoSz-D234M is revealed.

Perspective view of allogeneic IgG tumor immunotherapy

Allogeneic tumors are eradicated by host immunity; however, it is unknown how it is initiated until the report in Nature by Yaron Carmi et al. in 2015. Currently, we know that allogeneic tumors are eradicated by allogeneic IgG via dendritic cells. AlloIgG combined with the dendritic cell stimuli tumor necrosis factor alpha and CD40L induced tumor eradication via the reported and our proposed potential signaling pathways. AlloIgG triggers systematic immune responses targeting multiple antigens, which is proposed to overcome current immunotherapy limitations. The promising perspectives of alloIgG immunotherapy would have advanced from mouse models to clinical trials; however, there are only 6 published articles thus far. Therefore, we hope this perspective view will provide an initiative to promote future discussion.

Rapid depletion of "catch-and-release" anti-ASGR1 antibody in vivo

Targeting antigens with antibodies exhibiting pH/Ca2+-dependent binding against an antigen is an attractive strategy to mitigate target-mediated disposition and antigen buffering. Studies have reported improved serum exposure of antibodies exhibiting pH/Ca2+-binding against membrane-bound receptors. Asialoglycoprotein receptor 1 (ASGR1) is a membrane-bound receptor primarily localized in hepatocytes. With a high expression level of approximately one million receptors per cell, high turnover, and rapid recycling, targeting this receptor with a conventional antibody is a challenge. In this study, we identified an antibody exhibiting pH/Ca2+-dependent binding to ASGR1 and generated antibody variants with increased binding to neonatal crystallizable fragment receptor (FcRn). Serum exposures of the generated anti-ASGR1 antibodies were analyzed in transgenic mice expressing human FcRn. Contrary to published reports of increased serum exposure of pH/Ca2+-dependent antibodies, the pH/Ca2+-dependent anti-ASGR1 antibody had rapid serum clearance in comparison to a conventional anti-ASGR1 antibody. We conducted sub-cellular trafficking studies of the anti-ASGR1 antibodies along with receptor quantification analysis for mechanistic understanding of the rapid serum clearance of pH/Ca2+-dependent anti-ASGR1 antibody. The findings from our study provide valuable insights in identifying the antigens, especially membrane bound, that may benefit from targeting with pH/Ca2+-dependent antibodies to obtain increased serum exposure.

Efficient optimization of time-varying inputs in a fed-batch cell culture process using design of dynamic experiments

In cell culture process development, we rely largely on an iterative, one-factor-at-a-time procedure based on experiments that explore a limited process space. Design of experiments (DoE) addresses this issue by allowing us to analyze the effects of process inputs on process responses systematically and efficiently. However, DoE cannot be applied directly to study time-varying process inputs unless an impractically large number of bioreactors is used. Here, we adopt the methodology of design of dynamic experiments (DoDE) and incorporate dynamic feeding profiles efficiently in late-stage process development of the manufacture of therapeutic monoclonal antibodies. We found that, for the specific cell line used in this article, (1) not only can we estimate the effect of nutrient feed amount on various product attributes, but we can also estimate the effect, develop a statistical model, and use the model to optimize the slope of time-trended feed rates; (2) in addition to the slope, higher-order dynamic characteristics of time-trended feed rates can be incorporated in the design but do not have any significant effect on the responses we measured. Based on the DoDE data, we developed a statistical model and used the model to optimize several process conditions. Our effort resulted in a tangible improvement in productivity-compared with the baseline process without dynamic feeding, this optimized process in a 200-L batch achieved a 27% increase in titer and > 92% viability. We anticipate our application of DoDE to be a starting point for more efficient workflows to optimize dynamic process conditions in process development.

Cell-culture process optimization via model-based predictions of metabolism and protein glycosylation

In order to meet the rising demand for biologics and become competitive on the developing biosimilar market, there is a need for process intensification of biomanufacturing processes. Process development of biologics has historically relied on extensive experimentation to develop and optimize biopharmaceutical manufacturing. Experimentation to optimize media formulations, feeding schedules, bioreactor operations and bioreactor scale up is expensive, labor intensive and time consuming. Mathematical modeling frameworks have the potential to enable process intensification while reducing the experimental burden. This review focuses on mathematical modeling of cellular metabolism and N-linked glycosylation as applied to upstream manufacturing of biologics. We review developments in the field of modeling cellular metabolism of mammalian cells using kinetic and stoichiometric modeling frameworks along with their applications to simulate, optimize and improve mechanistic understanding of the process. Interest in modeling N-linked glycosylation has led to the creation of various types of parametric and non-parametric models. Most published studies on mammalian cell metabolism have performed experiments in shake flasks where the pH and dissolved oxygen cannot be controlled. Efforts to understand and model the effect of bioreactor-specific parameters such as pH, dissolved oxygen, temperature, and bioreactor heterogeneity are critically reviewed. Most modeling efforts have focused on the Chinese Hamster Ovary (CHO) cells, which are most commonly used to produce monoclonal antibodies (mAbs). However, these modeling approaches can be generalized and applied to any mammalian cell-based manufacturing platform. Current and potential future applications of these models for Vero cell-based vaccine manufacturing, CAR-T cell therapies, and viral vector manufacturing are also discussed. We offer specific recommendations for improving the applicability of these models to industrially relevant processes.

Modulating antibody effector functions by Fc glycoengineering

Antibody based drugs, including IgG monoclonal antibodies, are an expanding class of therapeutics widely employed to treat cancer, autoimmune and infectious diseases. IgG antibodies have a conserved N-glycosylation site at Asn297 that bears complex type N-glycans which, along with other less conserved N- and O-glycosylation sites, fine-tune effector functions, complement activation, and half-life of antibodies. Fucosylation, galactosylation, sialylation, bisection and mannosylation all generate glycoforms that interact in a specific manner with different cellular antibody receptors and are linked to a distinct functional profile. Antibodies, including those employed in clinical settings, are generated with a mixture of glycoforms attached to them, which has an impact on their efficacy, stability and effector functions. It is therefore of great interest to produce antibodies containing only tailored glycoforms with specific effects associated with them. To this end, several antibody engineering strategies have been developed, including the usage of engineered mammalian cell lines, in vitro and in vivo glycoengineering.

LC/MS Assessment of Glycoform Clearance of A Biotherapeutic MAb in Rabbit Ocular Tissues

Many biotherapeutics such as monoclonal antibodies (mAbs) consist of various glycoforms, which can have different PK properties upon administration to animals and human. As a result, it is necessary to monitor the abundance of glycoforms and limit lot-to-lot variability during the manufacturing process. However, limited information is known about the clearance of mAb glycoforms from ocular space upon intravitreal injection. We present here an assessment of glycoform clearance of a biotherapeutic mAb (IgG1) from rabbit vitreous humor, aqueous humor and retina tissue using LC/MS. The results show that G0, G0F and G1F have similar T1/2, while mannose-5 has a longer T1/2 and is cleared slower in rabbit ocular space, which contradicted with what has been reported in the literature in which Mann5 was cleared faster systematically.

A glyco-engineering approach for site-specific conjugation to Fab glycans

Effective processes for synthesizing antibody-drug conjugates (ADCs) require: 1) site-specific incorporation of the payload to avoid interference with binding to the target epitope, 2) optimal drug/antibody ratio to achieve sufficient potency while avoiding aggregation or solubility problems, and 3) a homogeneous product to facilitate approval by regulatory agencies. In conventional ADCs, the drug molecules are chemically attached randomly to antibody surface residues (typically Lys or Cys), which can interfere with epitope binding and targeting, and lead to overall product heterogeneity, long-term colloidal instability and unfavorable pharmacokinetics. Here, we present a more controlled process for generating ADCs where drug is specifically conjugated to only Fab N-linked glycans in a narrow ratio range through functionalized sialic acids. Using a bacterial sialytransferase, we incorporated N-azidoacetylneuraminic acid (Neu5NAz) into the Fab glycan of cetuximab. Since only about 20% of human IgG1 have a Fab glycan, we extended the application of this approach by using molecular modeling to introduce N-glycosylation sites in the Fab constant region of other therapeutic monoclonal antibodies. We used trastuzumab as a model for the incorporation of Neu5NAz in the novel Fab glycans that we designed. ADCs were generated by clicking the incorporated Neu5NAz with monomethyl auristatin E (MMAE) attached to a self-immolative linker terminated with dibenzocyclooctyne (DBCO). Through this process, we obtained cetuximab-MMAE and trastuzumab-MMAE with drug/antibody ratios in the range of 1.3 to 2.5. We confirmed that these ADCs still bind their targets efficiently and are as potent in cytotoxicity assays as control ADCs obtained by standard conjugation protocols. The site-directed conjugation to Fab glycans has the additional benefit of avoiding potential interference with effector functions that depend on Fc glycan structure.

Blueprint for antibody biologics developability

Large-molecule antibody biologics have revolutionized medicine owing to their superior target specificity, pharmacokinetic and pharmacodynamic properties, safety and toxicity profiles, and amenability to versatile engineering. In this review, we focus on preclinical antibody developability, including its definition, scope, and key activities from hit to lead optimization and selection. This includes generation, computational and in silico approaches, molecular engineering, production, analytical and biophysical characterization, stability and forced degradation studies, and process and formulation assessments. More recently, it is apparent these activities not only affect lead selection and manufacturability, but ultimately correlate with clinical progression and success. Emerging developability workflows and strategies are explored as part of a blueprint for developability success that includes an overview of the four major molecular properties that affect all developability outcomes: 1) conformational, 2) chemical, 3) colloidal, and 4) other interactions. We also examine risk assessment and mitigation strategies that increase the likelihood of success for moving the right candidate into the clinic.

Glycoconjugates: Synthesis, Functional Studies, and Therapeutic Developments

Glycoconjugates are major constituents of mammalian cells that are formed via covalent conjugation of carbohydrates to other biomolecules like proteins and lipids and often expressed on the cell surfaces. Among the three major classes of glycoconjugates, proteoglycans and glycoproteins contain glycans linked to the protein backbone via amino acid residues such as Asn for N-linked glycans and Ser/Thr for O-linked glycans. In glycolipids, glycans are linked to a lipid component such as glycerol, polyisoprenyl pyrophosphate, fatty acid ester, or sphingolipid. Recently, glycoconjugates have become better structurally defined and biosynthetically understood, especially those associated with human diseases, and are accessible to new drug, diagnostic, and therapeutic developments. This review describes the status and new advances in the biological study and therapeutic applications of natural and synthetic glycoconjugates, including proteoglycans, glycoproteins, and glycolipids. The scope, limitations, and novel methodologies in the synthesis and clinical development of glycoconjugates including vaccines, glyco-remodeled antibodies, glycan-based adjuvants, glycan-specific receptor-mediated drug delivery platforms, etc., and their future prospectus are discussed.

Immunoglobulin G glycans - Biomarkers and molecular effectors of aging

Immunoglobulin G (IgG) antibodies are post-translationally modified by the addition of complex carbohydrate molecules - glycans, which have profound effects on the IgG function, most significantly as modulators of its inflammatory capacity. Therefore, it is not surprising that the changes in IgG glycosylation pattern are associated with various physiological states and diseases, including aging and age-related diseases. Importantly, within the inflammaging concept, IgG glycans are considered not only biomarkers but one of the molecular effectors of the aging process. The exact mechanism by which they exert their function, however, remains unknown. In this review, we list and comment on, to our knowledge, all studies that examined changes in IgG glycosylation during aging in humans. We focus on the information obtained from studies on general population, but we also cover the insights obtained from studies of long-lived individuals and people with age-related diseases. We summarize the current knowledge on how levels of different IgG glycans change with age (i.e., the extent and direction of the change with age) and discuss the potential mechanisms and possible functional roles of changes in IgG glycopattern that accompany aging.

Role of Fc Core Fucosylation in the Effector Function of IgG1 Antibodies

The presence of fucose on IgG1 Asn-297 N-linked glycan is the modification of the human IgG1 Fc structure with the most significant impact on FcɣRIII affinity. It also significantly enhances the efficacy of antibody dependent cellular cytotoxicity (ADCC) by natural killer (NK) cells in vitro, induced by IgG1 therapeutic monoclonal antibodies (mAbs). The effect of afucosylation on ADCC or antibody dependent phagocytosis (ADCP) mediated by macrophages or polymorphonuclear neutrophils (PMN) is less clear. Evidence for enhanced efficacy of afucosylated therapeutic mAbs in vivo has also been reported. This has led to the development of several therapeutic antibodies with low Fc core fucose to treat cancer and inflammatory diseases, seven of which have already been approved for clinical use. More recently, the regulation of IgG Fc core fucosylation has been shown to take place naturally during the B-cell immune response: A decrease in α-1,6 fucose has been observed in polyclonal, antigen-specific IgG1 antibodies which are generated during alloimmunization of pregnant women by fetal erythrocyte or platelet antigens and following infection by some enveloped viruses and parasites. Low IgG1 Fc core fucose on antigen-specific polyclonal IgG1 has been linked to disease severity in several cases, such as SARS-CoV 2 and Dengue virus infection and during alloimmunization, highlighting the in vivo significance of this phenomenon. This review aims to summarize the current knowledge about human IgG1 Fc core fucosylation and its regulation and function in vivo, in the context of both therapeutic antibodies and the natural immune response. The parallels in these two areas are informative about the mechanisms and in vivo effects of Fc core fucosylation, and may allow to further exploit the desired properties of this modification in different clinical contexts.

Sialylation as an Important Regulator of Antibody Function

Antibodies play a critical role in linking the adaptive immune response to the innate immune system. In humans, antibodies are categorized into five classes, IgG, IgM, IgA, IgE, and IgD, based on constant region sequence, structure, and tropism. In serum, IgG is the most abundant antibody, comprising 75% of antibodies in circulation, followed by IgA at 15%, IgM at 10%, and IgD and IgE are the least abundant. All human antibody classes are post-translationally modified by sugars. The resulting glycans take on many divergent structures and can be attached in an N-linked or O-linked manner, and are distinct by antibody class, and by position on each antibody. Many of these glycan structures on antibodies are capped by sialic acid. It is well established that the composition of the N-linked glycans on IgG exert a profound influence on its effector functions. However, recent studies have described the influence of glycans, particularly sialic acid for other antibody classes. Here, we discuss the role of glycosylation, with a focus on terminal sialylation, in the biology and function across all antibody classes. Sialylation has been shown to influence not only IgG, but IgE, IgM, and IgA biology, making it an important and unappreciated regulator of antibody function.

Glycosylation site Asn168 is important for slow in vivo clearance of recombinant human diamine oxidase heparin-binding motif mutants

Elevated plasma and tissues histamine concentrations can cause severe symptoms in mast cell activation syndrome, mastocytosis or anaphylaxis. Endogenous and recombinant human diamine oxidase (rhDAO) can rapidly and completely degrade histamine, and administration of rhDAO represents a promising new treatment approach for diseases with excess histamine release from activated mast cells. We recently generated heparin-binding motif mutants of rhDAO with considerably increased in vivo half-lives in rodents compared with the rapidly cleared wildtype protein. Herein, we characterize the role of an evolutionary recently added glycosylation site asparagine 168 in the in vivo clearance and the influence of an unusually solvent accessible free cysteine 123 on the oligomerization of diamine oxidase (DAO). Mutation of the unpaired cysteine 123 strongly reduced oligomerization without influence on enzymatic DAO activity and in vivo clearance. Recombinant hDAO produced in ExpiCHO-S™ cells showed a 15-fold reduction in the percentage of glycans with terminal sialic acid at Asn168 compared with Chinese hamster ovary (CHO)-K1 cells. Capping with sialic acid was also strongly reduced at the other glycosylation sites. The high abundance of terminal mannose and N-acetylglucosamine residues in the four glycans expressed in ExpiCHO-S™ cells compared with CHO-K1 cells resulted in rapid in vivo clearance. Mutation of Asn168 or sialidase treatment also significantly increased clearance. Intact N-glycans at Asn168 seem to protect DAO from rapid clearance in rodents. Full processing of all glycoforms is critical for preserving the improved in vivo half-life characteristics of the rhDAO heparin-binding motif mutants.

Development of a CHO cell line for stable production of recombinant antibodies against human MMP9

Background

Human matrix metalloproteinase 9 (hMMP9) is a biomarker in several diseases, including cancer, and the need for developing detectors and inhibitors of hMMP9 is increasing. As an antibody against hMMP9 can be selectively bound to hMMP9, the use of anti-MMP9 antibody presents new possibilities to address hMMP9-related diseases. In this study, we aimed to establish a stable Chinese hamster ovary (CHO) cell line for the stable production of antibodies against hMMP9.

Results

Weconstructed recombinant anti-hMMP9 antibody fragment-expressing genes and transfected these to CHO cells. We chose a single clone, and successfully produced a full-sized antibody against hMMP9 with high purity, sensitivity, and reproducibility. Subsequently, we confirmed the antigen-binding efficiency of the antibody.

Conclusions

We developed a novel recombinant anti-hMMP9 antibody via a CHO cell-based mammalian expression system, which has a high potential to be used in a broad range of medical and industrial areas.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-022-00738-6.

Non-targeted characterization of attributes affecting antibody-FcγRIIIa V158 (CD16a) binding via online affinity chromatography-mass spectrometry

Antibodies facilitate targeted cell killing by engaging with immune cells such as natural killer cells through weak binding interactions with Fcγ receptors on the cell surface. Here, we evaluate the binding affinity of the receptor FcγRIIIa V158 (CD16a) for several therapeutic antibody classes, isoforms, and Fc-fusion proteins using an immobilized receptor affinity liquid chromatography (LC) approach coupled with online mass spectrometry (MS) detection. Aglycosylated FcγRIIIa was used in the affinity chromatography and compared with published affinities using glycosylated receptors. Affinity LC-MS differentiated the IgG1 antibodies primarily according to their Fc glycosylation patterns, with highly galactosylated species having greater affinity for the immobilized receptors and thus eluting later from the column (M5< G0F < G0 afucosylated ≅ G1F < G2F). Sialylated species bound weaker to their asialylated counterparts as reported previously. High mannose glycoforms bound weaker than G0F, contrary to previously published studies using glycosylated receptors. Also, increased receptor binding affinity associated with afucosylated antibodies was not observed with the aglycosylated FcγRIIIa. This apparent difference from previous findings highlighted the importance of the glycans on the receptors for mediating stronger binding interactions. Characterization of temperature-stressed samples by LC-MS peptide mapping revealed over 200 chemical and post-translational modifications, but only the Fc glycans, deamidation of EU N325, and an unknown modification to either proline or cysteine residues of the hinge region were found to have a statistically significant impact on binding.

Abbreviations: Antibody-dependent cell-mediated cytotoxicity (ADCC), chimeric antigen receptor (CAR), Chinese hamster ovary (CHO), dithiothreitol (DTT), electrospray ionization (ESI), hydrogen-deuterium exchange (HDX), filter aided-sample preparation (FASP), Fcγ receptor (FcγR), fragment crystallizable (Fc), high-pressure liquid chromatography (HPLC), immunoglobulin G (IgG), liquid chromatography (LC), monoclonal antibody (mAb), mass spectrometry (MS), natural killer (NK), N-glycolylneuraminic acid (NGNA), N-acetylneuraminic acid (NANA), principal component analysis (PCA), surface plasmon resonance (SPR), trifluoroacetic acid (TFA), and extracted mass chromatogram (XMC).

The current status of anti-citrullinated protein antibodies and citrullinated protein-reactive B cells in the pathogenesis of rheumatoid arthritis

Anti-citrullinated protein antibodies are a hallmark of rheumatoid arthritis. It is widely acknowledged that the presence of ACPAs is the result of the interaction of genes, the environment and epigenetic modifications. The mechanism by which the factors, especially citrullination and ACPA glycosylation, affect ACPAs is still unclear. In this article, we review the presence of the ACPAs in RA and their relationship with clinical manifestations. The pathogenicity of ACPAs and B cells in RA was also summarized. A growing body of evidence has shown that ACPA-positive patients have more serious bone erosion and destruction and poor clinical prognosis than ACPA-negative patients. Recently, with the direct study of citrullinated protein-reactive B cells, their role in the development of rheumatoid arthritis has been further understood. It indicates that further understanding of the mechanism of ACPAs and CP-reactive B cells would beneficial in the prevention and treatment of RA.

Production of scFv, Fab, and IgG of CR3022 Antibodies Against SARS-CoV-2 Using Silkworm-Baculovirus Expression System

COVID-19, caused by SARS-CoV-2, is currently spreading around the world and causing many casualties. Antibodies against such emerging infectious diseases are one of the important tools for basic viral research and the development of diagnostic and therapeutic agents. CR3022 is a monoclonal antibody against the receptor binding domain (RBD) of the spike protein (S protein) of SARS-CoV found in SARS patients, but it was also shown to have strong affinity for that of SARS-CoV-2. In this study, we produced large amounts of three formats of CR3022 antibodies (scFv, Fab and IgG) with high purity using a silkworm-baculovirus expression vector system. Furthermore, SPR measurements showed that the affinity of those silkworm-produced IgG antibodies to S protein was almost the same as that produced in mammalian expression system. These results indicate that the silkworm-baculovirus expression system is an excellent expression system for emerging infectious diseases that require urgent demand for diagnostic agents and therapeutic agents.

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.

Desalting Paper Spay Mass Spectrometry (DPS-MS) for Rapid Detection of Glycans and Glycoconjugates

The detection of glycans and glycoconjugates has gained increasing attention in biological fields. Traditional mass spectrometry (MS)-based methods for glycoconjugate analysis are challenged with poor intensity when dealing with complex biological samples. We developed a desalting paper spray mass spectrometry (DPS-MS) strategy to overcome the issue of signal suppression of carbohydrates in salted buffer. Glycans and glycoconjugates (i.e., glycopeptides, nucleotide sugars, etc.) in non-volatile buffer (e.g., Tris buffer) can be loaded on the paper substrate from which buffers can be removed by washing with ACN/H2O (90/10 v/v) solution. Glycans or glycoconjugates can then be eluted and spray ionized by adding ACN/H2O/formic acid (FA) (10/90/1 v/v/v) solvent and applying a high voltage (HV) to the paper substrate. This work also showed that DPS-MS is applicable for direct detection of intact glycopeptides and nucleotide sugars as well as determination of glycosylation profiling of antibody, such as NIST monoclonal antibody IgG (NISTmAb). NISTmAb was deglycosylated with PNGase F to release N-linked oligosaccharides. Twenty-six N-linked oligosaccharides were detected by DPS-MS within a 5-minute timeframe without the need for further enrichment or derivatization. This work demonstrates that DPS-MS allows fast and sensitive detection of glycans/oligosaccharides and glycosylated species in complex matrices and has great potential in bioanalysis.

The Role of Fc Receptors on the Effectiveness of Therapeutic Monoclonal Antibodies

Since the approval of the first monoclonal antibody (mAb) in 1986, a huge effort has been made to guarantee safety and efficacy of therapeutic mAbs. As of July 2021, 118 mAbs are approved for the European market for a broad range of clinical indications. In order to ensure clinical efficacy and safety aspects, (pre-)clinical experimental approaches evaluate the respective modes of action (MoA). In addition to antigen-specificity including binding affinity and -avidity, MoA comprise Fc-mediated effector functions such as antibody dependent cellular cytotoxicity (ADCC) and the closely related antibody dependent cellular phagocytosis (ADCP). For this reason, a variety of cell-based assays have been established investigating effector functions of therapeutic mAbs with different effector/target-cell combinations and several readouts including Fcγ receptor (FcγR)-mediated lysis, fluorescence, or luminescence. Optimized FcγR-mediated effector functions regarding clinical safety and efficacy are addressed with modification strategies such as point mutations, altered glycosylation patterns, combination of different Fc subclasses (cross isotypes), and Fc-truncation of the mAb. These strategies opened the field for a next generation of therapeutic mAbs. In conclusion, it is of major importance to consider FcγR-mediated effector functions for the efficacy of therapeutic mAbs.

Multiattribute Monitoring of Antibody Charge Variants by Cation-Exchange Chromatography Coupled to Native Mass Spectrometry

The aim of this study was to characterize the product variants of a therapeutic T-cell bispecific humanized monoclonal antibody (TCB Mab, ∼200 kDa, asymmetric) and to develop an online cation-exchange chromatography native electrospray mass spectrometry method (CEC-UV-MS) for direct TCB Mab charge variant monitoring during bioprocess and formulation development. For the identification and functional evaluation of the diverse and complex TCB Mab charge variants, offline fractionation combined with comprehensive analytical testing was applied. The offline fractionation of abundant product variant peaks enabled identification of coeluting acid charge variants such as asparagine deamidation, primary and secondary Fab glycosylation (with and without sialic acid), and the presence of O-glycosylation in the G4S-linker region. Consequently, a new nonconsensus N-glycosylation motif (N-338-FG) in the heavy chain CDR region was discovered. Functional evaluation by cell-based potency testing demonstrated a clear and negative impact of both asparagine deamidations, whereas the O-glycosylation did not affect the TCB Mab biological activity. We established an online native CEC-UV-MS method, with an ammonium acetate buffer and pH gradient, to directly monitor the TCB Mab charge variants. All abundant chemical degradations and post-translational amino acid modifications already identified by offline fraction experiments and liquid chromatography mass spectrometry peptide mapping could also be monitored by the online CEC-UV-MS method. The herein reported online native CEC-UV-MS methodology represents a complementary or even alternative approach for multiattribute monitoring of biologics, offering multiple benefits, including increased throughput and reduced sample handling and intact protein information in the near-native state.

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.

A study of the possible role of Fab-glycosylated IgG in tumor immunity

Previously we reported that administration of IgG could inhibit tumor progression in mouse models. At the same time, we also found that some IgGs have glycosylation modifications on their Fab fragments, which may have different biological functions than non-glycosylated IgG. In this study, we employed mouse tumor models to explore the roles of two different forms of IgG, i.e. Fab-glycosylated and Fab-non-glycosylated IgG, in tumor progression. The two types of IgGs were separated with ConA absorption which could react with glycan on the Fab arm but could not access glycan on the Fc fragment. In addition, we performed cytokine array, ELISA, western blotting, immunocytochemistry and other techniques to investigate the possible mechanisms of the actions of Fab-glycosylated IgG in the models. We found that Fab-glycosylated IgG, unlike Fab-non-glycosylated IgG, did not inhibit tumor growth and metastasis in the model. On the contrary, Fab-glycosylated IgG may bind to antigen-bound IgG molecules and macrophages through the glycosidic chain on the Fab fragment to affect antigen-antibody binding and macrophage polarization, which are likely to help tumor cells to evade the immune surveillance. A new mechanism of immune evasion with Fab-glycosylated IgG playing a significant role was proposed.

Preparation and biological activities of anti-HER2 monoclonal antibodies with multi-branched complex-type N-glycans

Immunoglobulin G (IgG) has a conserved N-glycosylation site at Asn297 in the fragment crystallizable (Fc) region. Previous studies have shown that N-glycosylation of this site is a critical mediator of the antibody's effector functions, such as antibody-dependent cellular cytotoxicity. While the N-glycan structures attached to the IgG-Fc region are generally heterogenous, IgGs engineered to be homogenously glycosylated with functional N-glycans may improve the efficacy of antibodies. The major glycoforms of the N-glycans on the IgG-Fc region are bi-antennary complex-type N-glycans, while multi-branched complex-type N-glycans are not typically found. However, IgGs with tri-antennary complex-type N-glycans have been generated using the N-glycan remodeling technique, suggesting that more branched N-glycans might be artificially attached. At present, little is known about the properties of these IgGs. In this study, IgGs with multi-branched N-glycans on the Fc region were prepared by using a combination of the glycosynthase/oxazoline substrate-based N-glycan remodeling technique and successive reactions with glycosyltransferases. Among the IgGs produced by these methods, the largest N-glycan attached was a bisecting N-acetylglucosamine (GlcNAc) containing a sialylated penta-antennary structure. Concerning the Fc-mediated effector functions, the majority of IgGs with tri- and tetra-antennary N-glycans on their Fc region showed properties similar to IgGs with ordinary bi-antennary N-glycans.

Developing a medium combination to attain similar glycosylation profile to originator by DoE and cluster analysis method

Glycosylation is critical for monoclonal antibody production because of its impact on pharmacokinetics and pharmacodynamics. Modulation of glycan profile is frequently needed in biosimilar development. However, glycosylation profile is not a single value like that of cell culture titer, hence making it challenging for the Design of Experiment (DoE) methodology to be directly applied. In this study, a Her2-binding antibody was developed as a biosimilar to Herceptin. Cluster analysis was introduced to demonstrate the similarity of glycan profiles between the samples and the reference with specific value-distance. The glycosylation was subsequently optimized with the DoE method. Basal medium and feed medium were found to be the significant factors to the glycosylation pattern. Moreover, a combination of medium and feed strategy was developed to attain the most similar glycoprotein molecule to that of the originator biologic drug. This study may provide an additional option to evaluate multivariable factors and assess biosimilarity and/or comparability in monoclonal antibody production.

Empirical and Rational Design of T Cell Receptor-Based Immunotherapies

The use of T cells reactive with intracellular tumor-associated or tumor-specific antigens has been a promising strategy for cancer immunotherapies in the past three decades, but the approach has been constrained by a limited understanding of the T cell receptor's (TCR) complex functions and specificities. Newer TCR and T cell-based approaches are in development, including engineered adoptive T cells with enhanced TCR affinities, TCR mimic antibodies, and T cell-redirecting bispecific agents. These new therapeutic modalities are exciting opportunities by which TCR recognition can be further exploited for therapeutic benefit. In this review we summarize the development of TCR-based therapeutic strategies and focus on balancing efficacy and potency versus specificity, and hence, possible toxicity, of these powerful therapeutic modalities.

Routine Analysis of N-Glycans Using Liquid Chromatography Coupled to Routine Mass Detection

Analysis of N-glycans are commonly conducted via enzymatic release, labeling, and liquid chromatography (LC) separation and fluorescent detection. Mass spectrometry (MS) has been increasingly used as an orthogonal detection method to provide additional structural information and increase the confidence of N-glycan analysis. In this chapter, we describe a method to perform routine analysis of N-glycans including the sample preparation with a signal-enhancement label, LC-MS data generation, and data analysis. Using this method, up to 24 N-glycan samples can be prepared at one time and analyzed by LC-MS. With the addition of automation platform, up to 96 N-glycan samples can be prepared and analyzed in a high-throughput manner.

Evaluating N-Glycosylation of a Therapeutic Monoclonal Antibody Using UHPLC-FLR-MS with RapiFluor-MS Labeling

Released N-glycan analysis using the fluorescent label 2-AB (2-aminobenzamide) has been the "gold standard" method for released glycan analysis for several years. The more recent RapiFluor-MS™ labeling technique, however, offers enhanced mass spectrometric detection of released N-glycans, improving the sensitivity and detection limits of the method. The optimized multidimensional detection offers increased confidence in glycan identification which can be further supported by an exoglycosidase digestion array (optional). Here we describe the PNGase F release of N-glycans from a typical IgG1 monoclonal antibody (mAb) with subsequent labeling with RapiFluor-MS™ for detection by HILIC-FLR-MS. The method output quantifies the relative proportion of each glycan species including core afucosylation, sialylation, and high-mannose content, and has a limit of detection (LOD) of 0.01% relative abundance.

Role of NMR in High Ordered Structure Characterization of Monoclonal Antibodies

Obtaining high ordered structure (HOS) information is of importance to guarantee the efficacy and safety of monoclonal antibodies (mAbs) in clinical application. Assessment of HOS should ideally be performed in a non-invasive manner under their formulated storage conditions, as any perturbation can introduce unexpected detritions. However, most of the currently available techniques only indirectly report HOS of mAbs and/or require a certain condition to conduct the analyses. Besides, the flexible multidomain architecture of mAbs has hampered atomic-resolution structural analyses using X-ray crystallography and cryo-electron microscopy. In contrast, the ability of nuclear magnetic resonance (NMR) spectroscopy to structurally analyze biomolecules in various conditions in a non-invasive and quantitative manner is suitable to meet the needs. However, the application of NMR to mAbs is not straightforward due to the high molecular weight of the system. In this review, we will discuss how NMR techniques have been applied to HOS analysis of mAbs, along with the recent advances of the novel 15N direct detection NMR strategy that allows for obtaining the structural fingerprint of mAbs at lower temperatures under multiple formulation conditions. The potential application of these NMR strategies will benefit next-generation mAbs, such as antibody-drug conjugates and bispecific antibodies.

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.

Modeling the Effect of Amino Acids and Copper on Monoclonal Antibody Productivity and Glycosylation: A Modular Approach

In manufacturing monoclonal antibodies (mAbs), it is crucial to be able to predict how process conditions and supplements affect productivity and quality attributes, especially glycosylation. Supplemental inputs, such as amino acids and trace metals in the media, are reported to affect cell metabolism and glycosylation; quantifying their effects is essential for effective process development. We aim to present and validate, through a commercially relevant cell culture process, a technique for modeling such effects efficiently. While existing models can predict mAb production or glycosylation dynamics under specific process configurations, adapting them to new processes remains challenging, because it involves modifying the model structure and often requires some mechanistic understanding. Here, a modular modeling technique for adapting an existing model for a fed-batch Chinese hamster ovary (CHO) cell culture process without structural modifications or mechanistic insight is presented. Instead, data is used, obtained from designed experimental perturbations in media supplementation, to train and validate a supplemental input effect model, which is used to "patch" the existing model. The combined model can be used for model-based process development to improve productivity and to meet product quality targets more efficiently. The methodology and analysis are generally applicable to other CHO cell lines and cell types.

The sialylation profile of IgG determines the efficiency of antibody directed osteogenic differentiation of iMSCs by modulating local immune responses and osteoclastogenesis

Antibody-mediated osseous regeneration (AMOR) has been proved as a promising strategy for osteogenic differentiation of induced pluripotent stem cells derived MSCs (iMSCs). The key characteristic of antibody that determines the AMOR potential is largely unknown. The glycosylation profile of immunoglobulin G (IgG) represents a key checkpoint that determines its effector functions. Herein, we modified the sialylation profile of BMP2 antibodies to investigate the effects of glycosylation on antibody-mediated osteogenic differentiation of iMSCs. We found that over-sialylated BMP2 antibodies stimulated the highest amount of new bone while those non- or low-sialylated led to bone porosity and collapse. The immune response aroused by BMP2 immune complexes (BMP2-ICs) was intensified by desialylation, which contributed to an environment that favored osteoclastogenesis while inhibited osteoblastogenesis. In vitro study further demonstrated that the osteogenic potential of BMP2-ICs was not significantly affected by the degree of sialylation. On the other hand, BMP2-ICs could stimulate osteoclastogenesis by binding FcγRs on preosteoclasts directly, which was significantly intensified by desialylation and attenuated by over-sialylation. Bone defects implanted with alginate microbeads loaded with iMSCs and over-sialylated antibodies showed more bone formation than those sites with non- or low sialylated antibodies. Taken together, our study demonstrated that sialylation profile is one of the traits that decide the AMOR potential of BMP2 antibodies. Enhancement of sialylation may be a promising strategy to optimize antibody for iMSCs application in bone tissue engineering. STATEMENT OF SIGNIFICANCE: Antibody-mediated osseous regeneration (AMOR) is a promising strategy for bone tissue engineering that takes advantage of the specific reactivity of antibodies to sequester endogenous BMP2 and present it to osteoprogenitor cells. We previously demonstrated that BMP2 immune complex can drive iPSCs derived MSCs to osteogenic lineage. In this study, we analyze the effects of glycosylation profile on antibody directed osteogenic differentiation of iMSCs because glycosylation profile represents a key checkpoint that determines the effector functions of antibodies, and it is susceptible to variations in different clones. The results showed that sialylation profile is one of the traits that decides the AMOR potential of BMP2 antibody, and the enhancement of sialylation maybe a promising strategy to optimize antibodies for AMOR.

Sialylated Immunoglobulins for the Treatment of Immuno-Inflammatory Diseases

Immunoglobulins are the potent effector proteins of the humoral immune response. In the course of evolution, immunoglobulins have formed extremely diverse types of molecular structures with antigen-recognizing, antigen-binding, and effector functions embedded in a single molecule. Polysaccharide moiety of immunoglobulins plays the essential role in immunoglobulin functioning. There is growing evidence that the carbohydrate composition of immunoglobulin-linked glycans, and especially their terminal sialic acid residues, provide a key effect on the effector functions of immunoglobulins. Possibly, sialylation of Fc glycan is a common mechanism of IgG anti-inflammatory action in vivo. Thus, the post-translational modification (glycosylation) of immunoglobulins opens up significant possibilities in the diagnosis of both immunological and inflammatory disorders and in their therapies. This review is focused on the analysis of glycosylation of immunoglobulins, which can be a promising addition to improve existing strategies for the diagnosis and treatment of various immuno-inflammatory diseases.

Traces matter: Targeted optimization of monoclonal antibody N-glycosylation based on/by implementing automated high-throughput trace element screening

The use of high-throughput systems in cell culture process optimization offers various opportunities in biopharmaceutical process development. Here we describe the potential for acceleration and enhancement of product quality optimization and de novo bioprocess design regarding monoclonal antibody N-glycosylation by using an iterative statistical Design of Experiments (DoE) strategy based on our automated microtiter plate-based system for suspension cell culture. In our example, the combination of an initial screening of trace metal building blocks with a comprehensive DoE-based screening of 13 different trace elemental ions at three concentration levels in one run revealed most effective levers for N-glycan processing and biomass formation. Obtained results served to evaluate optimal concentration ranges and the right supplementation timing of relevant trace elements at shake flask and 2 L bioreactor scale. This setup identified manganese, copper, zinc, and iron as major factors. Manganese and copper acted as inverse key players in N-glycosylation, showing a positive effect of manganese and a negative effect of copper on glycan maturation in a zinc-dependent manner. Zinc and iron similarly improved cell growth and biomass formation. These findings allowed determining optimal concentration ranges for all four trace elements to establish control on desired product quality attributes regarding premature afucosylated and mature galactosylated glycan species. Our results demonstrates the power of combining robotics with DoE screening to enhance product quality optimization and to improve process understanding, thus, enabling targeted product quality 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.

The biodistribution of therapeutic proteins: Mechanism, implications for pharmacokinetics, and methods of evaluation

Therapeutic proteins (TPs) are a diverse drug class that include monoclonal antibodies (mAbs), recombinantly expressed enzymes, hormones and growth factors, cytokines (e.g. chemokines, interleukins, interferons), as well as a wide range of engineered fusion scaffolds containing IgG1 Fc domain for half-life extension. As the pharmaceutical industry advances more potent and selective protein-based medicines through discovery and into the clinical stages of development, it has become widely appreciated that a comprehensive understanding of the mechanisms of TP biodistribution can aid this endeavor. This review aims to highlight the literature that has advanced our understanding of the determinants of TP biodistribution. A particular emphasis is placed on the multi-faceted role of the neonatal Fc receptor (FcRn) in mAb and Fc-fusion protein disposition. In addition, characterization of the TP-target interaction at the cell-level is discussed as an essential strategy to establish pharmacokinetic-pharmacodynamic (PK/PD) relationships that may lead to more informed human dose projections during clinical development. Methods for incorporation of tissue and cell-level parameters defining these characteristics into higher-order mechanistic and semi-mechanistic PK models will also be presented.

Multiplexed Comparative Analysis of Intact Glycopeptides Using Electron-Transfer Dissociation and Synchronous Precursor Selection Based Triple-Stage Mass Spectrometry

A recently developed synchronous precursor selection (SPS) mass spectrometry to the third (MS3) protocol enables more accurate multiplexed quantification of proteins/peptides using tandem mass tags (TMT) through comparison of reporter ion intensities at the MS3 level. However, challenges still exist for TMT-based simultaneous quantification and identification of intact glycopeptides due to inefficient peptide backbone fragmentation when using collision-induced dissociation (CID). To overcome this limitation, here we report an improved SPS/ETD workflow for TMT-based intact glycopeptide quantification and identification. The SPS/ETD approach was implemented on an Orbitrap Tribrid mass spectrometer and begins with selection of a parent ion in the MS scan, followed by tandem mass spectrometry (MS2) fragmentation by CID in the ion trap. Following MS2 fragmentation, SPS enables simultaneous isolation of the top 10 MS2 fragment ions for further higher energy collisional dissociation (HCD) fragmentation with the resulting MS3 fragments detected in an Orbitrap analyzer. Here, in addition to the standard SPS workflow, an electron-transfer dissociation (ETD) MS2 was performed and analyzed in the ion trap. The resultant ETD and CID spectra were used for the identification of the intact glycopeptides, while the quantitative comparison of site-specific glycans was achieved utilizing TMT reporter ions from HCD MS3 spectra. For intact glycopeptides, through systematic optimization and evaluation using a glycoprotein interference model, the SPS/ETD approach was demonstrated to offer improved accuracy, precision, and sensitivity compared to traditional data-dependent MS2 quantification, while maintaining the glycopeptide identification capability. Finally, this workflow was applied for the site-specific quantitative comparison of the glycoforms for two therapeutic enzymes (Cerezyme and VPRIV) and their different lots. The results demonstrate that this workflow is suitable for TMT-based intact glycopeptide characterization of glycoproteins.

Differentiation of focal autoimmune pancreatitis from pancreatic ductal adenocarcinoma

Autoimmune pancreatitis (AIP) is an inflammatory process of the pancreas that occurs most commonly in elderly males and clinically can mimic pancreatic adenocarcinoma and present with jaundice, weight loss, and abdominal pain. Mass-forming lesions in the pancreas are seen in the focal form of AIP and both clinical and imaging findings can overlap those of pancreatic cancer. The accurate distinction of AIP from pancreatic cancer is of utmost importance as it means avoiding unnecessary surgery in AIP cases or inaccurate steroid treatment in patients with pancreatic cancer. Imaging concomitantly with serological examinations (IgG4 and Ca 19-9) plays an important role in the distinction between these entities. Characteristic extra-pancreatic manifestations as well as favorable good response to treatment with steroids are characteristic of AIP. This paper will review current diagnostic parameters useful in differentiating between focal AIP and pancreatic adenocarcinoma.

Glycosylated Biotherapeutics: Immunological Effects of N-Glycolylneuraminic Acid

The emerging field of biotherapeutics provides successful treatments for various diseases, yet immunogenicity and limited efficacy remain major concerns for many products. Glycosylation is a key factor determining the pharmacological properties of biotherapeutics, including their stability, solubility, bioavailability, pharmacokinetics, and immunogenicity. Hence, an increased attention is directed at optimizing the glycosylation properties of biotherapeutics. Currently, most biotherapeutics are produced in non-human mammalian cells in light of their ability to produce human-like glycosylation. However, most mammals produce the sialic acid N-glycolylneuraminic acid (Neu5Gc), while humans cannot due to a specific genetic defect. Humans consume Neu5Gc in their diet from mammalian derived foods (red meat and dairy) and produce polyclonal antibodies against diverse Neu5Gc-glycans. Moreover, Neu5Gc can metabolically incorporate into human cells and become presented on surface or secreted glycans, glycoproteins, and glycolipids. Several studies in mice suggested that the combination of Neu5Gc-containing epitopes and anti-Neu5Gc antibodies could contribute to exacerbation of chronic inflammation-mediated diseases (e.g., cancer, cardiovascular diseases, and autoimmunity). This could potentially become complicated with exposure to Neu5Gc-containing biotherapeutics, bio-devices or xenografts. Indeed, Neu5Gc can be found on various approved and marketed biotherapeutics. Here, we provide a perspective review on the possible consequences of Neu5Gc glycosylation of therapeutic protein drugs due to the limited published evidence of Neu5Gc glycosylation on marketed biotherapeutics and studies on their putative effects on immunogenicity, drug efficacy, and safety.

Accelerating Biologics Manufacturing by Modeling: Process Integration of Precipitation in mAb Downstream Processing

The demand on biologics has been constantly rising over the past decades and has become crucial in modern medicine. Promising approaches to cope with widespread diseases like cancer and diabetes are gene therapy, plasmid DNA, virus-like particles, and exosomes. Due to progress that has been made in upstream processing (USP), difficulties arise in downstream processing and demand for innovative solutions. This work focuses on the integration of precipitation using a quality by design (QbD) approach for process development. Selective precipitation is achieved with PEG 4000 resulting in an HCP depletion of ≥80% respectively to IgG. Dissolution was executed with a sodium phosphate buffer (pH = 5/50 mM) reaching an IgG recovery of ≥95%. However, the central challenge in process development is still an optimal process design, which is transferable for a broad molecular variety of new products. This is where rigorous modeling becomes vital in order to generate digital twins to support early-stage process development and reduce the experimental overhead. Therefore, a model development and validation concept for construction of a process model for precipitation is also presented.

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

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