Glycosylation engineering of therapeutic IgG antibodies: challenges for the safety, functionality and efficacy

IgG N-glycosylation contributes to different severities of insulin resistance: implications for 3P medical approaches

Background

Reliable biomarkers capturing immunometabolic processes in insulin resistance (IR) remain limited. IgG N-glycosylation modulates immune responses and reflects metabolic disorders, yet its role in IR remains unclear. This study investigated its potential for early detection, risk stratification, and targeted prevention within the framework of predictive, preventive, and personalised medicine (PPPM/3PM).

Methods

A total of 313 participants were categorized into three groups based on the homeostatic model assessment for insulin resistance (HOMA-IR): insulin-sensitive (HOMA-IR < 2.69 without diabetes, n = 75), mild IR (HOMA-IR ≥ 2.69 without diabetes, n = 155), and severe IR (HOMA-IR ≥ 2.69 with type 2 diabetes, n = 83). Canonical correlation analysis was conducted to explore the overall relationship between IgG N-glycosylation and IR-related inflammation, indicated by tumour necrosis factor-α, interleukin- 6, C-reactive protein, and adiponectin. Mediation analysis was performed to evaluate the effect of IgG N-glycans on IR. Ordinal logistic regression was used to assess the association between IgG N-glycans and IR severity, with discriminative power evaluated using receiver operating characteristic curves.

Results

Pro-inflammatory IgG N-glycoforms, characterized by reduced sialylation and galactosylation, along with increased bisecting N-acetylglucosamine, were observed as IR severity increased. IgG N-glycosylation significantly correlated with inflammatory markers in the insulin-sensitive (r = 0.599, p < 0.05), mild (r = 0.461, p < 0.05), and severe (r = 0.666, p < 0.01) IR groups. IgG N-glycosylation significantly influenced IR (β = 0.406) partially via modulation of inflammation. Increased glycoforms FA2[6]G1 (OR: 0.86, 95% CI: 0.78-0.96) and A2G2S2 (OR: 0.88, 95% CI: 0.82-0.94) were associated with a lower IR risk, with respective area under the curves (AUCs) of 0.752, 0.683, and 0.764 for the insulin sensitive, mild, and severe IR groups.

Conclusions

IgG N-glycosylation contributes to IR by modulating inflammatory responses. Glycoforms FA2[6]G1 and A2G2S2 emerge as protective biomarkers, offering potential for predicting and preventing IR through primary prevention strategies within the PPPM framework.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-025-00410-x.

Microfluidic mimicry of the Golgi-linked N-glycosylation machinery

The complexity of the eukaryotic glycosylation machinery hinders the development of cell-free protein glycosylation since in vitro methods struggle to simulate the natural environment of the glycosylation machinery. Microfluidic technologies have the potential to address this limitation due to their ability to control glycosylation parameters, such as enzyme/substrate concentrations and fluxes, in a rapid and precise manner. However, due to the complexity and sensitivity of the numerous components of the glycosylation machinery, very few "glycobiology-on-a-chip" systems have been proposed or reported in the literature. Herein, we describe the design, fabrication and proof-of-concept of a droplet-based microfluidic platform able to mimic N-linked glycan processing along the secretory pathway. Within a single microfluidic device, glycoproteins and glycosylation enzymes are encapsulated and incubated in water-in-oil droplets. Additional glycosylation enzymes are subsequently supplied to these droplets via picoinjection, allowing further glycoprotein processing in a user-defined manner. After system validation, the platform is used to perform two spatiotemporally separated consecutive enzymatic N-glycan modifications, mirroring the transition between the endoplasmic reticulum and early Golgi.

Sensitive Fluorescence Quantitation and Efficient Free Radical Characterization of N-Glycans via LC-FLR-HRMS/MS with a Novel Fluorescent Free Radical Tag

Glycans are some of the most difficult biomolecules to analyze owing to their branching tendencies as well as their regiochemical and stereochemical diversity. Yet, the correlation between various pathological states and glycan quantity or structural alterations has demonstrated the importance and urgency for the development of a more robust glycan analytical technique. Furthermore, the manufacturing and regulation of biopharmaceuticals demands a feasible and improved analytical approach toward the characterization and quantitation of glycosylations. Unfortunately, multiple commercially available glycan tags lack, in combination, liquid chromatography detection sensitivity, chemical stability and, most importantly, optimal glycan characterization capabilities. Therefore, a novel fluorescent tag coupled with a free radical approach for glycan characterization was designed and developed to help address this gap in glycan analysis. The analytical capabilities of this novel tag were assessed via hydrophilic liquid chromatography-fluorescence quantitation and ESI/MS free radical-mediated characterization by using linear glycan standards, branched isobaric glycans lacto-N-difucohexaose I and lacto-N-difucohexaose II, and N-glycans released from ribonuclease B.

Characterization and application in recombinant N-GlcNAc-protein production of a novel endo-β-N-acetylglucosaminidase from Listeria booriae

Endo-β-N-acetylglucosaminidases (ENGases) are essential enzymes for hydrolyzing N-glycans, with applications in protein N-glycosylation analysis and glycoprotein synthesis. In this study, a novel GH18 family ENGase, Endo-LB, was identified from Listeria booriae FSL A5-0281. Composed of 593 amino acids (65.78 kDa), Endo-LB features with two domains: an Endo S-like catalytic domain and a mucin-binding protein (MucBP) domain. Recombinant Endo-LB, expressed in Escherichia coli BL21 (DE3) pLysS, exhibited a specific activity of 198.25 U/mg and hydrolyzed high mannose-type N-glycans at a temperature from 4 °C to 60 °C with optimal activity at 37 °C and pH 6.0 (range 3.0 to 10.0), making it versatile for various environmental conditions. The MucBP domain does not affect soluble Endo-LB activity but influences interaction with mucin on cell surface, suggesting potential application in targeting specific glycoproteins in complex biological environments. To address the heterogeneity of N-glycans in Pichia pastoris (Komagataella phaffii) expression, Endo-LB was further expressed in the Golgi of P. pastoris, efficiently producing glycoproteins, such as Erythropoietin (EPO) (37 mg/L) and Darbepoetin α (53 mg/L) with nearly complete N-glycans truncation, which can be further extended to generate diverse N-glycan structures. These findings highlight the versatility and potential utility of Endo-LB in glycoprotein engineering and biotechnological applications.

Sialylated IgG-activated integrin β4-Src-Erk axis stabilizes c-Myc in a p300 lysine acetyltransferase-dependent manner to promote colorectal cancer liver metastasis

BACKGROUND

Liver metastasis is a leading cause of colorectal cancer mortality. Therefore, the underlying mechanism and potential therapeutic target of colorectal cancer liver metastasis urge to be found. Mounting evidence indicates that cancer-derived sialylated IgG promotes tumor formation and progression. However, the role of sialylated IgG in colorectal cancer liver metastasis remains undefined.

MATERIALS AND METHODS

Analysis of sialylated IgG in paired tumor tissues and adjacent normal tissues from 65 colorectal cancer patients was performed using immunohistochemical staining. Functional assays of sialylated IgG were explored in vitro and in vivo. The downstream target of sialylated IgG was investigated by performing gene-set enrichment analysis, ubiquitination assay, cycloheximide chase assay, acetylation assay and co-immunoprecipitation.

RESULTS

Here, our investigation reveals that sialylated IgG is significantly upregulated in colorectal cancer and that the increase of IgG is positively associated with liver metastasis and poor overall survival in colorectal cancer patients. Sialylated IgG promotes colorectal cancer cell migration, invasion and liver metastasis. Notably, anti-sialylated IgG antibody effectively blocks colorectal cancer liver metastasis in mouse models. Mechanistically, sialylated IgG upregulates c-Myc protein level by decreasing c-Myc ubiquitination. Moreover, we find that p300/CBP can stabilize c-Myc by reducing c-Myc ubiquitination. Overexpression of p300/CBP protects c-Myc protein level from sialylated IgG-knockdown in a lysine acetyltransferase activity-dependent manner. Furthermore, sialylated IgG upregulates p300 protein level through integrin β4-FAK-Src-Erk signaling.

CONCLUSION

Collectively, these results indicate that a novel sialylated IgG-integrin β4-FAK-Src-Erk-p300-c-Myc signaling pathway promotes colorectal cancer liver metastasis, thus providing potential therapeutic targets for colorectal cancer liver metastasis.

Current Landscape and Future Directions in Cancer Immunotherapy: Therapies, Trials, and Challenges

Cancer remains a leading global health challenge, placing immense burdens on individuals and healthcare systems. Despite advancements in traditional treatments, significant limitations persist, including treatment resistance, severe side effects, and disease recurrence. Immunotherapy has emerged as a promising alternative, leveraging the immune system to target and eliminate tumour cells. However, challenges such as immunotherapy resistance, patient response variability, and the need for improved biomarkers limit its widespread success. This review provides a comprehensive analysis of the current landscape of cancer immunotherapy, highlighting both FDA-approved therapies and novel approaches in clinical development. It explores immune checkpoint inhibitors, cell and gene therapies, monoclonal antibodies, and nanotechnology-driven strategies, offering insights into their mechanisms, efficacy, and limitations. By integrating emerging research and clinical advancements, this review underscores the need for continued innovation to optimise cancer immunotherapy and overcome existing treatment barriers.

Enzymatic Desialylation Enables Reliable Charge Variant Characterization of Highly Glycosylated and Sialylated Fc Fusion Proteins

Fusion proteins constitute a class of engineered therapeutics and have emerged as promising candidates for disease treatment. However, the structural complexity and heterogeneity of fusion proteins make their characterization extremely challenging, and thus, an innovative and comprehensive analytical toolbox is needed. Here, for the first time, we demonstrate a novel and robust workflow to evaluate charge variants for a highly glycosylated fusion protein with heavy sialylation using imaged capillary isoelectric focusing (icIEF). In the development of the icIEF method, key factors that were systematically investigated include the desialylation level, the stability of the desialylated molecule, incubation time and temperature of desialylation, protein concentrations, urea and l-arginine effects on the tertiary structure, and instrumental comparability. Multivariate and correlation analyses were subsequently applied to confirm the impacts of the parameters evaluated. Furthermore, a microfluidic chip-based icIEF system coupled with ultraviolet detection and mass spectrometry (icIEF-UV/MS) was utilized to identify critical post-translational modifications and ameliorate the understanding of charge variants. Our study demonstrates that this workflow enables a mechanistic understanding of charge variants for heavily sialylated therapeutics.

Adaptation of Aglycosylated Monoclonal Antibodies for Improved Production in Komagataella phaffii

Monoclonal antibodies (mAbs) are a major class of biopharmaceuticals manufactured by well-established processes using Chinese Hamster Ovary (CHO) cells. Next-generation biomanufacturing using alternative hosts like Komagataella phaffii could improve the accessibility of these medicines, address broad societal goals for sustainability, and offer financial advantages for accelerated development of new products. Antibodies produced by K. phaffii, however, may manifest unique molecular quality attributes, like host-dependent, product-related variants, that could raise potential concerns for clinical use. We demonstrate here conservative modifications to the amino acid sequence of aglycosylated antibodies based on the human IgG1 isotype that minimize product-related variations when secreted by K. phaffii. A combination of 2-3 changes of amino acids reduced variations across six different aglycosylated versions of commercial mAbs. Expression of a modified sequence of NIST mAb in both K. phaffii and CHO cells showed comparable biophysical properties and molecular variations. These results suggest a path toward the production of high-quality mAbs that could be expressed interchangeably by either yeast or mammalian cells. Improving molecular designs of proteins to enable a range of manufacturing strategies for well-characterized biopharmaceuticals could accelerate global accessibility and innovations.

Simple endoglycosidase-assisted peptide mapping workflow for characterizing non-consensus n-glycosylation in therapeutic monoclonal antibodies

N-linked glycosylation, an extensively studied protein post-translational modification, was conventionally understood to occur at asparagine (Asn or N) sites with the consensus motif NXS/T, where X can be any amino acid residue except for proline, followed by serine or threonine. However, with advancements in characterization techniques and bioinformatic tools, increasing evidence indicates that Asn residues that are not located in the NXS/T consensus motif can also undergo N-glycosylation, which is also known as non-consensus or noncanonical N-glycosylation. Characterizing non-consensus N-glycosylation remains challenging because of the unpredictable sequon and its relatively low abundance. Here, we report an endoglycosidase-assisted peptide mapping workflow for mass spectrometry (MS) characterization of non-consensus N-glycosylation in monoclonal antibodies (mAbs). The feasibility of the workflow was demonstrated by a challenging case study, in which an atypical glycosite located within an NPNNXN sequence in a 25-residue tryptic peptide was identified in the fragment antigen-binding (Fab) region of a mAb. With the aids of endoglycosidase treatment, the resulting truncated glycan structures improved peptide ionization efficiency in MS and hence facilitated reliable quantitation of glycosite occupancy. Meanwhile, the remaining mono-/di-saccharides served as a large mass tag enabling differentiation between the glycopeptide and deamidated peptide, thus allowing for database searching for glycosite localization and semi-automation of the data processing workflow. This workflow offers a simple solution for characterizing non-consensus N-glycosylation for the development of therapeutic mAbs.

Enhancing monoclonal antibody production efficiency using CHO-MK cells and specific media in a conventional fed-batch culture

Chinese hamster ovary (CHO) cell lines, derived as subclones from the original CHO cell line, are widely used hosts for current biopharmaceutical productions. Recently, a highly proliferative host cell line, CHO-MK, was established from the Chinese hamster ovary tissue. In this study, we assessed the fundamental culture characteristics and capabilities of CHO-MK cells for monoclonal antibody (mAb) production using specified chemically defined media. To achieve this, we established fed-batch cultures of model CHO-MK cells in shake flasks and ambr15 and 2 L bioreactors under various conditions. The mAb-producing CHO-MK cell line A produced 12.6 g/L of antibody within 7 days in the fed-batch culture using a 2 L bioreactor, with a seeding density of 1 × 106 cells/mL. This performance corresponded to a space-time yield of 1.80 g/L/day, representing a productivity level that could be challengingly attained in fed-batch cultures using conventional CHO cells. In addition, when we subjected six different mAb-producing CHO-MK cell lines to fed-batch culture in the ambr15 bioreactor for 7 days, the antibody production ranged between 5.1 and 10.8 g/L, confirming that combining CHO-MK cells and specified media leads to enhanced versatility. These discoveries underscore that CHO-MK cells combined with specified media might represent a next-generation production platform, which could potentially respond to an increasing demand for antibody drugs, reducing production costs, and shortening antibody drug development times. This study is expected to serve as a benchmark for future production process development using CHO-MK cells.

A 2-year calorie restriction intervention reduces glycomic biological age biomarkers

Background/Objective

In a subset of participants from the CALERIE™ Phase 2 study we evaluated the effects of 2y of ~25% Calorie Restriction (CR) diet on IgG N-glycosylation (GlycAge), plasma and complement C3 N-glycome as markers of aging and inflammaging.

Methods

Plasma samples from 26 participants in the CR group who completed the CALERIE2 trial and were deemed adherent to the intervention (~>10 % CR at 12 mo) were obtained from the NIA AgingResearchBiobank. Glycomic investigations using UPLC or LC-MS analyses were conducted on samples from baseline (BL), mid-intervention (12 mo) and post-intervention (24 mo), and changes resulting from the 2y CR intervention were examined. In addition, anthropometric, clinical, metabolic, DNA methylation (epigenetic) and skeletal muscle transcriptomic data were analyzed to identify aging-related changes that occurred in tandem with the N-glycome changes.

Results

Following the 2y CR intervention, IgG galactosylation was higher at 24mo compared to BL (p = 0.051), digalactosylation and GlycAge (the IgG-based surrogate for biological age) were not different between BL and 12mo or BL and 24mo, but increased between 12mo and 24mo (p = 0.016, 0.027 respectively). GlycAge was also positively associated with TNF-α and ICAM-1 (p=0.030, p=0.017 respectively). Plasma highly branched glycans were decreased by the 2y intervention (BL vs 24 mo: p=0.013), but both plasma and IgG bisecting GlcNAcs were increased (BL vs 24mo: p<0.001, p = 0.01 respectively). Furthermore, total complement C3 protein concentrations were reduced (BL vs 24mo: p <0.001), as were Man9 glycoforms (BL vs 24mo: p<0.001), and Man10 (which is glucosylated) C3 glycoforms (BL vs 24mo: p = 0.046).

Conclusions

24-mos of CR was associated with several favorable, anti-aging, anti-inflammatory changes in the glycome: increased galactosylation, reduced branching glycans, and reduced GlycAge. These promising CR effects were accompanied by an increase in bisecting GlcNAc, a known pro-inflammatory biomarker. These intriguing findings linking CR, clinical, and glycomic changes may be anti-aging and inflammatory, and merit additional investigation.

Cellulose functionalized magnetic beads for high throughput glycosylation analysis in biotherapeutic modalities

The increasing demand for biotherapeutics has necessitated the evaluation of their critical quality attributes, one of which is glycosylation, an essential post-translational modification found on many biological molecules. In particular, the purification of N-glycans after their release from the proteins and derivatization is important in ensuring the removal of the deglycosylated protein, excess labelling reagents and salts for subsequent analysis. However, current methods of N-glycans purification are either expensive, laborious, time-consuming or not catered for high throughput analysis. To overcome these constraints, we developed a high throughput purification method for fluorescent derivatized N-glycans using cellulose functionalized magnetic beads (CMBs). We compared the method with two current purification methods, hydrophilic interaction chromatography solid phase extraction (HILIC-SPE) and gel filtration using human serum IgG (hsIgG) and bovine fetuin and assessed their reproducibility. The CMB method yielded highly similar glycan profiles to the two methods with very good precision. We then assessed the compatibility of the method to purify N-glycans derivatized with different fluorescent labels (RapiFluor MS, 2-aminobenzamide and procainamide). We also applied the methodology to analyse N-glycans in the biotherapeutic protein, recombinant alpha-1-antitrypsin (rAAT) which was modified with higher sialylation content. Importantly, the method successfully captured the differences in the glycan profiles between the modified and unmodified rAAT. Finally, we automated the method together with the digestion and labelling protocol onto a robotic liquid handler for high throughput glycosylation analysis. The versatility of the CMB method, together with its affordability and robustness, may provide an alternative workflow for the high throughput analysis of glycans in biotherapeutic modalities.

Harnessing the potential of microalgae for the production of monoclonal antibodies and other recombinant proteins

Monoclonal antibodies (mAbs) have become indispensable tools in various fields, from research to therapeutics, diagnostics, and industries. However, their production, primarily in mammalian cell culture systems, is cost-intensive and resource-demanding. Microalgae, diverse photosynthetic microorganisms, are gaining attention as a favorable option for manufacturing mAbs and various other recombinant proteins. This review explores the potential of microalgae as a robust expression system for biomanufacturing high-value proteins. It also highlights the diversity of microalgae species suitable for recombinant protein. Nuclear and chloroplast genomes of some microalgae have been engineered to express mAbs and other valuable proteins. Codon optimization, vector construction, and other genetic engineering techniques have significantly improved recombinant protein expression in microalgae. These accomplishments demonstrate the potential of microalgae for biopharmaceutical manufacturing. Microalgal biotechnology holds promise for revolutionizing the production of mAbs and other therapeutic proteins, offering a sustainable and cost-effective solution to address critical healthcare needs.

Multi-attribute method analysis of therapeutic monoclonal antibodies using an automated sample preparation system

The multi-attribute method (MAM) has attracted increased attention as an alternative strategy for evaluating structural heterogeneity using conventional separation techniques such as ion-exchange chromatography and capillary electrophoresis of therapeutic monoclonal antibodies (mAbs). One of the remaining challenges for the practical use of the MAM is reliable and robust continuous monitoring. In this study, we successfully established an automated sample preparation system as a solution to this issue. Through method optimization, we confirmed that the peptide purification step using a solid-phase extraction column, which is usually performed after the digestion step, was not mandatory and that the addition of methionine as an oxidation inhibitor was able to significantly reduce artificial oxidation. Importantly, the use of our system enabled high-precision analysis for targeted peptide monitoring without relying on the operator's knowledge and experience with peptide mapping using liquid chromatography/mass spectrometry (LC/MS). Our system could also be useful as a platform approach for targeted peptide monitoring in MAM workflow of traditional IgG-type mAbs. Furthermore, using common samples that were prepared using the automated system, we assessed the compatibility of LC/MS system in the targeted peptide monitoring via a collaborative study with MS vendors. The results showed that there was no significant difference in the mass accuracy, repeatability of the peak retention time and variations of intermediate precision of the measurement values among the four LC/MS systems, suggesting sufficient compatibility among the LC/MS systems. MAM system using our automated sample preparation method, which had high intermediate precision, will be useful for release and stability testing as well as characterization and manufacturing process development.

Tumor-Homing Antibody-Cytokine Fusions for Cancer Therapy

Recombinant cytokine products have emerged as a promising avenue in cancer therapy due to their capacity to modulate and enhance the immune response against tumors. However, their clinical application is significantly hindered by systemic toxicities already at low doses, thus preventing escalation to therapeutically active regimens. One promising approach to overcoming these limitations is using antibody-cytokine fusion proteins (also called immunocytokines). These biopharmaceuticals leverage the targeting specificity of antibodies to deliver cytokines directly to the tumor microenvironment, thereby reducing systemic exposure and enhancing the therapeutic index. This review comprehensively examines the development and potential of antibody-cytokine fusion proteins in cancer therapy. It explores the molecular characteristics that influence the performance of these fusion proteins, and it highlights key findings from preclinical and clinical studies, illustrating the potential of immunocytokines to improve treatment outcomes in cancer patients. Recent advancements in the field, such as novel engineering strategies and combination strategies to enhance the efficacy and safety of immunocytokines, are also discussed. These innovations offer new opportunities to optimize this class of biotherapeutics, making them a more viable and effective option for cancer treatment. As the field continues to evolve, understanding the critical factors that influence the performance of immunocytokines will be essential for successfully translating these therapies into clinical practice.

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.

A chemoenzymatic method for simultaneous profiling N- and O-glycans on glycoproteins using one-pot format

Glycosylation is generally characterized and controlled as a critical quality attribute for therapeutic glycoproteins because glycans can impact protein drug-product efficacy, half-life, stability, and safety. Analytical procedures to characterize N-glycans are relatively well established, but the characterization of O-glycans is challenging due to the complex workflows and lack of enzymatic tools. Here, we present a simplified chemoenzymatic method to simultaneously profile N- and O-glycans from the same sample using a one-pot format by mass spectrometry (MS). N-glycans were first released by PNGase F, followed by O-glycopeptide generation by proteinase K, selective N-glycan reduction, and O-glycan release by β-elimination during permethylation of both N- and O-glycans. Glycan structural assignments and determination of N- to O-glycan ratio was obtained from the one-pot mass spectra. The streamlined, one-pot method is a reliable approach that will facilitate advanced characterizations for quality assessments of therapeutic glycoproteins.

Mutations in the SLC35C1 gene, contributing to significant differences in fucosylation patterns, may underlie the diverse phenotypic manifestations observed in leukocyte adhesion deficiency type II patients

Congenital disorders of glycosylation (CDG) are a large family of genetic diseases resulting from defects in the synthesis of glycans and the attachment of glycans to macromolecules. The CDG known as leukocyte adhesion deficiency II (LAD II) is an autosomal, recessive disorder caused by mutations in the SLC35C1 gene, encoding a transmembrane protein of the Golgi apparatus, involved in GDP-fucose transport from the cytosol to the Golgi lumen. In this study, a cell-based model was used as a tool to characterize the molecular background of a therapy based on a fucose-supplemented diet. Such therapies have been successfully introduced in some (but not all) known cases of LAD II. In this study, the effect of external fucose was analyzed in SLC35C1 KO cell lines, expressing 11 mutated SLC35C1 proteins, previously discovered in patients with an LAD II diagnosis. For many of them, the cis-Golgi subcellular localization was affected; however, some proteins were localized properly. Additionally, although mutated SLC35C1 caused different α-1-6 core fucosylation of N-glycans, which explains previously described, more or less severe disorder symptoms, the differences practically disappeared after external fucose supplementation, with fucosylation restored to the level observed in healthy cells. This indicates that additional fucose in the diet should improve the condition of all patients. Thus, for patients diagnosed with LAD II we advocate careful analysis of particular mutations using the SLC35C1-KO cell line-based model, to predict changes in localization and fucosylation rate. We also recommend searching for additional mutations in the human genome of LAD II patients, when fucose supplementation does not influence patients' state.

"Find Me" and "Eat Me" signals: tools to drive phagocytic processes for modulating antitumor immunity

Phagocytosis, a vital defense mechanism, involves the recognition and elimination of foreign substances by cells. Phagocytes, such as neutrophils and macrophages, rapidly respond to invaders; macrophages are especially important in later stages of the immune response. They detect "find me" signals to locate apoptotic cells and migrate toward them. Apoptotic cells then send "eat me" signals that are recognized by phagocytes via specific receptors. "Find me" and "eat me" signals can be strategically harnessed to modulate antitumor immunity in support of cancer therapy. These signals, such as calreticulin and phosphatidylserine, mediate potent pro-phagocytic effects, thereby promoting the engulfment of dying cells or their remnants by macrophages, neutrophils, and dendritic cells and inducing tumor cell death. This review summarizes the phagocytic "find me" and "eat me" signals, including their concepts, signaling mechanisms, involved ligands, and functions. Furthermore, we delineate the relationships between "find me" and "eat me" signaling molecules and tumors, especially the roles of these molecules in tumor initiation, progression, diagnosis, and patient prognosis. The interplay of these signals with tumor biology is elucidated, and specific approaches to modulate "find me" and "eat me" signals and enhance antitumor immunity are explored. Additionally, novel therapeutic strategies that combine "find me" and "eat me" signals to better bridge innate and adaptive immunity in the treatment of cancer patients are discussed.

Direct Glycan Analysis of Biological Samples and Intact Glycoproteins by Integrating Machine Learning-Driven Surface-Enhanced Raman Scattering and Boronic Acid Arrays

Frequent monitoring of glycan patterns is a critical step in studying glycan-mediated cellular processes. However, the current glycan analysis tools are resource-intensive and less suitable for routine use in standard laboratories. We developed a novel glycan detection platform by integrating surface-enhanced Raman spectroscopy (SERS), boronic acid (BA) receptors, and machine learning tools. This sensor monitors the molecular fingerprint spectra of BA binding to cis-diol-containing glycans. Different types of BA receptors could yield different stereoselective reactions toward different glycans and exhibit unique vibrational spectra. By integration of the Raman spectra collected from different BA receptors, the structural information can be enriched, eventually improving the accuracy of glycan classification and quantification. Here, we established a SERS-based sensor incorporating multiple different BA receptors. This sensing platform could directly analyze the biological samples, including whole milk and intact glycoproteins (fetuin and asialofetuin), without tedious glycan release and purification steps. The results demonstrate the platform's ability to classify milk oligosaccharides with remarkable classification accuracy, despite the presence of other non-glycan constituents in the background. This sensor could also directly quantify sialylation levels of a fetuin/asialofetuin mixture without glycan release procedures. Moreover, by selecting appropriate BA receptors, the sensor exhibits an excellent performance of differentiating between α2,3 and α2,6 linkages of sialic acids. This low-cost, rapid, and highly accessible sensor will provide the scientific community with an invaluable tool for routine glycan screening in standard laboratories.

Ion Mobility-Mass Spectrometry and Collision-Induced Unfolding Rapidly Characterize the Structural Polydispersity and Stability of an Fc-Fusion Protein

Fc-fusion proteins are an emerging class of protein therapeutics that combine the properties of biological ligands with the unique properties of the fragment crystallizable (Fc) domain of an immunoglobulin G (IgG). Due to their diverse higher-order structures (HOSs), Fc-fusion proteins remain challenging characterization targets within biopharmaceutical pipelines. While high-resolution biophysical tools are available for HOS characterization, they frequently demand extended time frames and substantial quantities of purified samples, rendering them impractical for swiftly screening candidate molecules. Herein, we describe the development of ion mobility-mass spectrometry (IM-MS) and collision-induced unfolding (CIU) workflows that aim to fill this technology gap, where we focus on probing the HOS of a model Fc-Interleukin-10 (Fc-IL-10) fusion protein engineered using flexible glycine-serine linkers. We evaluate the ability of these techniques to probe the flexibility of Fc-IL-10 in the absence of bulk solvent relative to other proteins of similar size, as well as localize structural changes of low charge state Fc-IL-10 ions to specific Fc and IL-10 unfolding events during CIU. We subsequently apply these tools to probe the local effects of glycine-serine linkers on the HOS and stability of IL-10 homodimer, which is the biologically active form of IL-10. Our data reveals that Fc-IL-10 produces significantly more structural transitions during CIU and broader IM profiles when compared to a wide range of model proteins, indicative of its exceptional structural dynamism. Furthermore, we use a combination of enzymatic approaches to annotate these intricate CIU data and localize specific transitions to the unfolding of domains within Fc-IL-10. Finally, we detect a strong positive, quadratic relationship between average linker mass and fusion protein stability, suggesting a cooperative influence between glycine-serine linkers and overall fusion protein stability. This is the first reported study on the use of IM-MS and CIU to characterize HOS of Fc-fusion proteins, illustrating the practical applicability of this approach.

Immobilized enzyme cascade for targeted glycosylation

Glycosylation is a critical post-translational protein modification that affects folding, half-life and functionality. Glycosylation is a non-templated and heterogeneous process because of the promiscuity of the enzymes involved. We describe a platform for sequential glycosylation reactions for tailored sugar structures (SUGAR-TARGET) that allows bespoke, controlled N-linked glycosylation in vitro enabled by immobilized enzymes produced with a one-step immobilization/purification method. We reconstruct a reaction cascade mimicking a glycosylation pathway where promiscuity naturally exists to humanize a range of proteins derived from different cellular systems, yielding near-homogeneous glycoforms. Immobilized β-1,4-galactosyltransferase is used to enhance the galactosylation profile of three IgGs, yielding 80.2-96.3% terminal galactosylation. Enzyme recycling is demonstrated for a reaction time greater than 80 h. The platform is easy to implement, modular and reusable and can therefore produce homogeneous glycan structures derived from various hosts for functional and clinical evaluation.

Bispecific antibody drug conjugates: Making 1+1>2

Bispecific antibody‒drug conjugates (BsADCs) represent an innovative therapeutic category amalgamating the merits of antibody‒drug conjugates (ADCs) and bispecific antibodies (BsAbs). Positioned as the next-generation ADC approach, BsADCs hold promise for ameliorating extant clinical challenges associated with ADCs, particularly pertaining to issues such as poor internalization, off-target toxicity, and drug resistance. Presently, ten BsADCs are undergoing clinical trials, and initial findings underscore the imperative for ongoing refinement. This review initially delves into specific design considerations for BsADCs, encompassing target selection, antibody formats, and the linker-payload complex. Subsequent sections delineate the extant progress and challenges encountered by BsADCs, illustrated through pertinent case studies. The amalgamation of BsAbs with ADCs offers a prospective solution to prevailing clinical limitations of ADCs. Nevertheless, the symbiotic interplay among BsAb, linker, and payload necessitates further optimizations and coordination beyond a simplistic "1 + 1" to effectively surmount the extant challenges facing the BsADC domain.

Platform-Specific Fc N-Glycan Profiles of an Antisperm Antibody

IgG Fc N-glycosylation is necessary for effector functions and is an important component of quality control. The choice of antibody manufacturing platform has the potential to significantly influence the Fc glycans of an antibody and consequently alter their activity and clinical profile. The Human Contraception Antibody (HCA) is an IgG1 antisperm monoclonal antibody (mAb) currently in clinical development as a novel, non-hormonal contraceptive. Part of its development is selecting a suitable expression platform to manufacture HCA for use in the female reproductive tract. Here, we compared the Fc glycosylation of HCA produced in two novel mAb manufacturing platforms, namely transgenic tobacco plants (Nicotiana benthamiana; HCA-N) and mRNA-mediated expression in human vaginal cells (HCAmRNA). The Fc N-glycan profiles of the two HCA products were determined using mass spectrometry. Major differences in site occupancy, glycan types, and glycoform distributions were revealed. To address how these differences affect Fc function, antibody-dependent cellular phagocytosis (ADCP) assays were performed. The level of sperm phagocytosis was significantly lower in the presence of HCA-N than HCAmRNA. This study provides evidence that the two HCA manufacturing platforms produce functionally distinct HCAs; this information could be useful for the selection of an optimal platform for HCA clinical development and for mAbs in general.

Impact of Glycosylation on Protein-Protein Self-Interactions of Monoclonal Antibodies

Protein self-interactions measured via second osmotic virial coefficients (B22) and dynamic light scattering interaction parameter values (kD) are often used as metrics for assessing the favorability of protein candidates and different formulations during monoclonal antibody (MAb) product development. Model predictions of B22 or kD typically do not account for glycans, though glycosylation can potentially impact experimental MAb self-interactions. To the best of our knowledge, the impact of MAb glycosylation on the experimentally measured B22 and kD values has not yet been reported. B22 and kD values of two fully deglycosylated MAbs and their native (i.e., fully glycosylated) counterparts were measured by light scattering over a range of pH and ionic strength conditions. Significant differences between B22 and kD of the native and deglycosylated forms were observed at a range of low to high ionic strengths used to modulate the effect of electrostatic contributions. Differences were most pronounced at low ionic strength, indicating that electrostatic interactions are a contributing factor. Though B22 and kD values were statistically equivalent at high ionic strengths where electrostatics were fully screened, we observed protein-dependent qualitative differences, which indicate that steric interactions may also play a role in the observed B22 and kD differences. A domain-level coarse-grained molecular model accounting for charge differences was considered to potentially provide additional insight but was not fully predictive of the behavior across all of the solution conditions investigated. This highlights that both the level of modeling and lack of inclusion of glycans may limit existing models in making quantitatively accurate predictions of self-interactions.

Reducing Immunogenicity by Design: Approaches to Minimize Immunogenicity of Monoclonal Antibodies

Monoclonal antibodies (mAbs) have transformed therapeutic strategies for various diseases. Their high specificity to target antigens makes them ideal therapeutic agents for certain diseases. However, a challenge to their application in clinical practice is their potential risk to induce unwanted immune response, termed immunogenicity. This challenge drives the continued efforts to deimmunize these protein therapeutics while maintaining their pharmacokinetic properties and therapeutic efficacy. Because mAbs hold a central position in therapeutic strategies against an array of diseases, the importance of conducting comprehensive immunogenicity risk assessment during the drug development process cannot be overstated. Such assessment necessitates the employment of in silico, in vitro, and in vivo strategies to evaluate the immunogenicity risk of mAbs. Understanding the intricacies of the mechanisms that drive mAb immunogenicity is crucial to improving their therapeutic efficacy and safety and developing the most effective strategies to determine and mitigate their immunogenic risk. This review highlights recent advances in immunogenicity prediction strategies, with a focus on protein engineering strategies used throughout development to reduce immunogenicity.

High-Throughput Glycan Profiling of Human Serum IgG Subclasses Using Parallel Reaction Monitoring Peptide Bond Fragmentation of Glycopeptides and Microflow LC-MS

LC-MS-based N-glycosylation profiling in four human serum IgG subclasses (IgG1, IgG2, IgG3, and IgG4) often requires additional affinity-based enrichment of specific IgG subclasses, owing to the high amino acid sequence similarity of Fc glycopeptides among subclasses. Notably, for IgG4 and the major allotype of IgG3, the glycopeptide precursors share identical retention time and mass and therefore cannot be distinguished based on precursor or glycan fragmentation. Here, we developed a parallel reaction monitoring (PRM)-based method for quantifying Fc glycopeptides through combined transitions generated from both glycosidic and peptide bond fragmentation. The latter enables the subpopulation of IgG3 and IgG4 to be directly distinguished according to mass differences without requiring further enrichment of specific IgG subclasses. In addition, a multinozzle electrospray emitter coupled to a capillary flow liquid chromatograph was used to increase the robustness and detection sensitivity of the method for low-yield peptide backbone fragment ions. The gradient was optimized to decrease the overall run time and make the method compatible with high-throughput analysis. We demonstrated that this method can be used to effectively monitor the relative levels of 13 representative glycoforms, with a good limit of detection for individual IgG subclasses.

Recent advances in antibody glycoengineering for the gain of functions

Glycans play important roles in antibody functions, and antibody glycoengineering has long been an important research field. Here, we summarize the significant strategies of antibody glycoengineering, including expressed antibody glycoengineering in mammalian cell expression systems, chemo-enzymatic antibody glycoengineering, and yeast expression system-based antibody engineering, as well as the applications of glycoengineering in antibody-drug conjugates. These advances in antibody glycoengineering will provide a comprehensive understanding and inspire us to develop more advanced techniques to achieve glycoengineered antibodies.

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.

Plasma Glycomic Markers of Accelerated Biological Aging During Chronic HIV Infection

People with HIV (PWH) experience an increased vulnerability to premature aging and inflammation-associated comorbidities, even when HIV replication is suppressed by antiretroviral therapy (ART). However, the factors that contribute to or are associated with this vulnerability remain uncertain. In the general population, alterations in the glycomes of circulating IgGs trigger inflammation and precede the onset of aging-associated diseases. Here, we investigate the IgG glycomes of cross-sectional and longitudinal samples from 1,216 women and men, both living with virally suppressed HIV and those without HIV. Our glycan-based machine learning models indicate that living with chronic HIV significantly accelerates the accumulation of pro-aging-associated glycomic alterations. Consistently, PWH exhibit heightened expression of senescence-associated glycan-degrading enzymes compared to their controls. These glycomic alterations correlate with elevated markers of inflammatory aging and the severity of comorbidities, potentially preceding the development of such comorbidities. Mechanistically, HIV-specific antibodies glycoengineered with these alterations exhibit reduced anti-HIV IgG-mediated innate immune functions. These findings hold significant potential for the development of glycomic-based biomarkers and tools to identify and prevent premature aging and comorbidities in people living with chronic viral infections.

Introduction of Carbonyl Groups into Antibodies

Antibodies and their derivatives (scFv, Fabs, etc.) represent a unique class of biomolecules that combine selectivity with the ability to target drug delivery. Currently, one of the most promising endeavors in this field is the development of molecular diagnostic tools and antibody-based therapeutic agents, including antibody-drug conjugates (ADCs). To meet this challenge, it is imperative to advance methods for modifying antibodies. A particularly promising strategy involves the introduction of carbonyl groups into the antibody that are amenable to further modification by biorthogonal reactions, namely aliphatic, aromatic, and α-oxo aldehydes, as well as aliphatic and aryl-alkyl ketones. In this review, we summarize the preparation methods and applications of site-specific antibody conjugates that are synthesized using this approach.

Lignocellulosic biomass-based glycoconjugates for diverse biotechnological applications

Glycoconjugates are the ubiquitous components of mammalian cells, mainly synthesized by covalent bonds of carbohydrates to other biomolecules such as proteins and lipids, with a wide range of potential applications in novel vaccines, therapeutic peptides and antibodies (Ab). Considering the emerging developments in glycoscience, renewable production of glycoconjugates is of importance and lignocellulosic biomass (LCB) is a potential source of carbohydrates to produce synthetic glycoconjugates in a sustainable pathway. In this review, recent advances in glycobiology aiming on glycoconjugates production is presented together with the recent and cutting-edge advances in the therapeutic properties and application of glycoconjugates, including therapeutic glycoproteins, glycosaminoglycans (GAGs), and nutraceuticals, emphasizing the integral role of glycosylation in their function and efficacy. Special emphasis is given towards the potential exploration of carbon neutral feedstocks, in which LCB has an emerging role. Techniques for extraction and recovery of mono- and oligosaccharides from LCB are critically discussed and influence of the heterogeneous nature of the feedstocks and different methods for recovery of these sugars in the development of the customized glycoconjugates is explored. Although reports on the use of LCB for the production of glycoconjugates are scarce, this review sets clear that the potential of LCB as a source for the production of valuable glycoconjugates cannot be underestimated and encourages that future research should focus on refining the existing methodologies and exploring new approaches to fully realize the potential of LCB in glycoconjugate production.

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

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

Site-Specific Antibody Conjugation Using Modified Bisected N-Glycans: Method Development and Potential toward Tunable Effector Function

Antibody-drug conjugates (ADCs) have garnered worldwide attention for disease treatment, as they possess high target specificity, a long half-life, and outstanding potency to kill or modulate the functions of targets. FDA approval of multiple ADCs for cancer therapy has generated a strong desire for novel conjugation strategies with high biocompatibility and controllable bioproperties. Herein, we present a bisecting glycan-bridged conjugation strategy that enables site-specific conjugation without the need for the oligosaccharide synthesis and genetic engineering of antibodies. Application of this method is demonstrated by conjugation of anti-HER2 human and mouse IgGs with a cytotoxic drug, monomethyl auristatin E. The glycan bridge showed outstanding stability, and the resulting ADCs eliminated HER2-expressing cancer cells effectively. Moreover, our strategy preserves the feasibility of glycan structure remodeling to fine-tune the immunogenicity and pharmacokinetic properties of ADCs through glycoengineering.

Production and N-glycan engineering of Varlilumab in Nicotiana benthamiana

N-glycan engineering has dramatically evolved for the development and quality control of recombinant antibodies. Fc region of IgG contains two N-glycans whose galactose terminals on Fc-glycan have been shown to increase the stability of CH2 domain and improve effector functions. Nicotiana benthamiana has become one of the most attractive production systems for therapeutic antibodies. In this study, Varlilumab, a CD27-targeting monoclonal antibody, was transiently produced in fresh leaves of soil-grown and hydroponic-grown N. benthamiana, resulted in the yield of 174 and 618 µg/gram, respectively. However, the IgG produced in wild-type N. benthamiana lacked the terminal galactose residues in its N-glycan. Therefore, N-glycan engineering was applied to fine-tune recombinant antibodies produced in plant platforms. We further co-expressed IgG together with murine β1,4-galactosyltransferase (β1,4-GALT) to modify plant N-glycan with β1,4-linked Gal residue(s) and Arabidopsis thaliana β1,3-galactosylatransferase (β1,3-GALT) to improve galactosylation. The co-expression of IgG with each of GALTs successfully resulted in modification of N-glycan structures on the plant-produced IgG. Notably, IgG co-expressed with murine β1,4-GALT in soil-grown N. benthamiana had 42.5% of N-glycans variants having galactose (Gal) residues at the non-reducing terminus and 55.3% of that in hydroponic-grown N. benthamiana plants. Concomitantly, N-glycan profile analysis of IgG co-expressed with β1,3-GALT demonstrated that there was an increased efficiency of galactosylation and an enhancement in the formation of Lewis a structure in plant-derived antibodies. Taken together, our findings show that the first plant-derived Varlilumab was successfully produced with biantennary β1,4-galactosylated N-glycan structures.

The role of N-glycosylation in B-cell biology and IgG activity. The aspects of autoimmunity and anti-inflammatory therapy

The immune system is strictly regulated by glycosylation through the addition of highly diverse and dynamically changing sugar structures (glycans) to the majority of immune cell receptors. Although knowledge in the field of glycoimmunology is still limited, numerous studies point to the key role of glycosylation in maintaining homeostasis, but also in reflecting its disruption. Changes in oligosaccharide patterns can lead to impairment of both innate and acquired immune responses, with important implications in the pathogenesis of diseases, including autoimmunity. B cells appear to be unique within the immune system, since they exhibit both innate and adaptive immune activity. B cell surface is rich in glycosylated proteins and lectins which recognise glycosylated ligands on other cells. Glycans are important in the development, selection, and maturation of B cells. Changes in sialylation and fucosylation of cell surface proteins affect B cell signal transduction through BCRs, CD22 inhibitory coreceptor and Siglec-G. Plasmocytes, as the final stage of B cell differentiation, produce and secrete immunoglobulins (Igs), of which IgGs are the most abundant N-glycosylated proteins in human serum with the conserved N-glycosylation site at Asn297. N-oligosaccharide composition of the IgG Fc region affects its secretion, structure, half-life and effector functions (ADCC, CDC). IgG N-glycosylation undergoes little change during homeostasis, and may gradually be modified with age and during ongoing inflammatory processes. Hyperactivated B lymphocytes secrete autoreactive antibodies responsible for the development of autoimmunity. The altered profile of IgG N-glycans contributes to disease progression and remission and is sensitive to the application of therapeutic substances and immunosuppressive agents. In this review, we focus on the role of N-glycans in B-cell biology and IgG activity, the rearrangement of IgG oligosaccharides in aging, autoimmunity and immunosuppressive therapy.

Mixed IgG Fc immune complexes exhibit blended binding profiles and refine FcR affinity estimates

Immunoglobulin G (IgG) antibodies coordinate immune effector responses by interacting with effector cells via fragment crystallizable γ (Fcγ) receptors. The IgG Fc domain directs effector responses through subclass and glycosylation variation. Although each Fc variant has been extensively characterized in isolation, during immune responses, IgG is almost always produced in Fc mixtures. How this influences effector responses has not been examined. Here, we measure Fcγ receptor binding to mixed Fc immune complexes. Binding of these mixtures falls along a continuum between pure cases and quantitatively matches a mechanistic model, except for several low-affinity interactions mostly involving IgG2. We find that the binding model provides refined estimates of their affinities. Finally, we demonstrate that the model predicts effector cell-elicited platelet depletion in humanized mice. Contrary to previous views, IgG2 exhibits appreciable binding through avidity, though it is insufficient to induce effector responses. Overall, this work demonstrates a quantitative framework for modeling mixed IgG Fc-effector cell regulation.

Protein posttranslational modifications in health and diseases: Functions, regulatory mechanisms, and therapeutic implications

Protein posttranslational modifications (PTMs) refer to the breaking or generation of covalent bonds on the backbones or amino acid side chains of proteins and expand the diversity of proteins, which provides the basis for the emergence of organismal complexity. To date, more than 650 types of protein modifications, such as the most well-known phosphorylation, ubiquitination, glycosylation, methylation, SUMOylation, short-chain and long-chain acylation modifications, redox modifications, and irreversible modifications, have been described, and the inventory is still increasing. By changing the protein conformation, localization, activity, stability, charges, and interactions with other biomolecules, PTMs ultimately alter the phenotypes and biological processes of cells. The homeostasis of protein modifications is important to human health. Abnormal PTMs may cause changes in protein properties and loss of protein functions, which are closely related to the occurrence and development of various diseases. In this review, we systematically introduce the characteristics, regulatory mechanisms, and functions of various PTMs in health and diseases. In addition, the therapeutic prospects in various diseases by targeting PTMs and associated regulatory enzymes are also summarized. This work will deepen the understanding of protein modifications in health and diseases and promote the discovery of diagnostic and prognostic markers and drug targets for diseases.

Production of monoclonal antibodies for therapeutic purposes: A review

Monoclonal antibodies (mAbs) have been used in the development of immunotherapies that target a variety of diseases, such as cancer, autoimmune diseases, and even viral infections; they play a key role in immunization and are expected after vaccination. However, some conditions do not promote the development of neutralizing antibodies. Production and use of mAbs, generated in biofactories, represent vast potential as aids in immunological responses when the organism cannot produce them on their own, these convey unique specificity by recognizing and targeting specific antigen. Antibodies can be defined as heterotetrametric glycoproteins of symmetric nature, and they participate as effector proteins in humoral responses. Additionally, there are different types of mAbs (murine, chimeric, humanized, human, mAbs as Antibody-drug conjugates and bispecific mAbs) discussed in the present work. When these molecules are produced in vitro as mAbs, several common techniques, such as hybridomas or phage display are used. There are several preferred cell lines that function as biofactories, for the production of mAbs, the selection of which rely on the variation of adaptability, productivity and both phenotypic and genotypic shifts. After the cell expression systems and culture techniques are used, there are diverse specialized downstream processes to achieve desired yield and isolation as well as product quality and characterization. Novel perspectives regarding these protocols represent a potential improvement for mAbs high-scale production.

Enhancing pharmacokinetic and pharmacodynamic properties of recombinant therapeutic proteins by manipulation of sialic acid content

The circulatory half-life of recombinant therapeutic proteins is an important pharmacokinetic attribute because it determines the dosing frequency of these drugs, translating directly to treatment cost. Thus, recombinant therapeutic glycoproteins such as monoclonal antibodies have been chemically modified by various means to enhance their circulatory half-life. One approach is to manipulate the N-glycan composition of these agents. Among the many glycan constituents, sialic acid (specifically, N-acetylneuraminic acid) plays a critical role in extending circulatory half-life by masking the terminal galactose that would otherwise be recognised by the hepatic asialoglycoprotein receptor (ASGPR), resulting in clearance of the biotherapeutic from the circulation. This review aims to provide an illustrative overview of various strategies to enhance the pharmacokinetic/pharmacodynamic properties of recombinant therapeutic proteins through manipulation of their sialic acid content.

Beyond antibody fucosylation: α-(1,6)-fucosyltransferase (Fut8) as a potential new therapeutic target for cancer immunotherapy

Aberrant post-translational glycosylation is a well-established hallmark of cancer. Altered core fucosylation mediated by α-(1,6)-fucosyltransferase (Fut8) is one of the key changes in tumor glycan patterns that contributes to neoplastic transformation, tumor metastasis, and immune evasion. Increased Fut8 expression and activity are associated with many types of human cancers, including lung, breast, melanoma, liver, colorectal, ovarian, prostate, thyroid, and pancreatic cancer. In animal models, inhibition of Fut8 activity by gene knockout, RNA interference, and small analogue inhibitors led to reduced tumor growth/metastasis, downregulation of immune checkpoint molecules PD-1, PD-L1/2, and B7-H3, and reversal of the suppressive state of tumor microenvironment. Although the biologics field has long benefited tremendously from using FUT8 -/- Chinese hamster ovary cells to manufacture IgGs with greatly enhanced effector function of antibody-dependent cellular cytotoxicity for therapy, it is only in recent years that the roles of Fut8 itself in cancer biology have been studied. Here, we summarize the pro-oncogenic mechanisms involved in cancer development that are regulated by Fut8-mediated core fucosylation, and call for more research in this area where modifying the activity of this sole enzyme responsible for core fucosylation could potentially bring rewarding surprises in fighting cancer, infections, and other immune-related diseases.

Mechanism of antibody-specific deglycosylation and immune evasion by Streptococcal IgG-specific endoglycosidases

Bacterial pathogens have evolved intricate mechanisms to evade the human immune system, including the production of immunomodulatory enzymes. Streptococcus pyogenes serotypes secrete two multi-modular endo-β-N-acetylglucosaminidases, EndoS and EndoS2, that specifically deglycosylate the conserved N-glycan at Asn297 on IgG Fc, disabling antibody-mediated effector functions. Amongst thousands of known carbohydrate-active enzymes, EndoS and EndoS2 represent just a handful of enzymes that are specific to the protein portion of the glycoprotein substrate, not just the glycan component. Here, we present the cryoEM structure of EndoS in complex with the IgG1 Fc fragment. In combination with small-angle X-ray scattering, alanine scanning mutagenesis, hydrolytic activity measurements, enzyme kinetics, nuclear magnetic resonance and molecular dynamics analyses, we establish the mechanisms of recognition and specific deglycosylation of IgG antibodies by EndoS and EndoS2. Our results provide a rational basis from which to engineer novel enzymes with antibody and glycan selectivity for clinical and biotechnological applications.

A reflection on the improvement of Chinese Hamster ovary cell-based bioprocesses through advances in proteomic techniques

Chinese hamster ovary (CHO) cells are the preferred mammalian host for the large-scale production of recombinant proteins in the biopharmaceutical industry. Research endeavors have been directed to the optimization of CHO-based bioprocesses to increase protein quantity and quality, often in an empirical manner. To provide a rationale for those achievements, a myriad of CHO proteomic studies has arisen in recent decades. This review gives an overview of significant advances in LC-MS-based proteomics and sheds light on CHO proteomic studies, with a particular focus on CHO cells with superior bioprocessing phenotypes (growth, viability, titer, productivity and cQA), that have exploited novel proteomic or sub-omic techniques. These proteomic findings expand the current knowledge and understanding about the underlying protein clusters, protein regulatory networks and biological pathways governing such phenotypic changes. The proteomic studies, highlighted herein, will help in the targeted modulation of these cell factories to the desired needs.

Enhanced antibody-defucosylation capability of α-L-fucosidase by proximity-based protein fusion

Up to date, the reported fucosidases generally show poor activities toward the IgG core-fucose, which limits the efficiency of ENGase-catalyzed glycoengineering process. However, EndoS or EndoS2 owns excellent activity and great selectivity towards the N-glycosylation of IgGs, and their non-catalytic domains are deduced to have specific interactions to IgG Fc domain that result in the great activity and selectivity. Herein, we constructed a series fusion protein of AlfC (an α-l-fucosidase from Lactobacillus casei BL23) with EndoS/S2 non-catalytic domain by replacing the catalytic GH (glycan hydrolase) domain of EndoS/S2 with the AlfC. We found that all these fused AlfCs showed significantly enhanced defucosylation activity toward the deglycosylated IgGs (Fucα1,6GlcNAc-IgG). We also performed the kinetic study of these fusion enzymes, and our results tend to tell that the EndoS-based fusion proteins have higher k_cat values while the EndoS2-based ones possess lower K_m values other than higher k_cat. Conclusively, our research provides an effective approach to improve the activity of AlfC and remarkably shortened the defucosylation process within several minutes, which will significantly promote the development of glycoengineered antibodies in the future.

Mixed IgG Fc immune complexes exhibit blended binding profiles and refine FcR affinity estimates

Immunoglobulin (Ig)G antibodies coordinate immune effector responses by selectively binding to target antigens and then interacting with various effector cells via the Fcγ receptors. The Fc domain of IgG can promote or inhibit distinct effector responses across several different immune cell types through variation based on subclass and Fc domain glycosylation. Extensive characterization of these interactions has revealed how the inclusion of certain Fc subclasses or glycans results in distinct immune responses. During an immune response, however, IgG is produced with mixtures of Fc domain properties, so antigen-IgG immune complexes are likely to almost always be comprised of a combination of Fc forms. Whether and how this mixed composition influences immune effector responses has not been examined. Here, we measured Fcγ receptor binding to immune complexes of mixed Fc domain composition. We found that the binding properties of the mixed-composition immune complexes fell along a continuum between those of the corresponding pure cases. Binding quantitatively matched a mechanistic binding model, except for several low-affinity interactions mostly involving IgG2. We found that the affinities of these interactions are different than previously reported, and that the binding model could be used to provide refined estimates of these affinities. Finally, we demonstrated that the binding model can predict effector-cell elicited platelet depletion in humanized mice, with the model inferring the relevant effector cell populations. Contrary to the previous view in which IgG2 poorly engages with effector populations, we observe appreciable binding through avidity, but insufficient amounts to observe immune effector responses. Overall, this work demonstrates a quantitative framework for reasoning about effector response regulation arising from IgG of mixed Fc composition.

Summary points

The binding behavior of mixed Fc immune complexes is a blend of the binding properties for each constituent IgG species.An equilibrium, multivalent binding model can be generalized to incorporate immune complexes of mixed Fc composition.Particularly for low-affinity IgG-Fcγ receptor interactions, immune complexes provide better estimates of affinities.The FcγR binding model predicts effector-elicited cell clearance in humanized mice.

Engineering the enzyme toolbox to tailor glycosylation in small molecule natural products and protein biologics

Many glycosylated small molecule natural products and glycoprotein biologics are important in a broad range of therapeutic and industrial applications. The sugar moieties that decorate these compounds often show a profound impact on their biological functions, thus biocatalytic methods for controlling their glycosylation are valuable. Enzymes from nature are useful tools to tailor bioproduct glycosylation but these sometimes have limitations in their catalytic efficiency, substrate specificity, regiospecificity, stereospecificity, or stability. Enzyme engineering strategies such as directed evolution or semi-rational and rational design have addressed some of the challenges presented by these limitations. In this review, we highlight some of the recent research on engineering enzymes to tailor the glycosylation of small molecule natural products (including alkaloids, terpenoids, polyketides, and peptides), as well as the glycosylation of protein biologics (including hormones, enzyme-replacement therapies, enzyme inhibitors, vaccines, and antibodies).

Mass Spectrometry-Based Methods to Determine the Substrate Specificities and Kinetics of N-Linked Glycan Hydrolysis by Endo-β-N-Acetylglucosaminidases

Glycosylation is a common posttranslational modification of proteins and refers to the covalent addition of glycans, chains of polysaccharides, onto proteins producing glycoproteins. The glycans influence the structure, function, and stability of proteins. They also play an integral role in the immune system, and aberrantly glycosylated proteins have wide ranging effects, including leading to diseases such as autoimmune conditions and cancer. Carbohydrate-active enzymes (CAZymes) are produced in bacteria, fungi, and humans and are enzymes which modify glycans via the addition or subtraction of individual or multiple saccharides from glycans. One of the hurdles in studying these enzymes is determining the types of substrates each enzyme is specific for and the kinetics of enzymatic activity. In this chapter, we discuss methods which are currently used to study the substrate specificity and kinetics of CAZymes and introduce a novel mass spectrometry-based technique which enables the specificity and kinetics of CAZymes to be determined accurately and efficiently.

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.

Development of therapeutic antibodies for the treatment of diseases

Since the first monoclonal antibody drug, muromonab-CD3, was approved for marketing in 1986, 165 antibody drugs have been approved or are under regulatory review worldwide. With the approval of new drugs for treating a wide range of diseases, including cancer and autoimmune and metabolic disorders, the therapeutic antibody drug market has experienced explosive growth. Monoclonal antibodies have been sought after by many biopharmaceutical companies and scientific research institutes due to their high specificity, strong targeting abilities, low toxicity, side effects, and high development success rate. The related industries and markets are growing rapidly, and therapeutic antibodies are one of the most important research and development areas in the field of biology and medicine. In recent years, great progress has been made in the key technologies and theoretical innovations provided by therapeutic antibodies, including antibody-drug conjugates, antibody-conjugated nuclides, bispecific antibodies, nanobodies, and other antibody analogs. Additionally, therapeutic antibodies can be combined with technologies used in other fields to create new cross-fields, such as chimeric antigen receptor T cells (CAR-T), CAR-natural killer cells (CAR-NK), and other cell therapy. This review summarizes the latest approved or in regulatory review therapeutic antibodies that have been approved or that are under regulatory review worldwide, as well as clinical research on these approaches and their development, and outlines antibody discovery strategies that have emerged during the development of therapeutic antibodies, such as hybridoma technology, phage display, preparation of fully human antibody from transgenic mice, single B-cell antibody technology, and artificial intelligence-assisted antibody discovery.