Correct primary structure assessment and extensive glyco-profiling of cetuximab by a combination of intact, middle-up, middle-down and bottom-up ESI and MALDI mass spectrometry techniques

In-line buffer exchange in the coupling of Protein A chromatography with weak cation exchange chromatography for the determination of charge variants of immunoglobulin G derived from chinese hamster ovary cell cultures

Immunoglobulin G (IgG) is the most common monoclonal antibody (mAb) grown for therapeutic applications. While IgG is often selectively isolated from cell lines using protein A (ProA) chromatography, this is only a stepping stone for complete characterization. Further classification can be obtained from weak cation exchange chromatography (WCX) to determine IgG charge variant distributions. The charge variants of monoclonal antibodies can influence the stability and efficacy in vivo, and deviations in charge heterogeneity are often cell-specific and sensitive to upstream process variability. Current methods to characterize IgG charge variants are often performed off-line, meaning that the IgG eluate from the ProA separation is collected, diluted to adjust the pH, and then transferred to the WCX separation, adding time, complexity, and potential contamination to the sample analysis process. More recently, reports have appeared to streamline this separation using in-line two-dimensional liquid chromatography (2D-LC). Presented here is a novel, 2D-LC coupling of ProA in the first dimension (1D) and WCX in the second dimension (2D) chromatography. As anticipated, the initial direct column coupling proved to be challenging due to the pH incompatibility between the mobile phases for the two stages. To solve the solvent compatibility issue, a size exclusion column was placed in the switching valve loop of the 2D-LC instrument to act as a means for the on-line solvent exchange. The efficacy of the methodology presented was confirmed through a charge variant determination using the NIST monoclonal antibody standard (NIST mAb), yielding correct acidic, main, and basic variant compositions. The methodology was employed to determine the charge variant profile of IgG from an in-house cultured Chinese hamster ovary (CHO) cell supernatant. It is believed that this methodology can be easily implemented to provide higher-throughput assessment of IgG charge variants for process monitoring and cell line development.

CE-MS/MS and CE-timsTOF to separate and characterize intramolecular disulfide bridges of monoclonal antibody subunits and their application for the assessment of subunit reduction protocols

Characterization at the subunit level enables detailed mass spectrometric characterization of posttranslational modifications (PTMs) of monoclonal antibodies (mAbs). The implemented reduction often leaves the intramolecular disulfide bridges intact. Here, we present a capillary electrophoretic (CE) method based on a neutral-coated capillary for the separation of immunoglobulin G-degrading enzyme of Streptococcus pyogenes (IdeS) digested and reduced mAb subunits followed by mass spectrometry (MS), MS/MS identification, and trapped ion mobility mass spectrometry (timsTOF). Our CE approach enables the separation of (i) different subunit moieties, (ii) various reduction states, and (iii) positional isomers of these partly reduced subunit moieties. The location of the remaining disulfide bridges can be determined by middle-down electron transfer higher energy collisional dissociation (EThcD) experiments. All these CE-separated variants show differences in ion mobility in the timsTOF measurements. Applying the presented CE-MS/MS method, reduction parameters such as the use of chaotropic salts were studied. For the investigated antibodies, urea improved the subunit reduction significantly, whereas guanidine hydrochloride (GuHCl) leads to multiple signals of the same subunit in the CE separation. The presented CE-MS method is a powerful tool for the disulfide-variant characterization of mAbs on the subunit level. It enables understanding disulfide bridge reduction processes in antibodies and potentially other proteins.

A tailored lectin microarray for rapid glycan profiling of therapeutic monoclonal antibodies

Glycosylation plays a crucial role in determining the quality and efficacy of therapeutic antibodies. This necessitates a thorough analysis and monitoring process to ensure consistent product quality during manufacturing. In this study, we introduce a custom-designed lectin microarray featuring nine distinct lectins: rPhoSL, rOTH3, RCA120, rMan2, MAL_I, rPSL1a, PHAE, rMOA, and PHAL. These lectins have been specifically tailored to selectively bind to common N-glycan epitopes found in therapeutic IgG antibodies. By utilizing intact glycoprotein samples, our nine-lectin microarray provides a high-throughput platform for rapid glycan profiling, enabling comparative analysis of glycosylation patterns. Our results demonstrate the practical utility of this microarray in assessing glycosylation across various manufacturing batches or between biosimilar and innovator products. This capacity empowers informed decision-making in the development and production of therapeutic antibodies.

Plant glycoengineering for designing next-generation vaccines and therapeutic proteins

Protein glycosylation has a huge impact on biological processes in all domains of life. The type of glycan present on a recombinant glycoprotein depends on protein intrinsic features and the glycosylation repertoire of the cell type used for expression. Glycoengineering approaches are used to eliminate unwanted glycan modifications and to facilitate the coordinated expression of glycosylation enzymes or whole metabolic pathways to furnish glycans with distinct modifications. The formation of tailored glycans enables structure-function studies and optimization of therapeutic proteins used in different applications. While recombinant proteins or proteins from natural sources can be in vitro glycoengineered using glycosyltransferases or chemoenzymatic synthesis, many approaches use genetic engineering involving the elimination of endogenous genes and introduction of heterologous genes to cell-based production systems. Plant glycoengineering enables the in planta production of recombinant glycoproteins with human or animal-type glycans that resemble natural glycosylation or contain novel glycan structures. This review summarizes key achievements in glycoengineering of plants and highlights current developments aiming to make plants more suitable for the production of a diverse range of recombinant glycoproteins for innovative therapies.

Why is there no biosimilar of Erbitux®?

Monoclonal antibody (mAb)-based therapies have been a major advance in oncology patient care, even though they represent a significant healthcare cost. Biosimilars, launched in Europe in 2004 are an economically attractive alternative to expensive originator biological drugs. They also increase the competitiveness of pharmaceutical development. This article focuses on the case of Erbitux® (cetuximab). This anti-EGFR (Epidermal Growth Factor Receptor) monoclonal antibody is indicated for metastatic colorectal cancer (2004) and squamous cell carcinoma of the head and neck (2006). However, despite the expiration of the patent in Europe in 2014 and estimated annual sales of 1.681 million US dollars in 2022, Erbitux® has not yet faced any approved biosimilar challenges in the United States or in Europe. Here, we outline the unique structural complexity of this antibody highlighted by advanced orthogonal analytical characterization strategies resulting in risks to demonstrate biosimilarity, which may explain the lack of Erbitux® biosimilars in the European and US markets to date. The development of Erbitux® biobetters are also discussed as alternative strategies to biosimilars. These biologics offer expected additional safety and potency benefits over the reference product but require a full pharmaceutical and clinical development as for New Molecular Entities.

Exploring proteoforms of the IgG2 monoclonal antibody panitumumab using microchip capillary electrophoresis-mass spectrometry

The IgG2 type monoclonal antibody panitumumab is an anti-epidermal growth factor receptor (EGFR) drug used for the treatment of EGFR-expressing, chemotherapy resistant, metastatic colorectal carcinoma. In this study, panitumumab drug product was first analysed using size exclusion chromatography coupled to mass spectrometry for rapid identity testing. The experimental data led to the identification of two panitumumab isoforms with several prominent forms remaining unidentified, despite apparently low sample complexity. Microchip capillary electrophoresis-mass spectrometry (CE-MS) was subsequently utilised for a more detailed characterization. It was observed that panitumumab is subject to partial N-terminal pyroglutamate formation. Incomplete conversion is uncharacteristic for N-terminally exposed glutamines and in case of panitumumab gives rise to forms which show successive mass offsets of 17 Da, respectively. If not separated before mass spectrometric analysis, e.g. by capillary electrophoresis, such near isobaric species coalesce into single MS peaks, which subsequently hampers or prevents their assignment. With a total of 42 panitumumab isoforms assigned by CE-MS, these observations highlight a potential pitfall of commonly applied rapid identity testing workflows and demonstrate that even low complexity biopharmaceuticals can require separation strategies which offer high separation selectivity for species close in mass.

Bivalent non-human gal-α1-3-gal glycan epitopes in the Fc region of a monoclonal antibody model can be recognized by anti-Gal-α1-3-Gal IgE antibodies

Monoclonal antibody (mAb) production using non-human cells can introduce non-human glycan epitopes including terminal galactosyl-α1-3-galactose (α1-3-Gal) moieties. Cetuximab is a commercial mAb associated with causing anaphylaxis in some patients due to the binding of endogenous anti-α1-3-Gal IgE to the Fab (containing bi-α1-3-galactosylated glycans) but not to the Fc region (containing mono-α1-3-galactosylated glycans). Despite being low in abundance in typical commercial mAbs, the inherent sensitivity of cell culture conditions on glycosylation profiles, and the development of novel glycoengineering strategies, novel antibody-based modalities, and biosimilars by various manufacturers with varying procedures, necessitates a better understanding of the structural requirements for anti-α1-3-Gal IgE binding to the Fc region. Herein, we synthesized mAb glycoforms with varying degrees and regioisomers of α1-3-galactosylation and tested their binding to two commercial anti-α1-3-Gal human IgE antibodies derived from a human patient with allergies to red meat (comprising α1-3-Gal epitopes), as well as to the FcγRIIIA receptor. Our results demonstrate that unexpectedly, anti-α1-3-Gal human IgE antibodies can bind to Fc glycans, with bi-α1-3-galactosylation being the most important factor, highlighting that their presence in the Fc region may be considered as a potential critical quality attribute, particularly when using novel platforms in mAb-based biotherapeutics.

Specific targeting of glioblastoma with an oncolytic virus expressing a cetuximab-CCL5 fusion protein via innate and adaptive immunity

Chemokines such as C-C motif ligand 5 (CCL5) regulate immune cell trafficking in the tumor microenvironment (TME) and govern tumor development, making them promising targets for cancer therapy. However, short half-lives and toxic off-target effects limit their application. Oncolytic viruses (OVs) have become attractive therapeutic agents. Here, we generate an oncolytic herpes simplex virus type 1 (oHSV) expressing a secretable single-chain variable fragment of the epidermal growth factor receptor (EGFR) antibody cetuximab linked to CCL5 by an Fc knob-into-hole strategy that produces heterodimers (OV-Cmab-CCL5). OV-Cmab-CCL5 permits continuous production of CCL5 in the TME, as it is redirected to EGFR+ glioblastoma (GBM) tumor cells. OV-Cmab-CCL5 infection of GBM significantly enhances the migration and activation of natural killer cells, macrophages and T cells; inhibits tumor EGFR signaling; reduces tumor size; and prolongs survival of GBM-bearing mice. Collectively, our data demonstrate that OV-Cmab-CCL5 offers a promising approach to improve OV therapy for solid tumors.

One-Step Conversion of NHS Esters to Reagents for Site-Directed Labeling of IgG Antibodies

Antibody conjugates are extensively used for diagnostics and therapeutics, and as a tool for molecular biology. To prepare such conjugates N-hydroxysuccinimide (NHS) esters are most often used due to the straightforward experimental procedure and the commercial accessibility of the reagents. Such conjugates are however highly heterogeneous, since only the reactivity of the lysines determines the distribution of labels. This has inspired the development of methods that experimentally are as facile but produce conjugates of higher quality. Herein, we report the development of a reagent that can, in one step, be activated with an NHS ester of choice and subsequently can be directly used for site-directed labeling of antibodies. The reagent can be prepared in three synthetic steps and produces conjugates with similar ease as for NHS esters, however in a site-directed manner. We show that the reagent is quantitatively activated by a variety of NHS esters, and we use these to functionalize IgG1, IgG2, and IgG4 antibodies.

Advances in glycopeptide enrichment methods for the analysis of protein glycosylation over the past decade

Advances in bioanalytical technology have accelerated the analysis of complex protein glycosylation, which is beneficial to understanding glycosylation in drug discovery and disease diagnosis. Due to its biological uniqueness in the course of disease occurrence and development, disease-specific glycosylation requires quantitative characterization of protein glycosylation. We provide a comprehensive review of recent advances in glycosylation analysis, including workflows for glycoprotein digestion, glycopeptide separation and enrichment, and mass-spectrometry sequencing. We specifically focus on different strategies for glycopeptide enrichment through physical interaction, chemical oxidation, or metabolic labeling of intact glycopeptides. The recent advances and challenges of O-glycosylation analysis are presented, and the development of improved enrichment methods combining different proteases to analyze O-glycosylation is also proposed. This article is protected by copyright. All rights reserved.

[Quality Evaluation of Therapeutic Antibodies by Multi-attribute Method]

In the development of therapeutic monoclonal antibodies (mAbs), it is essential to characterize the modifications causing structural heterogeneity because certain modifications are associated with safety and efficacy. However, the rapid structural analysis of mAbs remains challenging due to their structural complexity. The multi-attribute method (MAM) is a structural analytical method based on peptide mapping using LC/MS, and has drawn attention as a new quality control method for therapeutic mAbs instead of conventional structural heterogeneity analyses using several chromatographic techniques. Peptide mapping, which is regarded as an identification test method, is used to confirm that the amino acid sequence corresponds to that deduced from the gene sequence for the desired product. In contrast, MAM is used for simultaneously monitoring the modification rates of individual amino acid residues of therapeutic mAbs, indicating that MAM is used as quantitative test rather than identification test. In this review, we summarized the typical structural heterogeneities of mAbs and the general scheme of MAM. We also introduced our optimized sample preparation method for MAM, and examples of simultaneous monitoring of several modifications including deamidation, oxidation, N-terminal pyroglutamination, C-terminal clipping and glycosylation by our MAM system.

Intact quantitative bioanalytical method development and fit-for-purpose validation of a monoclonal antibody and its related fab fragment in human vitreous and aqueous humor using LC-HRMS

Ranibizumab is an FDA-approved drug used to treat wet age-related macular degeneration (AMD), diabetic retinopathy, macular edema, and myopic choroidal neovascularization. Bevacizumab is another drug often used off-label to treat wet AMD. In order to reduce unwanted angiogenesis, ranibizumab and bevacizumab target circulating VEGF-A in the eye. Concentration levels in human vitreous and aqueous humor can be used to provide valuable efficacy information. However, vitreous and aqueous humor's aqueous environment, and vitreous humor's viscosity, as well as the stickiness of the analytes can provide bioanalytical challenges. In this manuscript, we describe the development, optimization, and fit-for-purpose validation of an LC-HRMS method designed for intact quantitative bioanalysis of ranibizumab and bevacizumab in human vitreous and aqueous humor following intravitreal administration. In order to fully develop this method, evaluations were conducted to optimize the conditions, including the data processing model (extracted ion chromatograms (XICs) vs deconvolution), carryover mitigation, sample preparation scheme optimization for surrogate and primary matrices, use of internal standard/immunocapture/deglycosylation, and optimization of the extraction and dilution procedure, as well as optimization of the liquid chromatography and mass spectrometry conditions. Once the method was fully optimized, a fit-for-purpose validation was conducted, including matrix parallelism, with a linear calibration range of 10 to 200 µg/mL. The development of this intact quantitative method using LC-HRMS provides a proof-of-concept template for challenging, but valuable new and exciting bioanalytical techniques.

Strategies for Glycoengineering Therapeutic Proteins

Almost all therapeutic proteins are glycosylated, with the carbohydrate component playing a long-established, substantial role in the safety and pharmacokinetic properties of this dominant category of drugs. In the past few years and moving forward, glycosylation is increasingly being implicated in the pharmacodynamics and therapeutic efficacy of therapeutic proteins. This article provides illustrative examples of drugs that have already been improved through glycoengineering including cytokines exemplified by erythropoietin (EPO), enzymes (ectonucleotide pyrophosphatase 1, ENPP1), and IgG antibodies (e.g., afucosylated Gazyva®, Poteligeo®, Fasenra™, and Uplizna®). In the future, the deliberate modification of therapeutic protein glycosylation will become more prevalent as glycoengineering strategies, including sophisticated computer-aided tools for "building in" glycans sites, acceptance of a broad range of production systems with various glycosylation capabilities, and supplementation methods for introducing non-natural metabolites into glycosylation pathways further develop and become more accessible.

Engineering an Enhanced EGFR Engager: Humanization of Cetuximab for Improved Developability

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase whose proliferative effects can contribute to the development of many types of solid tumors when overexpressed. For this reason, EGFR inhibitors such as cetuximab can play an important role in treating cancers such as colorectal cancer and head and neck cancer. Cetuximab is a chimeric monoclonal antibody containing mouse variable regions that bind to EGFR and prevent it from signaling. Although cetuximab has been used clinically since 2004 to successfully control solid tumors, advances in protein engineering have created the opportunity to address some of its shortcomings. In particular, the presence of mouse sequences could contribute to immunogenicity in the form of anti-cetuximab antibodies, and an occupied glycosylation site in FR3 can contribute to hypersensitivity reactions and product heterogeneity. Using simple framework graft or sequence-/structure-guided approaches, cetuximab was humanized onto 11 new frameworks. In addition to increasing humanness and removing the VH glycosylation site, dynamic light scattering revealed increases in stability, and bio-layer interferometry confirmed minimal changes in binding affinity, with patterns emerging across the humanization method. This work demonstrates the potential to improve the biophysical and clinical properties of first-generation protein therapeutics and highlights the advantages of computationally guided engineering.

Use of PASEF for Accelerated Protein Sequence Confirmation and De Novo Sequencing with High Data Quality

Biopharmaceutical sequences can be well confirmed by multiple protease digests-e.g., trypsin, elastase, and chymotrypsin-followed by LC-MS/MS data analysis. High quality data can be used for de novo sequencing as well. PASEF (Parallel Accumulation and Serial Fragmentation) on the timsTOF instrument has been used to accelerate proteome and protein sequence studies and increase sequence coverage concomitantly.Here we describe the protein chemical and LC-MS methods in detail to generate high quality samples for sequence characterization from only 3 digests. We applied PASEF to generate exhaustive protein sequence coverage maps by combination of results from the three enzyme digests using a short LC gradient. The data quality obtained was high and adequate for determining antibody sequences de novo.Nivolumab and dulaglutide were digested by 3 enzymes individually. For nivolumab, 94/94/90% sequence coverage and 86/84/85% fragment coverage were obtained from the individual digest analysis with trypsin/chymotrypsin/elastase, respectively. For dulaglutide, 96/100/90% sequence coverage and 92/90/83% fragment coverage were obtained. The merged peptide map from the 3 digests for nivolumab resulted in ∼550 peptides; enough to safely confirm the full sequences and to determine the nivolumab sequence de novo.

Capillary Isoelectric Focusing: Mass Spectrometry Method for the Separation and Online Characterization of Monoclonal Antibody Charge Variants at Intact and Subunit Levels

Monoclonal antibodies (mAbs) are one of the most widely used types of protein therapeutics. Charge variants are important quality attributes for evaluating developability, activity, and safety for mAb therapeutics. Here, we report a novel online capillary isoelectric focusing-mass spectrometry (CIEF-MS) method for mAb charge variant analysis using an electrokinetically pumped sheath-flow nanospray ion source on a time-of-flight (TOF) MS with a pressure-assisted chemical mobilization. Key factors that enable online CIEF-MS include effective capillary electrophoresis-MS (CE-MS) interface with enhanced sensitivity, utilization of MS-friendly electrolytes, beneficial effects of glycerol that reduces non-CIEF electrophoretic mobility and limits band broadening, appropriate ampholyte type and concentration selection for balanced separation resolution and MS detection sensitivity, optimized sheath liquid composition to realize high-resolution CIEF separation and effective MS electrospray ionization, as well as judiciously selected CIEF running parameters. The fundamental premise of CIEF has been verified by the linear correlation between isoelectric point (pI) values and migration time using a mixture of pI markers. By achieving high separation resolutions that are similar as those obtained from imaged CIEF (iCIEF), this method successfully provides highly sensitive MS identification for intact mAb charge variants. Furthermore, a middle-up sample treatment workflow can be adopted to provide in-depth charge variant analysis at subunit level for mAbs with complex charge heterogeneity. The mAb subunit CIEF-MS reveals the source of charge variant with enhanced resolution on both CIEF separation and MS spectra. This novel CIEF-MS method is a valuable tool with distinct advantage for objective and accurate assessment of charge heterogeneity of protein therapeutics.

Unambiguous identification of α-Gal epitopes in intact monoclonal antibodies by NMR spectroscopy

The α-Gal epitope consisting of the terminal trisaccharide Galα1,3Galβ1,4GlcNAc exposed on cell or protein surfaces can cause severe immune reactions, such as hypersensitivity reactions, in humans. This epitope is also called the xenotransplantation epitope because it is one of the main reasons for the rejection of non-human organ transplants by the human innate immune response. Recombinant therapeutic proteins expressed in murine cell lines may contain α-Gal epitopes, and therefore their absence or presence needs to be tightly monitored to minimize any undesired adverse effects. The analytical identification of α-Gal epitopes in glycoproteins using the common standard techniques based on liquid chromatography and mass spectrometry is challenging, mainly due to the isobaricity of hexose stereoisomers. Here, we present a straightforward NMR approach to detect the presence of α-Gal in biotherapeutics based on a quick screen with sensitive ¹H-¹H TOCSY spectra followed by a confirmation using ¹H-¹³C HSQC spectra.Abbreviations: α-Gal: α1,3-linked galactose; AGC: automatic gain control; CHO: Chinese hamster ovary; CE: capillary electrophoreses coupled to mass spectrometry; COSY: correlation spectroscopy; DSS: 2,2-dimethyl-2-silapentane-5-sulfonate; DTT: dithiothreitol; GlcNAc: N-acetyl glusomamine; HCD: higher-energy collisional dissociation; HMBC: heteronuclear multiple-bond correlation; HPLC: high-performance liquid chromatography; HSQC: heteronuclear single-quantum corre; LacNAc: N-acetyl lactosamine; mAb: monoclonal antibody; MS: mass spectrometry; NMR: nuclear magnetic resonance; NOESY: 2D) nuclear Overhauser spectroscopy; PEG: polyethylenglycol; pH*: observed pH meter reading without correction for isotope effects; PTM: post-translational modification; TCEP: tris(2-carboxyethyl) phosphine hydrochloride; TOCSY: total correlation spectroscopy; xCGE-LIF: multiplex capillary gel electrophoresis with laser-induced fluorescence detection.

Kinetics study of the natural split Npu DnaE intein in the generation of bispecific IgG antibodies

Rapid and efficient bispecific antibody (BsAb) production for industrial applications is still facing many challenges. We reported a technology platform for generating bispecific IgG antibodies, "Bispecific Antibody by Protein Trans-splicing (BAPTS)." While the "BAPTS" method has shown potential in high-throughput screening of BsAbs, further understanding and optimizing the methodology is desirable. A large number of BsAbs were selected to illustrate the conversion efficiency and kinetics parameters. The temperature of reaction makes no significant influence in conversion efficiency, which can reach more than 70% within 2 h, and CD3 × HER2 BsAb can reach 90%. By fitting trans-splicing reaction to single-component exponential decay curves, the apparent first-order rate constants at a series of temperatures were determined. The rate constant ranges from 0.02 to 0.11 min^-1 at 37 °C, which is a high rate reported for the protein trans-splicing reaction (PTS). The reaction process is activated rapidly with activation energy of 8.9 kcal·mol^-1 (CD3 × HER2) and 5.2 kcal·mol^-1 (CD3 × EGFR). The BsAbs generated by "BAPTS" technology not only had the similar post-translation modifications to the parental antibodies, but also demonstrated excellent in vitro and in vivo bioactivity. The kinetics parameters and activation energy of the reaction illustrate feasible for high-throughput screening and industrial applications using the "BAPTS" approach. KEY POINTS: • The trans-splicing reaction of Npu DnaE intein in "BAPTS" platform is a rapid process with low reaction activation and high rate. • The BsAb generated by "BAPTS" remained effective in tumor cell killing. • The kinetics parameters and activation energy of the reaction illustrate feasible for high-throughput screening and industrial applications using the "BAPTS" approach.

Epigenetic Priming of Bladder Cancer Cells With Decitabine Increases Cytotoxicity of Human EGFR and CD44v6 CAR Engineered T-Cells

Background

Treatment of B-cell malignancies with CD19-directed chimeric antigen receptor (CAR) T-cells marked a new era in immunotherapy, which yet has to be successfully adopted to solid cancers. Epigenetic inhibitors of DNA methyltransferases (DNMTi) and histone deacetylases (HDACi) can induce broad changes in gene expression of malignant cells, thus making these inhibitors interesting combination partners for immunotherapeutic approaches.

Methods

Urothelial carcinoma cell lines (UCC) and benign uroepithelial HBLAK cells pretreated with the DNMTi decitabine or the HDACi romidepsin were co-incubated with CAR T-cells directed against EGFR or CD44v6, and subsequent cytotoxicity assays were performed. Effects on T-cell cytotoxicity and surface antigen expression on UCC were determined by flow cytometry. We also performed next-generation mRNA sequencing of inhibitor-treated UCC and siRNA-mediated knockdown of potential regulators of CAR T-cell killing.

Results

Exposure to decitabine but not romidepsin enhanced CAR T-cell cytotoxicity towards all UCC lines, but not towards the benign HBLAK cells. Increased killing could neither be attributed to enhanced target antigen expression (EGFR and CD44v6) nor fully explained by changes in the T-cell ligands PD-L1, PD-L2, ICAM-1, or CD95. Instead, gene expression analysis suggested that regulators of cell survival and apoptosis were differentially induced by the treatment. Decitabine altered the balance between survival and apoptosis factors towards an apoptosis-sensitive state associated with increased CAR T-cell killing, while romidepsin, at least partially, tilted this balance in the opposite direction. Knockdown experiments with siRNA in UCC confirmed BID and BCL2L1/BCLX as two key factors for the altered susceptibility of the UCC.

Conclusion

Our data suggest that the combination of decitabine with CAR T-cell therapy is an attractive novel therapeutic approach to enhance tumor-specific killing of bladder cancer. Since BID and BCL2L1 are essential determinants for the susceptibility of a wide variety of malignant cells, their targeting might be additionally suitable for combination with immunotherapies, e.g., CAR T-cells or checkpoint inhibitors in other malignancies.

Rapid Analysis of Biotherapeutics Using Protein A Chromatography Coupled to Orbitrap Mass Spectrometry

Monoclonal antibodies (mAbs) and related products undergo a wide range of modifications, many of which can often be directly associated to culture conditions during upstream processing. Ideally, such conditions should be monitored and fine-tuned based on real-time or close to real-time information obtained by the assessment of the product quality attribute (PQA) profile of the biopharmaceutical produced, which is the fundamental idea of process analytical technology. Therefore, methods that are simple, quick and robust, but sufficiently powerful, to allow for the generation of a comprehensive picture of the PQA profile of the protein of interest are required. A major obstacle for the analysis of proteins directly from cultures is the presence of impurities such as cell debris, host cell DNA, proteins and small-molecule compounds, which usually requires a series of capture and polishing steps using affinity and ion-exchange chromatography before characterization can be attempted. In the current study, we demonstrate direct coupling of protein A affinity chromatography with native mass spectrometry (ProA-MS) for development of a robust method that can be used to generate information on the PQA profile of mAbs and related products in as little as 5 min. The developed method was applied to several samples ranging in complexity and stability, such as simple and more complex monoclonal antibodies, as well as cysteine-conjugated antibody–drug conjugate mimics. Moreover, the method demonstrated suitability for the analysis of protein amounts of <1 μg, which suggests applicability during early-stage development activities.

EGFR-targeted prodrug activation using bioorthogonal alkene-azide click-and-release chemistry

Epidermal growth factor receptor (EGFR) is overexpressed in many cancers and therefore serves as an excellent target for prodrug activation. Functionalised trans-cyclooctenes (TCO) were conjugated to an EGFR antibody (cetuximab), providing a reagent for pre-targeting and localisation of the bioorthogonal reagent. The TCOs react with a 4-azidobenzyl carbamate doxorubicin prodrug via a [3 + 2]-cycloaddition and subsequent self-immolation leads to release of doxorubicin (click-and-release). In vitro cell-based assays demonstrated proof-of-concept, that cetuximab conjugated to highly strained TCO (AB-d-TCO) could bind to the EGFR in a melanoma cell line, and selectively activate the doxorubicin prodrug. In a non-EGFR expressing melanoma cell line, no significant prodrug activation was observed. In vivo experiments using this combination of AB-d-TCO and the azido-doxorubicin prodrug in a murine melanoma model revealed no significant anti-tumour activity or increased survival, suggesting there was insufficient prodrug activation and drug release at the tumour site.

Comparison of glycoprofiles of rituximab versions licensed for sale in India and an analytical approach for quality assessment

Glycosylation affects clinical efficacy and safety; therefore, is a critical quality attribute of therapeutic monoclonal antibodies. Glycans are often labile and complex in patterns, giving rise to macro- and micro-heterogeneity. Recombinant production, diverse geographical locations, associated transportation and storage conditions further compound the problem. Two-way studies comparing glycoprofile of the originator and its given biosimilar are aplenty. However, the extent of analytical variation and similarity in glycoprofile across all approved versions of a drug is hardly explored. Using UHPLC and mass spectrometry, we compared the glycoprofiles of eight rituximab drug samples licensed for sale in India. While the types of glycans were found identical, the abundance of some glycans varied significantly within the tested population. The quality range of glycosylation parameters of the tested sample population differed significantly from the previously established values for US/EU licensed rituximab. As the mean abundance of the 90% of identified glycans falls within ±3SD, the extent of mutual variations amongst tested lots is less significant compared to the extreme deviation from previously established QR limits. Thus, we propose this approach as an orthogonal method to capture glycan variations in licensed versions of mAbs for quality surveillance and in cases where originator samples' are limiting. SIGNIFICANCE: As fluctuation in glycosylation may be of clinical significance, we identify that a one-to-one comparison with originator alone is insufficient in sensing the extent of variations in glycosylation parameters in licensed biosimilars of a given therapeutic mAb. Here we propose that future biosimilarity analysis may include an orthogonal approach of generating an additional combined QR range representing variations across the originator and its biosimilars. The glycosylation profiles of eight rituximab drug samples of different make obtained from the point of sale in India were found identical amongst the tested rituximab versions. However, the QR limits corresponding to important glycosylation parameters differed significantly across all tested samples from the previously established QR limits of US- and EU-licensed rituximab in statistical terms. Such an approach may be useful in defining the true range of glycan variations in licensed versions of therapeutic mAbs.

Multi-attribute method based characterization of antibody drug conjugates (ADC) at the intact and subunit levels

Antibody-drug conjugates (ADCs) represent an important class of new biopharmaceutical modalities. ADCs are highly complex and heterogeneous molecules, potentially containing numerous product-related structures, that can contribute to the quality, efficacy and safety of the product. To keep up with product life cycle related changes, wide-range and targeted characterization of product quality attributes (PQA) are of high demand. Multi-attribute methods (MAM) can screen numerous PQAs in a parallel fashion including product properties as well as product and process-related impurities. MAM is usually based on a bottom-up approach relying on the enzymatic digestion of the protein into peptides prior to mass spectrometry (MS). However, this processing workflow can result in considerable information loss, such as the drug distribution profile of an antibody-drug conjugate. Therefore, complementary MAM approaches, based on subunit and intact mass analyses, are necessary approaches offering the advantage of product identity confirmation, quantification of the different conjugated species and monitoring the drug-to-antibody ratio at the same time. In this work we introduce a high throughput MS based attribute tracking method for ADC characterization at the intact and subunit levels by simultaneously monitoring multiple PQAs. The workflow includes sample preparation and MS instrument suitability testing for heterogeneous lysine-linked ADCs, software solutions for routine PQAs tracking, method repeatability and an easy data review fitting perfectly into high throughput analyses. As methionine oxidation is one of the modifications that should be closely monitored at any step of process development, an important application to oxidative stress evaluation using forced degradation demonstrated the applicability of the workflow.

Analytical comparability assessment on glycosylation of ziv-aflibercept and the biosimilar candidate

Ziv-aflibercept (aflibercept) is a recombinant fusion protein which combines the portions of human vascular endothelial growth factor receptors extracellular domains fused to the Fc portion of human IgG1. It is a highly sialylated glycoprotein with 5 N-glycosylation sites. In this study, a comprehensive strategy for comparability study of the complex glycosylation was developed between aflibercept and the biosimilar candidate including the investigations on N-glycosylation sites, site occupancy, site-specific glycoforms, released glycans and sialic acids. The results indicated that same N-glycosylation sites were identified, site occupancy were 100% except N₆₈ site, site-specific glycoforms and released glycans showed similar glycan species, contents of NANA were at a same level for two products. Minor differences were found between two products. The biosimilar candidate presented lower level of aglycosylation, lower level of glycans containing one terminal sialic acid, higher level of glycans containing two terminal sialic acids, higher level of G0F and Man5, lower level of G1F and G2F compared with aflibercept. However, further studies exhibited no differences were observed in the cell-based biological potency and Fc effector function. Moreover, the biosimilar candidate showed a similar pharmacokinetics curve and bioequivalence compared with aflibercept.

Optimization and method validation for the quantitative analysis of a monoclonal antibody and its related fab fragment in human plasma after intravitreal administration, using LC-MS/MS

As biologic based drugs become an increasingly important sector of the pharmaceutical industry, accurate and precision techniques for bioanalysis are required to support clinical trials and beyond. Ranibizumab, a fab therapeutic, is an FDA approved drug to treat wet age-related macular degeneration (AMD), as well as other eye related diseases. Ranibizumab's mAb counterpart, bevacizumab, is often also used off-label to treat wet AMD. Ranibizumab and bevacizumab target circulating VEGF-A in the eye, reducing unwanted angiogenesis. Since these drugs are designed for local intravitreal administration, concentration levels in human plasma are expected to be significantly lower compared to vitreous fluid concentrations, presenting bioanalytical challenges. However, this is important for assessment of drug toxicity. In this manuscript, we describe the development, optimization, and validation of an LC-MS/MS method designed for quantitative bioanalysis of ranibizumab and bevacizumab in human plasma following intravitreal administration. In order to fully develop this method, evaluations were conducted to optimize the conditions, including selection of the surrogate peptide by in-silico experiments, optimizations of the immunocapture, denaturation, reduction, alkylation, and digestion extraction steps, as well as optimization of the LC-MS/MS conditions, and evaluation of a dissociation step to determine if there was interference from VEGF or ADAs. Once the method was fully optimized, it was then validated, following the 2018 FDA guidance on bioanalytical method validations. This method is now available for use during clinical trials and precision medicine, for the quantitative evaluation of systemic exposure of ranibizumab or bevacizumab in human plasma after intravitreal administration, with a linear calibration range of 0.300-100 ng/mL.

Monitoring glycation levels of a bispecific monoclonal antibody at subunit level by ultrahigh-resolution MALDI FT-ICR mass spectrometry

Bispecific monoclonal antibodies (BsAbs) are engineered proteins with multiple functionalities and properties. The "bi-specificity" of these complex biopharmaceuticals is a key characteristic for the development of novel and more effective therapeutic strategies. The high structural complexity of BsAbs poses a challenge to the analytical methods needed for their characterization. Modifications of the BsAb structure, resulting from enzymatic and non-enzymatic processes, further complicate the analysis. An important example of the latter type of modification is glycation, which can occur in the manufacturing process, during storage in the formulation or in vivo after application of the drug. Glycation affects the structure, function, and stability of monoclonal antibodies, and consequently, a detailed analysis of glycation levels is required. Mass spectrometry (MS) plays a key role in the structural characterization of monoclonal antibodies and top-down, middle-up and middle-down MS approaches are increasingly used for the analysis of modifications. Here, we apply a novel middle-up strategy, based on IdeS digestion and matrix-assisted laser desorption ionization (MALDI) Fourier transform ion cyclotron resonance (FT-ICR) MS, to analyze all six different BsAb subunits in a single high-resolution mass spectrum, namely two light chains, two half fragment crystallizable regions and two Fd' regions, thus avoiding upfront chromatography. This method was used to monitor glycation changes during a 168 h forced-glycation experiment. In addition, hot spot glycation sites were localized using top-down and middle-down MALDI-in-source decay FT-ICR MS, which provided complementary information compared to standard bottom-up MS.

Analysis of Monoclonal Antibodies by Capillary Electrophoresis: Sample Preparation, Separation, and Detection

Therapeutic monoclonal antibodies (mAbs) are dominating the biopharmaceutical field due to the fact of their high specificity in the treatment of diverse diseases. Nevertheless, mAbs are very complex glycoproteins exhibiting several macro- and microheterogeneities that may affect their safety, quality, and efficacy. This complexity is very challenging for mAbs development, formulation, and quality control. To tackle the quality issue, a combination of multiple analytical approaches is necessary. In this perspective, capillary electrophoresis has gained considerable interest over the last decade due to the fact of its complementary features to chromatographic approaches. This review provides an overview of the strategies of mAbs and derivatives analysis by capillary electrophoresis hyphenated to ultraviolet, fluorescence, and mass spectrometry detection. The main sample preparation approaches used for mAb analytical characterization (i.e., intact, middle-up/down, and bottom-up) are detailed. The different electrophoretic modes used as well as integrated analysis approaches (sample preparation and separation) are critically discussed.

Multi-dimensional LC-MS: the next generation characterization of antibody-based therapeutics by unified online bottom-up, middle-up and intact approaches

This review presents an overview of current analytical trends in antibody characterization by multidimensional LC-MS approaches.

Mass Spectrometry-Based Methods for Immunoglobulin G N-Glycosylation Analysis

Mass spectrometry and its hyphenated techniques enabled by the improvements in liquid chromatography, capillary electrophoresis, novel ionization, and fragmentation modes are truly a cornerstone of robust and reliable protein glycosylation analysis. Boost in immunoglobulin G (IgG) glycan and glycopeptide profiling demands for both applied biomedical and research applications has brought many new advances in the field in terms of technical innovations, sample preparation, improved throughput, and confidence in glycan structural characterization. This chapter summarizes mass spectrometry basics, focusing on IgG and monoclonal antibody N-glycosylation analysis on several complexity levels. Different approaches, including antibody enrichment, glycan release, labeling, and glycopeptide preparation and purification, are covered and illustrated with recent breakthroughs and examples from the literature omitting excessive theoretical frameworks. Finally, selected highly popular methodologies in IgG glycoanalytics such as liquid chromatography-mass spectrometry and matrix-assisted laser desorption ionization are discussed more thoroughly yet in simple terms making this text a practical starting point either for the beginner in the field or an experienced clinician trying to make sense out of the IgG glycomic or glycoproteomic dataset.

Analysis of Monoclonal Antibody Glycopeptides by Capillary Electrophoresis-Mass Spectrometry Coupling (CE-MS)

Glycosylation is a crucial posttranslational modification (PTM) that might affect the safety and efficacy of monoclonal antibodies (mAbs). Capillary electrophoresis-mass spectrometry (CE-MS) enables the characterization of the primary structure of mAbs. A bottom-up proteomic workflow is designed to provide detailed information about the glycosylation. In this chapter, we describe the validated experimental protocol applied for the characterization and relative quantification of mAbs N-glycosylation at the glycopeptide level.

Scientific Best Practices for Primary Sequence Confirmation and Sequence Variant Analysis in the Development of Therapeutic Proteins

In this commentary, we will provide a high-level introduction into LC-MS product characterization methodologies deployed throughout biopharmaceutical development. The ICH guidelines for early and late phase filings is broad so that it is applicable to diverse biotherapeutic products in the clinic and industry pipelines. This commentary is meant to address areas of protein primary sequence confirmation and sequence variant analysis where ambiguity exists in industry on the specific scope of work that is needed to fulfill the general guidance that is given in sections Q5b and Q6b. This commentary highlights the discussion and outcomes of two recent workshops centering on the application of LC-MS to primary structure confirmation and sequence variant analysis (SVA) that were held at the 2018 and 2019 CASSS Practical Applications of Mass Spectrometry in the Biotechnology Industry Symposia in San Francisco, CA and Chicago, IL, respectively. Recommendations from the conferences fall into two distinct but related areas; 1) consolidation of opinions amongst industry stakeholders on the specific definitions of peptide mapping and peptide sequencing for primary structure confirmation and the technologies used for both, as they relate to regulatory expectations and submissions and 2) development of fit-for-purpose strategy to define appropriate assay controls in SVA experiments.

Interlaboratory Study for Characterizing Monoclonal Antibodies by Top-Down and Middle-Down Mass Spectrometry

The Consortium for Top-Down Proteomics (www.topdownproteomics.org) launched the present study to assess the current state of top-down mass spectrometry (TD MS) and middle-down mass spectrometry (MD MS) for characterizing monoclonal antibody (mAb) primary structures, including their modifications. To meet the needs of the rapidly growing therapeutic antibody market, it is important to develop analytical strategies to characterize the heterogeneity of a therapeutic product's primary structure accurately and reproducibly. The major objective of the present study is to determine whether current TD/MD MS technologies and protocols can add value to the more commonly employed bottom-up (BU) approaches with regard to confirming protein integrity, sequencing variable domains, avoiding artifacts, and revealing modifications and their locations. We also aim to gather information on the common TD/MD MS methods and practices in the field. A panel of three mAbs was selected and centrally provided to 20 laboratories worldwide for the analysis: Sigma mAb standard (SiLuLite), NIST mAb standard, and the therapeutic mAb Herceptin (trastuzumab). Various MS instrument platforms and ion dissociation techniques were employed. The present study confirms that TD/MD MS tools are available in laboratories worldwide and provide complementary information to the BU approach that can be crucial for comprehensive mAb characterization. The current limitations, as well as possible solutions to overcome them, are also outlined. A primary limitation revealed by the results of the present study is that the expert knowledge in both experiment and data analysis is indispensable to practice TD/MD MS.

Top-Down Characterization of an Intact Monoclonal Antibody Using Activated Ion Electron Transfer Dissociation

Monoclonal antibodies (mAbs) are important therapeutic glycoproteins, but their large size and structural complexity make them difficult to rapidly characterize. Top-down mass spectrometry (MS) has the potential to overcome challenges of other common approaches by minimizing sample preparation and preserving endogenous modifications. However, comprehensive mAb characterization requires generation of many, well-resolved fragments and remains challenging. While ETD retains modifications and cleaves disulfide bonds-making it attractive for mAb characterization-it can be less effective for precursors having high m/z values. Activated ion electron transfer dissociation (AI-ETD) uses concurrent infrared photoactivation to promote product ion generation and has proven effective in increasing sequence coverage of intact proteins. Here, we present the first application of AI-ETD to mAb sequencing. For the standard NIST mAb, we observe a high degree of complementarity between fragments generated using standard ETD with a short reaction time and AI-ETD with a long reaction time. Most importantly, AI-ETD reveals disulfide-bound regions that have been intractable, thus far, for sequencing with top-down MS. We conclude AI-ETD has the potential to rapidly and comprehensively analyze intact mAbs.

Application of Native Ion Exchange Mass Spectrometry to Intact and Subunit Analysis of Site-Specific Antibody-Drug Conjugates Produced by AJICAP First Generation Technology

Antibody-drug conjugates (ADCs) are at the forefront of the next generation of oncology biopharmaceuticals. Conventional ADCs involve stochastic conjugation of the antibody to a cytotoxic drug, creating a highly heterogeneous product. The resulting stochastic distribution often leads to a narrow therapeutic index and makes it difficult to analyze the composition of heterogeneous ADCs. With the goal of overcoming these issues, we developed a site-specific conjugation technology, named AJICAP, for production of low heterogeneity ADCs. For analysis of these site-specific ADCs, we report herein strong cation exchange chromatography coupled with UV and mass spectrometry detection (SCX-UV-MS). Retention time reproducibility after SCX column equilibration enabled monitoring of important changes in product quality. SCX-UV-MS performed with MS-compatible mobile phases was conducted for intact native ADC analysis, allowing drug-antibody ratio characterization and charge variant characterization in single analysis. Furthermore, subunit analysis of the site-specific ADCs by native SCX-UV-MS confirmed the Fc site selectivity of ADCs generated by AJICAP conjugation.

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.

Comparative Elucidation of Cetuximab Heterogeneity on the Intact Protein Level by Cation Exchange Chromatography and Capillary Electrophoresis Coupled to Mass Spectrometry

Charge sensitive separation methods such as ion exchange chromatography (CEX) and capillary electrophoresis (CE) have recently been coupled to mass spectrometry to facilitate high resolution profiling of proteoforms present within the charge variant profile of complex biopharmaceuticals. Here we apply pH gradient cation exchange chromatography and microfluidic capillary electrophoresis using the ZipChip platform for comparative characterization of the monoclonal antibody Cetuximab. Cetuximab harbors four glycans per molecule, two on each heavy chain, of which the Fab glycans have been reported to be complex and multiply sialylated. The presence of these extra glycosylation sites in the variable region of the molecule causes significant charge variant and glycan heterogeneity, which makes comprehensive analysis on the intact protein level challenging. Both pH gradient CEX-MS and CE-MS were found to be powerful for the separation of Cetuximab charge variants with eight major peaks being baseline resolved using both separation platforms. Informative native-like mass spectra were collected for each charge variant peak using both platforms that facilitated deconvolution and further analysis. The total proteoform coverage was exceptionally high with >100 isoforms identified and relatively quantified with CEX-MS, in case of CE-MS the proteoform coverage was >200. A deep insight into the heterogeneity of Cetuximab was unveiled, the high level of sensitivity achievable enables the implementation of the presented technologies even at early stages of the biopharmaceutical development platform, such as in developability assessment, process development and also for monitoring process consistency.

Non-invasive targeted iontophoretic delivery of cetuximab to skin

Background: Cetuximab (CTX) is a glycosylated anti-EGFR monoclonal antibody of great interest in the treatment of non-melanoma skin cancers. Its intravenous administration is associated with severe side effects. This is the first report on the noninvasive iontophoretic-targeted topical delivery of CTX to skin.Methods: Iontophoretic transport of CTX (0.5 mA/cm²) was studied as a function of formulation pH (4, 5.5 and 7) and duration of current application (2, 4 and 8 h). CTX cutaneous biodistribution was determined; electrotransport mechanisms and penetration pathways were investigated.Results: Electrophoretic mobility measurements of CTX isoforms and co-iontophoresis of acetaminophen at each pH demonstrated that CTX electrotransport was due to electroosmosis: despite an ~8-fold reduction in charge, CTX skin deposition was greater at pH 7 than pH 4 (8.974 ± 1.952 and 0.482 ± 0.165 μg/mm³) - consistent with the increased electroosmotic flow at pH 7. Iontophoresis of an Alex488-CTX conjugate showed that skin penetration occurred by the intercellular and follicular routes. Therapeutic concentrations of CTX in the viable epidermis, upper dermis and lower dermis were achieved following iontophoresis for 2, 4 and 8 h, respectively.Conclusion: The results demonstrate the topical delivery of a 152 kDa monoclonal antibody into skin in a targeted, controlled and entirely noninvasive manner.

Versatile Bispidine-Based Bifunctional Chelators for 64 CuII -Labelling of Biomolecules

Bifunctional chelators as parts of modular metal-based radiopharmaceuticals are responsible for stable complexation of the radiometal ion and for covalent linkage between the complex and the targeting vector. To avoid loss of complex stability, the bioconjugation strategy should not interfere with the radiometal chelation by occupying coordinating groups. The C9 position of the very stable CuII chelator 3,7-diazabicyclo[3.3.1]nonane (bispidine) is virtually predestined to introduce functional groups for facile bioconjugation as this functionalisation does not disturb the metal binding centre. We describe the preparation and characterisation of a set of novel bispidine derivatives equipped with suitable functional groups for diverse bioconjugation reactions, including common amine coupling strategies (bispidine-isothiocyanate) and the Cu-free strain-promoted alkyne-azide cycloaddition. We demonstrate their functionality and versatility in an exemplary way by conjugation to an antibody-based biomolecule and validate the obtained conjugate in vitro and in vivo.

Alpha-Gal and Cross-Reactive Carbohydrate Determinants in the N-Glycans of Salivary Glands in the Lone Star Tick, Amblyomma americanum

Ticks are important ectoparasites and vectors of numerous human and animal pathogens. Ticks secrete saliva that contains various bioactive materials to evade the host defense system, and often facilitates the pathogen transmission. In addition, the Lone star tick saliva is thought to be the sensitizer in red meat allergy that is characterized by an allergic reaction to glycan moieties carrying terminal galactose-alpha-1,3-galactose (aGal). To assess N-glycome of Amblyomma americanum, we examined the N-glycan structures in male and female salivary glands at three different feeding stages and in carcasses of partially fed lone star ticks. We also surveyed the genes involved in the N-glycosylation in the tick species. The aGal epitopes and cross-reactive carbohydrate determinants (CCD) increases over time after the onset of blood feeding in both male and female A. americanum. These CCDs include xylosylation of the core mannose, 1,3-mono and 1,3- and 1,6-difucosylations of the basal GlcNac and mono- or diantennary aGal. Combinations of both xylosylation and aGal and fucosylation and aGal were also found on the N-glycan structures. While the enzymes required for the early steps of the N-glycosylation pathway are quite conserved, the enzymes involved in the later stages of N-glycan maturation in the Golgi apparatus are highly diverged from those of insects. Most of all, we propose that the aGal serves as a molecular mimicry of bioactive proteins during tick feedings on mammalian hosts, while it contributes as a sensitizer of allergy in atypical host human.

Anticorps monoclonaux biosimilaires

La mise sur le marché de biosimilaires requiert une démonstration stricte de la similarité avec l’anticorps de référence, au travers d’études précliniques et cliniques. Cet article synthétise l’ensemble des analyses physicochimiques et fonctionnelles mises en œuvre in vitro, préalables à la réalisation d’études cliniques. Pour chaque caractéristique critique de l’anticorps, nous avons détaillé les techniques analytiques communément employées, leur principe de fonctionnement, ainsi que le type d’informations que ces techniques permettent d’obtenir.

Proteoform-Resolved FcɤRIIIa Binding Assay for Fab Glycosylated Monoclonal Antibodies Achieved by Affinity Chromatography Mass Spectrometry of Fc Moieties

Fcɤ receptors (FcɤR) mediate key functions in immunological responses. For instance, FcɤRIIIa is involved in antibody-dependent cell-mediated cytotoxicity (ADCC). FcɤRIIIa interacts with the fragment crystallizable (Fc) of immunoglobulin G (IgG). This interaction is known to be highly dependent on IgG Fc glycosylation. Thus, the impact of glycosylation features on this interaction has been investigated in several studies by numerous analytical and biochemical techniques. FcɤRIIIa affinity chromatography (AC) hyphenated to mass spectrometry (MS) is a powerful tool to address co-occurring Fc glycosylation heterogeneity of monoclonal antibodies (mAbs). However, MS analysis of mAbs at the intact level may provide limited proteoform resolution, for example, when additional heterogeneity is present, such as antigen-binding fragment (Fab) glycosylation. Therefore, we investigated middle-up approaches to remove the Fab and performed AC-MS on the IgG Fc to evaluate its utility for FcɤRIIIa affinity assessment compared to intact IgG analysis. We found the protease Kgp to be particularly suitable for a middle-up FcɤRIIIa AC-MS workflow as demonstrated for the Fab glycosylated cetuximab. The complexity of the mass spectra of Kgp digested cetuximab was significantly reduced compared to the intact level while affinity was fully retained. This enabled a reliable assignment and relative quantitation of Fc glycoforms in FcɤRIIIa AC-MS. In conclusion, our workflow allows a functional separation of differentially glycosylated IgG Fc. Consequently, applicability of FcɤRIIIa AC-MS is extended to Fab glycosylated IgG, i.e., cetuximab, by significantly reducing ambiguities in glycoform assignment vs. intact analysis.