Heterogeneity of Monoclonal Antibodies

A comparison of different intensified upstream processes highlighting the advantage of WuXi Biologics' Ultra-high Productivity platform (WuXiUPTM) in improved product quality and purification yield

WuXiUPTM, WuXi Biologics' Ultra-high Productivity platform, is an intensified and integrated continuous bioprocess platform developed for production of various biologics including monoclonal antibodies, fusion proteins, and bispecific antibodies. This process technology platform has manifested its remarkable capability in boosting the volumetric productivity of various biologics and has been implemented for large-scale clinical material productions. In this paper, case studies of the production of different pharmaceutical proteins using two high-producing and intensified culture modes of WuXiUPTM and the concentrated fed-batch (CFB), as well as the traditional fed-batch (TFB) are discussed from the perspectives of cell growth, productivity, and protein quality. Both WuXiUPTM and CFB outperformed TFB regarding volumetric productivity. Additionally, distinctive advantages in product quality profiles in the WuXiUPTM process, such as reduced acidic charge variants and fragmentation, are revealed. Therefore, a simplified downstream purification process with only two chromatographic steps can be developed to deliver the target product at a satisfactory purity and an extremely-high yield.

Characterization of the Charge Heterogeneity of a Monoclonal Antibody That Binds to Both Cation Exchange and Anion Exchange Columns under the Same Binding Conditions

Therapeutic antibodies play an important role in the public healthcare system to treat patients with a variety of diseases. Protein characterization using an array of analytical tools provides in-depth information for drug quality, safety, efficacy, and the further understanding of the molecule. A therapeutic antibody candidate MAB1 exhibits unique binding properties to both cation and anion exchange columns at neutral pH. This uniqueness disrupts standard purification processes and necessitates adjustments in manufacturing. This study identifies that the charge heterogeneity of MAB1 is primarily due to the N-terminal cyclization of glutamine to pyroglutamine and, to a lesser extent, succinimide intermediate, deamidation, and C-terminal lysine. Using three approaches, i.e., deferential chemical labeling, H/D exchange, and molecular modeling, the binding to anion exchange resins is attributed to negatively charged patches on the antibody's surface, involving specific carboxylic acid residues. The methodologies shown here can be extended to study protein binding orientation in column chromatography.

Development of an organic polymer monolith column for the nano liquid chromatography fast analysis of monoclonal antibody in infusion bags prepared in a hospital pharmacy

Poly(butyl methacrylate-co-ethylene dimethacrylate) monolith was in situ prepared in a liquid chromatography capillary column with a 75 μm internal diameter. This monolith offered high permeability (5.3 ± 10-14 m2) and good peak capacity (140 for a 15 cm column length at 300 nl/min with a 20 min gradient time). This is exemplified by its separation ability in reversed mode for subunit analysis of monoclonal antibodies after IdeS digestion (middle-up analysis). The potential of this column was also illustrated for the fast analytical control of therapeutic monoclonal antibodies in standardized infusion bags prepared in advance in a pharmacy department. Linearity analysis revealed the column's capability for accurate quantification analysis of the different dose bandings (in mg) of monoclonal antibodies in <2 min. In addition, lifetime analysis data indicated that the column can be highly reproducible and has a long lifetime with stable and low back pressure. The variations observed on the peak shape and area between unstressed (intact) and stressed monoclonal antibodies indicated that our nano liquid chromatographic method was stability indicating. In addition, using a gradient elution mode, the presence of minor components in the infusion bags was visualized.

Isolation and characterization of rabies monoclonal antibody charge variants

Current postexposure prophylaxis of rabies includes vaccines, human rabies immunoglobulin (RIG), equine RIG, and recombinant monoclonal antibodies (mAb). In the manufacturing of rabies recombinant mAb, charge variants are the most common source of heterogeneity. Charge variants of rabies mAb were isolated by salt gradient cation exchange chromatography (CEX) to separate acidic and basic and main charge variants. Separated variants were further extensively characterized using orthogonal analytical techniques, which include secondary and tertiary structure determination by far and near ultraviolet circular dichroism spectroscopy. Charge and size heterogeneity were evaluated using CEX, isoelectric focusing (IEF), capillary-IEF, size exclusion chromatography, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and western blotting. Antigen binding affinity was assessed by enzyme linked immuno-sorbent assay and rapid florescence foci inhibition test. Results from structural and physicochemical characterizations concluded that charge variants are formed due to posttranslational modification demonstrating that the charge heterogeneity, these charge variants did neither show any considerable physicochemical change nor affect its biological function. This study shows that charge variants are effective components of mAb and there is no need of deliberate removal, until biological functions of rabies mAb will get affected.

Liquid-phase separations coupled with ion mobility-mass spectrometry for next-generation biopharmaceutical analysis

INTRODUCTION

The pharmaceutical industry continues to expand its search for innovative biotherapeutics. The comprehensive characterization of such therapeutics requires many analytical techniques to fully evaluate critical quality attributes, making analysis a bottleneck in discovery and development timelines. While thorough characterization is crucial for ensuring the safety and efficacy of biotherapeutics, there is a need to further streamline analytical characterization and expedite the overall timeline from discovery to market.

AREAS COVERED

This review focuses on recent developments in liquid-phase separations coupled with ion mobility-mass spectrometry (IM-MS) for the development and characterization of biotherapeutics. We cover uses of IM-MS to improve the characterization of monoclonal antibodies, antibody-drug conjugates, host cell proteins, glycans, and nucleic acids. This discussion is based on an extensive literature search using Web of Science, Google Scholar, and SciFinder.

EXPERT OPINION

IM-MS has the potential to enhance the depth and efficiency of biotherapeutic characterization by providing additional insights into conformational changes, post-translational modifications, and impurity profiles. The rapid timescale of IM-MS positions it well to enhance the information content of existing assays through its facile integration with standard liquid-phase separation techniques that are commonly used for biopharmaceutical analysis.

Novel purification platform based on multimodal preparative scale separation of mAb fragments and aggregates

Monoclonal antibodies (mAbs) continue to dominate the biopharmaceutical industry. Certain mAbs are prone to fragmentation and clipping and in these cases, adequate removal of these species is critical during manufacturing. Fragments can be generated during fermentation, purification, storage, formulation, and administration. Their addition to the acidic charge-variant of the purified mAb has been reported to decrease stability and potency of the final product. However, contrary to mAb aggregation, manufacturers have not given much attention to removal of fragments and clipped species and as a result most conventional mAb platforms offer at best limited capabilities for their removal. In this study, we propose a novel purification platform that uses multimodal chromatography and achieves complete removal of a range of mAb fragments and clipped products (25-120 kDa). The utility of the platform has been successfully demonstrated for 2 IgG1s and 2 IgG4s. Further, adequate removal of the various host cell impurities such as host cell proteins (<10 ppm) and host cell DNA (<5 ppb) has been achieved. Finally, the platform was able to deliver adequate removal of high molecular weight impurities (<1 %) and a 30 % clearance of the acidic charge variant. The proposed single step has been shown to deliver what the polishing chromatography and intermediate purification chromatography steps deliver in a traditional mAb platform.

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.

Characterization of charge variants, including post-translational modifications and proteoforms, of bispecific antigen-binding protein by cation-exchange chromatography coupled to native mass spectrometry

Charge variant characterization of biologics is critical to ensure that product meets the required quality and regulatory requirements to ensure safety and efficacy of the biotherapeutic. Charge variants arise from post-translation modifications (PTMs) during upstream processing and due to enzymatic and non-enzymatic chemical reactions that occur during downstream processing and storage. Some of these modifications may impact therapeutic potency, efficacy, or immunogenicity of a biotherapeutic. The traditional workflow for characterizing charge variants that involves fraction enrichment is time-consuming and labor-intensive. This approach can be especially challenging if the product is manufactured at low concentrations (e.g., ≤2 mg/mL). Recent advances in pH-based elution for ion-exchange chromatography utilizing volatile buffers have enabled rapid native mass-spectrometry-based identification of PTMs and proteoforms associated with protein therapeutics. In this study, we develop a novel workflow to rapidly and unambiguously characterize modifications associated with a new class of biotherapeutics known as bispecific antigen-binding protein (BsABP), including low-level modifications. A cation-exchange separation was optimized using volatile buffers to provide online hyphenation for native mass spectrometry to profile modifications and proteoforms present at the native level of a biotherapeutic, such as deamidation, O-glycosylation, amino acid substitution, N-linked glycosylation and oxidation. Furthermore, a limited proteolysis method was developed to specifically inform about modifications in the different domains of the bispecific antibody. Using this approach, we could efficiently identify PTMs in unstressed, thermally and photo-stressed samples, and provide information about the impact of downstream purification in clearing out modified BsABP species. Furthermore, peptide mapping was performed to identify and confirm modifications at the amino acid residue level. The developed workflow is less time-consumable and reduces sample processing- and analysis-related artifacts compared to traditional approaches.

A novel method for continuous chromatographic separation of monoclonal antibody charge variants by combining displacement mode chromatography and step elution

Charge heterogeneity of monoclonal antibodies is considered a critical quality attribute and hence needs to be monitored and controlled by the manufacturer. Typically, this is accomplished via separation of charge variants on cation exchange chromatography (CEX) using a pH or conductivity based linear gradient elution. Although an effective approach, this is challenging particularly during continuous processing as creation of linear gradient during continuous processing adds to process complexity and can lead to deviations in product quality upon slightest changes in gradient formation. Moreover, the long length of elution gradient along with the required peak fractionation makes process integration difficult. In this study, we propose a novel approach for separation of charge variants during continuous CEX chromatography by utilizing a combination of displacement mode chromatography and salt-based step elution. It has been demonstrated that while the displacement mode of chromatography enables control of acidic variants ≤26% in the CEX eluate, salt-based step gradient elution manages basic charge variant ≤25% in the CEX eluate. The proposed approach has been successfully demonstrated using feed materials with varying compositions. On comparing the designed strategy with 2-column concurrent (CC) chromatography, the resin specific productivity increased by 95% and resin utilization increased by 183% with recovery of main species >99%. Further, in order to showcase the amenability of the designed CEX method in continuous operation, the method was examined in our in-house continuous mAb platform.

Small conformational changes in IgG1 detected as acidic charge variants by cation exchange chromatography

Fully characterizing the post-translational modifications present in charge variants of therapeutic monoclonal antibodies (mAbs), particularly acidic variants, is challenging and remains an open area of investigation. In this study, to test the possibility that chromatographically separated acidic fractions of therapeutic mAbs contain conformational variants, we undertook a mAb refolding approach using as a case study an IgG1 that contains many unidentified acidic peaks with few post-translational modifications, and examined whether different acidic peak fractions could be generated corresponding to these variants. The IgG1 drug substance was denatured by guanidine hydrochloride, without a reducing agent present, and gradually refolded by stepwise dialysis against arginine hydrochloride used as an aggregation suppressor. Each acidic chromatographic peak originally contained in the IgG1 drug substance was markedly increased by this stepwise refolding process, indicating that these acidic variants are conformational variants. However, no conformational changes were detected by small-angle X-ray scattering experiments for the whole IgG1, indicating that the conformational changes are minor. Chromatographic, thermal and fluorescence analyses suggested that the conformational changes are a localized denaturation effect centred around the aromatic amino acid regions. This study provides new insights into the characterization of acidic variants that are currently not fully understood.

Combination of On-Line and Off-Line Two-Dimensional Liquid Chromatography-Mass Spectrometry for Comprehensive Characterization of mAb Charge Variants and Precise Instructions for Rapid Process Development

Charge variants, as an important quality attribute of mAbs, must be comprehensively characterized and monitored during development. However, due to their complex structure, the characterization of charge variants is challenging, labor-intensive, and time-consuming when using traditional approaches. This work combines on-line and off-line 2D-LC-MS to comprehensively characterize mAb charge variants and quickly offer precise instructions for process development. Six charge variant peaks of mAb 1 were identified using the developed platform. Off-line 2D-LC-MS analysis at the peptide level showed that the acidic peak P1 and the basic peaks P4 and P5 were caused by the deamidation of asparagine, the oxidation of methionine, and incomplete C-terminal K loss, respectively. On-line 2D-LC-MS at the intact protein level was used to identify the root causes, and it was found that the acidic peak P2 and the basic peak P6 were due to the glutathionylation of cysteine and succinimidation of aspartic acid, respectively, which were not found in off-line 2D-LC-MS because of the loss occurring during pre-treatment. These results suggest that process development could focus on cell culture for adjustment of glutathionylation. In this paper, we propose the concept of precision process development based on on-line 2D-LC-MS, which could quickly offer useful data with only 0.6 mg mAb within 6 h for precise instructions for process development. Overall, the combination of on-line and off-line 2D-LC-MS can characterize mAb charge variants more comprehensively, precisely, and quickly than other approaches. This is a very effective platform with routine operations that provides precise instructions for process development within hours, and will help to accelerate the development of innovative therapeutics.

Strategies for overcoming protein and peptide instability in biodegradable drug delivery systems

The global pharmaceutical market has recently shifted its focus from small molecule drugs to peptide, protein, and nucleic acid drugs, which now comprise a majority of the top-selling pharmaceutical products on the market. Although these biologics often offer improved drug specificity, new mechanisms of action, and/or enhanced efficacy, they also present new challenges, including an increased potential for degradation and a need for frequent administration via more invasive administration routes, which can limit patient access, patient adherence, and ultimately the clinical impact of these drugs. Controlled-release systems have the potential to mitigate these challenges by offering superior control over in vivo drug levels, localizing these drugs to tissues of interest (e.g., tumors), and reducing administration frequency. Unfortunately, adapting controlled-release devices to release biologics has proven difficult due to the poor stability of biologics. In this review, we summarize the current state of controlled-release peptides and proteins, discuss existing techniques used to stabilize these drugs through encapsulation, storage, and in vivo release, and provide perspective on the most promising opportunities for the clinical translation of controlled-release peptides and proteins.

SPECT Imaging of Lysyl Oxidase-like 2 in a Model of Idiopathic Pulmonary Fibrosis

Noninvasive imaging of idiopathic pulmonary fibrosis (IPF) remains a challenge. The aim of this study was to develop an antibody-based radiotracer targeting Lysyl Oxidase-like 2 (LOXL2), an enzyme involved in the fibrogenesis process, for SPECT/CT imaging of pulmonary fibrosis. The bifunctional chelator DOTAGA-PEG₄-NH₂ was chemoenzymatically conjugated to the murine antibody AB0023 using microbial transglutaminase, resulting in a degree of labeling (number of chelators per antibody) of 2.3. Biolayer interferometry confirmed that the binding affinity of DOTAGA-AB0023 to LOXL2 was preserved with a dissociation constant of 2.45 ± 0.04 nM. DOTAGA-AB0023 was then labeled with ¹¹¹In and in vivo experiments were carried out in a mice model of progressive pulmonary fibrosis induced by intratracheal administration of bleomycin. [¹¹¹In]In-DOTAGA-AB0023 was injected in three groups of mice (control, fibrotic, and treated with nintedanib). SPECT/CT images were recorded over 4 days p.i. and an ex vivo biodistribution study was performed by gamma counting. A significant accumulation of the tracer in the lungs of the fibrotic mice was observed at D18 post-bleomycin. Interestingly, the tracer uptake was found selectively upregulated in fibrotic lesions observed on CT scans. Images of mice that received the antifibrotic drug nintedanib from D8 up to D18 showed a decrease in [¹¹¹In]In-DOTAGA-AB0023 lung uptake associated with a decrease in pulmonary fibrosis measured by CT scan. In conclusion, we report the first radioimmunotracer targeting the protein LOXL2 for nuclear imaging of IPF. The tracer showed promising results in a preclinical model of bleomycin-induced pulmonary fibrosis, with high lung uptake in fibrotic areas, and accounted for the antifibrotic activity of nintedanib.

Discovery and Control of Succinimide Formation and Accumulation at Aspartic Acid Residues in The Complementarity-Determining Region of a Therapeutic Monoclonal Antibody

PURPOSE

Succinimide formation and isomerization alter the chemical and physical properties of aspartic acid residues in a protein. Modification of aspartic acid residues within complementarity-determining regions (CDRs) of therapeutic monoclonal antibodies (mAbs) can be particularly detrimental to the efficacy of the molecule. The goal of this study was to characterize the site of succinimide accumulation in the CDR of a therapeutic mAb and understand its effects on potency. Furthermore, we aimed to mitigate succinimide accumulation through changes in formulation.

METHODS

Accumulation of succinimide was identified through intact and reduced LC-MS mass measurements. A low pH peptide mapping method was used for relative quantitation and localization of succinimide formation in the CDR. Statistical modeling was used to correlate levels of succinimide with basic variants and potency measurements.

RESULTS

Succinimide accumulation in Formulation A was accelerated when stored at elevated temperatures. A strong correlation between succinimide accumulation in the CDR, an increase in basic charge variants, and a decrease in potency was observed. Statistical modeling suggest that a combination of ion exchange chromatography and potency measurements can be used to predict succinimide levels in a given sample. Reformulation of the mAb to Formulation B mitigates succinimide accumulation even after extended storage at elevated temperatures.

CONCLUSION

Succinimide formation in the CDR of a therapeutic mAb can have a strong negative impact on potency of the molecule. We demonstrate that thorough characterization of the molecule by LC-MS, ion exchange chromatography, and potency measurements can facilitate changes in formulation that mitigate succinimide formation and the corresponding detrimental changes in potency.

Next generation multimodal chromatography resins via an iterative mapping approach: Chemical diversity, high-throughput screening, and chromatographic modelling

Multimodal chromatography resins are becoming a key tool in the purification of biomolecules. The main objective of this research was the establishment of an iterative framework for the rapid development of new multimodal resins to provide novel selectivity for the future purification challenges. A large chemically diverse virtual library of 100 multimodal Capto™ MMC ligand analogues was created, and a broad array of chemical descriptors were calculated for each ligand in silico. Principal component analysis (PCA) was used to map the chemical diversity and guide selection of ligands for synthesis and coupling to the Capto ImpRes agarose base matrix. Twelve new ligands were prepared in two groups: 'group one' consist of L00-L07 and 'group two' consist of L08-L12. These ligands are diverse in the influence of varied secondary interactions such as hydrophobic interactions, H-bonding, etc. Additional resin prototypes were also prepared to look at the chromatographic impact of ligand density variation. High-throughput plate-based studies were performed for parallel resin screening for batch-binding of six model proteins at different chromatographic binding pH and sodium chloride concentration conditions. Principal component analysis of the binding data provided a chromatographic diversity map leading to the identification of ligands with improved binding. Further, the new ligands have improved separation resolution between a monoclonal antibody (mAb1) and product related impurities, a Fab fragment and high molecular weight (HMW) aggregates, using linear salt gradient elutions. To quantify the importance of secondary interactions, analysis of the retention factor of mAb1 on the ligands at various isocratic conditions lead to estimations of (a) the total number of water molecules and counter salt ions released during adsorption, and (b) hydrophobic contact area (HCA). The iterative mapping approach of chemical and chromatography diversity maps described in the paper proves to be a promising method for identifying new chromatography ligands for biopharmaceutical purification challenges.

Consistency of Product Quality for SB5, an Adalimumab Biosimilar

BACKGROUND

Biologics, regardless of whether they are biosimilars or reference products, are inherently variable due to their size, complexity, and the manufacturing process involved to produce them. Since a drift or evolution of quality attributes of a biologic may impact its clinical safety or efficacy, it is critical for the manufacturer to carefully control the manufacturing process and monitor the quality attributes of a biologic.

OBJECTIVE

The aim of this study was to demonstrate that the quality profile of the SB5 drug product has been consistent over its production history from 2013 to 2022. SB5 is a biosimilar referencing adalimumab (Humira, trademark of AbbVie Biotechnology Ltd) and SB5 has been approved by 14 regulatory authorities including the European Commission in August 2017 (brand name Imraldi™) and the US Food and Drug Administration in July 2019 (brand name Hadlima™).

METHODS

A total of 93 SB5 drug product batches manufactured between 2013 and 2022 were analyzed for a series of release parameters to evaluate the consistency in their critical quality attributes including purity, charge variants, and functional activities (TNF-α binding activity and TNF-α neutralizing potency).

RESULTS

The purity, charge variants, and functional activities of all batches were consistent over time and within the stringent acceptance criteria defined by regulatory agencies to ensure the safety and efficacy of SB5.

CONCLUSION

The data presented in this study provide evidence that the quality of SB5 has remained consistent and tightly controlled even through process changes such as manufacturing site transfers and change in formulation.

Protein Stability After Administration: A Physiologic Consideration

Regulatory authorities and the scientific community have identified the need to monitor the in vivo stability of therapeutic proteins (TPs). Due to the unique physiologic conditions in patients, the stability of TPs after administration can deviate largely from their stability under drug product (DP) conditions. TPs can degrade at substantial rates once immersed in the in vivo milieu. Changes in protein stability upon administration to patients are critical as they can have implications on patient safety and clinical effectiveness of DPs. Physiologic conditions are challenging to simulate and require dedicated in vitro models for specific routes of administration. Advancements of in vitro models enable to simulate the exposure to physiologic conditions prior to resource demanding pre-clinical and clinical studies. This enables to evaluate the in vivo stability and thus may allow to improve the safety/efficacy profile of DPs. While in vitro-in vivo correlations are challenging, benchmarking DP candidates enables to identify liabilities and optimize molecules. The in vivo stability should be an integral part of holistic stability assessments during early development. Such assessments can accelerate development timelines and lead to more stable DPs for patients.

Preferential precipitation of acidic variants from monoclonal antibody pools

Microheterogeneity of monoclonal antibodies (mAbs) can impact their activity and stability. Formation of charge variants is considered as the most important source of the microheterogeneity. In particular, controlling the content of the acidic species is often of major importance for the production process and regulatory approval of therapeutic proteins. In this study, the preferential precipitation process was developed for reducing the content of acidic variants in mAb downstream pools. The process design was preceded by the determination of phase behavior of mAb variants in the presence of different precipitants. It was shown that the presence of polyethylene glycol (PEG) in protein solutions favored precipitation of acidic variants of mAbs. Precipitation yield was influenced by the variant composition in the mAb feed solutions, the concentration of the precipitant and the protein, and the ionic strength of the solutions. To improve yield, multistage precipitation was employed, where the precipitate was recycled to the precipitation process. The final product was a mixture of supernatants pooled together from the recycling steps. Such an approach can be potentially used either instead or in a combination with chromatography for adjusting the acidic variant content of mAbs, which can benefit in improvement in throughput and reduction in manufacturing costs.

Microchip electrophoresis separation coupled to mass spectrometry (MCE-MS) for the rapid monitoring of multiple quality attributes of monoclonal antibodies

Therapeutic monoclonal antibodies (mAbs) are highly heterogeneous as a result of posttranslational modifications (PTMs) during bioprocessing and storage. The modifications that impact mAb product quality are regarded as critical quality attributes and require monitoring. The conventional LC-mass spectrometer (MS) method used for product quality monitoring may require protein A purification prior to analysis. In this paper, we present a high-throughput microchip electrophoresis (<4 min) in-line with MS (MCE-MS) that enables baseline separation and characterization of Fc, Fd', and light chain (LC) domains of IdeS-treated mAb sample directly from bioreactor. The NISTmAb was used to optimize the MCE separation and to assess its capability of multiple attribute monitoring. The MCE-MS can uniquely separate and characterize deamidated species at domain level compared to LC-MS method. Two case studies were followed to demonstrate the method capability of monitoring product quality of mAb samples from stability studies or directly from bioreactors.

Developability assessment at early-stage discovery to enable development of antibody-derived therapeutics

Developability refers to the likelihood that an antibody candidate will become a manufacturable, safe and efficacious drug. Although the safety and efficacy of a drug candidate will be well considered by sponsors and regulatory agencies, developability in the narrow sense can be defined as the likelihood that an antibody candidate will go smoothly through the chemistry, manufacturing and control (CMC) process at a reasonable cost and within a reasonable timeline. Developability in this sense is the focus of this review. To lower the risk that an antibody candidate with poor developability will move to the CMC stage, the candidate's developability-related properties should be screened, assessed and optimized as early as possible. Assessment of developability at the early discovery stage should be performed in a rapid and high-throughput manner while consuming small amounts of testing materials. In addition to monoclonal antibodies, bispecific antibodies, multispecific antibodies and antibody-drug conjugates, as the derivatives of monoclonal antibodies, should also be assessed for developability. Moreover, we propose that the criterion of developability is relative: expected clinical indication, and the dosage and administration route of the antibody could affect this criterion. We also recommend a general screening process during the early discovery stage of antibody-derived therapeutics. With the advance of artificial intelligence-aided prediction of protein structures and features, computational tools can be used to predict, screen and optimize the developability of antibody candidates and greatly reduce the risk of moving a suboptimal candidate to the development stage.

Expression of mammalian proteins for diagnostics and therapeutics: a review

BACKGROUND

Antibodies have proven to be remarkably successful for biomedical applications. They play important roles in epidemiology and medicine from diagnostics of diseases to therapeutics, treating diseases from incessant chronic diseases such as rheumatology to pandemic outbreaks. With no end in sight for the demand for antibody products, optimizations and new techniques must be expanded to accommodate this.

METHODS AND RESULTS

This review discusses optimizations and techniques for antibody production through choice of discovery platforms, expression systems, cell culture mediums, and other strategies to increase expression yield. Each system has its own merits and demerits, and the strategy chosen is critical in addressing various biological aspects.

CONCLUSIONS

There is still insufficient evidence to validate the efficacy of some of these techniques, and further research is needed to consolidate these industrial production systems. There is no doubt that more strategies, systems, and pipelines will contribute to enhance biopharmaceutical production.

Enhancement of effector functions of anti-CD20 monoclonal antibody by increased afucosylation in CHO cell line through cell culture medium optimization

Background

Recombinant therapeutic anti-CD20 monoclonal antibody (mAb) is used for the treatment of non-Hodgkin’s lymphoma, a common B cell lymphoma constituting 80% of all lymphomas. Anti-CD20 mAb contains an Fc-linked biantennary glycan. Although, anti-CD20 monoclonal antibodies are being increasingly used for immunotherapy, their efficacy is limited in a section of patients with drug resistance to immunotherapy. There is a need to improve the efficacy by increasing the effector functions, such as the antibody-dependent cellular cytotoxicity (ADCC) activity of anti-CD20 monoclonal antibodies.

Results

We developed a simple and cost-effective approach to enhance ADCC effector activity in an in-house developed clone of anti-CD20 monoclonal antibody by increasing afucosylation in a new clone of Chinese Hamster Ovary (CHO) cells using 8X uridine, manganese, and galactose (UMG) to modulate the osmolality of the medium. The purified anti-CD20 monoclonal antibody from 8X UMG-containing medium showed a 2-fold increase in afucose content and 203% ADCC activity in comparison to control antibody.

Conclusions

Our study reports enhanced ADCC activity by modulating afucosylation using osmolality by altering simple feed additives in the culture medium.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-022-00421-5.

Tools shaping drug discovery and development

Spectroscopic, scattering, and imaging methods play an important role in advancing the study of pharmaceutical and biopharmaceutical therapies. The tools more familiar to scientists within industry and beyond, such as nuclear magnetic resonance and fluorescence spectroscopy, serve two functions: as simple high-throughput techniques for identification and purity analysis, and as potential tools for measuring dynamics and structures of complex biological systems, from proteins and nucleic acids to membranes and nanoparticle delivery systems. With the expansion of commercial small-angle x-ray scattering instruments into the laboratory setting and the accessibility of industrial researchers to small-angle neutron scattering facilities, scattering methods are now used more frequently in the industrial research setting, and probe-less time-resolved small-angle scattering experiments are now able to be conducted to truly probe the mechanism of reactions and the location of individual components in complex model or biological systems. The availability of atomic force microscopes in the past several decades enables measurements that are, in some ways, complementary to the spectroscopic techniques, and wholly orthogonal in others, such as those related to nanomechanics. As therapies have advanced from small molecules to protein biologics and now messenger RNA vaccines, the depth of biophysical knowledge must continue to serve in drug discovery and development to ensure quality of the drug, and the characterization toolbox must be opened up to adapt traditional spectroscopic methods and adopt new techniques for unraveling the complexities of the new modalities. The overview of the biophysical methods in this review is meant to showcase the uses of multiple techniques for different modalities and present recent applications for tackling particularly challenging situations in drug development that can be solved with the aid of fluorescence spectroscopy, nuclear magnetic resonance spectroscopy, atomic force microscopy, and small-angle scattering.

Biosimilar monoclonal antibodies: Challenges and approaches towards formulation

Many biologic drug products, particularly monoclonal antibodies (mAbs), were off-patented between 2015 and 2020, and this process is continuing as the number of biologics approvals has increased. However, the availability of affordable biosimilars is delayed by secondary patents related to the formulation and manufacturing process. Therefore, an alternative formulation development is required to avoid infringement of formulation related patents. Several variables must be considered while developing alternative non-infringement formulations, including the time gap between the expiration of the molecule patent and the formulation patent, the ability not to infringe other secondary patents (process-related), and project timelines. As a part of life cycle management, innovator companies are adopting multiple strategies to delay biosimilar competition. Biosimilar companies could use the innovator formulation knowledge space to develop alternative formulations at the expense of time and cost. The present review discusses the key approaches in biosimilar formulation development, and further summarizes the use of innovator formulation knowledge space for biosimilar mAbs product development.

Structural and Functional Analysis of CEX Fractions Collected from a Novel Avastin® Biosimilar Candidate and Its Innovator: A Comparative Study

Avastin^® is a humanized recombinant monoclonal antibody used to treat cancer by targeting VEGF-A to inhibit angiogenesis. SIMAB054, an Avastin^® biosimilar candidate developed in this study, showed a different charge variant profile than its innovator. Thus, it is fractionated into acidic, main, and basic isoforms and collected physically by Cation Exchange Chromatography (CEX) for a comprehensive structural and functional analysis. The innovator product, fractionated into the same species and collected by the same method, is used as a reference for comparative analysis. Ultra-Performance Liquid Chromatography (UPLC) ESI-QToF was used to analyze the modifications leading to charge heterogeneities at intact protein and peptide levels. The C-terminal lysine clipping and glycosylation profiles of the samples were monitored by intact mAb analysis. The post-translational modifications, including oxidation, deamidation, and N-terminal pyroglutamic acid formation, were determined by peptide mapping analysis in the selected signal peptides. The relative binding affinities of the fractionated charge isoforms against the antigen, VEGF-A, and the neonatal receptor, FcRn, were revealed by Surface Plasmon Resonance (SPR) studies. The results show that all CEX fractions from the innovator product and the SIMAB054 shared the same structural variants, albeit in different ratios. Common glycoforms and post-translational modifications were the same, but at different percentages for some samples. The dissimilarities were mostly originating from the presence of extra C-term Lysin residues, which are prone to enzymatic degradation in the body, and thus they were previously assessed as clinically irrelevant. Another critical finding was the presence of different glyco proteoforms in different charge species, such as increased galactosylation in the acidic and afucosylation in the basic species. SPR characterization of the isolated charge variants further confirmed that basic species found in the CEX analyses of the biosimilar candidate were also present in the innovator product, although at lower amounts. The charge variants’ in vitro antigen- and neonatal receptor-binding activities varied amongst the samples, which could be further investigated in vivo with a larger sample set to reveal the impact on the pharmacokinetics of drug candidates. Minor structural differences may explain antigen-binding differences in the isolated charge variants, which is a key parameter in a comparability exercise. Consequently, such a biosimilar candidate may not comply with high regulatory standards unless the binding differences observed are justified and demonstrated not to have any clinical impact.

Investigation of Tryptic Protein Digestion in Microdroplets and in Bulk Solution

Recent studies have shown that ultrafast enzymatic digestion of proteins can be achieved in microdroplet within 250 μs. Further investigation of peptides resulting from microdroplet digestion (MD) would be necessary to evaluate it as an alternative to the conventional bulk digestion for bottom-up and biotherapeutic protein characterization. Herein we examined and compared protein tryptic digestion in both MD and bulk solution. In the case of MD of β-lactoglobulin B, the preservation of long peptides was observed due to the short digestion time. In addition, MD is applicable to digest both high- and low-abundance proteins in mixture. In the case of digesting NIST 8671 mAb antibody containing a low level of commonly encountered host cell protein (HCP) PLBL2 (mAb:PLBL2 = 100:1 by weight), MD produced lower levels of digestion-induced chemical modifications of asparagine/glutamine deamidation, compared with overnight digestion. No significant difference between MD and bulk digestion was observed in terms of trypsin digestion specificity based on examination of semi- and unspecific-cleaved peptides. Our study suggests that MD, a fast digestion approach, could be adopted for bottom-up proteomics research and for peptide mapping of mAbs to characterize site-specific deamidation and glycosylation, for the purpose of development of biopharmaceuticals.

Characterization and Value Assignment of a Monoclonal Antibody Reference Material, NMIJ RM 6208a, AIST-MAB

Monoclonal antibodies have been established as the largest product class of biopharmaceuticals. Since extensive characterization is required for development and quality control of monoclonal antibody, a widely available reference material (RM) is needed. Herein, a humanized IgG1κ monoclonal antibody reference material, RM 6208-a, AIST-MAB, was established by the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The monoclonal antibody solution was produced as a pharmaceutical grade using a Chinese hamster ovary-derived cell line. The assigned indicative value represents the concentration of the antibody with a heterotetrameric structure including oligomeric forms, determined by an amino acid analysis using isotope dilution mass spectrometry, and their homogeneity and stability were assessed. In addition to antibody concentration, various physicochemical properties, including peptide mapping data, charge variants, and aggregates, were examined. This RM is intended for use in validation of analytical procedures and instruments such as a system suitability test for quantification of antibody. It is also intended for comparing and evaluating the results of antibody analyses across analytical methods and analytical laboratories such as inter-laboratory comparison. Both the material and the set of data from our study provide a tool for an accurate and reliable characterization of product quality attributes of monoclonal antibodies in biopharmaceutical and metrology communities.

Method Development and Qualification of pH-Based CEX UPLC Method for Monoclonal Antibodies

Post-translational modifications (“PTMs”) in monoclonal antibodies (mAbs) contribute to charge variant distribution, which will affect biological efficacy and safety. For the characterization of mAbs, charge variants are used as a critical quality attributes for product quality, stability consistency and effectiveness. Charge variants in mAbs are characterized by a time-consuming and a multistep process starting from cation/anion exchange chromatography, acidic/basic fractions collection and subsequent reverse phase (RP) liquid chromatography, coupled with mass spectrometry (MS) analysis. Hence, an alternative characterization approach that would be highly selective for ion exchange chromatography-based charge variant analysis, which is compatible with on-line MS detection, is needed in the biopharma industry. Against this backdrop, multiple studies are being conducted to develop a simple straight on-line charge variant analysis method. In this regard, we apply the current study, which aims to develop a charge variant analytical method, based on volatile buffers with low ionic strength that can be used for on-line MS detection of charge variants of mAbs. This would enable the detection on “PTMs” using low ionic strength mobile phase compatible with MS. Hence, fruitful data can be obtained with a single chromatography run without any test sample preparation, eliminating the need for multiple steps of analysis, time-consuming process and multiple sample preparation steps. Thus, Charge Variant Analysis-MS technique will allow the characterization of charge-related PTMs on the intact protein stage. In this regard, this study is about development of a method having combination of chromatography and volatile mobile phase for mass spectrometry detection of mAbs being analyzed in native form. The method is qualified considering pharmacopeia guidelines because the ultimate aim is to transfer this method for Quality Control (QC) release testing of a monoclonal antibody, which is critical for batch release and the regulatory point of view. Acidic and basic variants have been separated with high resolution peak profile. Furthermore, there was no matrix interference and good separation selectivity in terms of specificity was obtained using this method. The experimental data suggested for the linearity of the method are 2.4 mg/mL to 3.6 mg/mL with % RSD below 2.0%. Additionally, Limit of Quantitation is found to be 0.15 mg/mL, which is 5% of loading amount. Consistently, the data show that the method is precise under the same operating conditions with a short time interval. Overall a simple, accurate, robust and precise pH gradient cation exchange chromatography method was developed and qualified for the characterization of a therapeutic native mAb. Additionally, this method can be used to claim a biosimilar product profile of an in-house product compare to an innovator.

Coupling Anion Exchange Chromatography with Native Mass Spectrometry for Charge Heterogeneity Characterization of Monoclonal Antibodies

Despite the recent success of coupling anion exchange chromatography with native mass spectrometry (AEX-MS) to study anionic proteins, the utility of AEX-MS methods in therapeutic monoclonal antibody (mAb) characterization has been limited. In this work, we developed and optimized a salt gradient-based AEX-MS method and explored its utility in charge variant analysis of therapeutic mAbs. We demonstrated that, although the developed AEX-MS method is less useful for IgG1 molecules that have higher isoelectric points (pIs), it is an attractive alternative for charge variant analysis of IgG4 molecules. By elevating the column temperature and lowering the mAb pI through PNGase F-mediated deglycosylation, the chromatographical resolution from AEX separation can be significantly improved. We also demonstrated that, after PNGase F and IdeS digestion, the AEX-MS method exhibited excellent resolving power for multiple attributes in the IgG4 Fc region, including unprocessed C-terminal Lys, N-glycosylation occupancy, and several conserved Fc deamidations, making it ideally suited for multiple attribute monitoring (MAM). Through fractionation and peptide mapping analysis, we also demonstrated that the developed AEX-MS method can provide site-specific and isoform-resolved separation of Fc deamidation products, allowing rapid and artifact-free quantitation of these modifications without performing bottom-up analysis.

Process- and Product-Related Foulants in Virus Filtration

Regulatory authorities place stringent guidelines on the removal of contaminants during the manufacture of biopharmaceutical products. Monoclonal antibodies, Fc-fusion proteins, and other mammalian cell-derived biotherapeutics are heterogeneous molecules that are validated based on the production process and not on molecular homogeneity. Validation of clearance of potential contamination by viruses is a major challenge during the downstream purification of these therapeutics. Virus filtration is a single-use, size-based separation process in which the contaminating virus particles are retained while the therapeutic molecules pass through the membrane pores. Virus filtration is routinely used as part of the overall virus clearance strategy. Compromised performance of virus filters due to membrane fouling, low throughput and reduced viral clearance, is of considerable industrial significance and is frequently a major challenge. This review shows how components generated during cell culture, contaminants, and product variants can affect virus filtration of mammalian cell-derived biologics. Cell culture-derived foulants include host cell proteins, proteases, and endotoxins. We also provide mitigation measures for each potential foulant.

Structural Characterization of RC28-E, a Recombinant Fusion Protein With Dual Targets on VEGF and FGF2

Vascular endothelial growth factor (VEGF) and fibroblast growthfactor (FGF) play important roles in angiogenesis-related diseases. RC28-E is a soluble fusion protein composed of the human VEGF receptor 1 (VEGFR1) extracellular domain 2 (ECD 2), VEGFR2 ECD 3, FGFR1 ECDs 2 and 3, and the Fc regions of human immunoglobulin G1. By targeting both VEGF and FGF2, RC28-E may represent a useful antiangiogenetic agent, but structural and functional characterizations of this fusion protein are needed. Liquid chromatography–tandem mass spectrometry, size exclusion high-performance liquid chromatography, capillary electrophoresis-sodium dodecyl sulfate, imaged capillary isoelectric focusing, and bio-layer interferometry were used to characterize the properties of RC28-E. The purity of RC28-E was confirmed to be 98% or greater. The glycosylation modification of RC28-E was found to be very complicated, with 11 potential N-linked glycosylation points and 23 types of N-glycans, causing high heterogeneity of the protein. The primary modifications of the amino acid sequence of RC28-E protein included C-terminal K truncation, N-deamidation, and M-oxidation modification. Notably, RC28-E demonstrated a higher affinity for both VEGF and FGF2 than VEGF trap or FGF trap for their respective targets.

Tricyclic cell-penetrating peptides for efficient delivery of functional antibodies into cancer cells

The intracellular environment hosts a large number of cancer- and other disease-relevant human proteins. Targeting these with internalized antibodies would allow therapeutic modulation of hitherto undruggable pathways, such as those mediated by protein-protein interactions. However, one of the major obstacles in intracellular targeting is the entrapment of biomacromolecules in the endosome. Here we report an approach to delivering antibodies and antibody fragments into the cytosol and nucleus of cells using trimeric cell-penetrating peptides (CPPs). Four trimers, based on linear and cyclic sequences of the archetypal CPP Tat, are significantly more potent than monomers and can be tuned to function by direct interaction with the plasma membrane or escape from vesicle-like bodies. These studies identify a tricyclic Tat construct that enables intracellular delivery of functional immunoglobulin-G antibodies and Fab fragments that bind intracellular targets in the cytosol and nuclei of live cells at effective concentrations as low as 1 μM.

Detailed Analytical Characterization of a Bispecific IgG1 CrossMab Antibody of the Knob-into-Hole Format Applying Various Stress Conditions Revealed Pronounced Stability

In recent years, a variety of new antibody formats have been developed. One of these formats allows the binding of one type of antibody to two different epitopes. This can for example be achieved by introduction of the "knob-into-hole" format and a combined CrossMab approach. Due to their complexity, these bispecific antibodies are expected to result in an enhanced variety of different degradation products. Reports on the stability of these molecules are still largely lacking. To address this, a panel of stress conditions, including elevated temperature, pH, oxidizing agents, and forced glycation via glucose incubation, to identify and functionally evaluate critical quality attributes in the complementary-determining and conserved regions of a bispecific antibody was applied in this study. The exertion of various stress conditions combined with an assessment by size exclusion chromatography, ion exchange chromatography, LC-MS/MS peptide mapping, and functional evaluation by cell-based assays was adequate to identify chemical modification sites and assess the stability and integrity, as well as the functionality of a bispecific antibody. Stress conditions induced size variants and post-translational modifications, such as isomerization, deamidation, and oxidation, albeit to a modest extent. Of note, all the observed stress conditions largely maintained functionality. In summary, this study revealed the pronounced stability of IgG1 "knob-into-hole" bispecific CrossMab antibodies compared to already marketed antibody products.

Eliminating protein oxidation artifacts during High Performance Liquid Chromatography peak fractionation processes

Therapeutic monoclonal antibodies (mAbs) are inherently heterogeneous and hence generally studied and controlled by an array of orthogonal separation methods. During drug candidate development, fractionation by HPLC is regularly employed to assist peak identification and product understanding. One overlooked challenge is the protein oxidation introduced by the fractionation process. In this study, we report the extent of fractionation-induced protein oxidation, which tends to complicate data interpretation and peak assignments. Higher-energy detectors such as fluorescence detectors and lower fraction concentration were found to exacerbate the oxidation artifacts. Other contributing factors than the detector-induced photostress were also found to contribute significantly to protein oxidation. Furthermore, our study showed that collecting fractions into a solution with oxidation scavengers, such as histidine and methionine, was effective in eliminating the oxidation artifacts introduced by detector exposure and fraction processing steps. Through an example, we demonstrate that the modified fractionation workflow improves the accuracy of peak assignments.

Separation of charge variants of a monoclonal antibody by overloaded ion exchange chromatography

A procedure for adjusting the content of charge variants of monoclonal antibody by ion exchange chromatography has been developed. The band splitting phenomenon was utilized to split the protein load into two parts, i.e., the flowthrough and bound fractions, which were either enriched or depleted with some of variants. The phenomenon was triggered by thermodynamic effects resulting from oversaturation of the resin binding sites at high column loadings as well as from kinetic effects arising from limited rates of mass transport. Cation exchange chromatography (CEX) and anion exchange chromatography (AEX) separations were examined, with the reverse order of the variant elution: acidic, main, basic in CEX, and basic, main, acidic in AEX, and the corresponding reverse enrichment tendency in the collected fractions. The separations were performed by pH gradient, whose course was simplified to two stages: isocratic loading and washing at mild pH to load and partly elute the protein, followed by a rapid pH change towards non-binding conditions to desorb the remains of the protein load. To improve yield of the operation, possibility of recycling of waste fractions was considered. To predict the process performance, a dynamic model was developed, which accounted for both adsorption kinetics and thermodynamics.

Identification of a CE-SDS shoulder peak as disulfide-linked fragments from common CH2 cleavages in IgGs and IgG-like bispecific antibodies

Fragmentation is a well-characterized degradation pathway of therapeutic antibodies and is usually monitored by capillary electrophoresis–sodium dodecyl sulfate (CE-SDS). Although fragments due to cleavage in C_H2 domains linked by intrachain disulfide bonds are common and can be detected by reduced reversed-phase – liquid chromatography mass spectrometry (RP-LCMS) and reduced CE-SDS methods, their separation in nonreduced CE-SDS (nrCE-SDS) has not been reported but speculated as comigrating with intact IgG. A shoulder peak in nrCE-SDS was observed in the stability samples of an IgG-like bispecific antibody and was determined to be mainly caused by fragments from clipping at the C-terminus of leucine (L)306 or L309 (EU numbering) in the C_H2 domain of both heavy chains (HCs) and, to a lesser degree, at the C-terminus of L182 in the C_H1 domain of the knob HC. Subunit LCMS analysis verified that the crystallizable fragment contained variants with one or multiple mass additions of ~18 Da due to clipping. Further investigation revealed that C_H2 clippings at L306 and L309 were largely due to proteolytic activity, and cleavages were present at various levels in all in-house IgG1 and IgG4 molecules studied. Our study shows that C_H2 domain cleavages, with complementary fragments still linked by intrachain disulfide, can be electrophoretically resolved as a front shoulder of the main peak in nrCE-SDS. Given the high occurrence of C_H2 cleavages in antibodies, these findings will have broad applicability and could help manufacturers of therapeutic antibodies in process improvement, product characterization, investigations, formulation stability, and stability comparability studies.

Multi-attribute method performance profile for quality control of monoclonal antibody therapeutics

Multi-attribute method (MAM) using peptide map analysis with high resolution mass spectrometry is increasingly common in product characterization and the identification of critical quality attributes (CQAs) of biotherapeutic proteins. Capable of providing structural information specific to amino acid residues, quantifying relative abundance of product variants or degradants, and detecting profile changes between product lots, a robust MAM can replace multiple traditional methods that generate profile-based information for product release and stability testing. In an effort to provide informative and efficient analytical monitoring for monoclonal antibody (mAb) products, from early development to manufacturing quality control, we describe the desired MAM performance profile and address the major scientific challenges in MAM method validation. Furthermore, to support fast speed investigational product development, we describe a platform method validation strategy and results of an optimized MAM workflow. This strategy is applied to support the use of MAM for multiple mAb products with similar structures and physicochemical properties, requiring minimal product-specific method validation activities. Three mAb products were used to demonstrate MAM performance for common and representative product quality attributes. Method validation design and acceptance criteria were guided by the Analytical Target Profile concept, as well as relevant regulatory guidelines to ensure the method is fit-for-purpose. A comprehensive system suitability control strategy was developed, and reported here, to ensure adequate performance of the method including sample preparation, instrument operation, and data analysis. Our results demonstrated sufficient method performance for the characteristics required for quantitative measurement of product variants and degradants.

Similarity demonstrated between isolated charge variants of MB02, a biosimilar of bevacizumab, and Avastin® following extended physicochemical and functional characterization

The majority of recombinant mAb products contain heterogeneous charge variants, commonly the result of post-translational modifications occurring during cell culture and accumulated during production, formulation and storage. MB02 is a biosimilar mAb to bevacizumab. Similarity data of charge variants for biosimilars against its reference products must be generated to demonstrate consistency in product quality and to ensure efficacy and safety. The goal of this work was to isolate seven charge variants of MB02 and Avastin® by semi-preparative cation exchange chromatography followed by purity test and extended analytical characterization to prove similarity. Although poor purity obtained for minor variants complicated data interpretation, an in-depth insight into the charge variants pattern of MB02 compared to Avastin® was obtained, contributing to a better understanding of modifications associated to microheterogeneity. To our knowledge, this is the first comparative analytical study of individual charge variants of a bevacizumab biosimilar following a head-to head approach and the most comprehensive N-glycosylation assessment of IgG1 charge variants. Although modifications related to N- and C-terminal, N-glycans, size heterogeneity or deamidation were specifically enriched among low abundant charge variants, they did not affect binding affinity to VEGF or FcRn and in vitro potency compared with the main species or unfractionated material.

A DFT calculation on nonenzymatic degradation of isoaspartic residue

βAsp is an isomer of Asp that can be formed by either deamidation of Asn or isomerization of Asp and known as biological clock. The presence of βAsp affects the proteolytic stability of the protein. Formation of the isomerized Asp plays a diverse and crucial role in aging, cancer, autoimmune, neurodegenerative, and other diseases. A number of methods have been developed to detect βAsp, and they are usually used in conjunction. Because of identical mass, differentiation of βAsp and Asp residues is challenged. Degradation of βAsp is still unclear and needed to be explored. The energetics and mechanism of five possible pathways for cleavages at βAsp in peptide model have been investigated by DFT/B3LYP/6-311 +  + G(d,p) level of the theory. The calculations show that peptide bond cleavage at α-chain (amino side) due to αO_C → αC_N ring closure is the most favorable reaction. The result is in agreement with experiment utilizing PSD/CRF method. The second most favorable pathway is due to αO_C → βC ring closure results in β-chain cleavage. The cleavage products βAsp and Asp fragments can be used to signify an abundance of βAsp residue in nonenzymatic condition. Other three cyclizations initiated by either α- or β-amino nitrogen result in various cleavages, isomerization to Asp, and reconversion to original βAsp. These three cyclization pathways are obstructed because they require mostly high activation barriers and their intermediates are quite less thermodynamically stable. Thus, computational results also confirm that βAsp → Asp is prohibited in case of nonenzymatic condition which means that protein L-isoaspartyl O-methyl transferase (PIMT) is needed for this modification.

Characterization of N-Terminal Glutamate Cyclization in Monoclonal Antibody and Bispecific Antibody Using Charge Heterogeneity Assays and Hydrophobic Interaction Chromatography

N-terminal glutamate (E) cyclization to form pyroglutamate (pE) generates charge heterogeneities for mAbs and proteins. Thus far, pE formation rate in lyophilized formulation as compared to in liquid formulation has not been reported. Impact of pE on antibody biological activity has only been predicted or assessed using stressed samples that may contain other confounding degradations besides pE. Additionally, application of hydrophobic interaction chromatography (HIC) to separate pE has not been reported. In our study, N-terminal E cyclization was identified as the major degradation pathway in lyophilized formulation at elevated temperature for both monoclonal antibody (mAb-A) and IgG-like bispecific antibody (bsAb-A). pE was enriched in salt-gradient ion exchange chromatography (IEC) as pre-peak and in HIC as post-peak for both mAb-A and bsAb-A. Structure-function studies with pE-enriched IEC and HIC fractions confirmed that pE did not affect binding activities for mAb-A and bsAb-A. In vitro incubation of bsAb-A in serum and PBS revealed that the serum matrix may play a role in pE conversion in human serum, in contrast to the chemical reaction mechanism reported. These techniques can help in characterization of N-terminal E-to-pE cyclization and quality attribute severity assessment during therapeutic protein product development.

Identification of Proteolysis Products in Protein Therapeutics through TMPP N-Terminal Tagging and Electron Transfer Dissociation Product Triggered Collisional Induced Dissociation Fragmentation

Thorough characterization of protein therapeutics is often challenging due to the heterogeneity arising from primary sequence variants, post-translational modifications, proteolytic clipping, or incomplete processing of the signal peptide. Modern mass spectrometry (MS) techniques are now routinely used to characterize such heterogeneous protein populations. Here, we present an LC-MS/MS method using (N-succinimidyloxycarbonylmethyl)-tris (2,4,6-trimethoxyphenyl) phosphonium bromide (TMPP-Ac-OSu) to label any free N-terminal α-amines to rapidly and selectively identify proteolytic clipping events. Electron transfer dissociation (ETD) fragmentation of these chemically tagged peptides generates two unique TMPP product ions, TMPP⁺ and TMPP-Ac-NH₂/c0. The presence of these signature ions following ETD is used to trigger subsequent collisional induced dissociation (CID) fragmentation of the precursor ion. This results in a small subset of CID tandem MS spectra that are used in a customized database search. Using a purified fusion monoclonal antibody (mAb) as an example, we demonstrate how TMPP labeling followed by ETD product ion triggered CID fragmentation is used to accurately identify two undesired clipping sites.

Interlaboratory method validation of capillary electrophoresis sodium dodecyl sulfate (CE-SDS) methodology for analysis of mAbs

Capillary electrophoresis sodium dodecyl sulfate (CE-SDS) is an analytical method to assess the purity of proteins, commonly applied to monoclonal antibodies (mAbs) in the biopharmaceutical industry. To address the need to standardize the CE-SDS method in the pharmaceutical industry and to enhance the confidence in method transfer between laboratories operating different commercial capillary electrophoresis (CE) instrument platforms, an interlaboratory CE-SDS method validation was organized involving 13 laboratories in 13 companies on four different types of commercial capillary electrophoresis instruments. In the validation, a commercial mAb therapeutic was used as the sample. The validation process followed the analytical guidelines set by the ICH guidelines (International Conference for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use). The method's precision, accuracy, linearity and range, and limit of quantitation (LOQ) were validated in the study. Variations of all the parameters validated in the study passed the pre-set criteria defined at the beginning of the study. The definition was based on previously published works and the intended application purpose of the CE-SDS method for mAbs. The study proved that the CE-SDS method fits its intended application purpose as a size impurity assay and size heterogeneity characterization assay for mAb therapeutic products. This study is the first time a CE-SDS method is validated by multiple laboratories using different commercial CE instrument platforms and on a commercial mAb therapeutic. Its results will enhance the confidence of the biopharmaceutical industry to develop CE-SDS methods and transfer CE-SDS methods between different laboratories.

Two-Dimensional Mass Spectrometry Analysis of IgG1 Antibodies

Two-dimensional mass spectrometry (2DMS) is a new, and theoretically ideal, data-independent analysis tool, which allows the characterization of a complex mixture and was used in the bottom-up analysis of IgG1 for the identification of post-translational modifications. The new peak picking algorithm allows the distinction between chimeric peaks in proteomics. In this application, the processing of 2DMS data correlates fragments to their corresponding precursors, with fragments from precursors which are <0.1 m/z at m/z 840 easily resolved, without the need for quadrupole or chromatographic separation.

Investigation of monoclonal antibody dimers in a final formulated drug by separation techniques coupled to native mass spectrometry

Therapeutic monoclonal antibodies (mAbs) are highly complex proteins that must be exhaustively characterized according to the regulatory authorities' recommendations. MAbs display micro-heterogeneity mainly due to their post-translational modifications, but also to their susceptibility to chemical and physical degradations. Among these degradations, aggregation is quite frequent, initiated by protein denaturation and then dimer formation. Here, we investigated the nature and structure of the high molecular weight species (HMW) present at less than 1% in an unstressed formulated roledumab biopharmaceutical, as a model of high purity mAb. HMW species were first purified through preparative size-exclusion chromatography (SEC) and then analyzed by a combination of chromatographic methods (ion-exchange chromatography (IEX), SEC) coupled to native mass spectrometry (MS), as well as sodium dodecyl sulfate–polyacrylamide gel electrophoresis and capillary gel electrophoresis under non-reducing conditions. Both covalently and non-covalently bound dimers were identified at a proportion of 50/50. In-depth characterization of the HMW fraction by SEC and IEX hyphenated to native MS revealed the presence of three mAb dimer forms having the same mass, but differing by their charge and size. They were attributed to different compact and elongated dimers. Finally, high-resolution middle-up approaches using different enzymes (IdeS and IgdE) were performed to determine the mAb domains implicated in the dimerization. Our results revealed that the roledumab dimers were associated mainly by a single Fab-to-Fab arm-bound association.

ID-MAM: A Validated Identity and Multi-Attribute Monitoring Method for Commercial Release and Stability Testing of a Bispecific Antibody

Post-translational modifications (PTMs) that impact the safety or efficacy of protein therapeutics are critical quality attributes (CQAs) that need to be controlled to ensure product quality. Peptide mapping with online mass spectrometry (MS) is a powerful tool that has been used for many years to monitor PTM CQAs during product development. However, operating peptide mapping methods with high-resolution mass spectrometers in GMP compliant, commercial quality control (QC) labs can be difficult. Peptide mapping is also required as an identity test in several countries. To address these two different needs, we utilized high-resolution peptide mapping for comprehensive characterization during development and then developed and validated a targeted multi-attribute monitoring (MAM) method using the low-resolution Waters QDa MS system with a fully automated data processing workflow that is suitable for identity (ID) testing, sequence variant control, and CQA quantitation in commercial QC labs. The ID-MAM method was validated for the quantitation of three selected PTM CQAs (CDR isomerization, Fc Met oxidation, and CDR Met oxidation) to ensure control of the oxidation and isomerization degradation pathways of a bispecific antibody (BsAb). This ID-MAM method was successfully validated in six labs (three analytical development and three QC labs) across four countries for commercial release and stability testing of a BsAb. CQA results obtained with the ID-MAM method were similar to results obtained using high-resolution peptide mapping, and the method was robust and reproducible. To our knowledge, this ID-MAM method is the first MS-based peptide mapping method implemented in GMP compliant QC labs for commercial release and stability testing of a biotherapeutic.

A comprehensive analysis of novel disulfide bond introduction site into the constant domain of human Fab

Generally, intermolecular disulfide bond contribute to the conformational protein stability. To identify sites where intermolecular disulfide bond can be introduced into the Fab’s constant domain of the therapeutic IgG, Fab mutants were predicted using the MOE software, a molecular simulator, and expressed in Pichia pastoris. SDS-PAGE analysis of the prepared Fab mutants from P. pastoris indicated that among the nine analyzed Fab mutants, the F130C(H):Q124C(L), F174C(H):S176C(L), V177C(H):Q160C(L), F174C(H):S162C(L), F130C(H):S121C(L), and A145C(H):F116C(L) mutants mostly formed intermolecular disulfide bond. All these mutants showed increased thermal stability compared to that of Fab without intermolecular disulfide bond. In the other mutants, the intermolecular disulfide bond could not be completely formed, and the L132C(H):F118C(L) mutant showed only a slight decrease in binding activity and β-helix content, owing to the exertion of adverse intermolecular disulfide bond effects. Thus, our comprehensive analysis reveals that the introduction of intermolecular disulfide bond in the Fab’s constant domain is possible at various locations. These findings provide important insights for accomplishing human Fab stabilization.