Methionine oxidation in human IgG2 Fc decreases binding affinities to protein A and FcRn

Visible light triggers the formation of reactive oxygen species in monoclonal antibody formulations

Most monoclonal antibody formulations require the presence of a surfactant, such as polysorbate, to ensure protein stability. The presence of high concentrations of polysorbate have been shown to enhance photooxidation of certain protein drug products when exposed to visible light. The current literature, however, suggest that photooxidation of polysorbate only occurs when exposed to visible light in combination with UVA light. This is probable as peroxides present in polysorbate solutions can be cleaved homolytically in the UVA region. In the visible region, photooxidation is not expected to occur as cleavage of peroxides is not expected at these wavelengths. This report presents findings suggesting that the presence of one or more photosensitiser(s) in polysorbate must be a cause and is required to catalyse the aerobic oxidation of polysorbate solutions upon exposure to visible light. Our investigation aimed to clarify the mechanism(s) of polysorbate photooxidation and explore the kinetics and the identity of the generated radicals and their impact on monoclonal antibody (mAb) degradation. Our study reveals that when polysorbate solutions are exposed to visible light between 400 - 800 nm in the absence of proteins, discolouration, radical formation, and oxygen depletion occur. We discuss the initial formation of reactive species, most likely occurring directly after reaction of molecular oxygen, with the presence of a triplet state photosensitiser, which is generated by intersystem crossing of the excited singlet state. When comparing the photooxidation of PS20 and PS80 in varying quality grades, we propose that singlet oxygen possesses potential for reacting with unsaturated fatty acids in PS80HP, however, PS20HP itself exhibited no measurable oxidation under the tested conditions. The study's final part delves into the photooxidation behaviour of different PS grades, examining its influence on the integrity of a mAb in the formulation. Finally, we examined the effect of photooxidation on the integrity of monoclonal antibodies. Our findings show that the exposure to visible light in polysorbate-containing mAb solutions at high PS concentrations of 4 mg·ml-1 results in increased monoclonal antibody degradation, highlighting the need for cautious evaluation of the correct PS concentration to stabilise protein therapeutics.

Assessing Physicochemical Stability of Monoclonal Antibodies in a Simulated Subcutaneous Environment

Monoclonal antibodies (mAbs) are being increasingly administered by the subcutaneous (SC) route compared to the traditional intravenous route. Despite the growing popularity of the subcutaneous route, our current knowledge regarding the intricate mechanistic changes happening in the formulation after injection in the subcutaneous space, as well as the in vivo stability of administered mAbs, remains quite limited. Changes in the protein environment as it transitions from a stabilized, formulated drug product in an appropriate container closure to the SC tissue environment can drastically impact the structural stability and integrity of the injected protein. Interactions of the protein with components of the extracellular matrix can lead to changes in its structure, potentially impacting both safety and efficacy. Investigating protein stability in the SC space can enable early assessment of risk and performance of subcutaneously administered proteins influencing clinical decisions and formulation development strategies. The Subcutaneous Injection Site Simulator (SCISSOR) is a novel in vitro system that mimics the subcutaneous injection site and models the events that a protein goes through as it transitions from a stabilized formulation environment to the dynamic physiological space. In this paper, we utilize the SCISSOR to probe for biophysical and chemical changes in seven mAbs post SC injection using a variety of analytical techniques. After 24 h, all mAbs demonstrated a relative decrease in conformational stability, an increase in fragmentation, and elevated acidic species. Higher order structure analysis revealed a deviation in the secondary structure from the standard and an increase in the number of unordered species. Our findings suggest an overall reduced stability of mAbs after subcutaneous administration. This reduced stability could have a potential impact on safety and efficacy. In vitro systems such as the SCISSOR combined with downstream analyses have potential to provide valuable information for assessing the suitability of lead molecules and aid in formulation design optimized for administration in the intended body compartment, thus improving chances of clinical success.

Stability of Protein Pharmaceuticals: Recent Advances

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

Development of a high throughput oxidation profiling strategy for monoclonal antibody products

Oxidation is one of the most common degradation pathways of biopharmaceutics, potentially leading to altered product stability, pharmacokinetics, reduced biological activity and/or an increased immunogenicity. However, it is often insufficiently assessed in early development stages, leaving potential molecule liabilities undiscovered. Aim of the present work was the development of a high throughput oxidation profiling strategy, applicable throughout various stages of biopharmaceutical development. The study demonstrates that the combination of multiple stress assays, including peroxide-based, visible light, and metal-catalyzed oxidation (MCO), enables a comprehensive understanding of a mAb's oxidation susceptibility. The most effective parameters to evaluate oxidation in a high-throughput screening workflow are aggregation, tryptophan oxidation and changes in the hydrophobicity profile of the Fc and Fab subunit measured via Size Exclusion Chromatography, Intrinsic Tryptophan Fluorescence Emission spectroscopy and Reversed-Phase Chromatography subunit analysis, respectively. This oxidation profiling approach is valuable tool to systematically characterize the oxidation susceptibility under relevant conditions, time effective and with minimal sample consumption.

Comparison of middle- and bottom-up mass spectrometry in forced degradation studies of bevacizumab and infliximab

Monoclonal antibodies (mAbs) used as therapeutics need comprehensive characterization for appropriate quality assurance. For analysis, cost-effective methods are of high importance, especially when it comes to biosimilar development which is based on extended physicochemical characterization. The use of forced degradation to study the occurrence of modifications for analysis is well established in drug development and may be used for the evaluation of critical quality attributes (CQAs). For mAb analysis different procedures of liquid chromatography hyphenated with mass spectrometry (LC-MS) analyses are commonly applied. In this study the middle-up approach is compared to the more expensive bottom-up analysis in a forced oxidation biosimilar comparability study. Bevacizumab and infliximab as well as biosimilar candidates for the two mAbs were forcefully oxidized by H2O2 for 24, 48 and 72 h. For bottom-up, the reduced and alkylated trypsin or Lys-C digested samples were analysed by LC-MS with quadrupole time-of-flight mass analyser (LC-QTOF-MS) to detect susceptible residues. By middle-up analysis several species of every subunit (Fc/2, light chain and Fd') were detected which differed in the number of oxidations. For the most abundant species, results from middle-up were in line with results from bottom-up analysis, confirming the strength of middle-up analysis. However, for less abundant species of some subunits, results differed between the two approaches. In both mAbs, the Fc was extensively oxidized. In infliximab, additional extensive oxidation was found in the Fab. Assignment to specific amino acid residues was finally possible using the results from bottom-up analyses. Interestingly, the C-terminal cysteine of the light chain was partially found triply oxidized in both mAbs. The comparison of susceptibility to oxidation showed high similarity between the reference products and their biosimilar candidates. It is suggested that the findings of middle-up experiments should be complemented by bottom-up analysis to confirm the assignments of the localization of modifications. Once the consistency of results has been established, middle-up analyses are sufficient in extended forced degradation biosimilar studies.

Expanding the Analytical Toolbox: Developing New Lys-C Peptide Mapping Methods with Minimized Assay-Induced Artifacts to Fully Characterize Antibodies

Peptide mapping is an important tool used to confirm that the correct sequence has been expressed for a protein and to evaluate protein post-translational modifications (PTMs) that may arise during the production, processing, or storage of protein drugs. Our new orally administered drug (Ab-1), a single-domain antibody, is highly stable and resistant to proteolysis. Analysis via the commonly used tryptic mapping method did not generate sufficient sequence coverage. Alternative methods were needed to study the Ab-1 drug substance (75 mg/mL) and drug product (3 mg/mL). To meet these analytical needs, we developed two new peptide mapping methods using lysyl endopeptidase (Lys-C) digestion. These newly developed protein digestion protocols do not require desalting/buffer-exchange steps, thereby reducing sample preparation time and improving method robustness. Additionally, the protein digestion is performed under neutral pH with methionine acting as a scavenger to minimize artifacts, such as deamidation and oxidation, which are induced during sample preparation. Further, the method for low-concentration samples performs comparably to the method for high-concentration samples. Both methods provide 100% sequence coverage for Ab-1, and, therefore, enable comprehensive characterization for its product quality attribute (PQA) assessment. Both methods can be used to study other antibody formats.

Facile Purification and Use of Tobamoviral Nanocarriers for Antibody-Mediated Display of a Two-Enzyme System

Immunosorbent turnip vein clearing virus (TVCV) particles displaying the IgG-binding domains D and E of Staphylococcus aureus protein A (PA) on every coat protein (CP) subunit (TVCVPA) were purified from plants via optimized and new protocols. The latter used polyethylene glycol (PEG) raw precipitates, from which virions were selectively re-solubilized in reverse PEG concentration gradients. This procedure improved the integrity of both TVCVPA and the wild-type subgroup 3 tobamovirus. TVCVPA could be loaded with more than 500 IgGs per virion, which mediated the immunocapture of fluorescent dyes, GFP, and active enzymes. Bi-enzyme ensembles of cooperating glucose oxidase and horseradish peroxidase were tethered together on the TVCVPA carriers via a single antibody type, with one enzyme conjugated chemically to its Fc region, and the other one bound as a target, yielding synthetic multi-enzyme complexes. In microtiter plates, the TVCVPA-displayed sugar-sensing system possessed a considerably increased reusability upon repeated testing, compared to the IgG-bound enzyme pair in the absence of the virus. A high coverage of the viral adapters was also achieved on Ta2O5 sensor chip surfaces coated with a polyelectrolyte interlayer, as a prerequisite for durable TVCVPA-assisted electrochemical biosensing via modularly IgG-assembled sensor enzymes.

Methionine oxidation selectively enhances T cell reactivity against a melanoma antigen

The impact of the peptide amino acids side-chain modifications on the immunological recognition has been scarcely explored. We investigate here the effect of methionine oxidation on the antigenicity of the melanoma immunodominant peptide 369-YMDGTMSQV-377 (YMD). Using CD8⁺ T cell activation assays, we found that the antigenicity of the sulfoxide form is higher when compared to the YMD peptide. This is consistent with free energy computations performed on HLA-A∗02:01/YMD/TCR complex showing that this is lowered upon oxidation, paired with a steep increase in order at atomic level. Oxidized YMD forms were identified at the melanoma cell surface by LC-MS/MS analysis. These results demonstrate that methionine oxidation in the antigenic peptides may generate altered peptide ligands with increased antigenicity, and that this oxidation may occur in vivo, opening up the possibility that high-affinity CD8⁺ T cells might be naturally primed in the course of melanoma progression, as a result of immunosurveillance.

Profiling Enzyme Activity of l-Asparaginase II by NMR-Based Methyl Fingerprinting at Natural Abundance

l-asparaginase II (MW 135 kDa) from E. coli is an FDA-approved protein drug used for the treatment of childhood leukemia. Despite its long history as a chemotherapeutic, the structural basis of enzyme action, in solution, remains widely contested. In this work, methyl-based 2D [¹H-¹³C]-heteronuclear single-quantum correlation (HSQC) NMR, at natural abundance, has been used to profile the enzymatic activity of the commercially available enzyme drug. The [¹H-¹³C]-HSQC NMR spectra of the protein reveal the role of a flexible loop segment in the activity of the enzyme, in solution. Addition of asparagine to the protein results in distinct conformational changes of the loop that could be signatures of intermediates formed in the catalytic reaction. To this end, an isothermal titration calorimetry (ITC)-based assay has been developed to measure the enzymatic reaction enthalpy, as a marker for its activity. Combining both ITC and NMR, it was shown that the disruption of the protein conformation can result in the loss of function. The scope, robustness, and validity of the loop fingerprints in relation to enzyme activity have been tested under different solution conditions. Overall, our results indicate that 2D NMR can be used reliably to gauge the structure-function of this enzyme, bypassing the need to label the protein. Such natural abundant NMR methods can be potentially extended to probe the structure-function aspects of high-molecular-weight protein therapeutics (glycosylated protein drugs, enzymes, therapeutic monoclonal antibodies, antibody-drug conjugates, and Fc-fusion proteins), where (a) flexible loops are required for their function and (b) isotope labeling may not be straightforward.

Preparation of N-2-Nitrophenylsulfenyl Imino Peptides and Their Catalyst-Controlled Diastereoselective Indolylation

N-2-Nitrophenylsulfenyl imino dipeptides bearing various functional groups were successfully prepared by MnO₂ -mediated oxidation and then subjected to diastereoselective indolylation. Each diastereomer of the adduct was selectively obtained from the same substrates using the appropriate chiral phosphoric acid catalysts. These transformations would be useful for synthesizing non-canonical amino acid-containing peptides as novel drug candidates.

A novel method for in silico assessment of Methionine oxidation risk in monoclonal antibodies: Improvement over the 2-shell model

Over the past decade, therapeutic monoclonal antibodies (mAbs) have established their role as valuable agents in the treatment of various diseases ranging from cancers to infectious, cardiovascular and autoimmune diseases. Reactive groups of the amino acids within these proteins make them susceptible to many kinds of chemical modifications during manufacturing, storage and in vivo circulation. Among these reactions, the oxidation of methionine residues to their sulfoxide form is a commonly observed chemical modification in mAbs. When the oxidized methionine is in the complementarity-determining region (CDR), this modification can affect antigen binding and thus abrogate biological activity. For these reasons, it is essential to identify oxidation liabilities during the antibody discovery and development phases. Here, we present an in silico method, based on protein modeling and molecular dynamics simulations, to predict the oxidation-liable residues in the variable region of therapeutic antibodies. Previous studies have used the 2-shell water coordination number descriptor (WCN) to identify methionine residues susceptible to oxidation. Although the WCN descriptor successfully predicted oxidation liabilities when the residue was solvent exposed, the method was much less accurate for partially buried methionine residues. Consequently, we introduce a new descriptor, WCN-OH, that improves the accuracy of prediction of methionine oxidation susceptibility by extending the theoretical framework of the water coordination number to incorporate the effects of polar amino acids side chains in close proximity to the methionine of interest.

Protein photodegradation in the visible range? Insights into protein photooxidation with respect to protein concentration

Visible light (400-800 nm) can lead to photooxidation of protein formulations, which might impair protein integrity. However, the relevant mechanism of photooxidation upon visible light exposure is still unclear for therapeutic proteins, since proteinogenic structures do not absorb light in the visible range. Here, we show that exposure of monoclonal antibody formulations to visible light, lead to the formation of reactive oxygen species (ROS), which subsequently induce specific protein degradations. The formation of ROS and singlet oxygen upon visible light exposure is investigated using electron paramagnetic resonance (EPR) spectroscopy. We describe the initial formation of ROS, most likely after direct reaction of molecular oxygen with a triplet state photosensitizer, generated from intersystem crossing of the excited singlet state. Since these radicals affect the oxygen content in the headspace of the vial, we monitored photooxidation of these mAb formulations. With increasing protein concentrations, we found (i) a decreasing headspace oxygen content in the sample, (ii) a higher relative number of radicals in solution and (iii) a higher protein degradation. Thus, the protein concentration dependence indicates the presence of higher concentration of a currently unknown photosensitizer.

Risk-Based Control Strategies of Recombinant Monoclonal Antibody Charge Variants

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

Multiattribute Monitoring of Charge-Based Heterogeneity of Recombinant Monoclonal Antibodies Using 2D HIC-WCX-MS

Charged heterogeneity of monoclonal antibody (mAb) products is regarded as a critical quality attribute (CQA) depending on its impact on the safety and efficacy profile of the product. Hence, manufacturers are expected to perform a comprehensive characterization of the charge heterogeneity to ensure that the manufactured product meets its specifications. Further, monitoring is also expected during the product lifecycle to demonstrate consistency in product quality. However, conventional analytical methods for characterization of hydrophobic and charge variants are nonvolatile salt-based and require manual fraction collection and desalting steps before analysis through mass spectrometry can be performed. In the present study, a workflow of a two-dimensional liquid chromatography method using mass spectrometry (MS)-compatible buffers coupled with native mass spectrometry was performed to characterize hydrophobic variants in the first dimension and charge variants in the second dimension without any need for manual fractionation. This novel two-dimensional (2D) hydrophobic interaction chromatography (HIC)-weak cation-exchange chromatography (WCX)-MS workflow identified 10 variants in mAb A, out of which 2 variants are exclusive to the 2D orthogonal method. Similarly, for mAb B, a total of 11 variants are identified, including 5 variants exclusive to the 2D orthogonal workflow. When compared to stand-alone, HIC resolved only 4 variants for both mAbs and WCX resolved 7 variants for mAb A and 6 variants for mAb B. In addition, the proposed method allows direct characterization of hydrophobic/charge variant peaks through native mass spectrometry in a single-run workflow.

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.

Optimized Methods for Analytical and Functional Comparison of Biosimilar mAb Drugs: A Case Study for Avastin, Mvasi, and Zirabev

Bevacizumab is a humanized therapeutic monoclonal antibody used to reduce angiogenesis, a hallmark of cancer, by binding to VEGF-A. Many pharmaceutical companies have developed biosimilars of Bevacizumab in the last decade. The official reports provided by the FDA and EMA summarize the analytical performance of biosimilars as compared to the originators without giving detailed analytical procedures. In the current study, several key methods were optimized and reported for analytical and functional comparison of bevacizumab originators (Avastin, Altuzan) and approved commercial biosimilars (Zirabev and Mvasi). This case study presents a comparative analysis of a set of biosimilars under optimized analytical conditions for the first time in the literature. The chemical structure of all products was analyzed at intact protein and peptide levels by high-resolution mass spectrometry; the major glycoforms and posttranslational modifications, including oxidation, deamidation, N-terminal PyroGlu addition, and C-terminal Lys clipping, were compared. The SPR technique was used to reveal antigen and some receptor binding kinetics of all products, and the ELISA technique was used for C1q binding affinity analysis. Finally, the inhibition performance of the samples was evaluated by an MTS-based proliferation assay in vitro. Major glycoforms were similar, with minor differences among the samples. Posttranslational modifications, except C-terminal Lys, were determined similarly, while unclipped Lys percentage was higher in Zirabev. The binding kinetics for VEGF, FcRn, FcγRIa, and C1q were similar or in the value range of originators. The anti-proliferative effect of Zirabev was slightly higher than the originators and Mvasi. The analysis of biosimilars under the same conditions could provide a new aspect to the literature in terms of the applied analytical techniques. Further studies in this field would be helpful to better understand the inter-comparability of the biosimilars.

Ligand-Bound Forced Degradation as a Strategy to Generate Functionally Relevant Analytical Challenge Materials for Assessment of CQAs

Therapeutic monoclonal antibodies (mAbs) contain a variety of amino acids that are susceptible to enzymatic, chemical, and physical modifications. These modifications can happen throughout production, purification, formulation, and storage and many are known to affect the biological activity of a mAb. Methods that are able to characterize and evaluate these attributes are critical in order to understand how they might alter biological activity. Methods capable of site-specific monitoring of these critical quality attributes are extremely valuable to biopharmaceutical research but also require well-defined materials with site-specific attribute modifications. Here, we describe the development and application of a strategy to generate functionally relevant analytical challenge materials that have unique site-specific attributes. This method involves the use of a ligand that is bound to the mAb during oxidative stress resulting in unique oxidation patterns with some methionine residues protected while others are exposed to oxidation. These unique materials were used to develop a rapid surface plasmon resonance (SPR) assay that could detect methionine oxidation in both the Fab and Fc regions using specific molecular probes. The addition of uniquely oxidized materials to our data set enabled us to determine specific methionine residues vital to binding. Further analysis showed that antibody oxidation could also be rapidly detected in multiple domains from qualitative thermal melting using intrinsic tryptophan fluorescence. Methionine oxidation of an antibody was explored in this study, but we envision this method could be useful to explore structure function relationships of a variety of antibody modifications and modifications to other biologically relevant protein drugs.

Quantifying methionine sulfoxide in therapeutic protein formulation excipients as sensitive oxidation marker

Methionine is a common excipient used in therapeutic protein liquid formulations as stabilizer and antioxidant. The oxidation of methionine to methionine sulfoxide can be regarded as a sensitive marker of oxidative stress for drug product storage conditions. In this study, a sensitive HPLC method for the quantification of methionine sulfoxide in formulated protein product was developed and qualified according to regulatory requirements using a SIELC® Primesep 100 column with UV detection. The separation involves a mixed-mode mechanism including reversed phase and cationic exchange modalities. The operating range of the method was established between 1 µM and 35 µM of methionine sulfoxide. In this testing range, the method was shown to be linear (R² > 0.99), accurate (Recovery 92.9 - 103.6%, average recovery = 99.8 ± 1.4%) and precise (intermediate precision at LoQ, CV = 2.9%). The developed test system was successfully applied to study the effects of temperature and storage conditions on methionine sulfoxide formation in complex therapeutic antibody formulations.

Photo-Oxidation of Therapeutic Protein Formulations: From Radical Formation to Analytical Techniques

UV and ambient light-induced modifications and related degradation of therapeutic proteins are observed during manufacturing and storage. Therefore, to ensure product quality, protein formulations need to be analyzed with respect to photo-degradation processes and eventually protected from light exposure. This task usually demands the application and combination of various analytical methods. This review addresses analytical aspects of investigating photo-oxidation products and related mediators such as reactive oxygen species generated via UV and ambient light with well-established and novel techniques.

Establishment of a highly precise multi-attribute method for the characterization and quality control of therapeutic monoclonal antibodies

The multi-attribute method (MAM) has garnered attention as a new quality control method of therapeutic monoclonal antibodies (mAbs). MAM analysis allows multiple relative quantifications of several structural attributes of therapeutic mAbs; however, some issues remain to be addressed in its procedures especially for sample preparation. The goal of this study was to optimize the sample preparation method for MAM analysis of mAbs. Using a model mAb, we compared five sample preparation methods based on sequence coverage, peptide redundancy, missed cleavage and chemical deamidation. It was found that low pH buffer and short digestion time reduced artificial deamidation. The desalting process after carboxymethylation was essential to obtaining high sequence coverage by a short digestion time. The generation of missed cleavage peptides was also improved by using a trypsin/lysyl endopeptidase (Lys-C) mixture. Next, we evaluated the usefulness of our method as a part of MAM analysis. Finally, 17 glycopeptides, 2 deamidated peptides and N- and C-terminal peptides of the heavy chain were successfully monitored with acceptable mass accuracy and coefficient of variation (CV, %) of the relative peak area. On the other hand, 4 oxidated peptides indicated the unavoidable slightly higher inter-assay CV (%) of the peak area ratio due to the instability in the MS sample solution. Collectively, we demonstrated that our method was applicable as an easy and reliable sample preparation method for MAM analysis, and the variation in the relative peak area could be influenced by the modification type rather than by the amount of each peptide.

Functional in vitro assessment of modified antibodies: Impact of label on protein properties

Labelling of therapeutic antibodies with radionuclides or fluorophores is routinely used to study their pharmacokinetic properties. A critical assumption in utilizing labelled therapeutic antibodies is that the label has no unfavourable effects on antibody charge, hydrophobicity, or receptor affinity. Ideally, the labelled protein should not have any significant deviations from the physiological properties of the original molecule. This article describes an established quality in vitro assessment workflow for labelled antibodies that ensures better prediction of changes in antibody pharmacokinetic (PK) properties after modifications. This analysis package considers degradation and aggregation analysis by size-exclusion chromatography, changes in neonatal-Fc-receptor (FcRn) affinity, and heparin interaction. FcRn binding is important for antibody recycling and half-life extension, whereas heparin affinity provides estimates on the rate of endocytosis through unspecific cell surface binding. Additionally, mass spectrometric analysis to determine the degree of labelling (DoL) completes the package and the combined analysis data allow to predict the label contribution to the PK properties of the modified antibody. This analytical strategy for labelling 11 IgGs has been investigated using 2 different IgG₁ constructs and applying 7 different types of labels. Each labelling resulted in a change in the physicochemical properties of the protein. Not only can the DoL of modified IgGs lead to a change in protein properties, but the type of label also can. Furthermore, it was demonstrated that the labelling process can also influence the behaviour of labelled mAbs. An identical label on different constructs of IgG₁ can cause different affinities for FcRn and heparin. Considering the assessment data, only 6 of the 11 modified antibodies from this study can be recommended for subsequent experiments. In conclusion, a suitability assessment of labelled antibodies prior to any pharmacokinetic studies is essential to reduce cost, allocate resources and reduce the number of animal experiments during pre-clinical drug development.

Investigating photodegradation of antibodies governed by the light dosage

The present study investigated the photodegradation of three different monoclonal antibodies (mAb) by visible light. Several chromatographic techniques, such as size-exclusion and hydrophobic interaction chromatography as well as mass spectrometry were used to measure relative changes of various oxidation related monoclonal antibody species. The results show that visible light is indeed capable of inducing the formation of protein photo-oxidation products, such as acidic, basic, hydrophilic, and several other protein species with altered physicochemical properties. Although, the formation rate of degradants of these three protein species was dependent on the light source's intensity (I), their yield is clearly correlated to the applied light dosage (ld), which is defined as the product of light intensity I and irradiation time t (light dosage = I·t). Hence, our findings indicate that the degradation of monoclonal antibodies can be described according to the Bunsen-Roscoe reciprocity law. This correlation can be useful to assess the impact of photodegradation of biologics with regards to changes in light intensity and/or duration of light exposure of the protein, e.g. during the manufacturing of biologics.

Optimization of therapeutic antibodies

In this review, we have summarized the current landscape of therapeutic antibody optimization for successful development. By engineering antibodies with display technology, computer-aided design and site mutagenesis, various properties of the therapeutic antibody candidates can be improved with the purpose of enhancing their safety, efficacy and developability. These properties include antigen binding affinity and specificity, biological efficacy, pharmacokinetics and pharmacodynamics, immunogenicity and physicochemical developability features. A best-in-class strategy may require the optimization of all these properties to generate a good therapeutic antibody.

Machine learning prediction of methionine and tryptophan photooxidation susceptibility

Photooxidation of methionine (Met) and tryptophan (Trp) residues is common and includes major degradation pathways that often pose a serious threat to the success of therapeutic proteins. Oxidation impacts all steps of protein production, manufacturing, and shelf life. Prediction of oxidation liability as early as possible in development is important because many more candidate drugs are discovered than can be tested experimentally. Undetected oxidation liabilities necessitate expensive and time-consuming remediation strategies in development and may lead to good drugs reaching patients slowly. Conversely, sites mischaracterized as oxidation liabilities could result in overengineering and lead to good drugs never reaching patients. To our knowledge, no predictive model for photooxidation of Met or Trp is currently available. We applied the random forest machine learning algorithm to in-house liquid chromatography-tandem mass spectrometry (LC-MS/MS) datasets (Met, n = 421; Trp, n = 342) of tryptic therapeutic protein peptides to create computational models for Met and Trp photooxidation. We show that our machine learning models predict Met and Trp photooxidation likelihood with 0.926 and 0.860 area under the curve (AUC), respectively, and Met photooxidation rate with a correlation coefficient (Q²) of 0.511 and root-mean-square error (RMSE) of 10.9%. We further identify important physical, chemical, and formulation parameters that influence photooxidation. Improvement of biopharmaceutical liability predictions will result in better, more stable drugs, increasing development throughput, product quality, and likelihood of clinical success.

In Translation: FcRn across the Therapeutic Spectrum

As an essential modulator of IgG disposition, the neonatal Fc receptor (FcRn) governs the pharmacokinetics and functions many therapeutic modalities. In this review, we thoroughly reexamine the hitherto elucidated biological and thermodynamic properties of FcRn to provide context for our assessment of more recent advances, which covers antigen-binding fragment (Fab) determinants of FcRn affinity, transgenic preclinical models, and FcRn targeting as an immune-complex (IC)-clearing strategy. We further comment on therapeutic antibodies authorized for treating SARS-CoV-2 (bamlanivimab, casirivimab, and imdevimab) and evaluate their potential to saturate FcRn-mediated recycling. Finally, we discuss modeling and simulation studies that probe the quantitative relationship between in vivo IgG persistence and in vitro FcRn binding, emphasizing the importance of endosomal transit parameters.

Development of syringes and vials for delivery of biologics: current challenges and innovative solutions

INTRODUCTION

Several new biopharmaceutical dosage forms have developed over time, such as lyophilized vial, liquid vial, and liquid prefilled syringe formulations. This review summarizes major pharmaceutical dosage forms and their advantages, disadvantages, and countermeasures against the shortcomings of each formulation. The appropriate combination of active pharmaceutical ingredients, excipients, and containers should be selected for the safe and less burdensome administration to the patients. Finally, we note certain opinions on the future development of not only therapeutic proteins but also gene therapeutics.

AREAS COVERED

This review is to discuss the challenges of the development of dosage forms to improve pharmaceutical stability and how they can be overcome.

EXPERT OPINION

Silicone oil-free syringes are highly preferable for minimizing subvisible particles in the drug. It can be proposed that materials with less protein adsorption property are preferable for the suppression of protein aggregation. It is required to minimize adverse effects of biopharmaceuticals through proper quality control of the drug in a container, based on the understating of physicochemical stability of the protein in solution, the physicochemical properties of the container, and their combinations.

Fractionated charge variants of biosimilars: A review of separation methods, structural and functional analysis

The similarity between originator and biosimilar monoclonal antibody candidates are rigorously assessed based on primary, secondary, tertiary, quaternary structures, and biological functions. Minor differences in such parameters may alter target-binding, potency, efficacy, or half-life of the molecule. The charge heterogeneity analysis is a prerequisite for all biotherapeutics. Monoclonal antibodies are prone to enzymatic or non-enzymatic structural modifications during or after the production processes, leading to the formation of fragments or aggregates, various glycoforms, oxidized, deamidated, and other degraded residues, reduced Fab region binding activity or altered FcR binding activity. Therefore, the charge variant profiles of the monoclonal antibodies must be regularly and thoroughly evaluated. Comparative structural and functional analysis of physically separated or fractioned charged variants of monoclonal antibodies has gained significant attention in the last few years. The fraction-based charge variant analysis has proved very useful for the biosimilar candidates comprising of unexpected charge isoforms. In this report, the key methods for the physical separation of monoclonal antibody charge variants, structural and functional analyses by liquid chromatography-mass spectrometry, and surface plasmon resonance techniques were reviewed.

Micro-Heterogeneity of Antibody Molecules

Therapeutic monoclonal antibodies (mAbs) are mostly of the IgG class and constitute highly efficacious biopharmaceuticals for a wide range of clinical indications. Full-length IgG mAbs are large proteins that are subject to multiple posttranslational modifications (PTMs) during biosynthesis, purification, or storage, resulting in micro-heterogeneity. The production of recombinant mAbs in nonhuman cell lines may result in loss of structural fidelity and the generation of variants having altered stability, biological activities, and/or immunogenic potential. Additionally, even fully human therapeutic mAbs are of unique specificity, by design, and, consequently, of unique structure; therefore, structural elements may be recognized as non-self by individuals within an outbred human population to provoke an anti-therapeutic/anti-drug antibody (ATA/ADA) response. Consequently, regulatory authorities require that the structure of a potential mAb drug product is comprehensively characterized employing state-of-the-art orthogonal analytical technologies; the PTM profile may define a set of critical quality attributes (CQAs) for the drug product that must be maintained, employing quality by design parameters, throughout the lifetime of the drug. Glycosylation of IgG-Fc, at Asn297 on each heavy chain, is an established CQA since its presence and fine structure can have a profound impact on efficacy and safety. The glycoform profile of serum-derived IgG is highly heterogeneous while mAbs produced in mammalian cells in vitro is less heterogeneous and can be "orchestrated" depending on the cell line employed and the culture conditions adopted. Thus, the gross structure and PTM profile of a given mAb, established for the drug substance gaining regulatory approval, have to be maintained for the lifespan of the drug. This review outlines our current understanding of common PTMs detected in mAbs and endogenous IgG and the relationship between a variant's structural attribute and its impact on clinical performance.

A Fiber Optic Interface Coupled to Nanosensors: Applications to Protein Aggregation and Organic Molecule Quantification

Fluorescent nanosensors hold promise to address analytical challenges in the biopharmaceutical industry. The monitoring of therapeutic protein critical quality attributes such as aggregation is a long-standing challenge requiring low detection limits and multiplexing of different product parameters. However, general approaches for interfacing nanosensors to the biopharmaceutical process remain minimally explored to date. Herein, we design and fabricate a integrated fiber optic nanosensor element, measuring sensitivity, response time, and stability for applications to the rapid process monitoring. The fiber optic-nanosensor interface, or optode, consists of label-free nIR fluorescent single-walled carbon nanotube transducers embedded within a protective yet porous hydrogel attached to the end of the fiber waveguide. The optode platform is shown to be capable of differentiating the aggregation status of human immunoglobulin G, reporting the relative fraction of monomers and dimer aggregates with sizes 5.6 and 9.6 nm, respectively, in under 5 min of analysis time. We introduce a lab-on-fiber design with potential for at-line monitoring with integration of 3D-printed miniaturized sensor tips having high mechanical flexibility. A parallel measurement of fluctuations in laser excitation allows for intensity normalization and significantly lower noise level (3.7 times improved) when using lower quality lasers, improving the cost effectiveness of the platform. As an application, we demonstrate the capability of the fully integrated lab-on-fiber system to rapidly monitor various bioanalytes including serotonin, norepinephrine, adrenaline, and hydrogen peroxide, in addition to proteins and their aggregation states. These results in total constitute an effective form factor for nanosensor-based transducers for applications in industrial process monitoring.

Human serum albumin presents isoform variants with altered neonatal Fc receptor interactions

Human serum albumin (HSA) is the most abundant protein in plasma and presents the particularity, with IgG, to have an extraordinary long serum half-life conferred by its interaction with the neonatal Fc receptor (FcRn). If the impact of IgG post-translational modifications (PTMs) on FcRn binding is well documented, it is far less reported for HSA despite numerous PTMs occurring on the protein in plasma. HSA is susceptible to numerous degradation reactions in plasma, because of aging, oxidative stress or liver and pancreas related pathologies. In the present study, we combined FcRn affinity chromatography and mass spectrometry to investigate the impact of HSA PTMs upon FcRn binding. This methodology presents the advantage to distinguish the effect of a single modification from a plasma HSA preparation made of a mixture of different isoforms. Cys₃₄ oxidation, Lys₅₂₅ glycation, and Leu₅₈₅ C-terminal truncation, which are modifications related to several pathological conditions, were demonstrated to act negatively on HSA-FcRn interaction. The HSA-FcRn binding alteration generated by these modifications is consistent with their vicinity with the interaction interface of the two proteins. Results were discussed regarding altered half-life of HSA observed in several disease states and pave the way toward new understandings of the hypoalbuminemia pathogenesis. SIGNIFICANCE STATEMENT: In this study, we investigated the impact of several post-translational modifications of HSA toward its ability to bind to the neonatal Fc receptor using in vitro affinity chromatography, mass spectrometry, and surface plasmon resonance. Cys34 oxidation, Lys525 glycation, and Leu585 C-terminal truncation were demonstrated to decrease HSA-FcRn binding. These modifications occurring in circulating HSA were discussed in relation to several pathologies as well as for the use of HSA as a therapeutic protein.

Engineering the interactions between a plant-produced HIV antibody and human Fc receptors

Plants can provide a cost-effective and scalable technology for production of therapeutic monoclonal antibodies, with the potential for precise engineering of glycosylation. Glycan structures in the antibody Fc region influence binding properties to Fc receptors, which opens opportunities for modulation of antibody effector functions. To test the impact of glycosylation in detail, on binding to human Fc receptors, different glycovariants of VRC01, a broadly neutralizing HIV monoclonal antibody, were generated in Nicotiana benthamiana and characterized. These include glycovariants lacking plant characteristic α1,3-fucose and β1,2-xylose residues and glycans extended with terminal β1,4-galactose. Surface plasmon resonance-based assays were established for kinetic/affinity evaluation of antibody-FcγR interactions, and revealed that antibodies with typical plant glycosylation have a limited capacity to engage FcγRI, FcγRIIa, FcγRIIb and FcγRIIIa; however, the binding characteristics can be restored and even improved with targeted glycoengineering. All plant-made glycovariants had a slightly reduced affinity to the neonatal Fc receptor (FcRn) compared with HEK cell-derived antibody. However, this was independent of plant glycosylation, but related to the oxidation status of two methionine residues in the Fc region. This points towards a need for process optimization to control oxidation levels and improve the quality of plant-produced antibodies.

Proteolysis and Oxidation of Therapeutic Proteins After Intradermal or Subcutaneous Administration

The intradermal (ID) and subcutaneous (SC) routes are commonly used for therapeutic proteins (TPs) and vaccines; however, the bioavailability of TPs is typically less than small molecule drugs given via the same routes. Proteolytic enzymes in the dermal, SC, and lymphatic tissues may be responsible for the loss of TPs. In addition, the TPs may be exposed to reactive oxygen species generated in the SC tissue and the lymphatic system in response to injection-related trauma and impurities within the formulation. The reactive oxygen species can oxidize TPs to alter their efficacy and immunogenicity potential. Mechanistic understandings of the dominant proteolysis and oxidative routes are useful in the drug discovery process, formulation development, and to assess the potential for immunogenicity and altered pharmacokinetics (PK). Furthermore, in vitro tools representing the ID or SC and lymphatic system can be used to evaluate the extent of proteolysis of the TPs after the injection and before systemic entry. The in vitro clearance data may be included in physiologically based pharmacokinetic models for improved PK predictions. In this review, we have summarized various physiological factors responsible for proteolysis and oxidation of TPs after ID and SC administration.

Fermented, ultrasonicated, and dehydrated bovine colostrum: Changes in antimicrobial properties and immunoglobulin content

This study evaluated the influence of fermentation with Lactobacillus plantarum LUHS135 and Lactobacillus paracasei LUHS244, ultrasonication, and different methods of dehydration on the content of IgG, IgA, and IgM in bovine colostrum (BC), as well as the antimicrobial activity of the treated and fresh BC samples [fresh = BC; freeze dried = BC_lyoph; vacuum dried (+45°C) = BC_vacdried; BC fermented with LUHS135 = BC_LUHS135; BC fermented with LUHS244 = BC_LUHS244; BC fermented with LUHS135 and freeze dried = BC_LUHS135lyoph; BC fermented with LUHS244 and freeze dried = BC_{LUHS244 lyoph}; BC fermented with LUHS135 and vacuum dried = BC_{LUHS135 vacdried}; BC fermented with LUHS244 and vacuum dried = BC_{LUHS244 vacdried}; BC ultrasonicated and freeze dried = BC_{ultr lyoph}; BC ultrasonicated and vacuum dried = BC_{ultr vacdried}]. The antimicrobial activity was assessed against Klebsiella pneumoniae, Salmonella enterica, Pseudomonas aeruginosa, Acinetobacter baumanni, Proteus mirabilis, methicillin-resistant Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium, Bacillus cereus, Streptococcus mutans, Enterobacter cloacae, Citrobacter freundii, Staphylococcus epidermis, Staphylococcus haemolyticus, and Pasteurella multocida using the agar well diffusion method, as well as in liquid medium. In liquid medium analysis showed that the fermented BC samples had the broadest antimicrobial spectrum (of 15 tested pathogenic strains, BC_{LUHS135 vacdried} and BC_LUHS135lyoph inhibited 13; BC_{LUHS244 vacdried} inhibited 12; and BC_LUHS135, BC_LUHS244, and BC_{LUHS244 lyoph} inhibited 11). Based on the inhibition zones, BC_LUHS135lyoph samples exhibited the broadest inhibition spectrum, inhibiting the growth of 12 of the 15 tested pathogenic strains). According to the lactic acid bacteria strain selected for BC fermentation, different properties of the BC will be obtained. To ensure a broad antimicrobial spectrum and high IgG content, fermentation with LUHS135 can be recommended (IgG concentration in BC_LUHS135 was retained), whereas fermentation with LUHS244 will provide a high IgM concentration (IgM concentration increased by 48.8 and 21.6% in BC_LUHS244 and BC_LUHS244lyoph samples, respectively). However, IgA is very sensitive for fermentation, and further studies are needed to increase IgA stability in BC. Finally, fermented BC can be recommended as a food/beverage ingredient, providing safety, as well as improved functionality through displaying a broad spectrum of antimicrobial activities.

Antibody Structure and Function: The Basis for Engineering Therapeutics

Antibodies and antibody-derived macromolecules have established themselves as the mainstay in protein-based therapeutic molecules (biologics). Our knowledge of the structure–function relationships of antibodies provides a platform for protein engineering that has been exploited to generate a wide range of biologics for a host of therapeutic indications. In this review, our basic understanding of the antibody structure is described along with how that knowledge has leveraged the engineering of antibody and antibody-related therapeutics having the appropriate antigen affinity, effector function, and biophysical properties. The platforms examined include the development of antibodies, antibody fragments, bispecific antibody, and antibody fusion products, whose efficacy and manufacturability can be improved via humanization, affinity modulation, and stability enhancement. We also review the design and selection of binding arms, and avidity modulation. Different strategies of preparing bispecific and multispecific molecules for an array of therapeutic applications are included.

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

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

Susceptibility of protein therapeutics to spontaneous chemical modifications by oxidation, cyclization, and elimination reactions

Peptides and proteins are preponderantly emerging in the drug market, as shown by the increasing number of biopharmaceutics already approved or under development. Biomolecules like recombinant monoclonal antibodies have high therapeutic efficacy and offer a valuable alternative to small-molecule drugs. However, due to their complex three-dimensional structure and the presence of many functional groups, the occurrence of spontaneous conformational and chemical changes is much higher for peptides and proteins than for small molecules. The characterization of biotherapeutics with modern and sophisticated analytical methods has revealed the presence of contaminants that mainly arise from oxidation- and elimination-prone amino-acid side chains. This review focuses on protein chemical modifications that may take place during storage due to (1) oxidation (methionine, cysteine, histidine, tyrosine, tryptophan, and phenylalanine), (2) intra- and inter-residue cyclization (aspartic and glutamic acid, asparagine, glutamine, N-terminal dipeptidyl motifs), and (3) β-elimination (serine, threonine, cysteine, cystine) reactions. It also includes some examples of the impact of such modifications on protein structure and function.

Radiolabeled IgG antibodies: Impact of various labels on neonatal Fc receptor binding

The number of therapeutic antibodies in research and development as well as their complexity increases from year to year. Novel therapeutic protein formats, such as Fc-fusions, bispecific, or multivalent antibodies, are currently in preclinical and clinical development. Therefore, the need for biodistribution and imaging studies, eg, with radiolabeled proteins are very high. However, the labeling process or the label itself can have an impact on binding to cellular receptors, eg, to neonatal Fc receptor (FcRn), which can lead to altered PK properties compared with the unlabeled antibody. FcRn affinity chromatography allows the assessment of immunoglobulin G (IgG) samples with respect to their pH-dependent FcRn interaction. We analyzed IgGs with different types of labels, namely, direct iodination with ¹²⁵ I; chelating agents, such as DOTA and DOTAM; and [³ H]propionate. Direct radio-iodination leads to shifts in FcRn column retention time, which might indicate a potentially faster clearance. Furthermore, high conjugation ratios of chelator lower the affinity to FcRn successively and thus may influence the lysosomal degradation of the antibody in endothelial cells. In contrast, IgGs labeled with [³ H]propionate did not show any timeshifts in FcRn affinity chromatography. This article is based on the oral presentation at the IIS 2018 Prague and highlights the importance of an affinity chromatography for characterization of potential changes in affinity to FcRn itself or charge and hydrophobicity.

Forced Degradation Testing as Complementary Tool for Biosimilarity Assessment

Oxidation of monoclonal antibodies (mAbs) can impact their efficacy and may therefore represent critical quality attributes (CQA) that require evaluation. To complement classical CQA, bevacizumab and infliximab were subjected to oxidative stress by H₂O₂ for 24, 48, or 72 h to probe their oxidation susceptibility. For investigation, a middle-up approach was used utilizing liquid chromatography hyphenated with mass spectrometry (LC-QTOF-MS). In both mAbs, the Fc/2 subunit was completely oxidized. Additional oxidations were found in the light chain (LC) and in the Fd’ subunit of infliximab, but not in bevacizumab. By direct comparison of methionine positions, the oxidized residues in infliximab were assigned to M55 in LC and M18 in Fd’. The forced oxidation approach was further exploited for comparison of respective biosimilar products. Both for bevacizumab and infliximab, comparison of posttranslational modification profiles demonstrated high similarity of the unstressed reference product (RP) and the biosimilar (BS). However, for bevacizumab, comparison after forced oxidation revealed a higher susceptibility of the BS compared to the RP. It may thus be considered a useful tool for biopharmaceutical engineering, biosimilarity assessment, as well as for quality control of protein drugs.

Rapid global characterization of immunoglobulin G1 following oxidative stress

Although peroxide and leachable metal-induced chemical modifications are among the most important quality attributes in bioprocess development, there is no mainstream characterization method covering all common modifications theoretically possible on therapeutic proteins that also gives consistent results quickly. Here, we describe a method for rapid and consistent global characterization of leachable metals- or peroxide-stressed immunoglobulin (Ig) G1 monoclonal antibodies (mAbs). Using two independent protease digestions, data-independent acquisition and data-dependent acquisition liquid chromatography high-resolution mass spectrometry, we monitored 55 potential chemical modifications on trastuzumab, a humanized IgG1 mAb. Processing templates including all observed peptides were developed on Skyline to consistently monitor all modifications throughout the stress conditions for both enzymatic digestions. The Global Characterization Data Processing Site, a universal automated data processing application, was created to batch process data, plot modification trends for peptides, generate sortable and downloadable modification tables, and produce Jmol code for three-dimensional structural models of the analyzed protein. In total, 53 sites on the mAb were found to be modified. Oxidation rates generally increased with the peroxide concentration, while leachable metals alone resulted in lower rates of modifications but more oxidative degradants. Multiple chemical modifications were found on IgG1 surfaces known to interact with FcɣRIII, complement protein C1q, and FcRn, potentially affecting activity. The combination of Skyline templates and the Global Characterization Data Processing Site results in a universally applicable assay allowing users to batch process numerous modifications. Applying this new method to stability studies will promote a broader and deeper understanding of stress modifications on therapeutic proteins.

High-Throughput Process Development for Biopharmaceuticals

The ability to conduct multiple experiments in parallel significantly reduces the time that it takes to develop a manufacturing process for a biopharmaceutical. This is particularly significant before clinical entry, because process development and manufacturing are on the "critical path" for a drug candidate to enter clinical development. High-throughput process development (HTPD) methodologies can be similarly impactful during late-stage development, both for developing the final commercial process as well as for process characterization and scale-down validation activities that form a key component of the licensure filing package. This review examines the current state of the art for HTPD methodologies as they apply to cell culture, downstream purification, and analytical techniques. In addition, we provide a vision of how HTPD activities across all of these spaces can integrate to create a rapid process development engine that can accelerate biopharmaceutical drug development. Graphical Abstract.