Distinct Aggregation Mechanisms of Monoclonal Antibody Under Thermal and Freeze-Thaw Stresses Revealed by Hydrogen Exchange

A rapid method to monitor structural perturbations of high-concentrated therapeutic antibody solutions using Intrinsic Tryptophan Fluorescence Emission spectroscopy

Drug product development of therapeutic antibody formulations is still dictated by the risk of protein particle formation during processing or storage, which can lead to loss of potency and potential immunogenic reactions. Since structural perturbations are the main driver for irreversible protein aggregation, the conformational integrity of antibodies should be closely monitored. The present study evaluated the applicability of a plate reader-based high throughput method for Intrinsic Tryptophan Fluorescence Emission (ITFE) spectroscopy to detect protein aggregation due to protein unfolding in high-concentrated therapeutic antibody samples. The impact of fluorophore concentration on the ITFE signal in microplate readers was investigated by analysis of dilution series of two therapeutic antibodies and pure tryptophan. At low antibody concentrations (< 5 mg/mL, equivalent to 0.8 mM tryptophan), the low inner filter effect suggests a quasi-linear relationship between antibody concentration and ITFE intensity. In contrast, the constant ITFE intensity at high protein concentrations (> 40 mg/mL, equivalent to 6.1 mM tryptophan) indicate that ITFE spectroscopy measurements of IgG1 antibodies are feasible in therapeutically relevant concentrations (up to 223 mg/mL). Furthermore, the capability of the method to detect low levels of unfolding (around 1 %) was confirmed by limit of detection (LOD) determination with temperature-stressed antibody samples as degradation standards. Change of fluorescence intensity at the maximum (ΔIaM) was identified as sensitive descriptor for protein degradation, providing the lowest LOD values. The results demonstrate that ITFE spectroscopy performed in a microplate reader is a valuable tool for high-throughput monitoring of protein degradation in therapeutic antibody formulations.

Understanding and controlling the molecular mechanisms of protein aggregation in mAb therapeutics

In antibody development and manufacturing, protein aggregation is a common challenge that can lead to serious efficacy and safety issues. To mitigate this problem, it is important to investigate its molecular origins. This review discusses (1) our current molecular understanding and theoretical models of antibody aggregation, (2) how various stress conditions related to antibody upstream and downstream bioprocesses can trigger aggregation, and (3) current mitigation strategies employed towards inhibiting aggregation. We discuss the relevance of the aggregation phenomenon in the context of novel antibody modalities and highlight how in silico approaches can be exploited to mitigate it.

Challenges in scaling up AAV-based gene therapy manufacturing

Accelerating the scale up of adeno-associated virus (AAV) manufacture is highly desirable to meet the increased demand for gene therapies. However, the development of bioprocesses for AAV gene therapies remains time-consuming and challenging. The quality by design (QbD) approach ensures bioprocess designs that meet the desired product quality and safety profile. Rapid stress tests, developability screens, and scale-down technologies have the potential to streamline AAV product and manufacturing bioprocess development within the QbD framework. Here we review how their successful use for antibody manufacture development is translating to AAV, but also how this will depend critically on improved analytical methods and adaptation of the tools as more understanding is gained on the critical attributes of AAV required for successful therapy.

Ion Mobility Mass Spectrometry (IM-MS) for Structural Biology: Insights Gained by Measuring Mass, Charge, and Collision Cross Section

The investigation of macromolecular biomolecules with ion mobility mass spectrometry (IM-MS) techniques has provided substantial insights into the field of structural biology over the past two decades. An IM-MS workflow applied to a given target analyte provides mass, charge, and conformation, and all three of these can be used to discern structural information. While mass and charge are determined in mass spectrometry (MS), it is the addition of ion mobility that enables the separation of isomeric and isobaric ions and the direct elucidation of conformation, which has reaped huge benefits for structural biology. In this review, where we focus on the analysis of proteins and their complexes, we outline the typical features of an IM-MS experiment from the preparation of samples, the creation of ions, and their separation in different mobility and mass spectrometers. We describe the interpretation of ion mobility data in terms of protein conformation and how the data can be compared with data from other sources with the use of computational tools. The benefit of coupling mobility analysis to activation via collisions with gas or surfaces or photons photoactivation is detailed with reference to recent examples. And finally, we focus on insights afforded by IM-MS experiments when applied to the study of conformationally dynamic and intrinsically disordered proteins.

Clip Formation in the Complementarity Determining Region of Bevacizumab Lowers Monomer Stability and Affinity for Both FcRn and FcγR: A Comprehensive Characterization of the Clipped Variant Including its Higher Order Structure

The presence of monoclonal antibody (mAb) fragments in pharmaceutical mAb products is a critical quality attribute and should be controlled for safety. Several mAb fragments derived from clip formation in the complementarity determining regions (CDRs), as well as from cleavage in the hinge region, have been reported. However, the properties of CDR-clipped variants are not fully understood because of difficulties in separating them from intact mAbs under non-denaturing conditions due to similarities in size. We have established a method for separating CDR-clipped variants under non-denaturing conditions using an appropriate size exclusion chromatography column.¹ In this report, we provide a comprehensive characterization of a CDR-clipped variant from bevacizumab. The variant exhibited a lower pI, a higher tendency to form dimers, and a lower affinity for both neonatal Fc receptor (FcRn) and Fcγ receptor (FcγR). The effects of clip formation in CDR H3 on the higher order structure were analyzed by hydrogen/deuterium exchange mass spectrometry, and the observed changes in the structures of the VH, CH2, and VL domains were in agreement with the lowered affinity for antigen, FcRn, and FcγR. These findings suggest that clip formation in the CDR may affect the efficacy, safety, and pharmacokinetics of pharmaceutical mAbs.

The effect of mAb and excipient cryoconcentration on long-term frozen storage stability – Part 1: Higher molecular weight species and subvisible particle formation

Cryoconcentration upon large-scale freezing of monoclonal antibody (mAb) solutions leads to regions of different ratios of low molecular weight excipients, like buffer species or sugars, to protein. This study focused on the impact of the buffer species to mAb ratio on aggregate formation after frozen storage at −80 °C, −20 °C, and − 10 °C after 6 weeks, 6 months, and 12 months. An optimised sample preparation was established to measure T_g′ of samples with different mAb to histidine ratios via differential scanning calorimetry (DSC). After storage higher molecular weight species (HMWS) and subvisible particles (SVPs) were detected using size-exclusion chromatography (SEC) and FlowCam, respectively. For all samples, sigmoidal curves in DSC thermograms allowed to precisely determine T_g′ in formulations without glass forming sugars. Storage below T_g′ did not lead to mAb aggregation. Above T_g′, at −20 °C and − 10 °C, small changes in mAb and buffer concentration markedly impacted stability. Samples with lower mAb concentration showed increased formation of HMWS. In contrast, higher concentrated samples led to more SVPs. A shift in the mAb to histidine ratio towards mAb significantly increased overall stability. Cryoconcentration upon large-scale freezing affects mAb stability, although relative changes compared to the initial concentration are small. Storage below T_g′ completely prevents mAb aggregation and particle formation.

The effect of mAb and excipient cryoconcentration on long-term frozen storage stability – part 2: Aggregate formation and oxidation

We examined the impact of monoclonal antibody (mAb) and buffer concentration, mimicking the cryoconcentration found upon freezing in a 2 L bottle, on mAb stability during frozen storage. Upon cryoconcentration, larger protein molecules and small excipient molecules freeze-concentrate differently, resulting in different protein to stabiliser ratios within a container. Understanding the impact of these shifted ratios on protein stability is essential. For two mAbs a set of samples with constant mAb (5 mg/mL) or buffer concentration (medium histidine/adipic acid) was prepared and stored for 6 months at −10 °C. Stability was evaluated via size-exclusion chromatography, flow imaging microscopy, UV/Vis spectroscopy at 350 nm, and protein A chromatography. Dynamic light scattering was used to determine k_D values. Soluble aggregate levels were unaffected by mAb concentration, but increased with histidine concentration. No trend in optical density could be identified. In contrast, increasing mAb or buffer concentration facilitated the formation of subvisible particles. A trend towards attractive protein-protein interactions was seen with higher ionic strength. MAb oxidation levels were negatively affected by increasing histidine concentration, but became less with higher mAb concentration. Small changes in mAb and buffer composition had a significant impact on stability during six-month frozen storage. Thus, preventing cryoconcentration effects in larger freezing containers may improve long-term stability.

Physical Instabilities of Therapeutic Monoclonal Antibodies: A Critical Review

The proteinaceous nature of monoclonal antibodies (mAbs) makes them highly sensitive to various physical and chemical conditions, thus leading to instabilities that are classified as physical and chemical instabilities. In this review, we are discussing in detail the physical instability of mAbs because a large number of articles previously published solely focus on the chemical aspect of the instability with little coverage on the physical side. The physical instabilities of mAbs are classified into denaturation and aggregation (precipitation, visible and subvisible particles). The mechanism involved in their formation is discussed in the article, along with the pathways correlating the denaturation of mAb or the formation of aggregates to immunogenicity. Further equations like Gibbs-Helmholtz involved in detecting and quantifying denaturation are discussed, along with various factors causing the denaturation. Moreover, questions related to aggregation like the types of aggregates and the pathway involved in their formation are answered in this article. Factors influencing the physical stability of the mAbs by causing denaturation or formation of aggregates involving the structure of the protein, concentration of mAbs, pH of the protein and the formulations, excipients involved in the formulations, salts added to the formulations, storage temperature, light and UV radiation exposure and processing factors are mentioned in this article. Finally, the analytical approaches used for detecting and quantifying the physical instability of mAbs at all levels of structural conformation like far and near UV, infrared spectroscopy, capillary electrophoresis, LC-MS, microflow imagining, circular dichroism and peptide mapping are discussed.

Impact of Extractables/Leachables from Filter Materials on the Stability of Protein-Based Pharmaceutical Products

The manufacturing of biopharmaceutical drug solutions can involve close contact with various polymeric components, including common filter membranes. Potential leachable substances from filters may interact with the protein and thereby increase the structural damage and aggregation. The main aim of the study deals with the assessment of extractable and leachable (E/L) from different filters and the potential effect of E/Ls on protein (human granulocyte-colony stimulating factor (rh-GCSF) stability. The present study examines the E/L profile of five different polymeric filter membranes using various chromatographic techniques including LC-MS and GC-MS. In order to investigate their effect on protein stability, G-CSF (human granulocyte colony-stimulating factor) formulations were spiked with filter leachable stock solutions at two different pH levels. The spiked formulations were further analyzed with respect to their aggregation behavior. The results demonstrated a higher E/L content in the case of polyamide (PA), polycarbonate (PC), and polyethersulfone (PES) filters as compared to the polytetrafluoroethylene (PTFE) and regenerative cellulose (RC) filter materials. The E/L from RC and PES was found surface-active, whereas E/L from PA and RC significantly altered the particle size/structure resulting in the aggregation of proteins. Furthermore, bisphenol A was found to be one of the E/L substances from PC filters and can impose significant health problems when administered along with pharmaceutical products. The present study reports a qualitative rank ordering of the filter membranes in terms of their propensity to generate E/Ls and thus can be helpful in selecting a suitable membrane filter.

Evaluation of Two Novel Scale-Down Devices for Testing Monoclonal Antibody Aggregation During Large-Scale Freezing

There is a need for representative small volume devices that reflect monoclonal antibody (mAb) aggregation during freezing and thawing (FT) in large containers. We characterised two novel devices that aim to mimic the stress in rectangular 2 L bottles. The first scale-down device (SDD) consists of a 125 mL bottle surrounded by a 3D printed cover that manipulates heat exchange. The second device, a micro scale-down device (mSDD), adapts cooling and heating of 10 mL vials to extend stress time. MAb aggregation upon repeated FT was evaluated considering formation of higher molecular weight species, subvisible particles, and the increase in hydrodynamic radius, polydispersity index, and optical density at 350 nm. Three different mAb solutions were processed. Both an unshielded 125 mL bottle and the SDD can be used to predict aggregation during FT in 2 L bottles. In specific cases the unshielded 125 mL bottle underestimates whereas the SDD slightly overestimates soluble aggregate formation. The mSDD increases aggregation compared to 10 mL vials but is less representative than the SDD. Ultimately, both SDDs enable characterisation of protein sensitivity to large-scale FT with two orders of magnitude less volume and are superior to simply using smaller bottles.

Post-Column Denaturation-Assisted Native Size-Exclusion Chromatography-Mass Spectrometry for Rapid and In-Depth Characterization of High Molecular Weight Variants in Therapeutic Monoclonal Antibodies

The high molecular weight (HMW) size variants present in therapeutic monoclonal antibody (mAb) samples need to be closely monitored and characterized due to their impact on product safety and efficacy. Because of the complexity and often low abundances in final drug substance (DS) samples, characterization of such HMW species is challenging and traditionally requires offline enrichment of the HMW species followed by analysis using various analytical tools. Here, we report the development of a postcolumn denaturation-assisted native SEC-MS method that allows rapid and in-depth characterization of mAb HMW species directly from unfractionated DS samples. This method not only provides high-confidence identification of HMW complexes based on accurate mass measurement of both the intact assembly and the constituent subunits but also allows in-depth analysis of the interaction nature and location. In addition, using the extracted ion chromatograms, derived from high-quality, native-like mass spectra, the elution profiles of each noncovalent and/or nondissociable complex can be readily reconstructed, facilitating the comprehension of a complex HMW profile. The utility of this novel method was demonstrated in different applications, ranging from enriched HMW characterization at late stage development, comparability assessment due to process changes, and forced degradation study of coformulated mAbs. As this method does not require prior enrichment, it is thus desirable for providing both rapid and in-depth characterization of HMW species during the development of therapeutic mAbs.

Innovative Drying Technologies for Biopharmaceuticals

In the past two decades, biopharmaceuticals have been a breakthrough in improving the quality of lives of patients with various cancers, autoimmune, genetic disorders etc. With the growing demand of biopharmaceuticals, the need for reducing manufacturing costs is essential without compromising on the safety, quality, and efficacy of products. Batch Freeze-drying is the primary commercial means of manufacturing solid biopharmaceuticals. However, Freeze-drying is an economically unfriendly means of production with long production cycles, high energy consumption and heavy capital investment, resulting in high overall costs. This review compiles some potential, innovative drying technologies that have not gained popularity for manufacturing parenteral biopharmaceuticals. Some of these technologies such as Spin-freeze-drying, Spray-drying, Lynfinity® Technology etc. offer a paradigm shift towards continuous manufacturing, whereas PRINT® Technology and Microglassification^TM allow controlled dry particle characteristics. Also, some of these drying technologies can be easily scaled-up with reduced requirement for different validation processes. The inclusion of Process Analytical Technology (PAT) and offline characterization techniques in tandem can provide additional information on the Critical Process Parameters (CPPs) and Critical Quality Attributes (CQAs) during biopharmaceutical processing. These processing technologies can be envisaged to increase the manufacturing capacity for biopharmaceutical products at reduced costs.

Monitoring heterogeneity in therapeutic samples using Schlieren

Antigen, antibodies, and other therapeutic biomolecule solutions are likely to undergo physical and chemical processes during their development, manufacturing, transport, and storage. This can induce internal stresses in the sample, resulting in aggregation, heterogeneities, and an overall reduction in the sample quality, e.g., freeze-thawing of samples for storage. Monitoring mixing is thus crucial to ensure homogeneity and consistency while further optimizing downstream processes. We present a simple and portable all-lens Schlieren setup to detect, visualize, and quantify heterogeneities in the protein/antigen or other pharmaceutical solutions during and after thawing in real-time. We illustrate the capabilities of the proposed method by visualizing and quantifying heterogeneities during the thawing of BSA and IgG in four different formulation buffers. The local concentration gradients in a thawing sample lead to light intensity variations which are captured using the Schlieren technique. The sample heterogeneity can then be quantified by relating these light intensity variations to concentration gradients. To this end, we first measure the refractive index of the sample solutions, which varies linearly with the sample concentration. This linear relation is then used to extract the concentration gradient field from the light intensity data. We establish the validity of the proposed approach by demonstrating its accuracy in measuring the diffusion coefficient of a diffusing interface. The portability of the setup and its applicability to a wide range of pharmaceutical solutions make this Schlieren-based technique suitable for monitoring the mixing, heterogeneity, and stability of pharmaceutical samples.

Interaction of Aluminum-adjuvanted Recombinant P[4] Protein Antigen With Preservatives: Storage Stability and Backbone Flexibility Studies

Eight antimicrobial preservatives used in parenteral multidose formulations (thimerosal, 2-phenoxy ethanol, phenol, benzyl alcohol, m-cresol, chlorobutanol, methyl paraben, propyl paraben) were examined for their effects on the storage stability (4 °C, 25 °C) of an Alhydrogel® (AH) adjuvanted formulation of the non-replicating rotavirus vaccine (NRRV) recombinant P[4] protein antigen. The stability of AH-adsorbed P[4] was monitored for antigen-antibody binding, conformational stability, and antigen-adjuvant interaction via competitive ELISA, DSC, and SDS-PAGE, respectively. There was an unexpected correlation between increasing storage stability of the AH-adsorbed P[4] and preservative hydrophobicity (log P) (e.g., the parabens and chlorobutanol were least destabilizing). We used hydrogen exchange-mass spectrometry (HX-MS) to better understand the destabilizing effects of temperature and preservative on backbone flexibility of AH-adsorbed P[4]. Thimerosal addition immediately increased the backbone flexibility across much of the AH-adsorbed P[4] protein backbone (except the N-terminal P2 region and residues G¹⁷-Y³⁸), and further increase in P[4] backbone flexibility was observed after storage (4 °C, 4 weeks). HX-MS analysis of AH-adsorbed P[4] stored for 4 weeks at 25 °C revealed structural alterations in some regions of the epitope involved in P[4] specific mAb binding. These combined results are discussed in terms of a generalized workflow for multi-dose vaccine formulation development for recombinant protein antigens.

Scaling Down Large-Scale Thawing of Monoclonal Antibody Solutions: 3D Temperature Profiles, Changes in Concentration, and Density Gradients

PURPOSE

Scale-down devices (SDD) are designed to simulate large-scale thawing of protein drug substance, but require only a fraction of the material. To evaluate the performance of a new SDD that aims to predict thawing in large-scale 2 L bottles, we characterised 3D temperature profiles and changes in concentration and density in comparison to 125 mL and 2 L bottles. Differences in diffusion between a monoclonal antibody (mAb) and histidine buffer after thawing were examined.

METHODS

Temperature profiles at six distinct positions were recorded with type T thermocouples. Size-exclusion chromatography allowed quantification of mAb and histidine. Polysorbate 80 was quantified using a fluorescent dye assay. In addition, the solution's density at different locations in bottles and the SDD was identified.

RESULTS

The temperature profiles in the SDD and the large-scale 2 L bottle during thawing were similar. Significant concentration gradients were detected in the 2 L bottle leading to marked density gradients. The SDD slightly overestimated the dilution in the top region and the maximum concentrations at the bottom. Fast diffusion resulted in rapid equilibration of histidine.

CONCLUSION

The innovative SDD allows a realistic characterisation and helps to understand thawing processes of mAb solutions in large-scale 2 L bottles. Only a fraction of material is needed to gain insights into the thawing behaviour that is associated with several possible detrimental limitations.

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.

The effects of intramolecular and intermolecular electrostatic repulsions on the stability and aggregation of NISTmAb revealed by HDX-MS, DSC, and nanoDSF

The stability and aggregation of NIST monoclonal antibody (NISTmAb) were investigated by hydrogen/deuterium exchange mass spectrometry (HDX-MS), differential scanning calorimetry (DSC), and nano-differential scanning fluorimetry (nanoDSF). NISTmAb was prepared in eight formulations at four different pHs (pH 5, 6, 7, and 8) in the presence and absence of 150 mM NaCl and analyzed by the three methods. The HDX-MS results showed that NISTmAb is more conformationally stable at a pH near its isoelectric point (pI) in the presence of NaCl than a pH far from its pI in the absence of NaCl. The stabilization effects were global and not localized. The midpoint temperature of protein thermal unfolding transition results also showed the C_H 2 domain of the protein is more conformationally stable at a pH near its pI. On the other hand, the onset of aggregation temperature results showed that NISTmAb is less prone to aggregate at a pH far from its pI, particularly in the absence of NaCl. These seemingly contradicting results, higher conformational stability yet higher aggregation propensity near the pI than far away from the pI, can be explained by intramolecular and intermolecular electrostatic repulsion using Lumry-Eyring model, which separates folding/unfolding equilibrium and aggregation event. The further a pH from the pI, the higher the net charge of the protein. The higher net charge leads to greater intramolecular and intermolecular electrostatic repulsions. The greater intramolecular electrostatic repulsion destabilizes the protein and the greater intermolecular electrostatic repulsion prevents aggregation of the protein molecules at pH far from the pI.

Local disorder of the C-terminal segment of the heavy chain as a common sign of stressed antibodies evidenced with a peptide affinity probe specific to non-native IgG

Therapeutic antibodies have many biopharmaceutical applications; however, characterization of their higher-order structures is a major concern in quality control. We have developed AF.2A1, an artificial protein, that specifically recognizes non-native, structured IgGs. We performed binding assays using various types of IgGs and fragments to investigate the mechanisms by which AF.2A1 interacts with the non-native IgG. AF.2A1 recognized the acid-stressed IgGs from human, mouse, and rat, but not rabbit. Binding assays using the human IgG1 fragments revealed that an interface emerged by deleting five C-terminal residues. We conclude that AF.2A1 recognizes an exposed hydrophobic core centered on the Trp417. Our results concur with those of the previous studies showing that C-terminal structural changes occur early during antibody denaturation and aggregation. Our findings explain the molecular rationale for using AF.2A1 in quality control of biopharmaceutical IgGs.

Freeze thaw and lyophilization induced alteration in mAb therapeutics: Trastuzumab as a case study

Long-term stability of therapeutic monoclonal antibody (mAb) products is necessary for their successful commercialization. Freeze-thaw (F/T) operations are often performed for a mAb product during processing, storage and distribution. Lyophilization (Lyo) is another unit operation that is commonly used for drug product manufacturing of mAbs. This paper aims to explore the impact of these operations on structure and function of a mAb therapeutic, as well as of biosimilars. Trastuzumab innovator and its five biosimilars were analysed for aggregation, charge heterogeneity, secondary structure, binding kinetics, and potency after each freeze-thaw and lyophilization cycle. It is observed that both F/T and Lyo induce protein aggregation, which in turn causes perturbations in the biological potency of the mAb therapeutic. The average value of the percentage of aggregation increased from 0.6 % (week 1) to 5.3 % (week 10) in F/T study and from 0.8 % (week 1) to 10.1 % (week 10) in Lyo study. The acidic pool increased from 26.5 % (week 1) to 44.4 % (week 10) and the basic variants from 13.9 % (week 1) to 24.0 % (week 10) in F/T study. Similarly, acidic pool increased from 27.1 % (week 1) to 42.0 % (week 10) and basic variants from 14.8 % (week 1) to 24.4 % (week 10) in Lyo study. The average percentage of beta-sheet increased from 58.4 % (week 1) to 60.9 % (week 10) in F/T study and from 59.7 % (week 1) to 72.6 % (week 10) in Lyo study. Lower binding affinity was found in week 7 as compared to week 1 in Lyo study whereas no change in binding affinity was observed in the F/T study. The average potency value gradually decreased from 0.97IU/ ml (week 1) to 0.75IU/ ml (week 10) in F/T study and from 1.0IU/ ml (week 1) to 0.66IU/ ml (week 10) in Lyo study. Results indicate that lyophilization has a bigger impact on binding affinity than freeze thaw and as expected, the impact was comparable across the innovator and biosimilar products.

Comparison of the pH- and thermally-induced fluctuations of a therapeutic antibody Fab fragment by molecular dynamics simulation

Successful development of protein therapeutics depends critically on achieving stability under a range of conditions. A deeper understanding of the drivers of instability across different stress conditions, will enable the engineering of more robust protein scaffolds. We compared the impacts of low pH and high temperature stresses on the structure of a humanized antibody fragment (Fab) A33, using atomistic molecular dynamics simulations, using a recent 2.5 Å crystal structure. This revealed that low-pH induced the loss of native contacts in the domain C_L. By contrast, thermal stress led to 5-7% loss of native contacts in all four domains, and simultaneous loss of >30% of native contacts in the V_L-V_H and C_L-C_H interfaces. This revealed divergent destabilising pathways under the two different stresses. The underlying cause of instability was probed using FoldX and Rosetta mutation analysis, and packing density calculations. These agreed that mutations in the C_L domain, and C_L-C_H1 interface have the greatest potential for stabilisation of Fab A33. Several key salt bridge losses underpinned the conformational change in C_L at low pH, whereas at high temperature, salt bridges became more dynamic, thus contributing to an overall destabilization. Lastly, the unfolding events at the two stress conditions exposed different predicted aggregation-prone regions (APR) to solvent, which would potentially lead to different aggregation mechanisms. Overall, our results identified the early stages of unfolding and stability-limiting regions of Fab A33, and the V_H and C_L domains as interesting future targets for engineering stability to both pH- and thermal-stresses simultaneously.

Interest of flow injection spectrophotometry as an orthogonal method for analyzing biomolecule aggregates: Application to stressed monoclonal antibody study

This study aimed to explore the suitability of flow injection spectrophotometry (FIS) to analyze three degraded therapeutic monoclonal antibodies (bevacizumab, nivolumab, and rituximab). For this purpose, aggregates were generated with stirring, freeze-thaw, and heat stresses. The intact and stressed mab samples were filtered with 0.22 µm hydrophilic filters and analyzed by size exclusion chromatography (SEC), cation-exchange chromatography (CEX), and FIS. In terms of quantitative and qualitative analysis, protein loss and structural changes were assessed. Various aggregates profiles were obtained according to the mabs and the stresses. FIS allowed performing very satisfactory quantifications for each mab with intermediate precision RSD < 3.0 % and recovery between 97.9 and 102.0 %. From the protein loss measurements, it appears that SEC underestimates the mab aggregate proportions up to two times less as compared with FIS since the latter avoids any non-specific interactions (electrostatic or hydrophobic interactions). Using second derivative spectroscopy and multivariate data analysis, we noticed apparent structural differences, located in the regions 245-265 nm for rituximab and nivolumab and 280-300 nm for bevacizumab, depending on the stress. The FIS complementarity with the other techniques used in this study allowed us to demonstrate that the three mabs behave differently for a given stress condition. While extreme mechanical stress formed large aggregates irrespective of the mabs, rituximab showed to be less stable and more sensitive than the two other mabs under freeze-thaw and heat stresses, generating large aggregates (>200 nm) and partial unfolding. Nivolumab tends to form small aggregates less than 50 nm when heated and freeze-thawed. Moreover, freeze-thaw seems to generate native IgG-1 aggregates with rituximab. Similarly, bevacizumab showed to form these IgG-1 aggregates and was resistant to freeze-thaw, likely thanks to trehalose cryoprotectant from its formulation. Finally, FIS associated with multivariate analysis can provide rich information in one single run and appears to be a fast, simple, and reliable method to set complementary and orthogonal approaches for protein aggregates monitoring.

Molecular Dynamics Simulation to Uncover the Mechanisms of Protein Instability During Freezing

Freezing is a common process applied in the pharmaceutical industry to store and transport biotherapeutics. Herewith, multi-scale molecular dynamics simulations of Lactate dehydrogenase (LDH) protein in phosphate buffer with/without ice formation performed to uncover the still poorly understood mechanisms and molecular details of protein destabilization upon freezing. Both fast and slow ice growing conditions were simulated at 243 K from one or two-side of the simulation box, respectively. The rate of ice formation at all-atom simulations was crucial to LDH stability, as faster freezing rates resulted in enhanced structural stability maintained by a higher number of intramolecular hydrogen bonds, less flexible protein's residues, lower solvent accessibility and greater structural compactness. Further, protein aggregation investigated by coarse-grained simulations was verified to be initiated by extended protein structures and retained by electrostatic interactions of the salt bridges between charged residues and hydrogen bonds between polar residues of the protein. Lastly, the study of free energy of dissociation through steered molecular dynamics simulation revealed LDH was destabilized by the solvation of the hydrophobic core and the loss of hydrophobic interactions. For the first time, experimentally validated molecular simulations revealed the detailed mechanisms of LDH destabilization upon ice formation and cryoconcentration of solutes.

Cryoconcentration and 3D Temperature Profiles During Freezing of mAb Solutions in Large-Scale PET Bottles and a Novel Scale-Down Device

PURPOSE

Small-scale models that simulate large-scale freezing of bulk drug substance of biopharmaceuticals are highly needed to define freezing and formulation parameters based on process understanding. We evaluated a novel scale-down device (SDD), which is based on a specially designed insulation cover, with respect to changes in concentration after freezing, referred to as cryoconcentration, and 3D temperature profiles. Furthermore, the effect of the initial monoclonal antibody (mAb) concentration on cryoconcentration was addressed.

METHODS

2 L and 125 mL bottles were utilized. Temperatures were mapped using type T thermocouples. Frozen blocks were cut and mAb and histidine concentrations were analysed by HPLC. In addition, concentration- and temperature-dependent viscosities were measured.

RESULTS

3D freezing profiles in the SDD were comparable to large-scale bottles. The SDD accurately predicted cryoconcentration of both mAb and histidine of large-scale freezing. Concentric changes in concentration were evident as well as an unforeseen diluted core at the last point to freeze. At low initial mAb concentration cryoconcentration was substantial, while high initial mAb concentration suppressed cryoconcentration almost completely.

CONCLUSION

The novel SDD gives detailed insights into large-scale freezing of mAb solutions using only a fraction of the simulated volume. It is a promising material- and cost-saving tool to understand large-scale freezing processes.

High Performance Size Exclusion Chromatography and High-Throughput Dynamic Light Scattering as Orthogonal Methods to Screen for Aggregation and Stability of Monoclonal Antibody Drug Products

The presence of aggregates in monoclonal antibody (mAb) drug product (DP) formulations can present product quality challenges. Here we show that use of High Performance Size Exclusion Chromatography (HP-SEC), in conjunction with high-throughput dynamic light scattering (HT-DLS) analyses of mAb DPs can be a useful strategy to determine monomer content and the presence of aggregates under simulated stress conditions. This analytical approach was used to evaluate four commercially available mAb DPs under different conditions i.e.; original formulations, diluted, and thermo-mechanical stressed condition. Due to particle size limitations of HP-SEC columns, resulting in particles accumulating in the column frits prior to reaching the detector for analysis, there is a possibility that large mAb aggregates may not be detected. Both HP-SEC and HT-DLS were able to detect and resolve the mAb monomer (~10-12 nm) of the DPs in their recommended storage conditions. However, the ability to detect large aggregates (>40 nm) by both analytical methods differed, and HT-DLS was able to detect aggregates between 60 nm and 1400 nm under stress conditions. Our data indicates that HP-SEC, in conjunction with HT-DLS, may be beneficial to detect both mAb DP monomer content and multiple aggregate species (1-1000 nm) in the submicron size range.

Covalent Labeling/Mass Spectrometry of Monoclonal Antibodies with Diethylpyrocarbonate: Reaction Kinetics for Ensuring Protein Structural Integrity

Diethylpyrocarbonate (DEPC)-based covalent labeling together with mass spectrometry is a promising tool for the higher-order structural analysis of antibody therapeutics. Reliable information about antibody higher-order structure can be obtained, though, only when the protein's structural integrity is preserved during labeling. In this work, we have evaluated the applicability of DEPC reaction kinetics for ensuring the structural integrity of monoclonal antibodies (mAbs) during labeling. By monitoring the modification extent of selected proteolytic fragments as a function of DEPC concentration, we find that a common DEPC concentration can be used for different monoclonal antibodies in formulated samples without perturbing their higher-order structure. Under these labeling conditions, we find that the antibodies can accommodate up to four DEPC modifications without being structurally perturbed, indicating that multidomain proteins can withstand more than one label, which contrasts to previously studied single-domain proteins. This more extensive labeling provides a more sensitive measure of structure, making DEPC-based covalent labeling-mass spectrometry suitable for the higher-order structural analyses of mAbs.

Inhomogeneous Distribution of Components in Solid Protein Pharmaceuticals: Origins, Consequences, Analysis, and Resolutions

Successful development of stable solid protein formulations usually requires the addition of one or several excipients to achieve optimal stability. In these products, there is a potential risk of an inhomogeneous distribution of the various ingredients, specifically the ratio of protein and stabilizer may vary. Such inhomogeneity can be detrimental for stability but is mostly neglected in literature. In the past, it was challenging to analyze inhomogeneous component distribution, but recent advances in analytical techniques have revealed new options to investigate this phenomenon. This paper aims to review fundamental aspects of the inhomogeneous distribution of components of freeze-dried and spray-dried protein formulations. Four key topics will be presented and discussed, including the sources of component inhomogeneity, its consequences on protein stability, the analytical methods to reveal component inhomogeneity, and possible solutions to prevent or mitigate inhomogeneity.

Native peptide mapping - A simple method to routinely monitor higher order structure changes and relation to functional activity

In the biopharmaceutical environment, controlling the Critical Quality Attributes (CQA) of a product is essential to prevent changes that affect its safety or efficacy. Physico-chemical techniques and bioassays are used to screen and monitor these CQAs. The higher order structure (HOS) is a CQA that is typically studied using techniques that are not commonly considered amenable to quality control laboratories. Here, we propose a peptide mapping-based method, named native peptide mapping, which could be considered as straightforward for HOS analysis and applicable for IgG4 and IgG1 antibodies. The method was demonstrated to be fit-for-purpose as a stability-indicating assay by showing differences at the peptide level between stressed and unstressed material. The unfolding pathway induced by a heat stress was also studied via native peptide mapping assay. Furthermore, we demonstrated the structure–activity relationship between HOS and biological activity by analyzing different types of stressed samples with a cell-based assay and the native peptide mapping. The correlation between both sets of results was highlighted by monitoring peptides located in the complementary-determining regions and the relative potency of the biotherapeutic product. This relationship represents a useful approach to interrogate the criticality of HOS as a CQA of a drug.

The impact of standard accelerated stability conditions on antibody higher order structure as assessed by mass spectrometry

Protein therapeutic higher order structure (HOS) is a quality attribute that can be assessed to help predict shelf life. To model product shelf-life values, possible sample-dependent pathways of degradation that may affect drug efficacy or safety need to be evaluated. As changes in drug thermal stability over time can be correlated with an increased risk of HOS perturbations, the effect of long-term storage on the product should be measured as a function of temperature. Here, complementary high-resolution mass spectrometry methods for HOS analysis were used to identify storage-dependent changes of biotherapeutics (bevacizumab (Avastin), trastuzumab (Herceptin), rituximab (Rituxan), and the NIST reference material 8671 (NISTmAb)) under accelerated or manufacturer-recommended storage conditions. Collision-induced unfolding ion mobility-mass spectrometry data showed changes in monoclonal antibody folded stability profiles that were consistent with the appearance of a characteristic unfolded population. Orthogonal hydrogen-deuterium exchange-mass spectrometry data revealed that the observed changes in unfolding occurred in parallel to changes in HOS localized to the periphery of the hinge region. Using intact reverse-phase liquid chromatography-mass spectrometry, we identified several mass species indicative of peptide backbone hydrolysis, located between the variable and constant domains of the heavy chain of bevacizumab. Taken together, our data highlighted the capability of these approaches to identify age- or temperature-dependent changes in biotherapeutic HOS.

Covalent labeling and mass spectrometry reveal subtle higher order structural changes for antibody therapeutics

Monoclonal antibodies are among the fastest growing therapeutics in the pharmaceutical industry. Detecting higher-order structure changes of antibodies upon storage or mishandling, however, is a challenging problem. In this study, we describe the use of diethylpyrocarbonate (DEPC)-based covalent labeling (CL) - mass spectrometry (MS) to detect conformational changes caused by heat stress, using rituximab as a model system. The structural resolution obtained from DEPC CL-MS is high enough to probe subtle conformation changes that are not detectable by common biophysical techniques. Results demonstrate that DEPC CL-MS can detect and identify sites of conformational changes at the temperatures below the antibody melting temperature (e.g., 55 ᴼC). The observed labeling changes at lower temperatures are validated by activity assays that indicate changes in the Fab region. At higher temperatures (e.g., 65 ᴼC), conformational changes and aggregation sites are identified from changes in CL levels, and these results are confirmed by complementary biophysical and activity measurements. Given the sensitivity and simplicity of DEPC CL-MS, this method should be amenable to the structural investigations of other antibody therapeutics.

Structure, heterogeneity and developability assessment of therapeutic antibodies

Increasing attention has been paid to developability assessment with the understanding that thorough evaluation of monoclonal antibody lead candidates at an early stage can avoid delays during late-stage development. The concept of developability is based on the knowledge gained from the successful development of approximately 80 marketed antibody and Fc-fusion protein drug products and from the lessons learned from many failed development programs over the last three decades. Here, we reviewed antibody quality attributes that are critical to development and traditional and state-of-the-art analytical methods to monitor those attributes. Based on our collective experiences, a practical workflow is proposed as a best practice for developability assessment including in silico evaluation, extended characterization and forced degradation using appropriate analytical methods that allow characterization with limited material consumption and fast turnaround time.

Impact of Tryptophan Oxidation in Complementarity-Determining Regions of Two Monoclonal Antibodies on Structure-Function Characterized by Hydrogen-Deuterium Exchange Mass Spectrometry and Surface Plasmon Resonance

Purpose

Tryptophan’s (Trp) unique hydrophobic and structural properties make it an important antigen binding motif when positioned in complementarity-determining regions (CDRs) of monoclonal antibodies (mAbs). Oxidation of Trp residues within the CDR can deleteriously impact antigen binding, particularly if the CDR conformation is altered. The goal of this study was to evaluate the conformational and functional impact of Trp oxidation for two mAb subtypes, which is essential in determining the structure-function relationship and establishing appropriate analytical control strategies during protein therapeutics development.

Methods

Selective Trp oxidation was induced by 2,2′-Azobis(2-amidinopropane) dihydrochloride (AAPH) treatment in the presence of free methionine (Met). The native and chemically oxidized mAbs were characterized by hydrogen-deuterium exchange mass spectrometry (HDX-MS) for conformational changes and surface plasmon resonance (SPR) for antigen-antibody binding.

Results

Treatment of mAbs with AAPH selectively oxidized solvent accessible Trp residues. Oxidation of Trp within or in proximity of CDRs increased conformational flexibility in variable domains and disrupted antigen binding.

Conclusions

Trp oxidation in CDRs can adversely impact mAbs’ conformation and antigen binding. Trp oxidation should be carefully evaluated as part of critical quality attribute assessments. Oxidation susceptible Trp should be closely monitored during process development for mAbs to establish appropriate analytical control for manufacturing of drug substance and drug product.

Electronic supplementary material

The online version of this article (10.1007/s11095-018-2545-8) contains supplementary material, which is available to authorized users.

MS-based conformation analysis of recombinant proteins in design, optimization and development of biopharmaceuticals

Mass spectrometry (MS)-based methods for analyzing protein higher order structures have gained increasing application in the field of biopharmaceutical development. The predominant methods used in this area include native MS, hydrogen deuterium exchange-MS, covalent labeling, cross-linking and limited proteolysis. These MS-based methods will be briefly described in this article, followed by a discussion on how these methods contribute at different stages of discovery and development of protein therapeutics.

Analytical comparability study of recombinant monoclonal antibody therapeutics

Process changes are inevitable in the life cycle of recombinant monoclonal antibody therapeutics. Products made using pre- and post-change processes are required to be comparable as demonstrated by comparability studies to qualify for continuous development and commercial supply. Establishment of comparability is a systematic process of gathering and evaluating data based on scientific understanding and clinical experience of the relationship between product quality attributes and their impact on safety and efficacy. This review summarizes the current understanding of various modifications of recombinant monoclonal antibodies. It further outlines the critical steps in designing and executing successful comparability studies to support process changes at different stages of a product's lifecycle.

Exploring conditions for redistribution of anti-tumor necrosis factors to reduce spillage: A study on the quality of anti-tumor necrosis factor home storage

BACKGROUND AND AIM

Biologicals are potent drugs for immune-mediated inflammatory diseases. After discontinuation or switch of therapy, many patients have unused biological injectors left. This study aimed to evaluate potential redistribution of unused injectors to prevent spillage of these costly drugs by assessing (i) the quality of transport and home storage through the proportion of injectors stored within the recommended temperature range (2-8 °C) and (ii) acceptance of redistribution by patients.

METHODS

All golimumab users, irrespective of the indication, at Maastricht University Medical Center were eligible for inclusion. Patients received golimumab in a sealed bag containing a validated temperature sensor, measuring temperature every 5 min. Patients were asked to store their medication as usual. Deviations from the recommended range were defined as any duration below 0 °C and > 30 min below 2 °C or above 8 °C. After 3 months, patients completed a questionnaire on their opinion towards potential redistribution of unused biologicals.

RESULTS

Fifty patients (42.0% male, mean age 53.2 ± 14.3 years) received 276 injectors. The mean storage time was 30.9 ± 33.1 days. Only 11.6% of the injectors were stored within the recommended temperature range. In addition, 11.2% were stored > 30 min below 0 °C and 33.2% were stored > 1 week above 8 °C. Of all patients, 95% would accept redistributed medication when product quality is ensured.

CONCLUSIONS

During transport and home storage, only one in eight biological injectors was stored within the recommended temperature range. This hinders redistribution of unused injectors but also raises concern regarding drug effectiveness in immune-mediated inflammatory disease patients.

Understanding the Increased Aggregation Propensity of a Light-Exposed IgG1 Monoclonal Antibody Using Hydrogen Exchange Mass Spectrometry, Biophysical Characterization, and Structural Analysis

This work compares the conformational stability, backbone flexibility, and aggregation propensity of monomer and dimer fractions of an IgG1 monoclonal antibody (mAb) generated on UVA light exposure for up to 72 h collected by preparative size-exclusion chromatography, compared with unstressed control. UVA light exposure induced covalent aggregation, and fragmentation as measured by size-exclusion chromatography, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and extensive oxidation of specific methionine residues (Met 257, Met 433, and Met 109) in both size fractions identified by reverse phase chromatography coupled to mass spectrometry. Compared with unstressed mAb, both the monomer and dimer fractionated from 72 h UVA light-exposed mAb had decreased thermal melting temperatures (T_m1) by 1.4°C as measured by differential scanning calorimetry, minor changes in tertiary structure as measured by near-UV CD, increased monomer loss, and aggregation on accelerated storage at 35°C. Hydrogen/deuterium exchange mass spectrometry identified local segments with increased flexibility in C_H2 and C_H3 domains of both size fractions, and decreased flexibility in few segments of F_ab and C_H1 domains in the dimer fraction. Segment 247-256 in heavy chain, an established aggregation hotspot in IgG1 mAbs had large increase in flexibility in both size fractions compared with unstressed mAb.

Engineering of Fc Fragments with Optimized Physicochemical Properties Implying Improvement of Clinical Potentials for Fc-Based Therapeutics

Therapeutic monoclonal antibodies and Fc-fusion proteins are successfully used in treatment of various diseases mainly including cancer, immune disease, and viral infection, which belong to the Fc-based therapeutics. In recent years, engineered Fc-derived antibody domains have also shown potential for Fc-based therapeutics. To increase the druggability of Fc-based therapeutic candidates, many efforts have been made in optimizing physicochemical properties and functions mediated by Fc fragment. The desired result is that we can simultaneously obtain Fc variants with increased physicochemical properties in vitro and capacity of mediating appropriate functions in vivo. However, changes of physicochemical properties of Fc may result in alternation of Fc-mediated functions and vice versa, which leads to undesired outcomes for further development of Fc-based therapeutics. Therefore, whether modified Fc fragments are suitable for achievement of expected clinical results or not needs to be seriously considered. Now, this question comes to be noticed and should be figured out to make better translation from the results of laboratory into clinical applications. In this review, we summarize different strategies on engineering physicochemical properties of Fc, and preliminarily elucidate the relationships between modified Fc in vitro and the subsequent therapeutic influence in vivo.

The growing role of structural mass spectrometry in the discovery and development of therapeutic antibodies

The comprehensive structural characterization of therapeutic antibodies is of critical importance for the successful discovery and development of such biopharmaceuticals, yet poses many challenges to modern measurement science. Here, we review the current state-of-the-art mass spectrometry technologies focusing on the characterization of antibody-based therapeutics.