Chromatographic analysis of the acidic and basic species of recombinant monoclonal antibodies

A three-point identity criteria tool for establishing product identity using icIEF method

Product identity is one of the release testing requirements that needs to be established to ensure that there is no misidentification of drugs. Here, we demonstrated the challenges that can come across while establishing a product identity method for monoclonal antibody (mAb) and mAb-related products using icIEF method. A unique three-point identity criteria tool (visual comparison, pI of individual peaks and ΔpIs) was applied to distinguish mAb1 from the other in-house mAbs. A reduction approach followed by icIEF showed higher potential for establishing identity for mAb1 product as compared to native and enzymatic digestion approach. In general, icIEF method lacks specificity required to unequivocally establish the identity for mAbs, therefore, risk analysis is recommended before implementing icIEF as a stand-alone identity method for monoclonal antibodies.

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.

Improving titer while maintaining quality of final formulated drug substance via optimization of CHO cell culture conditions in low-iron chemically defined media

During biopharmaceutical process development, it is important to improve titer to reduce drug manufacturing costs and to deliver comparable quality attributes of therapeutic proteins, which helps to ensure patient safety and efficacy. We previously reported that relative high-iron concentrations in media increased titer, but caused unacceptable coloration of a fusion protein during early-phase process development. Ultimately, the fusion protein with acceptable color was manufactured using low-iron media, but the titer decreased significantly in the low-iron process. Here, long-term passaging in low-iron media is shown to significantly improve titer while maintaining acceptable coloration during late-phase process development. However, the long-term passaging also caused a change in the protein charge variant profile by significantly increasing basic variants. Thus, we systematically studied the effect of media components, seed culture conditions, and downstream processing on productivity and quality attributes. We found that removing β-glycerol phosphate (BGP) from basal media reduced basic variants without affecting titer. Our goals for late-phase process development, improving titer and matching quality attributes to the early-phase process, were thus achieved by prolonging seed culture age and removing BGP. This process was also successfully scaled up in 500-L bioreactors. In addition, we demonstrated that higher concentrations of reactive oxygen species were present in the high-iron Chinese hamster ovary cell cultures compared to that in the low-iron cultures, suggesting a possible mechanism for the drug substance coloration caused by high-iron media. Finally, hypotheses for the mechanisms of titer improvement by both high-iron and long-term culture are discussed.

Differential Inhibition of Nav1.7 and Neuropathic Pain by Hybridoma-Produced and Recombinant Monoclonal Antibodies that Target Nav1.7 : Differential activities of Nav1.7-targeting monoclonal antibodies

The voltage-gated Na+ channel subtype Nav1.7 is important for pain and itch in rodents and humans. We previously showed that a Nav1.7-targeting monoclonal antibody (SVmab) reduces Na+ currents and pain and itch responses in mice. Here, we investigated whether recombinant SVmab (rSVmab) binds to and blocks Nav1.7 similar to SVmab. ELISA tests revealed that SVmab was capable of binding to Nav1.7-expressing HEK293 cells, mouse DRG neurons, human nerve tissue, and the voltage-sensor domain II of Nav1.7. In contrast, rSVmab showed no or weak binding to Nav1.7 in these tests. Patch-clamp recordings showed that SVmab, but not rSVmab, markedly inhibited Na+ currents in Nav1.7-expressing HEK293 cells. Notably, electrical field stimulation increased the blocking activity of SVmab and rSVmab in Nav1.7-expressing HEK293 cells. SVmab was more effective than rSVmab in inhibiting paclitaxel-induced mechanical allodynia. SVmab also bound to human DRG neurons and inhibited their Na+ currents. Finally, potential reasons for the differential efficacy of SVmab and rSVmab and future directions are discussed.

Assessment of structural and functional similarity of biosimilar products: Rituximab as a case study

Biosimilars are products that are similar in terms of quality, safety, and efficacy to an already licensed reference/ innovator product and are expected to offer improved affordability. The most significant source of reduction in the cost of development of a biosimilar is the reduced clinical examination that it is expected to undergo as compared to the innovator product. However, this clinical relief is predicated on the assumption that there is analytical similarity between the biosimilar and the innovator product. As a result, establishing analytical similarity is arguably the most important step towards successful development of a biosimilar. Here, we present results from an analytical similarity exercise that was performed with five biosimilars of rituximab (Ristova®, Roche), a chimeric mouse/ human monoclonal antibody biotherapeutic, that are available on the Indian market. The results show that, while the biosimilars exhibited similarity with respect to protein structure and function, there were significant differences with respect to size heterogeneity, charge heterogeneity and glycosylation pattern.

The in-use stability of the rituximab biosimilar Rixathon®/Riximyo® upon preparation for intravenous infusion

Purpose

The purpose of this study was to evaluate the in-use physicochemical and biological stability of the Sandoz rituximab biosimilar, marketed under the trade names Rixathon® and Riximyo® in the European Union, upon preparation for intravenous infusion.

Methods

Three batches of Rixathon®/Riximyo® in the final month of their 36 month shelf life were exposed to room temperature and light for 14 days to recapitulate a major temperature excursion. Samples were diluted to the lowest allowable concentration of 1 mg/mL in 0.9% NaCl solution in either polypropylene or polyethylene infusion bags and stored for 14 or 30 days at 5 ± 3℃ followed by an additional 24 h at room temperature to simulate product handling. Samples stored in infusion bags were analyzed using SEC, CEX, non-reducing CE-SDS, peptide mapping and CDC to assess physicochemical and biological stability.

Results

Analysis of Rixathon®/Riximyo® diluted to the lowest allowable concentration in 0.9% sodium chloride in either polypropylene or polyethylene infusion bags revealed no change in molecular weight variants, charge variants, deamidation, oxidation, overall composition or potency over a 31-day period.

Conclusion

Physicochemical and biological analyses demonstrate that Rixathon®/Riximyo® stability is not impacted by dilution and formulation conditions required for intravenous infusion, even under worst case conditions with regard to product shelf life, temperature excursion, light exposure, dilution factor and infusion bag storage time over a 31-day period.

Determination of isoelectric points and relative charge variants of 23 therapeutic monoclonal antibodies

Despite the popularity of therapeutic monoclonal antibodies (mAbs), data relative to their ionic physico-chemical properties are very scarce in the literature. In this work, isoelectric points (pIs) of 23 Food and Drug Administration (FDA) and European Medicines Agency (EMA) approved mAbs were determined by imaged capillary isoelectric focusing (icIEF), and ranged from 6.1 to 9.4. The obtained values were in good agreement with those calculated by both Vector NTI and MassLynx softwares. icIEF can therefore be considered as a reference technique for such a determination. The relative percentages of acidic and basic variants determined by cation exchange chromatography (CEX) using both salt- and pH-gradients were comprised between 15% and 30% for most mAbs and were in good agreement with each other, whereas generic icIEF seems to overestimate the amount of acidic charge variants in mAb products. To our knowledge, this is the first study focusing on the ionic properties of a wide range of FDA and EMA approved reference mAbs, using both generic chromatographic and electrophoretic methodologies. To illustrate the interest of the study for mAb developability purposes, ionic properties of a clinical mAb candidate (dalotuzumab) were also investigated.

A Quadrupole Dalton-based multi-attribute method for product characterization, process development, and quality control of therapeutic proteins

During manufacturing and storage process, therapeutic proteins are subject to various post-translational modifications (PTMs), such as isomerization, deamidation, oxidation, disulfide bond modifications and glycosylation. Certain PTMs may affect bioactivity, stability or pharmacokinetics and pharmacodynamics profile and are therefore classified as potential critical quality attributes (pCQAs). Identifying, monitoring and controlling these PTMs are usually key elements of the Quality by Design (QbD) approach. Traditionally, multiple analytical methods are utilized for these purposes, which is time consuming and costly. In recent years, multi-attribute monitoring methods have been developed in the biopharmaceutical industry. However, these methods combine high-end mass spectrometry with complicated data analysis software, which could pose difficulty when implementing in a quality control (QC) environment. Here we report a multi-attribute method (MAM) using a Quadrupole Dalton (QDa) mass detector to selectively monitor and quantitate PTMs in a therapeutic monoclonal antibody. The result output from the QDa-based MAM is straightforward and automatic. Evaluation results indicate this method provides comparable results to the traditional assays. To ensure future application in the QC environment, this method was qualified according to the International Conference on Harmonization (ICH) guideline and applied in the characterization of drug substance and stability samples. The QDa-based MAM is shown to be an extremely useful tool for product and process characterization studies that facilitates facile understanding of process impact on multiple quality attributes, while being QC friendly and cost-effective.

Optimizing the Bioavailability of Subcutaneously Administered Biotherapeutics Through Mechanochemical Drivers

The subcutaneous route offers myriad benefits for the administration of biotherapeutics in both acute and chronic diseases, including convenience, cost effectiveness and the potential for automation through closed-loop systems. Recent advances in parenteral administration devices and the use of additives which enhance drug dispersion have generated substantial additional interest in IV to SQ switching studies. Designing pre-clinical and clinical studies using SQ mediated delivery however requires deep understanding of complex inter-related physiologies and transport pathways governing the interstitial matrix, vascular system and lymphatic channels. This expert review will highlight key structural features which contribute to transport and biodistribution in the subcutaneous space and also assess the impact of drug formulations. Based on the rapidly growing interest in the SQ delivery route, a number of potential areas for future development are highlighted, which are likely to allow continued evolution and innovation in this important area.

High-Throughput Screening and Analysis of Charge Variants of Monoclonal Antibodies in Multiple Formulations

Among different biopharmaceutical products, monoclonal antibodies (mAbs) show a high level of complexity, including heterogeneity due to differences in size, hydrophobicity, charge, and so forth. Such heterogeneity can be related to both cell-based production and any of the stages of purification, storage, and delivery that the mAb is subjected to. Choosing the right formulation composition providing both physical and chemical stabilities can be a very challenging process, especially when done in the limited time frame required for a typical drug development cycle. Charge variants, a common type of heterogeneity for mAbs, are easy to detect by ion exchange, specifically cation exchange chromatography (CEX). We have developed and implemented a high-throughput CEX-based approach for the rapid screening and analysis of charge modifications in multiple formulation conditions. In this work, 96 different formulations of antistreptavidin IgG1 and IgG2 molecules were automatically prepared and analyzed after incubation at high temperature. Design of experiment and statistical analysis tools have been utilized to determine the major formulation factors responsible for chemical stability of antibodies. Regression models were constructed to find the optimal formulation conditions. The methodology can be applied to different stages of preformulation and formulation development of mAbs.

Main Quality Attributes of Monoclonal Antibodies and Effect of Cell Culture Components

The culture media optimization is an inevitable part of upstream process development in therapeutic monoclonal antibodies (mAbs) production. The quality by design (QbD) approach defines the assured quality of the final product through the development stage. An important step in QbD is determination of the main quality attributes. During the media optimization, some of the main quality attributes such as glycosylation pattern, charge variants, aggregates, and low-molecular-weight species, could be significantly altered. Here, we provide an overview of how cell culture medium components affects the main quality attributes of the mAbs. Knowing the relationship between the culture media components and the main quality attributes could be successfully utilized for a rational optimization of mammalian cell culture media for industrial mAbs production.

Physicochemical and Biological Characterization of the Proposed Biosimilar Tocilizumab

HS628 has been developed as a proposed biosimilar product of originator tocilizumab (Actemra®). An extensive physicochemical and biological characterization was conducted to assess similarity between HS628 and originator tocilizumab. The amino acid sequence was shown to be identical between HS628 and originator tocilizumab. The higher order structure was found to be indistinguishable from originator tocilizumab. Concerning purity and heterogeneity, HS628 was demonstrated to have similar posttranslational modifications, charge heterogeneity, size heterogeneity, and glycosylation to originator tocilizumab. Moreover, HS628 exhibited highly similar binding affinity and antiproliferative activity as well as capability of inhibiting STAT3 phosphorylation compared to originator tocilizumab. Taken together, HS628 can be considered as a highly similar molecule to originator tocilizumab in terms of physicochemical and biological properties.

Charge heterogeneity: Basic antibody charge variants with increased binding to Fc receptors

We identified active isoforms of the chimeric anti-GD2 antibody, ch14.18, a recombinant antibody produced in Chinese hamster ovary cells, which is already used in clinical trials.^1,2,3 We separated the antibody by high resolution ion-exchange chromatography with linear pH gradient elution into acidic, main and basic charge variants on a preparative scale yielding enough material for an in-depth study of the sources and the effects of microheterogeneity. The binding affinity of the charge variants toward the antigen and various cell surface receptors was studied by Biacore. Effector functions were evaluated using cellular assays for antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. Basic charge variants showed increased binding to cell surface receptor FcγRIIIa, which plays a major role in regulating effector functions. Furthermore, increased binding of the basic fractions to the neonatal receptor was observed. As this receptor mediates the prolonged half-life of IgG in human serum, this data may well hint at an increased serum half-life of these basic variants compared to their more acidic counterparts. Different glycoform patterns, C-terminal lysine clipping and N-terminal pyroglutamate formation were identified as the main structural sources for the observed isoform pattern. Potential differences in structural stability between individual charge variant fractions by nano differential scanning calorimetry could not been detected. Our in-vitro data suggests that the connection between microheterogeneity and the biological activity of recombinant antibody therapeutics deserves more attention than commonly accepted.

Cysteinylation of a monoclonal antibody leads to its inactivation

Post-translational modifications can have a signification effect on antibody stability. A comprehensive approach is often required to best understand the underlying reasons the modification affects the antibody's potency or aggregation state. Monoclonal antibody 001 displayed significant variation in terms of potency, as defined by surface plasmon resonance testing (Biacore), from lot to lot independent of any observable aggregation or degradation, suggesting that a post-translational modification could be driving this variability. Analysis of different antibody lots using analytical hydrophobic interaction chromatography (HIC) uncovered multiple peaks of varying size. Electrospray ionization mass spectrometry (ESI-MS) indicated that the antibody contained a cysteinylation post-translational modification in complementarity-determining region (CDR) 3 of the antibody light chain. Fractionation of the antibody by HIC followed by ESI-MS and Biacore showed that the different peaks were antibody containing zero, one, or two cysteinylation modifications, and that the modification interferes with the ability of the modified antibody arm to bind antigen. Molecular modeling of the modified region shows that this oxidation of an unpaired cysteine in the antibody CDR would block a potential antigen binding pocket, suggesting an inhibition mechanism.

SpeB proteolysis with imaged capillary isoelectric focusing for the characterization of domain-specific charge heterogeneities of reference and biosimilar Rituximab

The charge variations of therapeutic monoclonal antibody reveal important information of the post-translational modifications that may potentially impact the potency and safety of pharmaceutical products, especially during the evaluation of biosimilarity of therapeutic proteins. In this work, a novel SpeB-based proteolysis strategy coupling with imaged capillary isoelectric focusing was developed for the determination of domain-specific charge heterogeneities of innovator and generic Rituximab drug products from United States, European and Indian markets. It was observed that innovator Rituximab from the United States and Europe share highly similar peak distributions and charge heterogeneities with 26.2-26.6% Fc/2, 28.9-29.3% LC and 44.4-44.5% Fd peak areas detected, respectively, while multiple basic variations of Fc/2 and less acidic LC and Fd species were found from generic Rituximab from India with 20.9% Fc/2, 32.3% LC and 46.9% Fd peak areas detected. It was also demonstrated that structural changes caused by Carboxypeptidase B treatment and deamidation study at pH extremes could be sensitively captured with the established method, with the results further indicating that the generic product's basic variations of Fc/2 were un-cleaved Lysine residues, while the lack of certain acidic peaks on LC and Fd probably was due to the lower level of deamidation. This new strategy could become a useful tool to reveal domain-specific charge heterogeneities profiles of a variety of therapeutic monoclonal antibodies in regulated environments.

Liquid chromatography-fluorescence and liquid chromatography-mass spectrometry detection of tryptophan degradation products of a recombinant monoclonal antibody

Light exposure is one of several conditions used to study the degradation pathways of recombinant monoclonal antibodies. Tryptophan is of particular interest among the 20 amino acids because it is the most photosensitive. Tryptophan degradation forms several products, including an even stronger photosensitizer and several reactive oxygen species. The current study reports a specific peptide mapping procedure to monitor tryptophan degradation. Instead of monitoring peptides using UV 214 nm, fluorescence detection with an excitation wavelength of 295 nm and an emission wavelength of 350 nm was used to enable specific detection of tryptophan-containing peptides. Peaks that decreased in area over time are likely to contain susceptible tryptophan residues. This observation can allow further liquid chromatography-mass spectrometry (LC-MS) analysis to focus only on those peaks to confirm tryptophan degradation products. After confirmation of tryptophan degradation, susceptibility of tryptophan residues can be compared based on the peak area decrease.

Chemically defined media modifications to lower tryptophan oxidation of biopharmaceuticals

Oxidation of biopharmaceuticals is a major product quality issue with potential impacts on activity and immunogenicity. At Eli Lilly and Company, high tryptophan oxidation was observed for two biopharmaceuticals in development produced in Chinese hamster ovary cells. A switch from historical hydrolysate-containing media to chemically defined media with a reformulated basal powder was thought to be responsible, so mitigation efforts focused on media modification. Shake flask studies identified that increasing tryptophan, copper, and manganese and decreasing cysteine concentrations were individual approaches to lower tryptophan oxidation. When amino acid and metal changes were combined, the modified formulation had a synergistic impact that led to substantially less tryptophan oxidation for both biopharmaceuticals. Similar results were achieved in shake flasks and benchtop bioreactors, demonstrating the potential to implement these modifications at manufacturing scale. The modified formulation did not negatively impact cell growth and viability, product titer, purity, charge variants, or glycan profile. A potential mechanism of action is presented for each amino acid or metal factor based on its role in oxidation chemistry. This work served not only to mitigate the tryptophan oxidation issue in two Lilly biopharmaceuticals in development, but also to increase our knowledge and appreciation for the impact of media components on product quality.

Concentrated fed-batch cell culture increases manufacturing capacity without additional volumetric capacity

Biomanufacturing factories of the future are transitioning from large, single-product facilities toward smaller, multi-product, flexible facilities. Flexible capacity allows companies to adapt to ever-changing pipeline and market demands. Concentrated fed-batch (CFB) cell culture enables flexible manufacturing capacity with limited volumetric capacity; it intensifies cell culture titers such that the output of a smaller facility can rival that of a larger facility. We tested this hypothesis at bench scale by developing a feeding strategy for CFB and applying it to two cell lines. CFB improved cell line A output by 105% and cell line B output by 70% compared to traditional fed-batch (TFB) processes. CFB did not greatly change cell line A product quality, but it improved cell line B charge heterogeneity, suggesting that CFB has both process and product quality benefits. We projected CFB output gains in the context of a 2000-L small-scale facility, but the output was lower than that of a 15,000-L large-scale TFB facility. CFB's high cell mass also complicated operations, eroded volumetric productivity, and showed our current processes require significant improvements in specific productivity in order to realize their full potential and savings in manufacturing. Thus, improving specific productivity can resolve CFB's cost, scale-up, and operability challenges.

Assessing the Utility of Circular Dichroism and FTIR Spectroscopy in Monoclonal-Antibody Comparability Studies

Protein characterization is a necessary activity during development, technical transfers, and licensure. One important aspect of protein characterization is higher order structure assessment, which can be accomplished in a variety of ways. Circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopies provide global higher order structure and are routinely used to measure the overall structure for product characterization; however, their use as comparability tools is uncertain because of their insensitivity to local or small structure changes. We use a monoclonal antibody (mAb) to explore the usefulness of CD and FTIR compared with other indirect methods of structure characterization such as size-exclusion and ion-exchange chromatographies (SEC and IEC). A panel of degraded samples of a mAb was generated; their higher order structure evaluated using CD and FTIR and was found to be largely unchanged. However, the SEC and IEC chromatograms of certain degraded samples were found to have measurable changes. Based on these studies, we conclude that the application of CD and FTIR should be reserved for global higher order structure identification or product characterization only. The use of CD or FTIR comparability of mAbs should be carefully evaluated, as comparability can be sensitively determined using indirect methods based on chromatography.

Rapid quantitative analysis of monoclonal antibody heavy and light chain charge heterogeneity

An alternative method to traditional 2-dimensional gel electrophoresis (2D-PAGE) and its application in characterizing the inherent charge heterogeneity of chromatographically isolated monoclonal antibody heavy and light chains is described. This method, referred to as ChromiCE, utilizes analytical size-exclusion chromatography (SEC), performed under reducing and denaturing conditions, followed by imaged capillary isoelectric focusing (icIEF) of the chromatographically separated heavy and light chains. Under conditions suitable for the subsequent icIEF analysis, the absolute and relative SEC elution volumes of the heavy and light chains were found to be highly pH dependent, a phenomenon that can be exploited in optimizing chromatographic separation. Compared to 2D-PAGE, the ChromiCE method substantially decreases the time and labor needed to complete the analysis, improves reproducibility, and provides fully quantitative assessment of charge heterogeneity. The ChromiCE methodology was applied to a set of diverse monoclonal antibodies to demonstrate suitability for quantitative charge variant analysis of heavy and light chains. A typical application of ChromiCE in extended characterization and stability studies of a purified antibody is shown.

Cell culture media supplementation of bioflavonoids for the targeted reduction of acidic species charge variants on recombinant therapeutic proteins

Charge variants in recombinant proteins are an important series of protein modifications, whose potential role on protein stability, activity, immunogenicity, and pharmacokinetics continues to be studied. Monoclonal antibodies in particular have been shown to have a wide range of acidic species variants, including those associated with the addition of covalent modifications as well as the chemical degradation at specific peptide regions on the antibody. These variants play a significant role toward the overall heterogeneity of recombinant therapeutic proteins and are typically monitored during manufacturing to ensure they lie within proven acceptable ranges. In this work, it has been found that the supplementation of members of the bioflavonoid chemical family into mammalian cell culture media was effective toward the reduction of acidic species charge variants on recombinant monoclonal antibodies and dual variable domain immunoglobulins. The demonstrated reduction in acidic species through the use of bioflavonoids facilitates the manufacturing of a less heterogeneous product with potential improvements in antibody structure and function.

Purification of monoclonal antibodies from clarified cell culture fluid using Protein A capture continuous countercurrent tangential chromatography

Recent studies using simple model systems have demonstrated that continuous countercurrent tangential chromatography (CCTC) has the potential to overcome many of the limitations of conventional Protein A chromatography using packed columns. The objective of this work was to optimize and implement a CCTC system for monoclonal antibody purification from clarified Chinese Hamster Ovary (CHO) cell culture fluid using a commercial Protein A resin. Several improvements were introduced to the previous CCTC system including the use of retentate pumps to maintain stable resin concentrations in the flowing slurry, the elimination of a slurry holding tank to improve productivity, and the introduction of an "after binder" to the binding step to increase antibody recovery. A kinetic binding model was developed to estimate the required residence times in the multi-stage binding step to optimize yield and productivity. Data were obtained by purifying two commercial antibodies from two different manufactures, one with low titer (∼ 0.67 g/L) and one with high titer (∼ 6.9 g/L), demonstrating the versatility of the CCTC system. Host cell protein removal, antibody yields and purities were similar to those obtained with conventional column chromatography; however, the CCTC system showed much higher productivity. These results clearly demonstrate the capabilities of continuous countercurrent tangential chromatography for the commercial purification of monoclonal antibody products.