Comprehensive study on the effects of sodium and potassium additives in size exclusion chromatographic separations of protein biopharmaceuticals

Affinity-Resolved Size Exclusion Chromatography Coupled to Mass Spectrometry: A Novel Tool to Study the Attribute-and-Function Relationship in Therapeutic Monoclonal Antibodies

Assessment of critical quality attributes (CQAs) is an important aspect during the development of therapeutic monoclonal antibodies (mAbs). Attributes that affect either the target binding or Fc receptor engagement may have direct impacts on the drug safety and efficacy and thus are considered as CQAs. Native size exclusion chromatography (SEC)-based competitive binding assay has recently been reported and demonstrated significant benefits compared to conventional approaches for CQA identification, owing to its faster turn-around and higher multiplexity. Expanding on the similar concept, we report the development of a novel affinity-resolved size exclusion chromatography-mass spectrometry (AR-SEC-MS) method for rapid CQA evaluation in therapeutic mAbs. This method features wide applicability, fast turn-around, high multiplexity, and easy implementation. Using the well-studied Fc gamma receptor III-A (FcγRIIIa) and Fc interaction as a model system, the effectiveness of this method in studying the attribute-and-function relationship was demonstrated. Further, two case studies were detailed to showcase the application of this method in assessing CQAs related to antibody target binding, which included unusual N-linked glycosylation in a bispecific antibody and Met oxidation in a monospecific antibody, both occurring within the complementarity-determining regions (CDRs).

Comparative Pharmacokinetics and Safety Assessment of 1st- and 2nd-Generation Zinpentraxin Alfa Drug Products in Healthy Volunteers: A Randomized Crossover Study

Zinpentraxin alfa is a recombinant form of the human pentraxin-2 that was studied in idiopathic pulmonary fibrosis (IPF). To improve the purity and yield of the drug material, a 2nd-generation drug product was developed. To characterize and compare the pharmacokinetic (PK) properties of the 1st- and 2nd-generation zinpentraxin alfa, PK studies were conducted in healthy volunteers (HVs). In a phase 1 randomized, double-blind, 2-sequence crossover, sequential 2-stage study (ISRCTN59409907), single intravenous (IV) doses of 1st- and 2nd-generation zinpentraxin alfa at 10 mg/kg were studied with a blinded interim analysis (IA) at the end of stage 1. Bioequivalence (BE) was achieved for the maximum observed plasma concentration (Cmax), but the overall exposure was higher for the 2nd- compared to the 1st-generation zinpentraxin alfa. The study was stopped after stage 1 as the gating criteria were met based on the result of the blinded IA. Safety profiles were similar for the 1st- and 2nd-generation drug products, and antidrug antibody (ADA) was not observed in this study.

Size exclusion chromatography of biopharmaceutical products: From current practices for proteins to emerging trends for viral vectors, nucleic acids and lipid nanoparticles

The 21st century has been particularly productive for the biopharmaceutical industry, with the introduction of several classes of innovative therapeutics, such as monoclonal antibodies and related compounds, gene therapy products, and RNA-based modalities. All these new molecules are susceptible to aggregation and fragmentation, which necessitates a size variant analysis for their comprehensive characterization. Size exclusion chromatography (SEC) is one of the reference techniques that can be applied. The analytical techniques for mAbs are now well established and some of them are now emerging for the newer modalities. In this context, the objective of this review article is: i) to provide a short historical background on SEC, ii) to suggest some clear guidelines on the selection of packing material and mobile phase for successful method development in modern SEC; and iii) to highlight recent advances in SEC, such as the use of narrow-bore and micro-bore columns, ultra-wide pore columns, and low-adsorption column hardware. Some important innovations, such as recycling SEC, the coupling of SEC with mass spectrometry, and the use of alternative detectors such as charge detection mass spectrometry and mass photometry are also described. In addition, this review discusses the use of SEC in multidimensional setups and shows some of the most recent advances at the preparative scale. In the third part of the article, the possibility of SEC for the characterization of new modalities is also reviewed. The final objective of this review is to provide a clear summary of opportunities and limitations of SEC for the analysis of different biopharmaceutical products.

Accelerated development of a SEC-HPLC procedure for purity analysis of monoclonal antibodies using design of experiments

The complex structure of biopharmaceutical products poses an inherent need for their thorough characterization to ensure product quality, safety, and efficacy. Analytical size exclusion chromatography (SEC) is a widely used technique throughout the development and manufacturing of monoclonal antibodies (mAbs) which quantifies product size variants such as aggregates and fragments. Aggregate and fragment content are critical quality attributes (CQAs) in mAb products, as higher contents of such size heterogeneities impact product quality. Historically, SEC methods have achieved sufficient separation between the high molecular weight (HMW) species and the main product. In contrast, some low molecular weight (LMW) species are often not sufficiently different in molecular mass from the main product, making it difficult to achieve appropriate resolutions between the two species. This lack of resolution makes it difficult to consistently quantify the LMW species in mAb-based therapeutics. The following work uses a design of experiments (DoE) approach to establish a robust analytical SEC procedure by evaluating SEC column types and mobile phase compositions using two mAb products with different physiochemical properties. The resulting optimized procedure using a Waters™ BioResolve column exhibits an improved ability to resolve and quantify mAb size variants, highlighting improvement in the resolution of the LMW species. Additionally, the addition of L-arginine as a mobile phase additive showed to reduce secondary interactions and was beneficial in increasing the recoveries of the HMW species.

Characterization of antibody surface properties and selection of a diverse subset for development of a generic size-exclusion chromatography method

Aggregates are an important quality attribute for biotherapeutics because they can affect the safety and efficacy of the drug and they are therefore routinely monitored, mainly with size-exclusion chromatography (SEC). However, there is often a need to tailor a SEC method to a specific molecule. This study describes the development of a generic SEC method tested on 138 antibodies with the variable domains taken from clinical stage antibodies. We report on the discovery of a subset of 12 antibodies that represents the full range of physiochemical properties found in the 138 antibodies. This subset is shown to be an efficient and reliable test set when developing chromatographic methods for antibodies. An understanding of the nature of the analyte-stationary phase interactions was gained when using this set with its wide range of physiochemical properties. Highly hydrophobic antibodies interact strongly with some modern silica hybrid materials causing the elution time to increase significantly, while a hydrophilically modified hybrid surface showed highly reduced interactions for the hydrophobic antibodies. Highly hydrophilic antibodies, on the other hand, exhibited asymmetric peaks to a certain extent on all stationary phases, while the elution time was not affected. The developed SEC method was shown to have satisfactory performance in terms of linearity, repeatability, range, and accuracy and exhibit very narrow distributions of elution time and peak symmetry when testing the 138 antibodies indicating its generic performance.

Micro-flow size-exclusion chromatography for enhanced native mass spectrometry of proteins and protein complexes

Size-exclusion chromatography (SEC) employing aqueous mobile phases with volatile salts at neutral pH combined with native mass spectrometry (nMS) is a valuable tool to characterize proteins and protein aggregates in their native state. However, the liquid-phase conditions (high salt concentrations) frequently used in SEC-nMS hinder the analysis of labile protein complexes in the gas phase, necessitating higher desolvation-gas flow and source temperature, leading to protein fragmentation/dissociation. To overcome this issue, we investigated narrow SEC columns (1.0 mm internal diameter, I.D.) operated at 15-μL/min flow rates and their coupling to nMS for the characterization of proteins, protein complexes and higher-order structures (HOS). The reduced flow rate resulted in a significant increase in the protein-ionization efficiency, facilitating the detection of low-abundant impurities and HOS up to 230 kDa (i.e., the upper limit of the Orbitrap-MS instrument used). More-efficient solvent evaporation and lower desolvation energies allowed for softer ionization conditions (e.g., lower gas temperatures), ensuring little or no structural alterations of proteins and their HOS during transfer into the gas phase. Furthermore, ionization suppression by eluent salts was decreased, permitting the use of volatile-salt concentrations up to 400 mM. Band broadening and loss of resolution resulting from the introduction of injection volumes exceeding 3% of the column volume could be circumvented by incorporating an online trap-column containing a mixed-bed ion-exchange (IEX) material. The online IEX-based solid-phase extraction (SPE) or "trap-and-elute" set-up provided on-column focusing (sample preconcentration). This allowed the injection of large sample volumes on the 1-mm I.D. SEC column without compromising the separation. The enhanced sensitivity attained by the micro-flow SEC-MS, along with the on-column focusing achieved by the IEX precolumn, provided picogram detection limits for proteins.

Multiattribute Monitoring of Aggregates and Charge Variants of Monoclonal Antibody through Native 2D-SEC-MS-WCX-MS

Monitoring of critical quality attributes such as size and charge-related heterogeneities is essential for biopharmaceutical manufacturers. Size-exclusion chromatography (SEC) is the preferred analytical technique for the quantification of aggregates and fragments in the product, whereas weak-cation exchange chromatography (WCX) is widely used for the characterization of charge variants of biotherapeutic products, in particular monoclonal antibodies (mAbs). Multiattribute monitoring offers the ability to monitor these attributes in a single run flow using two-dimensional liquid chromatography (2D-LC). Typically, in this approach, only the second-dimension samples are directly analyzed through mass spectrometry, as the first dimension has limitations concerning direct coupling with mass spectrometry. In the present study, a novel 2D-SEC-MS/WCX-MS workflow has been proposed, in which chromatography of both dimensions (D¹ and D²) was directly coupled with mass spectrometry, through which size-related and charge-related variants of monoclonal antibody mAb A were analyzed simultaneously in their native form. In comparison to stand-alone SEC and WCX methods, this method enables simultaneous analysis of size and charge variants in a single workflow without manual intervention, allowing analysis of low abundant variants. Further, this method has 75% less sample requirement and a shorter analysis time (25 min vs 90 min) when size and charge variants were analyzed individually. The proposed native 2D-LC-MS workflow was used to analyze a stressed sample of mAb A, in which D¹ analysis revealed the presence of aggregates (8-20%), which were primarily dimers, whereas D² analysis showed an increment in acidic variants (9-21%).

3D Printed Instrument for Taylor Dispersion Analysis with Two-Point Laser-Induced Fluorescence Detection

Precisely controlling the size of engineered biomolecules and pharmaceutical compounds is often critical to their function. Standard methods for size characterization, such as dynamic light scattering or size exclusion chromatography, can be sample intensive and may not provide the sensitivity needed for mass- or concentration-limited biological systems. Taylor dispersion analysis (TDA) is a proven analytical method for direct, calibration-free size determination which utilizes only nL-pL sample volumes. In TDA, diffusion coefficients, which are mathematically transformed to hydrodynamic radii, are determined by characterizing band broadening of an analyte under well-controlled laminar flow conditions. Here, we describe the design and development of a 3D printed instrument for TDA, which is the first such instrument to offer dual-point laser-induced fluorescence (LIF) detection. The instrument utilized a fully 3D printed eductor as a vacuum source for precise and stable pressure-driven flow within a capillary, evidenced by a linear response in generated static pressure to applied gas pressure (R² = 0.997) and a 30-fold improvement in stability of static pressure (0.05% RSD) as compared to a standard mechanical pump (1.53%). Design aspects of the LIF detection system were optimized to maximize S/N for excitation and emission optical axes, and high sensitivity was achieved as evidenced by an 80 pM limit of detection for the protein R-Phycoerythrin and low nM limits of detection for three additional fluorophores. The utility of the instrument was demonstrated via sizing of R-Phycoerythrin at pM concentrations.

Direct coupling of size exclusion chromatography and mass spectrometry for the characterization of complex monoclonal antibody products

The present study describes the possibilities offered by an innovative bioinert size exclusion chromatography column for size variant characterization of complex monoclonal antibody products. This size exclusion chromatography column includes a novel column hardware surface. The column was prepared from metallic hardware components that were treated to have prototype hydrophilically modified hybrid organic–inorganic silica surfaces called hybrid surface technology. This provides a significant reduction in nondesired hydrophobic and electrostatic interactions that can occur between column and analyte when performing size exclusion chromatography analysis with volatile mobile phase.

Compared to a reference stainless‐steel column packed with the same batch of packing material, peak tailing, band broadening, and above all recovery of high molecular weight species were distinctly improved for all types of monoclonal antibody products. Based on our observations, we found that 50 mM ammonium acetate in water was a suitable mobile phase offering good compromise in terms of liquid chromatography performance and mass spectrometry sensitivity. In addition, method repeatability (intra‐ and interday relative standard deviations) on elution times and high molecular weight species peak areas were found to be excellent.

By using this innovative size exclusion chromatography material, the low and high molecular weight species contained in various stressed and nonstressed monoclonal antibody products were successfully characterized with mass spectrometry detection.

The importance of being metal-free: The critical choice of column hardware for size exclusion chromatography coupled to high resolution mass spectrometry

The goal of the study was to evaluate the possibilities offered by a new generation of metal-free SEC column to perform direct SEC-MS of protein biopharmaceuticals using ammonium acetate as the main mobile phase additive. The prototype metal-free SEC column hardware used in this work was a polyether ether ketone (PEEK) infused stainless steel tube including PEEK frits. This PEEK-lined column provides a fully bioinert and metal-free fluidic path, while maintaining the stability of the metal hardware, and could be a good solution to limit possible undesired interactions between proteins and column wall/frits. This prototype metal-free SEC column was systematically compared with a conventional stainless-steel SEC column hardware packed with the same stationary phase material. Four different mAb products, namely trastuzumab, palivizumab, bevacizumab and NISTmAb, and one antibody drug conjugate (ADC), trastuzumab emtansine, were selected as test samples. It appears that peak symmetry, separation of low molecular weight species (LMWS), and the recovery of high molecular weight species (HMWS) were significantly improved for the different biopharmaceutical products on the metal-free SEC column. It has also been demonstrated that the largest differences between standard and metal-free SEC columns were observed for the most basic mAbs (high pI), which confirms that electrostatic interactions between the mAb and the metallic parts of the column (frits and inlet tube) could be responsible for the issues observed when performing SEC analysis with volatile mobile phase. Finally, it was feasible to perform SEC-MS analysis for a wide range of biopharmaceutical products using volatile mobile phase. Our results also highlight that an inappropriate column could bias the quantification of size variants when using MS-compatible mobile phases. Therefore, metal-free column, such as the PEEK-lined column, should be preferentially selected for SEC-MS analysis.

Identification of critical chemical modifications by size exclusion chromatography of stressed antibody-target complexes with competitive binding

Chemical modifications (attributes) in the binding regions of stressed therapeutic proteins may affect binding to target and efficacy of therapeutic proteins. The method presented here describes the criticality assessment of therapeutic antibody modifications by size-exclusion chromatography (SEC) of competitive binding between a stressed antibody and its target, human epidermal growth factor receptor-2 (HER2), followed by SEC fractionation and peptide mapping characterization of bound and unbound antibodies. When stressed antibody and its target were mixed at a stoichiometric molar ratio of 1:2, only antibody-receptor complex eluted from SEC, indicating that binding was not decreased to break the complex. When a smaller amount of the receptor was provided (1:1), the antibody species with modifications reducing binding eluted as unbound from SEC, while the antibody-receptor complex eluted as the bound fraction. Peptide mapping revealed ratios of modifications between unbound and bound fractions. Statistical analysis after triplicate measurements (n = 3) indicated that heavy chain (HC) D102 isomerization and light chain (LC) N30 deamidation were four-fold higher in unbound fraction with high statistical significance. Although HC N55 deamidation and M107 oxidation were also abundant, they were not statistically different between unbound and bound. Our findings agree with previously published potency measurements of collected CEX fractions and the crystal structure of antibody and HER2. Overall, competitive SEC of stressed antibody-receptor mixture followed by peptide mapping is a useful tool in revealing critical residues and modifications involved in the antibody-target binding, even if they elute as a complex from SEC when mixed at 1:2 stoichiometric ratio.

Unraveling the mysteries of modern size exclusion chromatography - the way to achieve confident characterization of therapeutic proteins

Modern size exclusion chromatography (SEC) can be defined by the use of relatively small columns (e.g., 150 × 4.6 mm) packed with sub-3 μm particles, allowing a 3- to 5-fold increase in method throughput compared to that of conventional SEC. The quick success of the first sub-2 μm SEC column introduced in 2010 led to the development of numerous ultra-high performance (UHP)-SEC columns for the analysis of therapeutic monoclonal antibody (mAb)-based products. Aggregates also known as high-molecular-weight species (HMWS) are indeed one of the most important critical quality attributes (CQAs) of mAbs, as HMWS may decrease the product efficacy or cause immunogenicity effects. Therefore, the confident characterization of mAbs requires strong knowledge of not only modern SEC performance (i.e., selectivity and efficiency) but also the inherent limitations caused by non-specific interactions more likely to occur with complex antibody drug conjugates (ADCs) and some commercial mAb products. This review discusses the importance of liquid chromatographic (LC) instrumentation in order to exploit the full potential of modern SEC columns and current trends to hyphenate SEC to mass spectrometry (MS). Recent applications for antibody-based products (i.e., mAbs, ADCs, Fc-Fusion proteins and bispecific antibodies) are presented. Finally, tips and tricks are provided to further optimize SEC separations and maintaining their performance over time with better understanding of unexpected SEC results.

Analytical techniques for the characterization of Antibody Drug Conjugates: Challenges and prospects

Antibody drug conjugates are increasingly being researched for the treatment of cancer. Accurate and reliable characterization of ADCs is inevitable for their development as potential therapeutic agent. Different analytical techniques have been used in order to decipher heterogeneous nature of antibody drug conjugates, enabling successful characterization. This review will summarize specially three major analytical tools i.e. UV-Vis spectroscopy, liquid chromatography, and mass spectrometry used in characterization of antibody drug conjugates. In this review, major challenges during analysis due to the inherent features of analytical techniques and antibody drug conjugates are summarized along with the modifications intended to address each challenge.

Current possibilities of liquid chromatography for the characterization of antibody-drug conjugates

Antibody Drug Conjugates (ADCs) are innovative biopharmaceuticals gaining increasing attention over the last two decades. The concept of ADCs lead to new therapy approaches in numerous oncological indications as well in infectious diseases. Currently, around 60 CECs are in clinical trials indicating the expanding importance of this class of protein therapeutics. ADCs show unprecedented intrinsic heterogeneity and address new quality attributes which have to be assessed. Liquid chromatography is one of the most frequently used analytical method for the characterization of ADCs. This review summarizes recent results in the chromatographic characterization of ADCs and supposed to provide a general overview on the possibilities and limitations of current approaches for the evaluation of drug load distribution, determination of average drug to antibody ratio (DAR_av), and for the analysis of process/storage related impurities. Hydrophobic interaction chromatography (HIC), reversed phase liquid chromatography (RPLC), size exclusion chromatography (SEC) and multidimensional separations are discussed focusing on the analysis of marketed ADCs. Fundamentals and aspects of method development are illustrated with applications for each technique. Future perspectives in hydrophilic interaction chromatography (HILIC), HIC, SEC and ion exchange chromatography (IEX) are also discussed.