CE methods for charge variant analysis of mAbs and complex format biotherapeutics

Charge heterogeneity analysis of monoclonal antibodies (mAbs) and complex formats, such as bispecifics, is crucial for therapeutic applications. In this study, we developed two capillary electrophoresis (CE)-based methods, capillary zone electrophoresis (CZE) and imaged capillary isoelectric focusing (iCIEF), for analyzing a broad spectrum of mAbs and complex mAb formats. For CZE, we introduced a new buffer system and optimized the background electrolyte (BGE) with an alternative dynamic coating agent and a superior polymeric additive. The pH of the BGE was increased, leading to enhanced resolution of high pI and complex format mAbs. In iCIEF, we identified an ampholyte combination offering a highly linear pH gradient and covering a suitable pH range. We also investigated alternatives to denaturing stabilizers and found that non-detergent sulfobetaine 195 exhibited excellent properties for iCIEF applications. These optimized methods provide a framework for the charge heterogeneity analysis of therapeutic mAbs and complex formats.

Analytical Techniques for the Characterization and Quantification of Monoclonal Antibodies

Monoclonal antibodies (mAbs) are a fast-growing class of biopharmaceuticals. They are widely used in the identification and detection of cell makers, serum analytes, and pathogenic agents, and are remarkably used for the cure of autoimmune diseases, infectious diseases, or malignancies. The successful application of therapeutic mAbs is based on their ability to precisely interact with their appropriate target sites. The precision of mAbs rely on the isolation techniques delivering pure, consistent, stable, and safe lots that can be used for analytical, diagnostic, or therapeutic applications. During the creation of a biologic, the key quality features of a particular mAb, such as structure, post-translational modifications, and activities at the biomolecular and cellular levels, must be characterized and profiled in great detail. This implies the requirement of powerful state of the art analytical techniques for quality control and characterization of mAbs. Until now, various analytical techniques have been developed to characterize and quantify the mAbs according to the regulatory guidelines. The present review summarizes the major techniques used for the analyses of mAbs which include chromatographic, electrophoretic, spectroscopic, and electrochemical methods in addition to the modifications in these methods for improving the quality of mAbs. This compilation of major analytical techniques will help students and researchers to have an overview of the methodologies employed by the biopharmaceutical industry for structural characterization of mAbs for eventual release of therapeutics in the drug market.

Analysis of Denosumab by a Validated CZE Method and Determination of Sialic Acids by the RP-HPLC Method

A capillary zone electrophoresis (CZE) method was developed and validated to quantitate the monoclonal antibody denosumab (DmAb) and its charge variants in pharmaceutical products, demonstrating excellent precision, linearity and accuracy. Separations were obtained with migration times of 11.3 min for DmAb and the calibration curve was linear in the range of 0.95-20 mg/mL. The analytical comparability of seven batches of Prolia® showed mean differences of the estimated content/potencies of 1.87% lower, and 0.84 and 1.21% higher compared with the size-exclusion and reversed-phase liquid chromatography (SE-HPLC and RP-HPLC) methods and the osteoclast antiproliferative bioassay, respectively, with non-significant differences (P > 0.05). An RP-HPLC method with fluorescence detection (RP-HPLC-F), performed on a Kinetex® EVO C18 column (5 μm, 100 Å, 250 mm × 4.6 mm), was optimized to determine the levels of sialic acids of DmAb biomolecules, giving mean concentrations of 0.16 and 0.17 μg N-acetylneuraminic acid/mg DmAb for Prolia® and Xgeva® pharmaceutical products, respectively. The results demonstrated the capability of each one of the methods, and their use in combination constitutes a strategy to monitor instability, thereby assuring the quality and the batch-to-batch consistency of the biotechnology-derived medicine.

Structural identification and absolute quantification of monoclonal antibodies in suspected counterfeits using capillary electrophoresis and liquid chromatography-tandem mass spectrometry

Monoclonal antibodies (mAbs) represent a major category of biopharmaceutical products which due to their success as therapeutics have recently experienced the emergence of mAbs originating from different types of trafficking. We report the development of an analytical strategy which enables the structural identification of mAbs in addition to comprehensive characterization and quantification in samples in potentially counterfeit samples. The strategy is based on the concomitant use of capillary zone electrophoresis analysis (CZE-UV), size exclusion chromatography coupled to multi-angle light scattering (SEC-MALS) and liquid chromatography hyphenated to tandem mass spectrometry (LC-MS/MS). This analytical strategy was applied to the investigation of different samples having unknown origins seized by the authorities, and potentially incorporating an IgG 4 or an IgG 1. The results achieved from the different techniques demonstrated to provide orthogonal and complementary information regarding the nature and the structure of the different mAbs. Therefore, they allowed to conclude unequivocally on the identification of the mAbs in the potentially counterfeit samples. Finally, a LC-MS/MS quantification method was developed which specificity was to incorporate a different mAbs labeled with stable isotopes as internal standard. The LC-MS/MS quantification method was validated and thus demonstrated the possibility to use common peptides with the considered IgG in order to achieve limit of quantification as low as 41.4 nM. The quantification method was used to estimate the concentration in the investigated samples using a single type of internal standard and experimental conditions, even in the case of mAbs with no stable isotope labeled homologues available.

Applications of capillary electrophoresis for biopharmaceutical product characterization

Capillary electrophoresis (CE), after being introduced several decades ago, has carved out a niche for itself in the field of analytical characterization of biopharmaceutical products. It does not only offer fast separation, high resolution in miniaturized format, but equally importantly represents an orthogonal separation mechanism to high-performance liquid chromatography. Therefore, it is not surprising that CE-based methods can be found in all major pharmacopoeias and are recommended for the analysis of biopharmaceutical products during process development, characterization, quality control, and release testing. Different separation formats of CE, such as capillary gel electrophoresis, capillary isoelectric focusing, and capillary zone electrophoresis are widely used for size and charge heterogeneity characterization as well as purity and stability testing of therapeutic proteins. Hyphenation of CE with MS is emerging as a promising bioanalytical tool to assess the primary structure of therapeutic proteins along with any impurities. In this review, we confer the latest developments in capillary electrophoresis, used for the characterization of critical quality attributes of biopharmaceutical products covering the past 6 years (2015-2021). Monoclonal antibodies, due to their significant share in the market, have been given prioritized coverage.

Recent biopharmaceutical applications of capillary electrophoresis methods on recombinant DNA technology-based products

Biopharmaceuticals (recombinant technology-based products, vaccines, whole blood and blood components, gene therapy, cells, tissues, etc.,) are described as biological medical products produced from various living sources such as human, microbial, animal, and so on by manufacturing, extraction, or semi-synthesis. They are complex molecules having high molecular weights. For their safety and efficacy, their structural, clinical, physicochemical, and chemical features must be carefully controlled, and they must be well characterized by analytical techniques before the approval of the final product. Capillary electrophoresis (CE) having versatile modes can provide valuable safety and efficacy information, such as amino acid sequence, size variants (low and high molecular weight variants), charged variants (acidic and basic impurities), aggregates, N-linked glycosylation, and O-linked glycosylation. There are numerous applications of CE in the literature. In this review, the most significant and recent studies on the analysis of recombinant DNA technology-based products using different CE modes in the last ten years have been overviewed. It was seen that the researches mostly focus on the analysis of mAbs and IgG. In addition, in recent years, researchers have started to prefer CE combined mass spectrometry (MS) techniques to provide a more detailed characterization for protein and peptide fragments.

Analysis of Monoclonal Antibodies by Capillary Electrophoresis: Sample Preparation, Separation, and Detection

Therapeutic monoclonal antibodies (mAbs) are dominating the biopharmaceutical field due to the fact of their high specificity in the treatment of diverse diseases. Nevertheless, mAbs are very complex glycoproteins exhibiting several macro- and microheterogeneities that may affect their safety, quality, and efficacy. This complexity is very challenging for mAbs development, formulation, and quality control. To tackle the quality issue, a combination of multiple analytical approaches is necessary. In this perspective, capillary electrophoresis has gained considerable interest over the last decade due to the fact of its complementary features to chromatographic approaches. This review provides an overview of the strategies of mAbs and derivatives analysis by capillary electrophoresis hyphenated to ultraviolet, fluorescence, and mass spectrometry detection. The main sample preparation approaches used for mAb analytical characterization (i.e., intact, middle-up/down, and bottom-up) are detailed. The different electrophoretic modes used as well as integrated analysis approaches (sample preparation and separation) are critically discussed.

Monitoring of immunoglobulin N- and O-glycosylation in health and disease

Protein N- and O-glycosylation are well known co- and post-translational modifications of immunoglobulins. Antibody glycosylation on the Fab and Fc portion is known to influence antigen binding and effector functions, respectively. To study associations between antibody glycosylation profiles and (patho) physiological states as well as antibody functionality, advanced technologies and methods are required. In-depth structural characterization of antibody glycosylation usually relies on the separation and tandem mass spectrometric (MS) analysis of released glycans. Protein- and site-specific information, on the other hand, may be obtained by the MS analysis of glycopeptides. With the development of high-resolution mass spectrometers, antibody glycosylation analysis at the intact or middle-up level has gained more interest, providing an integrated view of different post-translational modifications (including glycosylation). Alongside the in-depth methods, there is also great interest in robust, high-throughput techniques for routine glycosylation profiling in biopharma and clinical laboratories. With an emphasis on IgG Fc glycosylation, several highly robust separation-based techniques are employed for this purpose. In this review, we describe recent advances in MS methods, separation techniques and orthogonal approaches for the characterization of immunoglobulin glycosylation in different settings. We put emphasis on the current status and expected developments of antibody glycosylation analysis in biomedical, biopharmaceutical and clinical research.

Stepwise optimization and sensitivity improvement of green micellar electrokinetic chromatography method to simultaneously determine some fluoroquinolones and glucocorticoids present in various binary ophthalmic formulations

A sensitive micellar electrokinetic chromatography method is presented to simultaneously quantify ofloxacin, gatifloxacin, dexamethasone sodium phosphate and prednisolone acetate. The method has the advantages of being rapid, accurate, reproducible, ecologically acceptable and sensitive. The electrophoretic separation utilized 20 mm borate buffer as background electrolyte with pH 10.0 ± 0.1 and 50 mm sodium dodecyl sulfate as a micelle forming molecule. A capillary tube (50 μm i.d., 33 cm) of fused silica was used and on-column diode array detection at 243 nm for dexamethasone sodium phosphate and prednisolone acetate, and 290 nm for ofloxacin and gatifloxacin. Various factors were optimized such as the background electrolyte (type, concentration and pH), addition of sodium dodecyl sulfate and its concentration, detection wavelength, applied voltage and injection parameters. The studied drugs were efficiently separated in 6.2 min, at 20 kV with high resolution. The greenness of the method was estimated using an eco-scale tool and the presented method was found to have excellent green characteristics. The method was validated in conformance with International Conference on Harmonization guidelines, with acceptable accuracy, precision and selectivity. The suggested method can be employed for the economic analysis of the four drugs in dissimilar binary combinations of eye drops saving solvents and chemicals.

Non-invasive targeted iontophoretic delivery of cetuximab to skin

Background: Cetuximab (CTX) is a glycosylated anti-EGFR monoclonal antibody of great interest in the treatment of non-melanoma skin cancers. Its intravenous administration is associated with severe side effects. This is the first report on the noninvasive iontophoretic-targeted topical delivery of CTX to skin.Methods: Iontophoretic transport of CTX (0.5 mA/cm²) was studied as a function of formulation pH (4, 5.5 and 7) and duration of current application (2, 4 and 8 h). CTX cutaneous biodistribution was determined; electrotransport mechanisms and penetration pathways were investigated.Results: Electrophoretic mobility measurements of CTX isoforms and co-iontophoresis of acetaminophen at each pH demonstrated that CTX electrotransport was due to electroosmosis: despite an ~8-fold reduction in charge, CTX skin deposition was greater at pH 7 than pH 4 (8.974 ± 1.952 and 0.482 ± 0.165 μg/mm³) - consistent with the increased electroosmotic flow at pH 7. Iontophoresis of an Alex488-CTX conjugate showed that skin penetration occurred by the intercellular and follicular routes. Therapeutic concentrations of CTX in the viable epidermis, upper dermis and lower dermis were achieved following iontophoresis for 2, 4 and 8 h, respectively.Conclusion: The results demonstrate the topical delivery of a 152 kDa monoclonal antibody into skin in a targeted, controlled and entirely noninvasive manner.

Application of affinity capillary electrophoresis for charge heterogeneity profiling of biopharmaceuticals

Charge heterogeneity profiling is important for the quality control (QC) of biopharmaceuticals. Because of the increasing complexity of these therapeutic entities [1], the development of alternative analytical techniques is needed. In this work, flow-through partial-filling affinity capillary electrophoresis (FTPFACE) has been established as a method for the analysis of a mixture of two similar monoclonal antibodies (mAbs). The addition of a specific ligand results in the complexation of one mAb in the co-formulation, thus changing its migration time in the electric field. This allows the characterization of the charged variants of the non-shifted mAb without interferences. Adsorption of proteins to the inner capillary wall has been circumvented by rinsing with guanidine hydrochloride before each injection. The presented FTPFACE approach requires only very small amounts of ligands and provides complete comparability with a standard CZE of a single mAb.

Comparative charge-based separation study with various capillary electrophoresis (CE) modes and cation exchange chromatography (CEX) for the analysis of monoclonal antibodies

Charge heterogeneity is an important critical quality attribute for the analysis of monoclonal antibodies (mAbs). For this, (imaged) capillary isoelectric focusing ((i)cIEF), ion exchange chromatography (IEC) and, recently, capillary zone electrophoresis (CZE) are the predominantly used techniques. In order to investigate which one is most suitable to answer a specific analytical question, here, the four aforementioned separation techniques were systematically evaluated using NISTmAb and Infliximab as test molecules. The performance parameters (precision, separation efficiency, linearity and sensitivity) were determined under comparable conditions. Moreover, important aspects for daily routine such as speed and ease of use were considered. Each technique has its own pros and cons. The (i)cIEF methodology is distinguished by its excellent separation efficiency. In addition, the native fluorescence mode in icIEF is a good tool to analyze small sample amounts (LOQ: 2.8 mg/l for Infliximab). Nevertheless, high performance liquid chromatography (HPLC) still has superior precision. CZE, and also micellar electrokinetic chromatography (MEKC), have emerged as further interesting alternatives. For all techniques, variations connected to the sample preparation strongly influence precision. Looking at the relative standard deviation (RSD) values of the relative peak areas, all techniques provide acceptable performance (RSD: 0.6-1.6%).

Intact monoclonal antibodies separation and analysis by sheathless capillary electrophoresis-mass spectrometry

Capillary electrophoresis-mass spectrometry coupling is a growing technique in biopharmaceutics characterization. Assessment of monoclonal antibodies is well known at middle-up and bottom-up levels to obtain information about the sequence, post-translational modifications and degradation products. Intact protein analysis is an actual challenge to be closer to the real protein structure. At this level, actual techniques are time consuming or cumbersome processes. In this work, a 20 minutes separation method has been developed to optimize characterization of intact monoclonal antibodies. Thus, separation has been done on a positively charged coated capillary with optimized volatile background electrolyte and sample buffer. Three world-wide health authorities approved monoclonal antibodies have been used to set up a rapid and ease of use method. Intact trastuzumab, rituximab and palivizumab isoforms have been partially separated with this method in less than 20 minutes under denaturing conditions. For each monoclonal antibody, 2X-glycosylated and 1X-glycosylated structures have been identified and separated. Concerning basic and acidic variants, potential aspartic acid isomerization modification and asparagine deamidation have been observed. Accurate mass determination for high-mass molecular species remains a challenge, but the progress in intact monoclonal antibodies separation appears very promising for biopharmaceutics characterization.

Characterization of recombinant monoclonal antibody charge variants using WCX chromatography, icIEF and LC-MS/MS

Charge heterogeneity is an important aspect of research into the development of monoclonal antibody drugs. In the present study, charge variants were separated into four fractions using weak cation exchange chromatography and were thoroughly analyzed using liquid chromatography-mass spectrometry at multiple levels. Molecular weight analysis of intact antibody and subunits confirmed the presence of heavy-chain leader sequences, light-chain leader sequences, dehydration, and cysteinylation. Peptide mapping of the fractions using different enzymes further localized the modified sites. Modified proportions identified at peptide level were compared with the purity detected by imaged capillary isoelectric focusing, the results showed that basic variant 1 consisted of cysteinylation and dehydration of asparagine, and basic variant 2 fully accounted for the N-terminal leader sequence of the heavy chain. About 14.8% of the acidic variant can be explained by N-terminal leader sequences in the light chain, and 18% of the acidic variant was demonstrated to be deamidation of asparagine in the heavy chain. There was approximately 54.2% of the acidic variant still cannot be explained. It was hypothesized that those acidic variants that have not yet been identified are an ensemble of molecules with slight molecular weight differences or the same molecular weight but different structures.