Dilute-and-shoot analysis of therapeutic monoclonal antibody variants in fermentation broth: a method capability study

Characterization of large transgene integrations in Chinese hamster ovary cells using a bioengineered mammalian transposase

We present the first use of a bioengineered mammalian transposase system derived from Myotis lucifugus (bMLT) for integration of expression vectors into the CHO genome, focusing on GFP and trastuzumab production. Initially, CHO-K1 cells are transfected with a GFP reporter and varying amounts of bMLT DNA or mRNA. GFP expression is monitored over 17 weeks without selective pressure. Transfection efficiency shows around 90% GFP-positive cells, but in control cultures GFP expression disappears after 10 days. In contrast, bMLT-treated cultures maintain stable GFP expression, with a dose-dependent integration efficiency of up to 60%. The highest GFP expression per cell is observed with lower bMLT amounts. Next-generation sequencing analysis reveals multiple integration sites, with 85% correctly integrated sequences. Next, CHO-GS-/- cells are transfected with trastuzumab and bMLT DNA or mRNA. Cells are selected in glutamine-free medium with varying methionine sulfoximine (MSX) concentrations. Recovery is faster without MSX, and no difference is observed between bMLT DNA and mRNA transfections. bMLT-treated cultures show a higher percentage of trastuzumab-secreting cells (40%-55%) compared with random integration (0.3%-0.5%). The absence of insulators in the trastuzumab plasmid likely affects selection behavior, as integration in heterochromatic regions results in gene repression. Overall, bMLT-mediated integration proves efficient, generating stable cell pools with high expression profiles without selective pressure. The integration sites' genomic location significantly impacts productivity, with favorable regions supporting higher expression. This method shows promise for the rapid and efficient generation of high-producing cell lines and for rapid evaluation of long-term effects of different cell engineering approaches.

Research of saccharides and related biocomplexes: A review with recent techniques and applications

Saccharides and biocompounds as saccharide (sugar) complexes have various roles and biological functions in living organisms due to modifications via nucleophilic substitution, polymerization, and complex formation reactions. Mostly, mono-, di-, oligo-, and polysaccharides are stabilized to inactive glycosides, which are formed in metabolic pathways. Natural saccharides are important in food and environmental monitoring. Glycosides with various functionalities are significant in clinical and medical research. Saccharides are often studied with the chromatographic methods of hydrophilic interaction liquid chromatography and anion exchange chromatograpy, but also with capillary electrophoresis and mass spectrometry with their on-line coupling systems. Sample preparation is important in the identification of saccharide compounds. The cases discussed here focus on bioscience, clinical, and food applications.

Stability assessment of FDA-approved ramucirumab monoclonal antibody; validated SE-HPLC method for degradation pattern evaluation

Ramucirumab (RAMU) is a recently US Food and Drug Administration-approved monoclonal antibody that is included in various anticancer protocols. It has a structural complexity and high degradation risk that have a significant effect on its safety and effectiveness. The major aim of this work was to assess the degradation pattern of RAMU based on physicochemical characterization. Mechanical agitation, repeated freeze-thaw cycles, pH and temperature were the selected stress conditions to which RAMU samples were subjected. The SE-HPLC method was applied and validated to monitor the RAMU monomer along with its aggregates and/or fragments. The purity of the separated peaks together with system suitability parameters were determined through the calculation of percentage purity and percentage drop in RAMU concentration. The results were interpreted by correlating them with those of dynamic light scattering and reducing and non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Samples incubated at pH 2.0-10.0 and 37°C for up to 4 weeks were analysed, recording detection of reversed phase (RP) aggregates and low molecular weight peptide fragments. Similarly, samples under short-term storage conditions of 4 weeks at different temperatures (-20, 2-8, 25, 37 and 50°C) showed low molecular weight peptide fragments but to a lesser extent. These results highlight the alarming effect on RAMU multidose vial efficacy and safety.

High throughput glycosylation analysis of intact monoclonal antibodies by mass spectrometry coupled with capillary electrophoresis and liquid chromatography

The analysis of monoclonal antibodies glycosylation is a crucial quality control attribute of biopharmaceutical drugs. High throughput screening approaches for antibody glycoform analysis are required in various stages of process optimization. Here, we present high throughput screening suitable mass spectrometry-based workflows for the analysis of intact antibody glycosylation out of cell supernatants. Capillary electrophoresis and liquid chromatography were coupled with quadrupole time-of-flight MS or Orbitrap MS. Both separation methods offer fast separation (10-15 min) and the capability to prevent the separated cell supernatant matrix to enter the MS by post-separation valving. Both MS instruments provide comparable results and both are sufficient to determine the glycosylation pattern of the five major glycoforms of the measured antibodies. However, the Orbitrap yields higher sensitivity of 25 μg/mL (CE-nanoCEasy-Orbitrap MS) and 5 μg/mL (LC-Orbitrap MS). Data processing was optimized for a faster processing and easier detection of low abundant glycoforms based on averaged charge-deconvoluted mass spectra. This approach combines a non-target glycoform analysis, while yielding the same glycosylation pattern as the traditional approach based on extracted ion traces. The presented methods enable the high throughput screening of the glycosylation pattern of antibodies down to low μg/mL-range out of cell supernatant without any sample preparation. This article is protected by copyright. All rights reserved.

Uncertainty of Size-Exclusion Chromatography Method in Quality Control of Bevacizumab Batches

In addition to the analytical challenges related to the size and complexity of biopharmaceutical drugs, the inherent variability that arises due to their manufacturing process requires monitoring throughout the production process to ensure the safety and efficacy of the finished product. In this step, validation data should demonstrate that the process is controlled and reproducible, whereas the manufacturing process must ensure the quality and consistency of the product. For this, the manufacturer sets specification limits according with regulatory guidance. In such a situation, the comparison of different batches is required in order to describe and analyze the variability between them. However, it is unclear how great the variability of the analytical method would be or that in producing the batches. The estimation of the β-expectation tolerance intervals based on the variance components to account for both between-batch and within-batch variability was proposed as a specification limit to control the heterogeneity between batches at the time of manufacture and to verify whether batches meet specification limits. At this point, the variance components were computed by the maximum likelihood method using a linear random model. For this, the protein content, expressed as a percentage of the actual concentration relative to the claim value, and the dimer content (expressed as percentage) were used as critical quality attributes (CQAs) in the monitoring and control process. We used real data from six bevacizumab commercial batches.

Bioanalytical strategies in drug discovery and development

A reliable, rapid, and effective bioanalytical method is essential for the determination of the pharmacokinetic, pharmacodynamic, and toxicokinetic parameters that inform the safety and efficacy profile of investigational drugs. The overall goal of bioanalytical method development is to elucidate the procedure and operating conditions under which a method can sufficiently extract, qualify, and/or quantify the analyte(s) of interest and/or their metabolites for the intended purpose. Given the difference in the physicochemical properties of small and large molecule drugs, different strategies need to be adopted for the development of an effective and efficient bioanalytical method. Herein, we provide an overview of different sample preparation strategies, analytical platforms, as well as procedures for achieving high throughput for bioanalysis of small and large molecule drugs.

Simultaneous Monitoring of Monoclonal Antibody Variants by Strong Cation-Exchange Chromatography Hyphenated to Mass Spectrometry to Assess Quality Attributes of Rituximab-Based Biotherapeutics

Different manufacturing processes and storage conditions of biotherapeutics can lead to a significant variability in drug products arising from chemical and enzymatic post-translational modifications (PTMs), resulting in the co-existence of a plethora of proteoforms with different physicochemical properties. To unravel the heterogeneity of these proteoforms, novel approaches employing strong cation-exchange (SCX) high-performance liquid chromatography (HPLC) hyphenated to mass spectrometry (MS) using a pH gradient of volatile salts have been developed in recent years. Here, we apply an established SCX-HPLC-MS method to characterize and compare two rituximab-based biotherapeutics, the originator MabThera® and its Indian copy product Reditux™. The study assessed molecular differences between the two drug products in terms of C-terminal lysine variants, glycosylation patterns, and other basic and acidic variants. Overall, MabThera® and Reditux™ displayed differences at the molecular level. MabThera® showed a higher degree of galactosylated and sialylated glycoforms, while Reditux™ showed increased levels of oligomannose and afucosylated glycoforms. Moreover, the two drug products showed differences in terms of basic variants such as C-terminal lysine and N-terminal truncation, present in Reditux™ but not in MabThera®. This study demonstrates the capability of this fast SCX-HPLC-MS approach to compare different drug products and simultaneously assess some of their quality attributes.

Combining direct urinary injection with automated filtration and nanoflow LC-MS for the confirmatory analysis of doping-relevant small peptide hormones

Nano-liquid chromatography (nanoLC) has proven itself as a powerful tool and its scope entails various applications in (bio)analytical fields. Operation at low (nL/min) flow rates in combination with reduced inner dimensions (ID < 100 µm), leads to significantly enhanced sensitivity when coupled with electrospray ionization-mass spectrometry (ESI-MS). Challenges that remain for the routine implementation of such miniaturized setups are related to clogging of the system and robustness in general, and thus the application of tedious sample preparation steps. To improve ruggedness, a filter placed upstream in the LC prevents particles from entering and clogging the system. This so-called online automatic filtration and filter back-flush (AFFL) system was combined with nanoLC and the direct injection principle for the sensitive confirmatory analysis of fifty different doping-relevant peptides in urine. The presented assay was fully validated for routine purposes according to selectivity and matrix interference, limit of identification (LOI), carryover, matrix effect, sample extract stability, analysis of educational external quality assessment (EQAS) samples, robustness of the online AFFL-setup and retention time stability. It was also fully compliant with the most recent minimum required performance levels (MRPL) and chromatographic/mass spectrometric identification criteria (IDCR), as imposed by the World Anti-Doping Agency (WADA). In the absence of labor-intensive sample preparation, the application of AFFL allowed for the injection of diluted urine samples without any noticeable pressure buildup in the nanoLC system. Contrary to earlier observations by our group and others, the addition of dimethylsulfoxide (DMSO) to the mobile phase did not enhance sensitivity in the presented nanoflow setup, yet was beneficial to reduce carry over. Although the robustness of the presented setup was evaluated only for the analysis of diluted urine samples, it is entirely conceivable that routine applications employing other matrices and currently running on analytical scale LC instruments could be transferred to micro/nanoLC scale systems to reach lower detection limits.

Exploring the Chemical Space of Protein Glycosylation in Noncovalent Protein Complexes: An Expedition along Different Structural Levels of Human Chorionic Gonadotropin by Employing Mass Spectrometry

Modern analytical approaches employing high-resolution mass spectrometry (MS) facilitate the generation of a vast amount of structural data of highly complex glycoproteins. Nevertheless, systematic interpretation of this data at different structural levels remains an analytical challenge. The glycoprotein utilized as a model system in this study, human chorionic gonadotropin (hCG), exists as a heterodimer composed of two heavily glycosylated subunits. In order to unravel the multitude of glycoforms of recombinant hCG (drug product Ovitrelle), we combine established techniques, such as released glycan and glycopeptide analysis, with novel approaches employing high-performance liquid chromatography-mass spectrometry (HPLC-MS) to characterize protein subunits and native MS to analyze the noncovalent hCG complex. Starting from the deconvoluted mass spectrum of dimeric hCG comprising about 50 signals, it was possible to explore the chemical space of hCG glycoforms and elucidate the complexity that hides behind just 50 signals. Systematic, stepwise integration of data obtained at the levels of released glycans, glycopeptides, and subunits using a computational annotation tool allowed us to reveal 1031 underlying glycoforms. Additionally, critical quality attributes such as sialylation and core fucosylation were compared for two batches of Ovitrelle to assess the potential product variability.

Towards middle-up analysis of polyclonal antibodies: subclass-specific N-glycosylation profiling of murine immunoglobulin G (IgG) by means of HPLC-MS

In recent years, advanced HPLC-MS strategies based on intact protein (“top-down”) or protein subunit (“middle-up/middle-down”) analysis have been implemented for the characterization of therapeutic monoclonal antibodies. Here, we assess feasibility of middle-up/middle-down analysis for polyclonal IgGs exhibiting extensive sequence variability. Specifically, we addressed IgGs from mouse, representing an important model system in immunological investigations. To obtain Fc/2 portions as conserved subunits of IgGs, we made use of the bacterial protease SpeB. For this purpose, we initially determined SpeB cleavage sites in murine IgGs. The resulting Fc/2 portions characteristic of different subclasses were subsequently analysed by ion-pair reversed-phase HPLC hyphenated to high-resolution mass spectrometry. This enabled simultaneous relative quantification of IgG subclasses and their N-glycosylation variants, both of which influence IgG effector functions. To assess method capabilities in an immunological context, we applied the analytical workflow to polyclonal antibodies obtained from BALB/c mice immunized with the grass pollen allergen Phl p 6. The study revealed a shift in IgG subclasses and Fc-glycosylation patterns in total and antigen-specific IgGs from different mouse cohorts, respectively. Eventually, Fc/2 characterization may reveal other protein modifications including oxidation, amino acid exchanges, and C-terminal lysine, and may thus be implemented for quality control of functional antibodies.

A Simple Strategy to Eliminate Hexosylation Bias in the Relative Quantification of N-Glycosylation in Biopharmaceuticals

N‐glycosylation may affect the safety and efficacy of biopharmaceuticals and is thus monitored during manufacturing. Mass spectrometry of the intact protein is increasingly used to reveal co‐existing glycosylation variants. However, quantification of N‐glycoforms via this approach may be biased by single hexose residues as introduced by glycation or O‐glycosylation. Herein, we describe a simple strategy to reveal actual N‐glycoform abundances of therapeutic antibodies, involving experimental determination of glycation levels followed by computational elimination of the “hexosylation bias”. We show that actual N‐glycoform abundances may significantly deviate from initially determined values. Indeed, glycation may even obscure considerable differences in N‐glycosylation patterns of drug product batches. Our observations may thus have implications for biopharmaceutical quality control. Moreover, we solve an instance of the problem of isobaricity, which is fundamental to mass spectrometry.

Development, characterization, and application of a 2-Compartment system to investigate the impact of pH inhomogeneities in large-scale CHO-based processes

Large-scale bioreactors for the production of monoclonal antibodies reach volumes of up to 25 000 L. With increasing bioreactor size, mixing is however affected negatively, resulting in the formation of gradients throughout the reactor. These gradients can adversely affect process performance at large scale. Since mammalian cells are sensitive to changes in pH, this study investigated the effects of pH gradients on process performance. A 2-Compartment System was established for this purpose to expose only a fraction of the cell population to pH excursions and thereby mimicking a large-scale bioreactor. Cells were exposed to repeated pH amplitudes of 0.4 units (pH 7.3), which resulted in decreased viable cell counts, as well as the inhibition of the lactate metabolic shift. These effects were furthermore accompanied by increased absolute lactate levels. Continuous assessment of molecular attributes of the expressed target protein revealed that subunit assembly or N-glycosylation patterns were only slightly influenced by the pH excursions. The exposure of more cells to the same pH amplitudes further impaired process performance, indicating this is an important factor, which influences the impact of pH inhomogeneity. This knowledge can aid in the design of pH control strategies to minimize the effects of pH inhomogeneity in large-scale bioreactors.