Articles tagged ”LC-MS”
FabRICATOR used to Locate Modification Sites of IgG Caused by Reducing Agents
A charge heterogeneity is an unfavorable phenomenon observed for mAbs and is considered as a critical quality attribute since it can alter the efficacy and pharmacokinetics of biopharmaceuticals. Acidic and basic species of an IgG are due to various chemical modifications on the molecule. The origin of acidic species has previously been reported to be formed by deamidation, oxidation of side-chains, cysteinylation, glycosylation, glycation, sialylation and fragmentation while the basic species comes from C-terminal lysine clipping, pyro-glu cyclization, succinimide formation and aggregation. Scientists at Boehringer Ingelheim together with scientists at NMI at University of Tübingen recently published a study characterizing the root cause of charged species of an IgG1 mAb.
Generating Antibody Mimetics with GingisKHAN
Antibodies formulated as solid-state depots can potentially be used for local treatments and minimize the need for large systemic doses. Bevacizumab may for instance be administered locally to control post-operative scarring following glaucoma filtration surgery. A solid-state form would however be required in order to obtain a proper slow release of the antibody. Read more »
GlyCLICK® and Middle-up LC-MS Enables Robust ADC Development
Scientists at the University of Geneva and CNRS present site-specific ADCs generated using the GlyCLICK technology and an analytical middle-up LC-HRMS workflow as a potential core module for ADC development.
Antibody-drug conjugates (ADCs) are efficient therapeutic agents that possess the cell-targeting properties of monoclonal antibodies combined with the potency of cytotoxic drugs. Early generation ADCs were predominantly obtained through non-selective conjugation methods by incorporation of a drug payload at randomly distributed sites. Such methods result in highly heterogenous subpopulations of varying antibody-drug ratio (DAR) leading to potential loss of efficacy and impaired pharmacokinetics. While alternative strategies exploring genetic engineering have emerged for conjugation at non-natural amino acids, challenges related to both production and analytical characterization persist.
Glycan-mediated bioconjugation using the GlyCLICK technology is an attractive option to overcome the challenges of conventional bioconjugation without the need for genetic engineering to produce custom ADCs. By utilizing a unique combination of enzymes, the conserved Fc-glycans are remodeled and site-specifically conjugated using click chemistry for ADCs carrying two payloads per antibody (DAR=2.0) having controlled drug stoichiometry and preserved immunoreactivity. In this paper, Duivelshof et al. developed a site-specific ADC by coupling trastuzumab to DM1 using the GlyCLICK technology and evaluated the quality of the conjugation process using complementary reversed phase (RPLC) and hydrophilic interaction chromatography (HILIC) coupled to high-resolution mass spectrometry (HRMS).
The trastuzumab antibody was site-specifically conjugated to DBCO-functionalized DM1 (DBCO-PEG4-Ahx-DM1) using the GlyCLICK technology. To reduce sample complexity, the antibodies were digested with FabRICATOR® (Ides) or FabALACTICA® (IgdE) and reduced for comparison of native and GlyCLICK conjugated trastuzumab at the subunit level. The complementary HILIC and RPLC workflow allowed the authors to observe the significant shift in retention between the lipophilic drug payloads on the ADC and the hydrophilic N-glycans on native trastuzumab. These results enabled the scientists to confirm site-specific conjugation at the Fc-glycans sites, while hyphenation to HRMS detection allowed accurate determination of a DAR of 2.0 for GlyCLICK conjugated trastuzumab, which was not possible at the intact ADC level.
“Most ADCs are produced with non-selective bioconjugation of drug payloads to lysine or cysteine residues creating a wide variety of drug-antibody ratios (DAR). In the frame of new ADC product development, we believe that having control over the DAR and drug load distribution (DLD) is of crucial importance, as is the ability to accurately monitor these two CQAs. Therefore, the combination of the GlyCLICK technology to create homogeneous site-specific ADCs with the middle-up LC/HRMS approach to rapidly determine both the DLD and DAR has a great potential for ADC development.”
ADC Biotransformation Analysis using FabRICATOR and LC-MS
Current strategies for analyzing in vivo biotransformation of antibody-drug conjugates (ADCs) are limited by the site of conjugation, extensive sample preparation and insufficient sensitivity. In this paper by Kotapati et al., the authors developed a universal affinity capture method for assessing the effects of biotransformation on any site-specific ADC using generic reagents and LC-HRMS analysis.
Antibody-Drug Conjugates (ADCs) can undergo in vivo biotransformation where the payload can be metabolized to an inactive species or be subjected to deconjugation releasing the payload into systemic circulation. Strategically selected conjugation sites can minimize proteolytic cleavage or steric hindrance of the surrounding mAb domains, ultimately improving the potency and stability in vivo. The process of screening for optimal conjugation sites is therefore an important part of ADC discovery and development.
ADCs prepared from various antibodies and payloads with site-specific conjugation sites at the LC, HC-Fab and HC-Fc were prepared and analyzed using a mono- or dual affinity capture method. Streptavidin magnetic beads coated with anti-human F(ab’)2 captured ADCs from mouse serum and were processed on a KingFisher Flex automated magnetic extraction instrument. The captured ADCs were then, according to conjugation site, either subjected to reduction, on-bead digestion with only the FabRICATOR enzyme or in combination with PNGaseF for complete Fc-deglycosylation. The samples were then either reduced or eluted directly for analysis using high resolution LC-TOF mass spectrometer.
With this method, the authors were able to successfully study biotransformation of site-specific ADCs independent of antibody type, conjugation type or linker-payload chemistry. Using the site-specific FabRICATOR enzyme, HC-Fab and HC-Fc ADCs were digested below the hinge into homogenous F(ab’)2 and Fc subunits for the generation of antibody fragments. Compared to intact ADC analysis, this middle-level approach increased the resolution and sensitivity for identification of the conjugated payload and its metabolites at exceptional sensitivity and resolution.
SmartEnzymes™ in Quality Control of Commercial Antibodies
In a recent paper, Sokolowska and colleagues at Janssen Research and Development qualified and covalidated a subunit LC-MS method for quality control and stability testing of the oxidation status of commercial antibodies.
LC-MS is commonly used for therapeutic antibody development and characterization within the biopharmaceutical industry due to the inherent strengths to provide site-specific identification and quantitation of post-translational modifications. However, the implementation of LC-MS methods to commercial QC labs is challenging, since there are not many options for fully GMP compliant systems. In addition, the methods often require extensive MS expertise and suffer from time-consuming sample preparation and lack of robustness. To counter these obstacles, Sokolowska et al. have developed an LC-MS method that requires minimum analyst training. It uses validated GMP compliant software and is based on subunit analysis, which is proved to be faster and more robust compared to peptide mapping.
The assay uses FabRICATOR® (IdeS) and IgGZERO® (EndoS) enzymes to generate deglycosylated IgG subunits suitable for MS analysis. FabRICATOR digests the antibody below the hinge and IgGZERO hydrolyzes the Fc N-glycans. The subunits are analyzed using reversed phase-ultraperformance liquid chromatography coupled to a quadrupole time-of-flight (RP-UPLC-QTOF) MS to monitor antibody oxidation for stability testing and commercial product release.
The developed subunit LC-MS assay was covalidated in three laboratories and showed comparable performance. The robustness was tested by varying both the LC-MS settings and the sample preparation. The enzymatic conditions included variations in protein concentration, enzyme lots, enzyme-to-protein ratio, digestion time and temperature, reduction time and temperature, and reagent concentrations. Minor variations in sample preparation all led to measured Fc oxidation within the method variation +/- 0.9%.
Figure 1. mAb subunit oxidation assay using FabRICATOR and IgGZERO (Sokolowska et al., 2020.)
The approval of this method opens the door for implementing other subunit LC-MS and multiattribute methods in QC laboratories to modernize commercial QC and stability testing.
Learn more by reading the full paper, follow the link below.
https://pubs.acs.org/doi/full/10.1021/acs.analchem.9b05036
