Fast Characterization of Fc-Containing Proteins by Middle-Down Mass Spectrometry Following IdeS Digestion

CE-MS and CE-MS/MS for the multiattribute analysis of monoclonal antibody variants at the subunit level

The analysis of product-related substances and impurities is a critical step in the biopharmaceutical quality control of multiattribute monoclonal antibodies (mAbs), as posttranslational modifications or other variants can influence the product's biological activity. Many approaches are available for variant analysis; however, they are either variant-specific, mAb-specific, time-consuming, or require expensive equipment. Here, we present a generic capillary electrophoretic method based on a neutral-coated capillary which was coupled to mass spectrometry (MS) via the nanoCEasy interface for mAb variant analysis at the subunit level (enzymatically digested and reduced mAb). The method enabled the separation of several (i) size variants (e.g. glycosylation variants) and (ii) charge variants (e.g. c-terminal lysin clipping) as well as (iii) multiple other proteoforms (e.g. additional glycation) and (iv) incompletely reduced subunits. Separated variants were confirmed by MS/MS fragmentation even for small mass deviations like deamidation or open disulfide bridges. The system, initially developed for one mAb, was tested with nine other IgG1s to show the general applicability of the system. The presented multiattribute method enables fast and detailed characterization of mAb variants with little sample preparation and relatively simple separation equipment enabling the separation of a large set of mAb variants.

Rapid Mass Spectrometry-Based Multiattribute Method for Glycation Analysis with Integrated Afucosylation Detection Capability

The multiattribute method (MAM) has emerged as a powerful tool for simultaneously screening multiple product quality attributes of therapeutic antibodies. One such potential critical quality attribute (CQA) is glycation, a common modification that can impact the heterogeneity, functional activity, and immunogenicity of therapeutic antibodies. However, current methods for monitoring glycation levels in MAM are rare and not sufficiently rapid and accurate. In this study, an improved mass spectrometry (MS)-based MAM was developed to simultaneously monitor glycation and other quality attributes including afucosylation. The method was evaluated using two therapeutic antibodies with different glycosylation site numbers. Treatment with IdeS, Endo F2, and dithiothreitol generated three distinct subunits, and the glycation results obtained were similar to those treated with PNGase F, which is routinely used to release glycans; the sample processing time was greatly reduced while providing additional quality attribute information. The MS-based MAM was also employed to assess the glycation progression following forced glycation in various buffer solutions. A significant increase in oxidation was observed when forced glycation was conducted in an ammonium bicarbonate buffer solution, and a total of 23 potential glycation sites and 4 significantly oxidized sites were identified. Notably, we found that ammonium bicarbonate was found to specifically stimulate oxidation, while glycation had a synergistic effect on oxidation. These findings establish this study as a novel methodology for achieving a technologically advanced platform and concept that enhances the efficacy of product development and quality control, characterized by its broad-spectrum, rapid, and accurate nature.

CE-MS/MS and CE-timsTOF to separate and characterize intramolecular disulfide bridges of monoclonal antibody subunits and their application for the assessment of subunit reduction protocols

Characterization at the subunit level enables detailed mass spectrometric characterization of posttranslational modifications (PTMs) of monoclonal antibodies (mAbs). The implemented reduction often leaves the intramolecular disulfide bridges intact. Here, we present a capillary electrophoretic (CE) method based on a neutral-coated capillary for the separation of immunoglobulin G-degrading enzyme of Streptococcus pyogenes (IdeS) digested and reduced mAb subunits followed by mass spectrometry (MS), MS/MS identification, and trapped ion mobility mass spectrometry (timsTOF). Our CE approach enables the separation of (i) different subunit moieties, (ii) various reduction states, and (iii) positional isomers of these partly reduced subunit moieties. The location of the remaining disulfide bridges can be determined by middle-down electron transfer higher energy collisional dissociation (EThcD) experiments. All these CE-separated variants show differences in ion mobility in the timsTOF measurements. Applying the presented CE-MS/MS method, reduction parameters such as the use of chaotropic salts were studied. For the investigated antibodies, urea improved the subunit reduction significantly, whereas guanidine hydrochloride (GuHCl) leads to multiple signals of the same subunit in the CE separation. The presented CE-MS method is a powerful tool for the disulfide-variant characterization of mAbs on the subunit level. It enables understanding disulfide bridge reduction processes in antibodies and potentially other proteins.

Mass spectrometry-based multi-attribute method for mutation analysis in the early development of therapeutic proteins

The early intervention is essential, and later development cannot compensate for this initial generation of an antibody drug. Especially for sequence variants (SVs), should cause concern during the early bioprocess development. The advancement of bioprocess development is paralleled by development of state-of-the-art analytical methods that will provide further information. In the present study, a mass spectrometry (MS)-based multi-attribute method (MAM) was used to simultaneously monitor the SVs and other quality attributes in the early bioprocess development of ofatumumab, and a sequence variant (SV) was detected by a subunit-based MAM. Subsequently, the variant was further identified by MS/MS and confirmed by adding a synthetic peptide. Furthermore, the content of the SV was detected via DNA sequencing. The levels of the variant (T175A mutant) in the light chain were demonstrate to be nearly consistent at the DNA and protein levels, suggesting that the mutation may have negligible effect on both the transcriptional and translational levels. Collectively, these results indicate that broad-spectrum, rapid, and accurate platform such as MS-based MAM should be implemented to quality control for the early development of therapeutic proteins, it will also be important to establish an effective and integrated MAM to control SVs during therapeutic proteins development.

Identification, Efficacy, and Stability Evaluation of Succinimide Modification With a High Abundance in the Framework Region of Golimumab

Succinimide (Asu) is the intermediate for asparagine deamidation in therapeutic proteins, and it can be readily hydrolyzed to form aspartate and iso-aspartate residues. Moreover, Asu plays an important role in the protein degradation pathways, asparagine deamidation, and aspartic acid isomerization. Here, Asu modification with a high abundance in the framework region (FR) of golimumab was first reported, the effect of denaturing buffer pH on the Asu modification homeostasis was studied, and the results revealed that it was relatively stable over a pH range of 6.0–7.0 whereas a rapid decrease at pH 8.0. Then, the peptide-based multi-attribute method (MAM) analyses showed that the Asu formation was at Asn 43 in the FR of the heavy chain. Meanwhile, the efficacy [affinity, binding and bioactivity, complement-dependent cytotoxicity (CDC) activity, and antibody-dependent cell-mediated cytotoxicity (ADCC) activity] and stability of the Asu modification of golimumab were evaluated, and the current results demonstrated comparable efficacy and stability between the Asu low- and high-abundance groups. Our findings provide valuable insights into Asu modification and its effect on efficacy and stability, and this study also demonstrates that there is a need to develop a broad-spectrum, rapid, and accurate platform to identify and characterize new peaks in the development of therapeutic proteins, particularly for antibody drugs.

Analyzing protein glycosylation using UHPLC: a review

Ultrahigh performance liquid chromatography (UHPLC) uses small stationary-phase particle size (<2 μm) and high pressure in order to achieve rapid and efficient separations. The speed and high resolution of this method has made it a valuable tool for analyzing the complex glycosylation patterns found in post-translationally modified proteins. This article highlights the differences between UHPLC and HPLC and reviews recent UHPLC applications and developments for detecting glycosylated proteins (e.g., glycomics studies) and characterizing glycosylated pharmaceuticals (e.g., monoclonal antibodies).