Detection and quantitation of afucosylated N-linked oligosaccharides in recombinant monoclonal antibodies using enzymatic digestion and LC-MS

Orthogonal liquid chromatography-mass spectrometry methods for the comprehensive characterization of therapeutic glycoproteins, from released glycans to intact protein level

Proteins are increasingly used as therapeutics. Their characterization is challenging due to their size and inherent heterogeneity notably caused by post-translational modifications, among which glycosylation is probably the most prominent. The glycosylation profile of therapeutic proteins must therefore be thoroughly analyzed. Here, we illustrate how the use of a combination of various cutting-edge LC or LC/MS(/MS) methods, and operating at different levels of analysis allows the comprehensive characterization of both the N- and O-glycosylations of therapeutic proteins without the need for other approaches (capillary electrophoresis, MALDI-TOF). This workflow does not call for the use of highly specialized/custom hardware and software nor an extensive knowledge of glycan analysis. Most notably, we present the point of view of a contract research organization, with the constraints associated to the work in a regulated environment (GxP). Two salient points of this work are i) the use of mixed-mode chromatography as a fast and straightforward mean of profiling N-glycans sialylation as well as an orthogonal method to separate N-glycans co-eluting in the HILIC mode; and ii) the use of widepore HILIC/MS to analyze challenging N/O-glycosylation profiles at both the peptide and subunit levels. A particular attention was given to the sample preparations in terms of duration, specificity, versatility, and robustness, as well as the ease of data processing.

General solutions to decompose heterogeneous compositions using antibody afucosylation as a model system

Methods involving the use of mathematical models of competitive ligand-receptor binding to characterize mixtures of ligands in terms of compositions and properties of the component ligands have been developed. The associated mathematical equations explicitly relate component ligand physical-chemical properties and mole fractions to measurable properties of the mixture including steady state binding activity, 1/K_d,apparent or equivalently 1/EC50, and kinetic rate constants k_on,apparent and k_off,apparent allowing: (1) component ligand physical property determination and (2) mixture property predictions. Additionally, mathematical equations accounting for combinatorial considerations associated with ligand assembly are used to compute ligand mole fractions. The utility of the methods developed is demonstrated using published experimental ligand-receptor binding data obtained from mixtures of afucosylated antibodies that bind FcγRIIIa (CD16a) to: (1) extract component ligand physical property information that has hitherto evaded researchers, (2) predict experimental observations, and (3) provide explanations for unresolved experimental observations. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:500-510, 2017.

Novel strategy for herbal species classification based on UPLC-HRMS oligosaccharide profiling

Oligosaccharides, which exist widely in herbs, present diverse important pharmacological activities. However, the complexity of oligosaccharides seriously challenges their profiling, quality control, and elucidation of activity. In this paper, a novel oligosaccharide analytical method based on a new derivatization pretreatment and ultra-performance liquid chromatography coupled with high resolution tandem mass spectrometry (UPLC-HRMS) procedure was developed to rapidly profile and identify the oligosaccharides of Epimedium. Oligosaccharides are easily derivatized by 2,4-bis(diethylamino)-6-hydrazino-1,3,5-triazine under convenient and mild conditions. Without any further purification steps, oligosaccharides were analyzed by an established UPLC-HRMS/MS method with high sensitivity, good separation efficiency and speed. Benefitting from the derivatization, the oligosaccharides generated a response in the MS two orders of magnitude higher than that of the free oligosaccharide. Oligosaccharides of 52 Epimedium samples were profiled and identified based on the high-resolution mass spectral data. A total of 66 oligosaccharide compounds detected in 52 Epimedium herbs were relatively quantified and statistically processed by principal component analysis (PCA). The 52 Epimedium herbs could be classified into different species based on their oligosaccharide composition and content. Thirteen oligosaccharide compounds demonstrated potential as markers for Epimedium species classification, and their structures were preliminarily identified using MS/MS spectra.

Development of orally active inhibitors of protein and cellular fucosylation

The key role played by fucose in glycoprotein and cellular function has prompted significant research toward identifying recombinant and biochemical strategies for blocking its incorporation into proteins and membrane structures. Technologies surrounding engineered cell lines have evolved for the inhibition of in vitro fucosylation, but they are not applicable for in vivo use and drug development. To address this, we screened a panel of fucose analogues and identified 2-fluorofucose and 5-alkynylfucose derivatives that depleted cells of GDP-fucose, the substrate used by fucosyltransferases to incorporate fucose into protein and cellular glycans. The inhibitors were used in vitro to generate fucose-deficient antibodies with enhanced antibody-dependent cellular cytotoxicity activities. When given orally to mice, 2-fluorofucose inhibited fucosylation of endogenously produced antibodies, tumor xenograft membranes, and neutrophil adhesion glycans. We show that oral 2-fluorofucose treatment afforded complete protection from tumor engraftment in a syngeneic tumor vaccine model, inhibited neutrophil extravasation, and delayed the outgrowth of tumor xenografts in immune-deficient mice. The results point to several potential therapeutic applications for molecules that selectively block the endogenous generation of fucosylated glycan structures.