FabRICATOR, SialEXO and OglyZOR in Middle-up HILIC/HRMS Approach

In an article by Valentina D’Atri et al. recently published in Analytical Chemistry (2019), the scientists developed a middle-up HILIC/HRMS workflow for detailed characterisation of the Fc fusion protein etanercept.  The etanercept molecule consists of an IgG1 Fc domain fused to a tumour necrosis factor receptor (TNFR) and is used in the treatment of autoimmune diseases such as rheumatoid arthritis. The protein is highly glycosylated and contains numerous O- and N-glycosylation sites that require extensive characterization.

To develop a strategy that would work with a mass spec instrument of limited resolution, the authors used FabRICATOR enzyme to specifically digest the etanercept molecule and generate TNFR and Fc/2 subunits. Combinations of the O- and N- glycosidases SialEXO, OglyZOR and PNGaseF were applied to allow evaluation of the O- and N-glycosylation patterns of TNFR and Fc/2 respectively. In addition, complete deglycosylation allowed for primary structure analysis. By using a wide-pore HILIC stationary phase, appropriate separation of the subunits with different degrees of remaining glycans was achieved, and this significantly facilitated spectra deconvolution.

Applying this workflow, D’Atri and colleagues were able to assess the main PTMs, the subunit distribution of glycans, the overall N/O glycan composition and the sialylation profiles of each subunit.

Read more about the SmartEnzymes in this publication

• FabRICATOR – Enabling middle level analytics
• OglyZOR – Efficient removal of O-glycans
• SialEXO – Getting rid of sialic acids 

Reference:

D’Atri, V. et al., 2018. Orthogonal Middle-up Approaches for Characterization of the Glycan Heterogeneity of Etanercept by Hydrophilic Interaction Chromatography Coupled to High-Resolution Mass Spectrometry. Analytical Chemistry, 91(1), pp.873–880.

Study on Glycoform Heterogeneity using Enzymatic Digestion and Native Mass Spectrometry

In a study by Wohlschlager et al. (2018), FragIT™ kit was used to digest the Fc-fusion protein etanercept, and the resulting fragments were analyzed using high-resolution native mass spectrometry (MS). Native MS offers a higher spatial resolution at a lower charge state, enabling studies of glycan heterogeneity, and FragIT digestion reduces sample complexity, enabling a detailed annotation of glycoforms on complex compounds.

A detailed knowledge about structure and post-translational modifications (PTMs) is required for biopharmaceuticals to be approved for clinical use, and an important quality attribute that may affect both the efficacy and safety of biopharmaceuticals is glycosylation.

Etanercept is a highly glycosylated Fc-fusion protein that is used to treat autoimmune diseases such as rheumatoid arthritis, and it consists of the TNF-? receptor domain fused to the Fc domain of human IgG1. FragIT – an immobilized version of the FabRICATOR® (IdeS) enzyme – digests IgG from several species and subclasses at a specific site below the hinge region. The resulting fragments are easily purified using the Fc-specific affinity resin that, together with FragIT, comprises the FragIT kit.

In this study, the researchers analyzed the glycosylation of etanercept on both the intact level, and on the middle-down level after FragIT digestion. By combining native MS analysis with enzymatic remodelling of etanercept, a detailed annotation of glycoforms could be achieved and transferred from subunit to whole protein level.

The authors end by concluding:

“Comprehensive information on glycoform heterogeneity, fast analysis with minimal sample preparation and product-characteristic fingerprints render our method highly attractive for the quality control of biologics as well as for comparability studies following changes in the manufacturing process.”(Wohlschalger et al. 2018).

Read more about FragIT and FabRICATOR

References:

Subunit Comparability Analysis of Etanercept and Biosimilar

Researchers at the Free University of Berlin have performed a comparability study of the Fc-fusion protein etanercept and a biosimilar using FabRICATOR^® and subunit analysis. The etanercept molecule consists of an IgG1 Fc domain fused to a tumor necrosis factor alpha receptor (TNFaR) and is used for autoimmune diseases such as rheumatoid arthritis. The originator etanercept (Enbrel^®) was compared to its biosimilar Altebrel™ (AryoGen Pharmed), that has been launched in Iran.

The scientists used FabRICATOR to digest the Fc-fusion protein and studied the subunits, TNFaR and Fc/2 separately using middle-up mass spectrometry. Interestingly, differences in the glycosylation pattern,  the level of C-terminal lysine clipping and oxidation status of the two biopharmaceuticals were observed. The c-terminal lysine clipping was only observed in the originator molecule whereas the biosimilar showed no lysine clipping. Looking at the Fc/2 glycosylation profile using middle-up is a rapid way of determining the glycan content and the relative abundance of the species. In this case, the pattern was similar although the peak intensities differed, indicating a variation between the originator and the biosimilar.

Taken together, this paper highlights the use of FabRICATOR for comparability assessment of Fc-fusion proteins and shows that the middle-level approach can be used for fingerprinting of originator and biosimilar biopharmaceuticals.

• Read more about FabRICATOR

Find the article using this link:

Montacir, O. et al., 2018. Physicochemical Characterization, Glycosylation Pattern and Biosimilarity Assessment of the Fusion Protein Etanercept. The protein journal, 8(6), pp.1136–16.