Rapid High-Throughput Profiling and Quantitation of Sialic Acids in Biotherapeutics

Importance of the Topic

The terminal sialic acids on therapeutic glycoproteins influence immunogenicity, pharmacokinetics and pharmacodynamics. Monitoring both total sialic acid content and distinct species such as Neu5Ac and Neu5Gc is crucial for ensuring product safety and efficacy in biopharmaceutical development.

Study Objectives and Overview

This study presents a high-throughput 96-well plate workflow for the release, derivatization and rapid UHPLC-based analysis of sialic acids from biotherapeutics. Using rituximab, etanercept, NISTmAb and cetuximab as examples, the method aims to provide both qualitative profiling and absolute quantitation with picomole sensitivity.

Methodology

• Acid hydrolysis in a 96-well format to release sialic acids without a drying step, reducing hands-on time by 1–2 hours.
• Derivatization of released residues with 1,2-diamino-4,5-methylenedioxybenzene (DMB) in a two-step thermocycler procedure (80 °C for desialylation, 50 °C for labeling).
• Reversed-phase UHPLC separation on an Agilent Poroshell 120 EC-C18 column using a 10-minute method at 0.4 mL/min, followed by fluorescence detection (λEx 373 nm/λEm 448 nm).

Instrumentation

• Agilent 1290 Infinity II UHPLC system with InfinityLab Poroshell 120 EC-C18, 2.1 × 75 mm, 2.7 µm column.
• Agilent 1260 Infinity II fluorescence detector.
• Optional Agilent 6545XT AdvanceBio LC/Q-TOF for mass confirmation with Dual AJS ESI (m/z range 400–1000 for MS, 100–550 for MS/MS).

Key Results and Discussion

The workflow achieved baseline separation of six DMB-labeled sialic acid derivatives, including Neu5Ac, Neu5Gc and various di- and tri-acetylated forms. Calibration curves for Neu5Ac (R² = 0.9998) and Neu5Gc (R² = 0.9999) demonstrated limits of quantitation of 0.053 pmol and 0.040 pmol, respectively. Application to commercial biotherapeutics revealed low Neu5Gc in rituximab, high Neu5Ac in etanercept and contrasting profiles in NISTmAb and cetuximab, consistent with expected glycoforms.

Benefits and Practical Applications

• High sensitivity for low-abundance sialic acids, enabling robust analysis of monoclonal antibodies and fusion proteins.
• Reduced preparation time and increased throughput by eliminating drying steps and adopting a plate-based format.
• Dual qualitative and quantitative capability supports QC release testing and comparability studies.

Future Trends and Opportunities

Integration of automated liquid handling will further increase throughput. Expansion to comprehensive glycan profiling with additional derivatization chemistries and high-resolution MS could provide deeper structural insights. Implementation in continuous manufacturing and real-time release testing represents a promising extension.

Conclusion

The described DMB-based workflow offers a rapid, sensitive and reproducible approach for profiling and quantifying sialic acids in biotherapeutics. Its high-throughput 96-well format and compatibility with UHPLC-FLD/MS make it well suited for routine QC and research applications.

References

1. Liu, L. Antibody Glycosylation and Its Impact on the Pharmacokinetics and Pharmacodynamics of Monoclonal Antibodies and Fc-Fusion Proteins. Journal of Pharmaceutical Sciences. 2015, 104(6), 1866–1884.
2. Varki, A. Sialic Acids in Human Health and Disease. Trends in Molecular Medicine. 2008, 14(8), 351–360.
3. Li, Y. et al. Sialylation on O-glycans Protects Platelets from Clearance by Liver Kupffer Cells. Proceedings of the National Academy of Sciences USA. 2017, 114(31), 8360–8365.
4. Scallon, B. J. et al. Higher Levels of Sialylated Fc Glycans in Immunoglobulin G Molecules Can Adversely Impact Functionality. Molecular Immunology. 2007, 44(7), 1524–1534.
5. Kaneko, Y. et al. Anti-inflammatory Activity of Immunoglobulin G Resulting from Fc Sialylation. Science. 2006, 313, 670–673.