Analyzing Monoclonal Antibody (mAbs) and mAb-Derived Therapeutics Using Native SEC-MS

Importance of the Topic

Accurate measurement of monoclonal antibody (mAb) aggregates and structural variants is essential for ensuring the safety and efficacy of protein-based therapeutics. Aggregates can influence immunogenicity, while post-translational modifications and drug-to-antibody ratios (DAR) affect potency and pharmacokinetics. Native SEC-MS offers a non-denaturing, high-resolution approach to profile intact proteins and their derivatives under near-physiological conditions.

Objectives and Overview of the Method

The primary objective of integrating size exclusion chromatography (SEC) with native mass spectrometry (MS) is to combine the separation power of SEC for monomers, high molecular weight (HMW) and low molecular weight (LMW) species with the precise mass measurement capabilities of native-MS. This approach enables simultaneous quantification of aggregates, confirmation of molecular weight, characterization of DAR in antibody-drug conjugates (ADCs), and detection of subtle modifications without disrupting fragile non-covalent complexes.

Methodology and Instrumentation

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Chromatography system: High-performance LC equipped with AdvanceBio SEC columns (1.9 µm particles; 120 Å or 200 Å pore size; 2.1 or 4.6 mm ID; PEEK-lined stainless steel).

Mobile phase: Volatile buffer (e.g., 80 mM ammonium acetate) at neutral pH to preserve native structure and ensure MS compatibility.

Flow rates: 0.05–0.7 mL/min optimized by column ID and length to balance resolution and desolvation efficiency.

Mass spectrometer: High-resolution native-MS capable instrument, e.g., Agilent 6545XT AdvanceBio LC/Q-TOF, with source conditions adjusted to minimize adduct formation.

System maintenance: Use of guard columns, in-line filters, low-dispersion tubing, and regular cleaning of LC and MS source to prolong column life and maintain sensitivity.

Main Results and Discussion

Native SEC-MS using AdvanceBio SEC columns achieved high-resolution separation of mAb monomer from dimer and fragment species while preserving native assemblies. The method allowed clear determination of intact molecular weights and DAR for ADCs, even for cysteine-linked constructs. Optimization of column dimensions and flow conditions reduced secondary interactions and adduct formation, improving mass accuracy and sensitivity. The dual compatibility of AdvanceBio SEC columns with denaturing and native conditions provided a streamlined workflow for method development and validation.

Benefits and Practical Applications

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Non-denaturing analysis preserves native structure and weak interactions.

Accurate aggregate quantification and impurity profiling supports quality control and regulatory compliance.

Direct DAR measurement for ADC characterization accelerates bioconjugate development.

Minimal method transfer effort between denaturing and native workflows.

Reduced sample consumption when using narrow columns with low flow rates.

Future Trends and Possibilities

Advances in column chemistries and MS instrumentation will further enhance resolution and throughput of native SEC-MS workflows. Emerging trends include sub-2 µm hybrid particles for faster separations, integration of microfluidic platforms for automated sample handling, and machine learning algorithms for data interpretation. Expansion of native MS to even larger complexes and real-time process monitoring are foreseeable applications.

Conclusion

Native SEC-MS combines the selectivity of size-based separations with accurate mass analysis to deliver comprehensive characterization of mAbs and derived therapeutics. Careful selection of column parameters, mobile phase conditions, and MS settings enables reliable aggregate profiling, DAR determination, and PTM mapping, supporting accelerated development and robust quality control of biopharmaceuticals.

References

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Sensitive Native Mass Spectrometry of Macromolecules using Standard Flow LC/MS (5994-1739EN).

Analysis of Antibody Fragment-Drug Conjugates Using an Agilent AdvanceBio SEC 120 Å 1.9 µm PEEK-Lined Column (5994-3045EN).

Mass Spectrometric Characterization of Antibody-siRNA Conjugates using the Agilent 6545XT AdvanceBio LC/Q TOF (5994-2155EN).

Agilent AdvanceBio SEC 1.9 µm Column User Guide (5994-0739EN).

Analysis of Nanobodies Agilent AdvanceBio SEC 120 Å 1.9 μm and AdvanceBio HIC Columns (5994-1869EN).

Elevate Your mAb Aggregate Analysis (5994-2709EN).