Characterization of Monoclonal Antibodies and ADCs using a Benchtop Orbitrap Mass Spectrometer

Importance of the Method

Biotherapeutic monoclonal antibodies (mAbs) and antibody–drug conjugates (ADCs) are complex molecules whose efficacy and safety depend on precise structural and modification profiles. High-resolution mass spectrometry combined with liquid chromatography enables comprehensive analysis of intact mass, subunit masses and peptide-level modifications. Such characterization supports quality control, regulatory compliance and accelerated development of next-generation biopharmaceuticals.

Objectives and Study Overview

This study demonstrates a workflow for full characterization of Herceptin® and the ADC T-DM1® using a benchtop Orbitrap mass spectrometer. Key goals were:

• Accurate determination of intact molecule molecular weight.
• Separate measurement of heavy and light chain masses for the ADC.
• 100% peptide sequence coverage and mapping of post-translational and drug-conjugation sites.
• Evaluation of glycoform distribution and drug-to-antibody ratio (DAR).

Methodology and Instrumentation

Sample preparation involved reduction of disulfides with DTT, alkylation with iodoacetamide and chymotrypsin digestion for peptide mapping. Liquid chromatography methods were optimized for intact and peptide analyses using reversed-phase columns and formic acid gradients. Data acquisition employed data-dependent MS and MS/MS scans in narrow m/z ranges for intact proteins and peptides.

Instrumentation Used

• Thermo Scientific Accela HPLC system for chromatographic separation.
• BioBasic C4 (5 μm, 10×2.1 mm) and C8 (5 μm, 50×2.1 mm) columns for intact mass analysis.
• Accucore-150 C18 (2.6 μm, 100×2.1 mm) column for peptide mapping.
• Thermo Scientific Q Exactive Plus Orbitrap mass spectrometer for high-resolution MS and MS/MS.
• PepFinder™ software (v1.0) for peptide mapping and modification identification.
• Protein Deconvolution software (v3.0) with ReSpect algorithm for intact mass deconvolution.

Main Results and Discussion

Intact mass analysis of Herceptin resolved seven predominant glycoforms, each within 1 Da of theoretical masses. T-DM1 showed an average DAR of 3.34, consistent with product specifications. Light and heavy chains of T-DM1 were analyzed separately, revealing heterogeneous drug loading and glycosylation patterns. Peptide mapping achieved complete sequence coverage and confidently localized DM1 conjugation sites. Lysine residues K42 and K103 were fully modified, while K190 and K251 showed partial occupancy, demonstrating method sensitivity to site-specific heterogeneity.

Benefits and Practical Applications

• High confidence intact mass and subunit analysis for lot-to-lot consistency monitoring.
• Comprehensive peptide mapping to confirm sequence integrity and modification patterns.
• Accurate DAR measurement to ensure therapeutic efficacy and safety.
• Adaptable workflow for new mAbs, ADCs and biosimilar development.

Future Trends and Opportunities

Advances in hybrid column chemistries and ultrahigh-resolution mass analyzers will further improve sensitivity for low-abundance glycoforms and drug conjugates. Integration of ion mobility separation and automated data-analysis pipelines promises higher throughput and real-time monitoring in biomanufacturing. Machine-learning algorithms may enable predictive modeling of modification hotspots and streamline regulatory submissions.

Conclusion

This workflow combining high-performance liquid chromatography with Orbitrap mass spectrometry and dedicated data-analysis tools provides a robust platform for full characterization of mAbs and ADCs. It delivers accurate intact and subunit mass measurements, complete peptide mapping and reliable site-specific modification profiling, meeting critical quality and regulatory requirements.

Reference

(No external references cited in this summary.)