Waters Application Notes - ProteinWorks

Significance of the Topic

Advances in therapeutic proteins—including monoclonal antibodies (mAbs) and antibody–drug conjugates (ADCs)—demand robust, sensitive, and reproducible bioanalytical methods. LC-MS workflows offer superior specificity, multiplex capability and broad dynamic range compared with traditional ligand-binding assays, but the inherent complexity of protein sample preparation (affinity capture, digestion, clean-up) poses challenges for method development, reproducibility, and inter-laboratory transfer.

Objectives and Study Overview

This collection of application studies presents a unified, generic kit-based strategy for quantifying mAbs and ADCs in plasma by LC-MS/MS. Key goals were to demonstrate:

• A standardized, streamlined protocol for protein bioanalysis using ProteinWorks eXpress Digest Kits
• High sensitivity quantification of drugs such as infliximab, bevacizumab, trastuzumab, adalimumab, and T-DM1
• Broad dynamic range, low limits of quantification, and high reproducibility across analysts, days, kit lots and sample volumes
• Compatibility with pre-fractionation (affinity capture, protein precipitation) and optimized SPE clean-up
• Use of an intact murine mAb as a generic internal standard and workflow check

Methodology and Instrumentation

All studies used:

• ProteinWorks eXpress Direct Digest or Digest Kit protocols (pre-measured, lot-traceable reagents; reduction, alkylation, trypsin digestion)
• Affinity purification (Protein A/G) or pellet digestion for albumin depletion when required
• Oasis MCX µElution SPE Clean-up Kit for targeted peptide clean-up without evaporation
• ACQUITY UPLC Peptide BEH C18, 300 Å, 1.7 µm, 2.1×150 mm columns on ACQUITY UPLC systems
• Xevo TQ-S triple quadrupole mass spectrometer in ESI+ MRM mode

Main Results and Discussion

Key performance metrics included:

• Sensitivity: Limits of quantification as low as 10 ng/mL for infliximab; 100 ng/mL for bevacizumab; 0.5–1 µg/mL for trastuzumab and T-DM1 from 35 µL plasma
• Linearity: 3–4 orders of magnitude (R² ≥ 0.99) with 1/x or 1/x² weighting across mAb and ADC signature peptides
• Precision and accuracy: Single-digit %CV and mean accuracy within 95–110% for standards and QCs; inter- and intra-kit CVs < 10%
• Reproducibility: Consistent results across five kit lots, two analysts, two days, and plasma volumes from 15–70 µL
• SPE recovery: > 90% average recovery of diverse tryptic peptides without evaporation; optimized µElution format yields peptide concentration and minimal matrix effects
• PPT enrichment: Simple protein precipitation (e.g. 1:10 IPA/TFA) removed > 90% of albumin peptides, boosting mAb peptide signal by 2–8×
• ADCs: T-DM1 conjugated peptides (miscleavage products) were detected as diastereomeric pairs, enabling total antibody quantification alongside non-lysine signature peptides
• Internal standard: Intact murine mAb standard provided reliable compensation for affinity capture, digestion efficiency, and sample loss

Benefits and Practical Applications

Implementing the ProteinWorks kit-based approach delivers:

• Rapid, discovery-stage implementation with no custom method optimization
• Consistent sample prep across analysts and labs, facilitating seamless method transfer
• High throughput: 96-well plate formats for digestion and SPE complete in < 6 hours, enabling same-day LC-MS analysis
• Enhanced sensitivity and specificity for both mAbs and heterogeneous ADCs
• Integrated workflow controls via murine mAb check standard to monitor system health and analyst proficiency

Future Trends and Opportunities

Continued evolution is expected in:

• Automation of kit-based workflows to further reduce hands-on time
• Expansion to additional biotherapeutic formats (bispecifics, antibody fragments, oligonucleotide conjugates)
• Integration with high-resolution MS for intact protein and middle-down analyses
• Enhanced data analytics and informatics for bioanalysis decision support
• Standardization of workflows across CROs and global sites to meet regulatory expectations

Conclusion

The generic kit-based strategy using ProteinWorks eXpress Digest and µElution SPE Clean-up Kits streamlines LC-MS bioanalysis of mAbs and ADCs. This approach achieves low limits of quantification, robust reproducibility, and broad dynamic range from small plasma volumes without extensive method development. Incorporating a murine mAb internal standard further improves workflow control and reliability, providing novice and experienced laboratories alike a proven path to high-quality protein quantification.

Reference

• FDA Guidance for Industry: Bioanalytical Method Validation, CDER
• McKinsey & Company, Evaluate Pharma: US Patent Expiration Dates
• PhRMA report “Medicines in Development: Biologics” 2013
• Bergsland E, Dickler MN. The Oncologist, 2004;9(Suppl 1):36–42