A Generic Kit-Based Approach for Quantifying Monoclonal Antibody Drugs Through Direct Digestion of Discovery Study Samples

Importance of the Topic

Monoclonal antibody (mAb) therapeutics represent a rapidly growing segment of pharmaceutical development, driving demand for robust bioanalytical methods in discovery and pre-clinical workflows. Traditional immunoassays often suffer from limited dynamic range, poor standardization, and reagent variability. Consequently, liquid chromatography–mass spectrometry (LC-MS) has emerged as a preferred platform for protein quantification, yet conventional LC-MS sample preparation can span more than a day and requires extensive optimization. A simplified, kit-based approach promises to accelerate data generation and improve reproducibility, particularly in discovery settings where throughput and consistency are critical.

Objectives and Study Overview

The primary objective was to evaluate a generic, kit-based sample preparation protocol for direct digestion and quantification of four therapeutic mAbs (infliximab, bevacizumab, trastuzumab, adalimumab) in human plasma. Key performance metrics—sensitivity, linearity, accuracy, and precision—were assessed using signature peptides and multiple reaction monitoring (MRM) on a triple quadrupole mass spectrometer. Critical goals included minimizing method development, reducing total sample-to-analysis time, and achieving quantification limits suitable for early‐phase discovery studies.

Methodology

Plasma samples (35 µL) spiked with each mAb were directly digested using a standardized kit protocol that combined denaturation, reduction, alkylation, and tryptic digestion. Peptide extracts underwent solid-phase extraction cleanup before LC-MS analysis. Calibration curves and quality control (QC) samples spanned low to high concentration ranges to evaluate assay performance under a single universal workflow.

Used Instrumentation

• UPLC system with Peptide BEH C18 column (300 Å, 1.7 µm, 2.1 mm × 150 mm)
• Xevo TQ-S triple quadrupole mass spectrometer with electrospray ionization
• ProteinWorks eXpress Direct Digest Kit and ProteinWorks µElution SPE Clean-up Kit

Results and Discussion

Limit of quantification ranged from 0.25 µg/mL to 2.5 µg/mL across the four mAbs, with linear dynamic ranges extending over 3.5–4 orders of magnitude and correlation coefficients (r2) above 0.996. Accuracy for calibration points averaged within 95–105%, and QC precision (%CV) remained below 15%, often in the low single digits. Representative low-QC chromatograms demonstrated clear, interference-free signals at discovery-relevant levels. The universal kit protocol delivered high sensitivity and reproducibility without individual method optimization for each mAb.

Benefits and Practical Applications

The streamlined kit-based workflow reduces hands-on preparation to approximately 4 hours and enables same-day data acquisition, facilitating rapid decision-making in discovery programs. Lot-traceable reagents and a uniform protocol support method transferability across laboratories and analysts, lowering the barrier to adopting LC-MS bioanalysis for laboratories with limited protein analysis expertise.

Future Trends and Opportunities

Advances in automation and high-throughput sample processing will further increase assay capacity. Application of similar kit-based strategies to emerging modalities—such as bispecific antibodies, antibody–drug conjugates, and fusion proteins—can broaden the impact of generic workflows. Integration with next-generation LC-MS platforms and data analysis tools will enhance sensitivity and expedite regulatory compliance in translational research and clinical monitoring.

Conclusion

A generic, kit-based direct digestion approach effectively quantifies multiple mAb drugs in plasma with minimal method development, high accuracy, and rapid turnaround. This standardized workflow addresses key challenges in discovery-stage bioanalysis, delivering consistent results and supporting high-throughput decision-making.

References

• Dalzell K. Managed Care, October 2013.
• McKinsey & Company; Evaluate Pharma – U.S. patent expirations for key mAbs.
• FDA Guidance for Industry: Bioanalytical Method Validation, CDER.