Analysis of Drug-to-Antibody Ratio in Antibody- Drug Conjugates—Multifaceted Evaluation by LCQTOF and MALDI Analysis—

Significance of the Topic

Antibody-drug conjugates (ADCs) merge the targeting specificity of monoclonal antibodies with the potency of cytotoxic drugs. The drug-to-antibody ratio (DAR) is a key quality attribute that influences efficacy, safety, and pharmacokinetics, making rapid and accurate DAR assessment crucial in ADC development and quality control.

Objectives and Study Overview

This application note evaluates a complementary workflow for DAR determination using two benchtop mass spectrometry platforms: the MALDI-8030 linear TOF MS for rapid, straightforward screening and the Nexera + LCMS-9030 Q-TOF system for high-resolution, software-driven analysis. The goal is to compare throughput, ease of interpretation, and measurement precision.

Sample Preparation

Human plasma was spiked with brentuximab vedotin and processed by PNGase F deglycosylation, TCEP reduction, and affinity purification. Final solutions contained reduced light and heavy chains at 10 µg/mL. For MALDI, aliquots were mixed with sinapinic acid matrix and air-dried. For LC-QTOF, samples were directly injected into the LC system.

Used Instrumentation

• MALDI-8030: Linear MALDI-TOF MS with 355 nm solid laser, sinapinic acid matrix (10 mg/mL in 50% ACN, 0.1% TFA), linear TOF, external calibration with BSA.
• Nexera + LCMS-9030: UHPLC with reversed-phase column (30 °C), 0.1% formic acid–water/ACN gradient, 0.2 mL/min, ESI in positive mode, Q-TOF detection, data analysis via Byos software.

Main Results and Discussion

• MALDI-8030 delivered full DAR profiles (light chains d0/d1, heavy chains D0–D4) in under 30 minutes as simple singly charged spectra, yielding a total DAR of 3.32.
• LCMS-9030 generated complex multiply charged spectra deconvoluted to molecular weights; software-assisted analysis confirmed the same DAR distribution with high mass accuracy.
• Precision tests showed intra-day DAR RSD ≤2% and inter-day RSD ≤3%. A slight decline in higher payload species over days suggested potential payload dissociation.

Benefits and Practical Applications

• MALDI-8030 offers rapid, user-friendly DAR screening without specialized software, ideal for high-throughput QC.
• LCMS-9030 provides detailed, high-resolution DAR profiling and robust precision, suited for in-depth characterization and regulatory support.
• Combining both platforms yields a multifaceted workflow that balances speed and analytical rigor in ADC development and manufacturing.

Future Trends and Potential Applications

• Automation of sample preparation and data processing to further increase throughput.
• Expansion of mass spectrometry platforms for intact ADC characterization, including glycoforms and linker variants.
• Implementation of high-throughput DAR analysis in biopharmaceutical production, lot release, and stability studies.

Conclusion

The integrated use of MALDI-TOF and LC-QTOF mass spectrometers delivers a robust, complementary strategy for rapid and precise DAR determination in ADC research and QA/QC. This dual-platform approach streamlines workflows, enhances data confidence, and supports accelerated biopharmaceutical development.

References

• Shen L. et al. ADCdb: the database of antibody-drug conjugates. Nucleic Acids Research. 2024;52(D1):D1097–D1109.