Stable Isotope Labeling Peptide Mapping for ADC Conjugation Quantitation
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Solution Overview
Problem
Current methods for analyzing site-specific conjugation levels of cysteine-conjugated antibody drug conjugates (ADCs) face challenges due to differential ionization efficiencies of peptides, making it difficult to accurately quantify conjugation levels, especially when multiple sites on a single peptide are involved.
Innovation Solution
The method involves stable isotope labeling (SIL) peptide mapping, where unoccupied cysteine sites of ADCs are conjugated with isotopically-labeled cytotoxins, allowing for accurate site-specific conjugation level quantitation through LC-MS/MS analysis by minimizing mass and hydrophobicity differences between labeled and unlabeled peptides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional peptide mapping is used to analyze ADCs, then protein sequence and PTMs can be characterized, but site-specific conjugation levels cannot be accurately quantified due to differential ionization efficiencies
Solution Approach 1:
The patent changes the mass parameter of the cytotoxin by using isotopically labeled versions (e.g., 13C6-MMAF, 15N2-MMAF) to create distinguishable mass differences between labeled and unlabeled peptides. This allows accurate quantitation of site-specific conjugation levels by comparing peak areas of peptides with different isotopic compositions, eliminating the interference of differential ionization efficiencies.
2Measurement precision
If stable isotope labeling is applied to minimize mass differences, then quantitation accuracy improves, but the complexity of the analytical method increases
Solution Approach 1:
The patent performs preliminary stable isotope labeling of the cytotoxin before conjugation to the ADC. By pre-labeling the cytotoxin with isotopes, the method simplifies the subsequent analysis because the mass difference is already established, and only a single LC-MS/MS run is needed to quantify both conjugated and unconjugated forms, rather than requiring multiple separate experiments.
Solution Approach 2:
The isotopically labeled cytotoxin acts as an intermediary that bridges the gap between the antibody and the detection system. The labeled cytotoxin allows the conjugated peptide to be distinguished from the unconjugated peptide through mass spectrometry, serving as a detectable marker that simplifies the quantitation process while maintaining accuracy.
3Adaptability or versatility
If multiple conjugation sites exist on a single peptide, then the heterogeneity of the ADC increases, but accurate site-specific quantitation becomes more difficult
Solution Approach 1:
The patent applies local quality by specifically labeling only the cysteine-containing peptides that have undergone conjugation, while leaving other peptides unlabeled. This selective labeling approach allows the method to focus on the specific conjugation sites of interest, enabling accurate quantitation even in the presence of multiple conjugation sites on a single peptide or across different peptides in the ADC.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise determination of conjugation levels at specific sites, providing a multi-attribute analytical method that characterizes protein sequence and post-translational modifications simultaneously, overcoming the limitations of previous methods.
Implementation Method 1
stable isotope labeling (SIL) peptide mapping, where unoccupied cysteine sites of ADCs are conjugated with isotopically-labeled cytotoxins, allowing for accurate site-specific conjugation level quantitation through LC-MS/MS analysis by minimizing mass and hydrophobicity differences between labeled and unlabeled peptides
Data Source
AI summary
Disclosed herein are stable isotope labeling (SIL) peptide mapping methods for accurate and sensitive conjugation site quantitation. Also disclosed herein are compositions comprising antibody drug conjugates (ADCs) that target BCMA.