Heavy Peptide Standards for Antibody C-Terminal Lysine Quantification

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Solution Overview

Problem

Current methods for quantifying post-translational modifications (PTMs) in proteins, particularly unprocessed C-terminal lysine in therapeutic antibodies, face challenges due to differences in ionization efficiency between modified and unmodified peptides, leading to inaccurate measurements.

Innovation Solution

The use of heavy peptide standards with varying isotopic ratios to generate a calibration curve for liquid chromatography-mass spectrometry analysis, allowing for precise quantification of PTMs by normalizing detection differences between modified and unmodified peptides.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional peptide mapping quantification is used to measure unprocessed C-terminal K, then the method is simple and widely applicable, but the measurement precision is compromised due to ionization efficiency differences between modified and unmodified peptides

Engineering Contradiction:

Improvequantification accuracy of unprocessed C-terminal KVSAvoidcomplexity of quantification method

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Heavy peptide standards serve as intermediary substances that co-elute with endogenous peptides but have distinct mass signatures. These heavy peptides experience identical ionization conditions as the native peptides, allowing the system to measure and correct for ionization efficiency differences without disrupting the native peptide behavior. The heavy peptides act as internal references that mediate between the unknown ionization efficiency and the quantification calculation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The method changes the mass parameter of peptide standards by incorporating heavy isotopes (13C, 15N), creating distinguishable mass shifts while maintaining identical chemical and physical properties. This parameter change allows simultaneous detection of both light (endogenous) and heavy (standard) peptides through mass spectrometry, enabling correction of ionization efficiency variations while preserving the natural ionization behavior of the analyte peptides.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If correction factors are used to compensate for ionization efficiency differences, then measurement accuracy can be improved, but the reliability decreases when coeluting peptides or different mass spectrometers are involved due to static correction factors

Engineering Contradiction:

Improvequantification accuracyVSAvoidconsistency across different conditions

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The correction approach transitions from static pre-determined factors to dynamic, sample-specific correction. By injecting heavy peptide standards with each sample and generating calibration curves specific to each run, the system adapts to varying ionization conditions, coeluting peptides, and instrument variations in real-time. This dynamic calibration ensures reliability across different samples, instruments, and experimental conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The method implements feedback by using heavy peptide standards to continuously monitor and characterize ionization efficiency throughout each analysis run. The calibration curves generated from heavy peptide responses provide real-time feedback on system performance, allowing for accurate quantification that accounts for run-to-run variations, instrument drift, and matrix effects specific to each sample analysis.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If heavy peptide standards with isotopic labeling are used to generate calibration curves, then quantification accuracy is significantly improved, but the manufacturing complexity and cost increase

Engineering Contradiction:

ImprovePTM quantification accuracyVSAvoidease of implementing heavy peptide approach

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

Heavy peptide standards are synthesized copies of the endogenous peptides with modified mass properties through isotopic labeling. These copies replicate the exact sequence, charge state, and ionization behavior of the native peptides while having distinguishable mass. This copying approach allows the system to model and correct for ionization efficiency without requiring complex modifications to the analytical workflow or instrumentation.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS12123879B2Heavy peptide approach to accurately measure unprocessed C-terminal lysine

Publication Date: 2024.10.22 REGENERON PHARMACEUTICALS INC

AI summary

The present disclosure provides a method for accurately measuring post-translational modifications in proteins such as antibodies. In particular, the method pertains to the use of heavy isotopic standards to generate a calibration curve to allow for accurate quantitation of a modified peptide. The method may be used to accurately quantify C-terminal truncation in antibodies using mass spectrometry.