# Antibody–Drug Conjugate Stability Probed by Variable-Temperature Electrospray Ionization Mass Spectrometry

## TL;DR

This paper introduces a new method using variable-temperature mass spectrometry to study the stability of antibody-drug conjugates at the molecular level.

## Contribution

The study introduces variable-temperature electrospray ionization mass spectrometry as a novel method to assess ADC stability at the individual drug-load level.

## Key findings

- Variable-temperature electrospray ionization mass spectrometry can resolve distinct stabilities for individual drug-loaded ADC variants.
- The method provides molecular-level insights into ADC stability, which traditional bulk methods cannot achieve.
- ADC stability is influenced by the drug conjugation chemistry and drug load distribution.

## Abstract

Antibody–drug
conjugates (ADCs) are effective anticancer
biotherapeutics, often referred to as “magic bullets”
due to their high specificity and cytotoxicity. This unique drug class
consists of cytotoxic drugs coupled to monoclonal antibodies that
target antigens on cancer cell surfaces. Different modes of drug conjugation
are used to produce ADCs, whereby it has been shown that the employed
linkage chemistries influence the drug load distribution as well as
the stability of the product. While different methods to assess ADC
stability are available, they mostly assess bulk properties and thus
fail to assess stabilities at an individual stoichiometric drug-load
level. Here, we demonstrate that variable-temperature electrospray
ionization mass spectrometry can be used to study the heat stability
of antibody–drug conjugates, resolving distinct stabilities
for individual drug-loaded variants. As this stability is a key attribute
of ADCs, we propose that variable-temperature electrospray ionization
mass spectrometry may become an asset in the toolbox of analytical
chemistry approaches to characterize ADCs in molecular fine detail.