Monitoring Intact Light Chain of Therapeutic Monoclonal Antibodies in Human Serum by LC-MS for Clinical Research with Live Q&A

Each year, more monoclonal antibodies (mAbs) are approved by regulatory agencies to treat a wide range of diseases with an expected market value of over $200 billion by 2026. The advantage of using therapeutic mAbs lies in their inherent specificities for recognizing and counteracting foreign substances (so-called antigens). Due to their molecular complexity, including post-translational modifications, biopharmaceutical companies have embraced many advanced analytical techniques such as mass spectrometry to better characterize and quantify mAbs during the development stages. In clinical testing, the presence of endogenous immunoglobulins in patients' samples with nearly identical structures to therapeutic mAbs adds an additional challenge to the accurate quantitation of therapeutic mAbs. Accordingly, mass spectrometry has also gained substantial popularity for therapeutic mAb monitoring (i.e., TDM of mAb) in clinical laboratories due to its great versatility to detect both tryptic peptides and intact light and heavy chains quantitatively.

Here we present the intact light chain quantitation approach for measuring concentrations of therapeutic mAbs in human serum using the Orbitrap Exploris 240 MS for clinical research. One of the benefits of intact light chain quantitation is a simplified workflow with faster sample preparation compared to peptide quantitation. Additionally, it can provide a solution for mAbs that contain limited or no signature tryptic peptides and are not possible to differentiate from endogenous IgG. Protein L magnetic beads were used for the selective purification of antibodies containing kappa light chains. This way, endogenous lambda light chains from human serum are not captured, which can improve the purity of isolated antibodies and potentially be applied to other modality antibodies or Fab fragments containing kappa light chains.

Learning Objectives:

1. Discuss how HRAM mass spectrometry is applied for monitoring therapeutic mAbs.

2. Explain the purification process to accurately analyze intact proteins such as mAbs.

3. Define how intact proteins can be measured by mass spectrometry and why isotopic distribution is important.