A multiplexed hybrid LC–MS/MS pharmacokinetic assay to measure two co-administered monoclonal antibodies in a clinical study

Background: Combination therapies with monoclonal antibodies (mAbs) enhance therapeutic activity and may circumvent drug resistance. However, these studies present bioanalytical challenges for ligand-binding assays (LBAs). Recent MS-based protein quantification offers an alternative for bioanalysis. Results: A hybrid LC–MS/MS assay was developed to simultaneously measure human serum concentrations of two mAbs. Anti-idiotypic reagents that did not work in LBAs were successfully used for mAb affinity capture enrichment. Stable isotope-labeled peptide internal standards were employed. The mAb quantification involved measuring a signature CDR peptide derived from each mAb as a surrogate. Selected clinical samples were successfully analyzed. Conclusion: The multiplexed LC–MS/MS method provided a powerful quantitative tool for clinical PK assessment of co-administered mAbs without the requirement for stringent affinity capture reagents.

Recombinant monoclonal antibodies (mAbs) have become a major class of biotherapeutic agents used extensively and successfully in treating different types of cancers and autoimmune diseases [1,2]. The strong binding affinity of mAbs allows them to bind specifically to target cells or proteins, which enhances efficacy, reduces systemic toxicity and, therefore, potentially increases the therapeutic index. In addition, mAbs have been increasingly explored in the therapy of infectious diseases, such as in various types of viral infections including herpes simplex virus (HSV) [3], hepatitis C virus (HCV) [4], or human immunodeficiency virus (HIV) [5]. Particularly, in the situations where drug resistance is developed in patients undergoing conventional antiviral treatments, mAbs offer novel and effective treatment alternatives as they demonstrate no significant cross-reactivity to human tissues. Therapeutic mAbs can be administered as a single agent, in conjunction with other drugs or via a combination therapy approach of multiple mAbs, to achieve optimal therapeutic effect.

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