Therapeutic monoclonal antibodies (mAbs) represent the majority of therapeutics biologics now on the market, with more than 20 mAbs approved as drugs (1–3). During preclinical development of therapeutic antibodies, multiple variants of each antibody are assessed for pharmacokinetic (PK) characteristics across model systems such as rodents, beagles and  primates. Ligand-binding assays (LBA) are the standard technology used to perform the PK studies for mAb candidates (4). Ligand-binding assays (LBAs) are methods used  to detect and measure a macromolecular interaction between a ligand and a binding molecule. In LBAs, a therapeutic monoclonal antibody is considered to be the ligand, or analyte of interest, while the binding molecule is usually a target protein.

LBAs have certain well-documented limitations (5). Specific assay reagents are often not available early in a program. Interferences from endogenous proteins, antidrug antibodies, and soluble target ligands are potential complicating factors.

Liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS)-based methods represent a viable and complementary addition to LBA for mAb quantification in biological matrixes. LC–MS/MS provides specificity, sensitivity, and multiplexing capability.

A recent reference (6) illustrates an automated method to perform LC–MS/MS-based quantitation, with IgG1 conserved peptides, a heavy isotope labeled mAb internal standard,and anti-human Fc enrichment. The method was applied to the pharmacokinetic study of a mAb dosed in cynomolgus monkey, and the results were compared with the immunoassay data. The interesting finding of the difference between ELISA and LC–MRM-MS data indicated that those two methods can provide complementary information regarding the drug’s PK profile.

Literature Cited

1. Mao, T. et al. (2013) Top-Down Structural Analysis of an Intact Monoclonal Antibody by Electron Capture Dissociation-Fourier Transform Ion Cyclotron Resonance-Mass Spectrometry. Anal.Chem. 85, 4239–46.
2. Weiner, L. M. et al. (2010) Monoclonal antibodies: versatile platforms for cancer immunotherapy. Nat. Rev. Immunol. 10, 317–27.
3. Nelson, A. et al. (2010) Development trends for human monoclonal antibody therapeutics. Nat. Rev. Drug Discovery. 9, 767–74.
4. DeSilva, B. et al. (2003) Recommendations for the Bioanalytical Method Validation of Ligand-Binding Assays to Support Pharmacokinetic Assessments of Macromolecules. Pharm. Res. 20, 1885–00.
5. Ezan, E.et al. (2009) Critical comparison of MS and immunoassays for the bioanalysis of therapeutic antibodies. Bioanalysis 1, 1375–88.
6. Zhang, Q. et al. (2014) Generic Automated Method for Liquid Chromatography–Multiple Reaction Monitoring Mass Spectrometry Based Monoclonal Antibody Quantitation for Preclinical Pharmacokinetic Studies. Anal.Chem. 86, 8776–84.