Application and challenges in using LC–MS assays for absolute quantitative analysis of therapeutic proteins in drug discovery

As more protein therapeutics enter the drug-discovery pipeline, the traditional ligand-binding assay (LBA) faces additional challenges to meet the rapid and diverse bioanalytical needs in the early drug-discovery stage. The high specificity and sensitivity afforded by LC–MS, along with its rapid method development, is proving invaluable for the analysis of protein therapeutics in support of drug discovery. LC–MS not only serves as a quantitative tool to complement LBA in drug discovery, it also provides structural details at a molecular level, which are used to address issues that cannot be resolved using LBA alone. This review will describe the key benefits and applications, as well as the techniques and challenges for applying LC–MS to support protein quantification in drug discovery.