Glycoanalysis allows drug formulators to increase compound stability, reduce toxicity, and increase activity, leading to better efficacy and improved patient outcomes. Variability in the number, location, and identity of various glycans leads to variation in drug stability, toxicity, and activity.1
In 2012 the U.S. National Research Council called for a new focus on “glycoscience,” the study of the structure and function of glycans in areas as diverse as medicine, energy generation, and materials science. New mass-spectrometry-based techniques — each of which provides various aspects of characterization — contribute to our ability to perform accurate glyconanalyses. There are two common analytic techniques for glycoprotein characterization. In one approach, nonspecific proteolysis is combined with a two-tiered mass spectrometry approach using matrix-assisted laser desorption/ionization — time-of-flight (MALDI-TOF) with liquid crystal-fluorescence and tandem mass spectrometry (LC-MS/MS) to obtain glycosylation sites and glycan identity. In the second approach, glycans are enzymatically released, labeled with a fluorescent dye, and analyzed using LC-MS/MS to provide glycan identification and relative quantification.2
Certainly our improving ability to perform a comprehensive glyconanalysis is contributing to our ability to formulate more effective therapeutic agents. One area in which glycoanalysis has helped in drug formulations is monoclonal antibodies, which can be genetically or chemically engineered with different properties. Most monoclonal antibodies are produced as recombinant glycoproteins. Glycosylation depends on multiple factors, including the drug production system used, the selected clonal population, and manufacturing processes. As well, there is always the possibility that glycoforms not commonly synthesized in the human body may produce allergic or immunogenic reactions and/or may accelerate linked antibody clearance, reducing efficacy and introducing unwanted side effects. 3
The US Food and Drug Administration has approved more than 20 drugs based on recombinant monoclonal antibody glycoproteins. Several hundred more are in trials for oncology, inflammatory diseases, organ transplantation, cardiology, viral infection, allergy, and tissue growth and repair. 3 As drug companies formulate new compounds based on glycoproteins, mass spectrometry offers a key new method for validating drug design prior to clinical trials.
1. Soláj, R.J. (2009) ‘Effects of glycosylation on the stability of protein pharmaceuticals‘, Journal of Pharmaceutical Sciences, 98 (4), (pp. 1223-1245)
2. Schiel, J.E., et al. (2012) ‘LC-MS/MS biopharmaceutical glycoanalysis: Identification of desirable reference material characteristics‘, Analytical and Bioanalytical Chemistry, 403 (8), (pp. 2279-2289)
3. Beck, A., et al. (2008) ‘Trends in glycosylation, glycoanalysis and glycoengineering of therapeutic antibodies and Fc-fusion proteins‘, Current Pharmaceutical Biotechnology, 9 (6), (pp. 482-501)