Getting at Glycosylation

The use of many methods and variability pose a biotherapeutic challenge.

Pharmaceutical scientists face an increasing need to understand the structure of biologics, and more demand lies ahead. Variant Market Research, for example, forecasts that the world market for biologics will reach $394 billion by 2024.1 In particular, scientists must characterize the addition of sugars—glycosylation—but that’s no small feat.

In a recent report, Lorna De Leoz—formerly at the U.S. National Institute of Standards and Technology (NIST) and now a mass spectrometry specialist at Agilent—and her colleagues noted that glycoproteins make up two-thirds of approved biologics.2 Working with NIST fellow Stephen Stein and others, De Leoz explored reports from 76 laboratories around the world to compare various methods of analyzing glycosylation of monoclonal antibodies (mAbs)—particularly a NIST reference (NISTmAb PS) and a modified version of it.

“NIST runs an initiative to develop better ways to measure quality in biomanufacturing,” Stein explained. “We’re just trying to measure things better.” Part of that involves glycosylation of mAbs, which make up a common class of biotherapeutics.

“Glycosylation is a crucial post-translational modification in monoclonal antibodies, and it’s inherently heterogeneous,” De Leoz said. Plus, labs use many methods to analyze glycosylation. So, De Leoz and her colleagues set out to determine the variability in the results.

Some labs perform analysis based on the glycan composition in a sample, and others focus on isomers. “We need to pull all of those data together,” De Leoz noted. “Diversity of the results was the biggest issue.” In fact, NIST research chemist David Duewer—also an author of the article—developed new methods to analyze the disparate methods and data.

The findings reveal more work to be done. “Glycosylation analysis is the most important and least precise area of chemical analysis,” Stein said. “The methods for identifying the chemical structures are not well developed at this time.” Even two results from the same lab using the same method on the same sample can vary.

In thinking about the reports analyzed for this study, De Leoz said, “There is no magic method for analyzing glycosylation in monoclonal antibodies.” Then, she makes one suggestion: “A lab can do better internally, and make sure that it’s getting results that are sensible to other labs.”

2. De Leoz, M.L.A., Duewer, D.L., Fung, A., et al. NIST interlaboratory study on glycosylation analysis of monoclonal antibodies: Comparison of results from diverse analytical methods. Mol. Cell Proteomics. 2019. doi: 10.1074/mcp.RA119.001677. [Epub ahead of print]

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