Therapeutic Glycoprtein
One of the fastest-growing fields in the pharmaceutical industry is the market for therapeutic glycoproteins. A major fraction of the currently available is produced as secreted glycoproteins from mammalian cell cultures. The glycosylation profile of these proteins is one of the most important quality attributes. Glycosylation involves the enzymatic addition of monosaccharides or oligosaccharides to specific amino acids in the polypeptide chain and can occur on virtually all proteins from mammalian cells. Mammalian glycans consist of 10 common monosaccharides: glucose, fucose, xylose, mannose, galactose, N-acetylglucosamine, glucuronic acid, iduronic acid, N-acetylgalactosamine, sialic acid, or 5-N-acetylneuraminic acid.
Glycosylation and Its Impact on Protein Functionality and Immunogenicity
The capacity for glycosylation varies significantly among different eukaryotes, as well as in different mammalian species. Moreover, the glycosylation profile of proteins produced in nonhuman mammalian cell lines may contain glycans that are immunogenic in humans. Humans, unlike other mammals, have lost the ability to biosynthesize both the terminal glycans alpha-Gal and N-glycolylneuraminic acid. Hamster and murine cells used in the industry express considerably higher levels of these epitopes; therefore, recombinant products derived from these cells have a higher chance of presenting immunogenicity when compared to products derived from human cells.
Besides the immunogenicity, N- and O-linked glycans have been shown to have also a large effect on the product efficacy, bioactivity, pharmacokinetics, and pharmacodynamics. Erythropoietin (EPO), a glycoprotein hormone used for the treatment of anemia, has been documented to be very sensitive to its attached carbohydrates, therefore affecting the resulting pharmacokinetics. Studies have shown that the sialylated EPO presented a half-life of about 3 h, in contrast to the 2 min half-life of the desialylated EPO. Another study examined the differences in the glycosylation of 12 proteins of different sizes produced by transient expression in two commonly used cell lines, Human Embryonic Kidney and Chinese Hamster Ovary (CHO). For all recombinant proteins, significant differences in glycosylation were detected with higher sialylation in CHO cells, which can result in reduced antibody-dependent cell-mediated cytotoxicity activity of an antibody.
Fig.1 Glycan structures commonly found in the therapeutic antibodies. (Cymer, 2018)
The expression systems used for glycoprotein productions have significantly different glycosylation machinery. Plants, yeasts and non-human cell lines can generate glycans that are often absent from endogenous human proteins. For example, yeasts and insect cells can produce high-mannose or pauci-mannose oligosaccharides, while plant cells introduce undesirable α 1,3- fucose and β1,2-xylose. Moreover, as opposed to human cells, CHO and BHK cells do not express any α 2,6- sialyltransferase activity and can generate glycans with terminal Neu5Gc and α-gal. However, both Neu5Gc and α-gal levels are significantly higher in murine cells such as NS0 and Sp2/0, compared to hamster cells. To avoid any potential immunogenic response, glycans present on biotherapeutic proteins should be compatible with human hosts. Consequently, several glycoengineering strategies have emerged to recreate these beneficial profiles on recombinant proteins. In particular, fucosylation and sialylation strategies are now popular glycoengineering approaches for biologics.
Services at Creative Biolabs
The importance of therapeutic proteins in drug applications has grown rapidly since the emergence of the biotechnology industry more than 30 years ago. More and more protein pharmaceuticals are being developed. Expression systems used for the commercial production of therapeutic glycoproteins are the result of many years of improvements and process developments.
Accumulated extensive experience in improving therapeutic glycoprotein production, Creative Biolabs has the world's leading glycoengineering technology platform and professional scientific staff. We master the therapeutic glycoprotein production technology of various expression systems and provide personalized glycoengineering services according to customer requirements. If you have any questions about therapeutic glycoproteins, or you have any needs in glycoengineering, please contact us for more information.
Reference
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Cymer, F., et al. Therapeutic monoclonal antibody N-glycosylation - Structure, function and therapeutic potential. Biologicals: journal of the International Association of Biological Standardization. 2018, 52: 1-11.
For Research Use Only.
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