Glycosylated proteins, including erythropoietin (EPO), monoclonal antibodies (MAb) and various hormones, constitute a large part of approved therapeutic biological drugs. Sialic acid is a negatively charged monosaccharide and exists as a terminal epitope on many glycans. The two most common sialic acids in biopharmaceuticals are N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc). Neu5Ac is found in both human and non-human cells. Neu5Gc is synthesized by all mammalian cells except human cells. Neu5Gc and its homologue Neu5Ac have only one oxygen atom difference, which is enough to make Neu5Gc immunogenic in humans (Figure 1). A common modification of sialic acid is acetylation. O-acetylation can reduce the kinetics of enzyme-catalyzed glycan desialylation, which may affect clinical efficacy. Since the amount and type of sialylation affect the clinical manifestations of therapeutic glycoproteins (serum half-life, immunogenicity, activity, etc.), it is considered a critical quality attribute (CQA). Therefore, characterizing sialylation throughout the product life cycle is a regulatory requirement (ICHQ6B) to monitor the following metrics:
Figure 1: Structural Differences between Neu5Ac and Neu5Gc Sialic acids.
The benefits of using Creative Biolabs' glycan profiling analysis scheme and related products for sialic acid analysis are:
Under the condition of maintaining N-acetyl, N-glycolyl and O-acetylation, sialic acid is released from glycoprotein by mild acid hydrolysis. Use LudgerTag DMB analysis kit (LT-KDMB-A1) to derivatize the keto group of free sialic acid with DMB. For highly sialylated samples, the typical starting amount is 50 µg glycoprotein, and for low-sialylated glycoproteins, the typical starting amount is 100-500 µg. The DMB-labeled sialic acid was then analyzed by RP-HPLC and DMB-labeled standard solution for quantification.
Figure 2: Workflow for Sialic Acid analysis using Creative Biolabs’ DMB Kit .
With extensive experience in glycan characterization, our team can work on custom solutions to meet the unique requirements of each product. With flexible global capabilities, you can provide services where you need it most. Contact our expert scientists today to discuss how our range of glycan analytical services can improve your unique process.
Creative Biolabs provides luciferase-based ADCC assay. This Jurkat cell based assay is pioneered by Creative Biolabs, and the methodology is very well accepted by the field. See attached ADCC Reporter Assay Protocol for further details.
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