On-line CE-LIF-MS technology for the direct characterization of N-linked glycans from therapeutic antibodies

Glycan characterization of therapeutic proteins is of utmost importance due to the role of carbohydrates in protein stability, half-life, efficacy and mechanism of action. The primary assay for characterization and lot release of N-linked glycans on glycoprotein products at Genentech, Inc., is a capillary electrophoresis (CE) based assay, wherein PNGase F-released, APTS-labeled glycans are separated by CE with laser induced fluorescence (LIF) detection. With the growing number of new molecular entities in the pipeline, a fast and direct characterization approach is of increasing importance. This paper describes the development of CE-MS technology with on-line LIF detection that allows identification of major and minor glycan species (1-5% of total glycans) by providing accurate mass information. Data is presented for therapeutic rMAbs which presented previously unidentified, minor peaks during routine CE-LIF analysis. CE-LIF-MS was then used to provide accurate mass on these species, identifying CE peaks corresponding to sialylated (G1 + NANA, G2 + NANA), afucosylated (G0-GlcNAc-fucose) and low-level isomers of major APTS-labeled glycans G0, G1, G1' and G2.