The effect of Fc glycan forms on human IgG2 antibody clearance in humans

Several studies using a variety of approaches have investigated the impact of the Fc glycan structure on IgG clearance rates. Most, but not all, of these studies have concluded that glycan structural differences do not affect clearance. Here we investigated the impact of glycan on the clearance of a human antibody in humans. To monitor glycan-dependent changes, a human IgG2 was affinity purified in a single step from serum samples from a human pharmacokinetic study. The glycan profile from the purified antibody samples was determined by RP-HPLC/MS analysis of the 2-aminobenzamide-labeled glycans. Relative levels of high-mannose species (M6-M9) decreased over circulation time. Differences in the individual high-mannose structural isoform clearance rates were measured from extracted ion current profiles. Similar changes to the glycan profile could be achieved through incubation of the antibody in serum in vitro, suggesting that the changes observed in vivo were the result of glycan cleavage, not differential antibody clearance. These results confirm that antibody clearance is not significantly affected by the Fc glycan structure and provide evidence for the presence of circulating mannosidase activity in humans.