Influence of glycan modification on IgG1 biochemical and biophysical properties

Abstract

Monoclonal antibodies (mAbs) are the fastest growing class of biopharmaceuticals. The specific therapeutic tasks vary among different mAbs, which may include neutralization of soluble targets, activation of cytotoxic pathways, targeted drug delivery, and diagnostic imaging. The specific therapeutic goal defines which interactions of the antibody with its multiple physiological partners are most critical for function, and which ones are irrelevant or indeed detrimental. In this work, we explored the ability of the glycan chains to affect IgG1 interaction with two key receptor families, FcRn and γ-type Fc receptors, as well as the influence of glycan composition on the conformation and stability of the antibody molecule. Three different glycan-modified forms of IgG1 (fully deglycosylated, hypergalactosylated and hypersialylated) were produced and characterized alongside the unmodified mAb molecule. Biophysical measurements did not reveal any changes that would be indicative of alterations in the higher order structure or increased aggregation propensity for any of the three glycoforms compared to the unmodified mAb, although the CH2 domain was shown to have reduced thermal stability in the fully deglycosylated form. No significant changes were observed for the hypergalactosylated and hypersialylated forms of IgG1 with regards to binding to FcRn, FcγRIIA and FcγRIIIA, suggesting that neither half-life in circulation nor their ability to induce an immune response are likely to be affected by these modifications of the glycan chains. In contrast, no measurable binding was observed for the deglycosylated form of IgG1 with either FcγRIIA or FcγRIIIA, although this form of the antibody retained the ability to associate with FcRn. These highly specific patterns of attenuation of Fc receptor recognition can be exploited in the future for therapeutic purposes.

Keywords: Mass spectrometry; Monoclonal antibody; Protein glycosylation; Protein stability; Protein therapeutics; Receptor binding.