Why is glycosylation important for therapeutic proteins and how is it controlled?

Glycosylation (attachment of sugar chains) affects therapeutic protein properties: 1) Efficacy - antibody effector functions depend on Fc glycans; afucosylated antibodies have enhanced ADCC. 2) Stability - glycans protect from aggregation and degradation. 3) Pharmacokinetics - sialylation affects clearance through asialoglycoprotein receptor. 4) Immunogenicity - non-human glycans (alpha-Gal, NGNA) can trigger immune responses. 5) Solubility - glycans increase hydrophilicity. Control strategies: cell line selection (CHO produces human-like glycans), media optimization (manganese, galactose supplementation), process parameters (pH, temperature, dissolved oxygen), gene knockout/knockin (FUT8 knockout for afucosylation), and in vitro glycoengineering. Glycan analysis (LC-MS, HILIC, capillary electrophoresis) monitors consistency. Critical quality attribute requiring tight control for biosimilar development.