PEGylation: Definition

Detailed Explanation

PEGylation is the covalent attachment of one or more polyethylene glycol (PEG) polymer chains to a peptide or protein molecule. PEG is a biocompatible, non-toxic, non-immunogenic polymer that creates a 'water shield' around the conjugated molecule. This shield increases the peptide's hydrodynamic radius (making it appear larger to the kidney's filtration system), protects it from protease degradation, and reduces antibody recognition — all of which extend circulating half-life.

The technology was pioneered in the 1970s by Frank Davis and first reached the market with PEGylated adenosine deaminase (Adagen) in 1990. PEGylated interferon alpha (PEG-Intron, Pegasys) transformed hepatitis C treatment by enabling once-weekly instead of thrice-weekly dosing. For peptides specifically, PEGylation can extend half-life from minutes to hours or even days. However, PEGylation has limitations: it adds significant molecular weight, can reduce receptor binding affinity if the PEG is attached near the binding site, and anti-PEG antibodies have been detected in some patients after repeated dosing.

In modern peptide drug design, acylation (fatty acid attachment) has increasingly replaced PEGylation for extending half-life, particularly for GLP-1 drugs like semaglutide and liraglutide, because acylation leverages albumin binding rather than simply increasing molecular size. PEGylation remains important for protein drugs and some peptide conjugates, but the trend in peptide therapeutics is toward lipidation strategies.

Key Facts

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