Home > Technology > PEGylation

PEGylation

Peptides play a key role in the drug therapeutic development and pharmaceutical industry; however, their applications in vivo are sometimes limited due to fast degradation by proteases, poor solubility, antigenic responses, and glomerular filtration in the kidney. The covalent attachment of polyethylene glycol (PEG) chains to peptides is one approach that can reduce immunogenicity, improve solubility, and reduce renal clearance. PEGylation is now a well-established technique in the field of targeted drug delivery systems. As more PEGylated therapeutic agents receive FDA approval, more attention has been given to site-specific PEGylation of discrete or monodispersed PEG chains. HongTide can perform site-specific PEGylation at a variety of sites on the peptide.
PEGylations Methodologies
N-terminal PEGylation can be accomplished by direct PEG carboxylic acid coupling or native chemical ligation with PEG thioester and a cysteine residue. C-terminal is more complicated, but can be achieved through a thiocarboxylic acid modification and sulfone-azide PEG reagent. Hydrazide modifications combined with a pyruvoyl PEG reagent is also a useful approach to C-terminal PEGylation. Here are three methodologies which are often used for site-specific PEGylations:

  • Click Chemistry : 

    which takes place between an azide group of the PEG reagent and an alkyne group of the peptide, or vice versa;

  • Suzuki-Miyaura Coupling : 

    which takes place between the iodophenyl group of the PEG reagent and an aryl boronic acid group of peptide, or vice versa;

  • Sonogashira Coupling : 

    which takes place between an iodophenyl group of the PEG reagent and an alkyne group of the peptide, or vice versa.

Common PEG Linkers for Peptide Conjugation

Abbreviation

PEG

mini-PEG2

mini-PEG3

NH2-PEG2-acid

PEG750

PEG1000

PEG2000

PEG5000

Full PEG Chain Name

tetraethylene glycol

8-amino-3,6-dioxaoctanoic acid

amino-3,6,9-trioxaundecanoic acid

3-(2-(2-Aminoethoxy)ethoxy)-propanoic acid

Poly(ethylene glycol) methyl ether (average Mn 750)

Poly(ethylene glycol) methyl ether (average Mn 1000)

Poly(ethylene glycol) methyl ether (average Mn 2000)

Poly(ethylene glycol) methyl ether (average Mn 5000)

PEGylation and Peptide Bioavailability Introduction
PEGylation offers multiple physiochemical and pharmacokinetic benefits to peptide-based therapeutics. Following covalent attachment of a PEG chain to a peptide, the PEG-peptide conjugate has longer blood circulation times, increased solubility, and reduced immunogenicity. Longer circulation times (i.e., enhanced bioavailability) also results in a lower frequency of dosings and lower dosing amounts. The increased steric hindrance from the PEG chain can hinder much of the non-specific protease interactions. N-terminal PEGylation can specifically block endopeptidases and provide steric hindrance to proteolytic enzymes. In a similar fashion, PEG chains can block epitope sites on the peptide from antibody binding. With the advancement of more sensitive and non-invasive imaging techniques (e.g. PET, SPECT), more interest has focused on the drugability of targeting peptide-chelate conjugates. Spacers between the peptide and chelate (e.g., DOTA, NOTA, etc) are often incorporated to improve the peptide binding affinity. PEG spacers offer advantages over hydrocarbon spacers due to their increased hydrophilicity. Profound increases in tumor uptake and retention have been observed in PEGylated RGD-based probes. Imaging peptide-based probes can be easily modified to improve and extend the duration of target uptake. Vascular endothelial growth factor (VEGF) is an important target for imaging probes because it is over-expressed in cerain cancer cells that stimulate angiogenesis. Anti-VEGF monoclonal antibody, bevacizumab, successfully targets VEGF and has been approved by the FDA for noninvasive PET and SPECT imaging of VEGF. The v107 peptide also binds to VEGF, but only with micromolar affinity that is insufficient for targeted molecular imaging. Marquez and co-workers redesigned the peptide by substituting leucine-19 for a lysine residue and incorporating a chelating moiety, 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA), at the N-terminus separated by a PEG4 spacer (figure below). The resultant sequence, NOTA-PEG4- GGNECDIARMWEWECFERK-NH2, was then cross-linked with 5-fluoro-2,4-dinitrobenzene to form a covalent bond with lysine-19 (L19K-FDNB). This modification increases binding affinity because it enables the peptide probe to irreversibly bind to VEGF by a covalent attachment to a site inside the binding pocket of the protein. The inert and flexible characteristic of the PEG linker provides distance between the peptide cargo carrier (e.g., NOTA) for optimal binding to the receptor.

HongTide

Services

Products

Technical Support

Customer Support

Contact

Copyright 2022 Shanghai HongTide Biotechnology Co.,Ltd. All rights reserved.