Cyclic peptides as broad-spectrum antiviral agents

Cyclic peptides as broad-spectrum antiviral agent

Cyclic peptides as broad-spectrum antiviral agents

Antiviral drugs and vaccines are the most powerful tools to combat viral diseases. Most drugs and vaccines only target a single virus. However, the broad-spectrum antivirals can be used for rapid management of new or drug-resistant viral strains. Cyclized peptides and peptide analogs are excellent examples of broad-spectrum antivirals.

An artificial peptide molecule was found to neutralize a broad range of group 1 influenza A viruses, including H5N1. The peptide design was based on complementarity determining region (CDR) loops have been reported for other viral targets. The optimized peptides bind to the highly conserved stem epitope and block the low pH-induced conformational rearrangements associated with membrane fusion.

These peptidic compounds and their advantageous biological properties should accelerate development of novel small molecule and peptide-based therapeutics against influenza virus.

The linear peptide is Suc-SQLRSLEYFEWLSQ-NH2. Three cyclization strategies were used: head to tail, side chain to side chain and side chain to tail. An ornithine (Orn) side chain was fused with the carboxyl terminus of β-alanine for lactam formation.

Check here for more details: Potent peptidic fusion inhibitors of influenza virus, Science 28 Sep 2017, DOI: 10.1126/science.aan0516

Lately, more broad-spectrum antiviral agents were found to target viruses. It was found that 55 compounds can target eight different RNA and DNA viruses. Dalbavancin is a novel lipo-glycopeptide antibiotic. The lipoglycopeptide disrupts bacterial cell wall formation by binding to
the terminal d-alanyl-d-alanine peptidoglycan sequence in Gram-positive bacteria in a linear, concentration-dependent manner. The dalbavancin has effects on echovirus 1, ezetimibe against HIV1 and Zika virus.

More details:

Polypeptides pegylation as new drug candidates

Polypeptides are used as new drug candidates to target specific disease symptoms. However, peptide drugs are rapidly degraded by proteolytic enzymes and neutralized by antibodies. Pegylation of polypeptide drugs improves their pharmacodynamic and pharmacokinetic profiles. Pegylating specifically can minimize the loss of biological activity and reduce immunogenicity. LifeTein offers peptide pegylation service and the PEG-modification of peptides through primary amines and sulfhydryl groups.

A significant limitation of the present PEGylated peptides is their heterogeneous nature because PEG is conjugated at many different nucleophilic amine residues. LifeTein’s approach to peptide PEGylation can address the fundamental issues of site-specific conjugation and high-efficiency conjugation. The click chemistry is widely used in the pegylation process.

The efficient ratio of 1:1 PEGylation of a peptide can be completed in 24 hours and purification of the PEG-protein conjugate in another three hours, without destroying their tertiary structure or abolishing their biological activity.

LifeTein’s improved technology is the use of branched structures, in contrast to the linear structures. Branched PEGs have increased molecular masses of up to 60 kDa or more, which is good at cloaking the attached polypeptide drug from the immune system and proteolytic enzymes.

Pegylation is the established method for improving the pharmacokinetics and pharmacodynamics of peptide pharmaceuticals.

New frontiers for the technology are now emerging for PEG-based hydrogels and PEG-modified liposomes, small-molecule modification, and the primary targets for pegylation of small-molecule drugs, oligonucleotides, lipids, cofactors, antibodies, saccharides, and nanoparticles.

Pegylation service from LifeTein

Pegylation service from LifeTein

Amino acid composition of cell-penetrating peptides (CPPs)

Cell-penetrating peptides (CPPs) such as the HIV TAT peptides are able to enter cells by direct translocation and endocytosis. Click here to see details about the CPP:

About Cell-Penetrating Peptides

cell penetrating peptide entry mechanism

Cell Penetrating Peptides

The following table shows a selection of currently known CPPs, their origins, and sequences.



Tat (48-60)

HIV-1 protein



Igl-1 homeodomain



Stearly-RRRRRRRR-amide (Stearyl = CH3(CH2)16CO-)


Stearly-(RxR)4-amide (X=6-aminohexanoic acid)

Obesity Treatment: A New Peptide Drug

Targeted Drug Melts Fat in Obese Monkeys Currently, only two Food and Drug Administration (FDA) approved drugs for weight loss are available in the United States: the appetite suppressant phentermine and the inhibitor of fat absorption orlistat.

Peptide Drug for Obesity

An MD Anderson group designed a new peptide drug: CKGGRAKDC-GG-D(KLAKLAK)2 (adipotide). This is a synthetic peptide that triggers cell death. These data showed that the peptide might be helpful in treating obesity in humans. The MD Anderson group used a peptide library to screen and identify regions that bind to specific vascular cells. The interaction identified will be used as effective drugs to target particular protein functions. This video explains factors that have contributed to the obesity epidemic.

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