Plant-derived cyclotides serve as ultra-stable scaffolds that can be engineered to carry bioactive sequences, creating orally active peptide drugs targeting G protein-coupled receptors.
Oral peptide activity achievedCyclotide scaffolds confer oral bioavailability and enzymatic stability to grafted bioactive peptide sequences
What the researchers found
Molecular grafting of bioactive epitopes into cyclotide scaffolds produces GPCR ligands with improved oral activity, enzymatic stability, and selectivity compared to linear peptide counterparts.
Why it matters
Peptide drugs typically cannot be taken orally and degrade quickly. Cyclotide scaffolds solve both problems, potentially enabling a new generation of oral peptide medicines targeting the largest class of drug targets.
The numbers in context
GPCRs: ~34% of approved drug targets; cyclotides: cyclic cystine knot, 3 disulfide bonds; some show oral activity in vivo
How the study worked
Review of molecular grafting approaches using cyclotide scaffolds to engineer novel GPCR-targeting peptide ligands, with examples of improved pharmacokinetics.
Who was studied
Review of cyclotide-based GPCR ligand engineering and molecular grafting approaches
What this study cannot tell us
Review — most examples are preclinical; oral bioavailability improvements vary by construct; manufacturing scalability of cyclotide-based drugs not fully addressed.
How to read the evidence
Well-supported review with concrete examples of successful grafting approaches, but most applications remain preclinical.
When this study was published
Published in 2020; cyclotide engineering has continued to advance with new GPCR targets and improved grafting strategies.
The bigger picture
Cyclotides bridge the gap between small molecules (orally available but limited) and biologics (potent but injectable), creating a hybrid approach to drug design with the best of both worlds.
Questions still open
- Which GPCR targets are most amenable to cyclotide-based drug design?
- Can cyclotide scaffolds accommodate larger bioactive sequences without losing stability?
- How do manufacturing costs of cyclotide drugs compare to conventional peptide therapeutics?
Common questions
What are cyclotides?
Can peptide drugs be taken orally?
Read the original research
Harnessing cyclotides to design and develop novel peptide GPCR ligands.
RSC chemical biology, 1(4), 177-191
Citation
Muratspahić, Edin; Koehbach, Johannes; Gruber, Christian W; Craik, David J. (2020). Harnessing cyclotides to design and develop novel peptide GPCR ligands.. RSC chemical biology, 1(4), 177-191. https://doi.org/10.1039/d0cb00062k