Plectasin
The first defensin found in a fungus: a 40-residue peptide that cured pneumococcal infections in mice by binding lipid II. Preclinical only.
Plectasin is a 40-residue defensin from the saprophytic fungus Pseudoplectania nigrella, the first defensin isolated from a fungus. Recombinant plectasin was especially active against Streptococcus pneumoniae, including antibiotic-resistant strains, showed very low toxicity in mice, and cured mice of experimental pneumococcal peritonitis and pneumonia (2005). A 2024 study showed it targets the cell-wall precursor lipid II. It has not been tested in people.
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Recommended Dosing
No dosing data yet
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Mechanism of action
Binds lipid II, the bacterial cell-wall precursor, through a calcium-sensitive supramolecular mechanism (2024 study). Its structure closely resembles defensins of spiders, scorpions, dragonflies and mussels (2005).
Primary uses
- Preclinical antibiotic lead (Gram-positive bacteria)
- Template for engineered defensins
Typical dosing
No human dose: it has been studied only in the laboratory and in animals.
Regulatory status
Not approved and not in human trials: Drugs@FDA, the EMA medicines list and ClinicalTrials.gov hold no record (searched October 28, 2026).
Status as of this entry's last review, October 28, 2026. Approvals, compounding rules and sport rules change; the regulatory tracker is checked more often.
What we checked
Plectasin is a fungal defensin studied as an antibiotic lead; this section records what can be checked.
Identity, computed
| Sequence | GFGCNGPWDEDDMQCHNHCKSIKGYKGGYCAKGGFVCKCY (UniProt Q53I06, chain 56 to 95) |
| Length | 40 residues, six cysteines |
The mature sequence is UniProt's chain annotation; no formula or mass is given here because the published records read do not state the disulfide pattern of the product tested.
Regulatory status, read October 28, 2026
Drugs@FDA: 0 records for “plectasin”. EMA medicines list: 0 records for “plectasin”. Run for semaglutide, the same queries return 6 and 5 records (and the registry search 85 trials), so a zero here is an absence, not a broken search. Not named on the WADA 2026 and 2027 Prohibited Lists. As a substance with no current approval for human therapeutic use, it falls under section S0 (non-approved substances), which is prohibited at all times; the lists were read on October 28, 2026.
What the studies show
Recombinant plectasin was made at high yield, was active against resistant S. pneumoniae, and cured mouse peritonitis and pneumonia (Mygind et al., 2005).
It binds lipid II in a calcium-sensitive supramolecular complex (Jekhmane et al., 2024).
What we looked for and did not find
No human study, no registry record and no approval.
| Source | Query | Results, October 28, 2026 | What it was |
|---|---|---|---|
| PubMed | plectasin[tiab] | 85 | |
| ClinicalTrials.gov | plectasin | 0 | |
| Drugs@FDA (openFDA) | plectasin | 0 | |
| EMA medicines list | plectasin | 0 |
References
- [other] UniProt Q53I06: fungal defensin plectasin, Pseudoplectania nigrella; mature chain residues 56 to 95. Read October 28, 2026. https://www.uniprot.org/uniprotkb/Q53I06/entry
- [pubmed] Mygind PH, et al. "Plectasin is a peptide antibiotic with therapeutic potential from a saprophytic fungus." Nature, 2005;437(7061):975-80. PMID: 16222292.
- [pubmed] Jekhmane S, et al. "Host defence peptide plectasin targets bacterial cell wall precursor lipid II by a calcium-sensitive supramolecular mechanism." Nat Microbiol, 2024;9(7):1778-1791. PMID: 38783023.
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Guides & tools
This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.