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Research Only Immune & Anti-Inflammatory

Magainin

also known as: Magainin 2, MSI-78, Pexiganan

The frog-skin peptide that launched antimicrobial peptide research — discovered in 1987 when a researcher noticed surgical frogs never developed infections.

A 23-amino-acid cationic amphipathic peptide from the African clawed frog (Xenopus laevis) that kills bacteria by forming pores in their membranes — the foundational discovery that launched the modern AMP field.

Mechanism of action

Adopts an amphipathic alpha-helical structure on bacterial membranes. The cationic face binds anionic phospholipids. At threshold concentration, forms toroidal pores causing depolarization and lysis. Selective for bacterial over mammalian membranes due to cholesterol and zwitterionic lipid differences.

Primary uses

  • Research: foundational model for AMP membrane disruption
  • Template for synthetic AMP drug design
  • Broad-spectrum antibacterial research

Typical dosing

N/A N/A N/A (topical (research))

Not approved for clinical use. Research MICs 10-100 mcg/mL.

Regulatory status

Magainin itself is not approved. Its analog pexiganan (MSI-78) reached Phase III for diabetic foot ulcers but was rejected by the FDA in 1999 and 2017.

References

  1. [pubmed] Zasloff M. "Magainins, a class of antimicrobial peptides from Xenopus skin." Proc Natl Acad Sci USA. 1987;84(15):5449-5453.
  2. [review] Zasloff M. "Antimicrobial peptides of multicellular organisms." Nature. 2002;415(6870):389-395.

Related peptides

Pexiganan

A Xenopus-magainin-derived antimicrobial peptide (Locilex; Dipexium Pharmaceuticals / later acquired by PLx Pharma) developed for topical treatment of mildly infected diabetic foot ulcers. Twice rejected by the FDA — once in 1999 (Magainin Pharmaceuticals) and again in 2017 (Dipexium) after the OneStep-1 and OneStep-2 Phase 3 trials failed to show superiority over placebo cream. Instructive regulatory case study in antimicrobial peptide drug development.

LL-37

The only human cathelicidin — an antimicrobial peptide with direct activity against bacteria, fungi, viruses, and biofilms, with additional roles in wound healing and immune signaling.

Cecropin

The insect immune system's first-line antibiotic — among the earliest AMPs discovered, proving innate immunity uses peptide weapons across the animal kingdom.

Melittin

The main weapon in bee venom — a powerful membrane-disrupting peptide being repurposed as an antimicrobial and anticancer research tool.

Cathelicidin

The parent of LL-37 — the sole human cathelicidin, whose expression is directly regulated by vitamin D and whose cleavage product LL-37 is a key effector of innate antimicrobial defense.
Disclaimer

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.