LL-37
Also known as: Cathelicidin, CAP-18, hCAP18
A naturally occurring antimicrobial peptide produced by the human immune system. It is part of the cathelicidin family and has broad activity against bacteria, fungi, and viruses. It remains a research compound with limited human clinical data.
How it works
LL-37 is a 37-amino-acid peptide that your body naturally makes as part of its first line of defense against infection. It kills microbes by punching holes in their cell membranes. It also disrupts biofilms (protective coatings that bacteria build around themselves) and signals other immune cells to come help fight infection. Research shows it is effective against over 38 types of bacteria, 16 fungi, and 16 viruses.
Common uses
- Antimicrobial defense (research)
- Biofilm disruption
- Wound healing support
- Immune modulation
Side effects
- Dose-dependent toxicity to human cells at higher concentrations
- Potential hemolytic effects (damage to red blood cells)
- Injection site irritation
- Risk of immunogenicity (immune reaction against the peptide itself)
- Very limited human safety data
Key research
- Extensive lab research demonstrates broad-spectrum antimicrobial activity against bacteria, fungi, viruses, and parasites
- Studies show LL-37 effectively disrupts bacterial biofilms
- Early-phase clinical trials underway for wound healing and chronic infections
- 2025 research explores modified LL-37 analogs with improved stability and reduced toxicity
Safety notes
- Expected to remain on FDA Category 2 (restricted) due to limited human safety data and immunogenicity concerns
- Rapid enzymatic breakdown in the body limits its practical use
- High production costs remain a barrier to clinical development
- Not recommended for self-administration
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