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Peptides / LL-37

Review scheduledCathelicidin, antimicrobial peptideNot FDA approved

LL-37

LL-37 is the only human cathelicidin, a 37-amino-acid peptide made by skin and immune cells as part of the body's first line of defence against germs.

Main use
Infection and wound healing
Committee review
Review by Feb 2027
Strongest evidence
Small human studies
Legal to compound in the US
Not yet

Effects studied or claimed

What it is promoted for, and where each effect has actually been seen

  • Kills bacteria, fungi and some virusesLab studies
  • Faster healing of chronic woundsSmall human trial
  • Adjusts the immune responseLab studies

How it is thought to work

It punches holes in the outer membranes of microbes and signals immune cells to the site of an infection.

What the evidence shows

In animals and the lab

Infection and wound models in animals.

In people

A small early trial applied it to chronic leg ulcers and reported faster healing. There are no studies of injected use.

Safety and unknowns

High natural levels are linked to inflammatory skin conditions such as rosacea and psoriasis. The effects of injecting it are unknown.

FDA review

Scheduled for review by the FDA's compounding advisory committee before the end of February 2027.

Committee votes are advice to the FDA. A peptide can only be compounded legally once the FDA adds it to the 503A bulks list through formal rulemaking, which has no fixed deadline.

Sources

Analysis

The body's own antibiotic, with a double edge

Peptide Evidence IndexBiology 7.5/10In people 4/10Index 4.9, rank 4 of 15See the full index

LL-37 is the only human member of the cathelicidin family, a group of peptides that kill bacteria, fungi and some viruses. The body makes more of it when vitamin D levels are adequate: a 2006 study in Science showed that vitamin D drives immune cells to produce cathelicidin to fight tuberculosis bacteria (Liu and colleagues).

It is one of the few peptides on this list with a controlled human trial. In a Swedish study of 34 people with hard-to-heal venous leg ulcers, a gel containing LL-37 improved the healing rate against placebo at the two lower doses, while the highest dose caused more local reactions (Grönberg and colleagues, 2014). The same peptide has a darker side: too much of it, or a faulty version, drives inflammation in rosacea and helps trigger psoriasis (Yamasaki and colleagues, 2007; Lande and colleagues, 2007).

Our view. applied to chronic wounds under medical supervision, LL-37 shows genuine promise. Injecting it for general immune support is another matter, given its links to inflammatory skin disease and the lack of any trials for that use.

Studies and reports cited

  1. Liu PT et al. Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response. Science, 2006
  2. Grönberg A et al. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial. Wound Repair Regen, 2014
  3. Yamasaki K et al. Increased serine protease activity and cathelicidin promotes skin inflammation in rosacea. Nat Med, 2007

Summary of published research for general information. It is not medical advice and not a recommendation to use this substance.

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General information, not medical advice. Do not buy or inject unregulated peptides.