As of September 2026, no LL-37 product holds FDA or EMA approval. The human body makes LL-37 itself, as part of its defense against microbes. As a treatment it has been studied mostly in lab dishes and animals. One small randomized, placebo-controlled trial, in 34 people with hard-to-heal leg ulcers, was published in 2014. None of that tells you what is in a vial sold as LL-37.
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What is LL-37?
LL-37 is the only cathelicidin-family antimicrobial peptide the human body makes, in immune cells and skin cells, as a first defense against microbes. Its name comes from the two leucines it starts with and its length of 37 amino acids. Researchers study it for infected and hard-to-heal wounds, and no LL-37 product holds FDA or EMA approval.
Does LL-37 work?
Nobody knows yet. One randomized, double-blind, placebo-controlled trial in 34 people with hard-to-heal leg ulcers was published in 2014, and its authors reported improved healing. It was the first trial in people, and it was small and short. Most of the other evidence comes from lab dishes or animals.
What we found. 1 completed randomized trial, in 34 people with leg ulcers, published in 2014. 1 study of human wound fluid samples, which is not a trial. 2 animal studies.
| Study | Tested in | Status | What it shows |
|---|---|---|---|
| LL-37 as a possible treatment for wounds infected with several microbes | Animals | Published | Fewer bacteria and improved healing in infected wound models |
| Wound-healing activities of LL-37, in lab dishes and in animals | Animals | Published | Reported wound-healing activity |
| Stability of LL-37 in a non-healing wound environment | People | Published. A study of wound fluid samples | LL-37 was degraded or inactivated in chronic wound fluid. The record says this limits its potential as a treatment as it stands |
| LL-37 on hard-to-heal venous leg ulcers, first trial in people | People | Published in 2014. Randomized, double-blind, placebo-controlled | The authors reported improved healing and called the treatment safe. 34 people, four weeks of treatment |
Lab and animal results make up most of the evidence. They cannot tell you what happens in people.
How we count a trialIs LL-37 safe?
The evidence is thin. The one human trial, in 34 people, was called safe by its authors over a four-week course on leg ulcers. Besides the thin human data, the record names two concerns. The peptide is unstable in real wound environments, and its roles in inflammatory skin diseases are complex and sometimes contradictory. The animal studies on the record report on bacteria and healing, with no safety result. That is where the molecule stands. A vial sold under its name is a separate question, covered below.
Is LL-37 legal?
- United States
- Not approved by the FDA. No LL-37-based pharmaceutical product holds FDA approval.
- European Union
- No EMA marketing authorisation.
- Sport
- Not named on WADA's list. That is not clearance.
Not medical advice. Approval and sport status as of . Medical disclaimer
What is in a vial sold as LL-37?
The record describes LL-37 as a subject of research, with no LL-37 product approved by the FDA or the EMA. It does not say how vials sold under this name reach people. A "research use only" label guarantees nothing about purity. A certificate of analysis counts only if it names your lot number, a lab with no stake in the result, and the method used. Purity and identity are separate tests.
Three questions to ask the seller:
- Which lot number is this certificate for?
- Who ran the test, and are they independent of you?
- Does the report confirm identity by mass spectrometry, or purity alone?
What don't we know?
- Whether LL-37 works as a treatment in people. The record lists one trial, in 34 people.
- Whether a stabilized form would hold up in a real wound. Native LL-37 degrades quickly there.
- What its roles in inflammatory skin diseases mean. The record calls them complex and sometimes contradictory.
- What is in any given vial.
The other side
A personal result is real to the person who had it. It cannot separate the compound from the vial, or from a wound that was closing on its own.
What would change this record?
- A registered, completed human trial that tests a stabilized LL-37 formulation against a wound-healing or infection outcome.
Change log
- Count corrected from 0 to 1 and grade from D to B. A randomized, placebo-controlled trial in 34 people, published in 2014, is now listed.
- Record checked. No change logged yet.
Three questions to ask next
- What does 'research use only' actually mean?
- How can you tell if a peptide vendor is legitimate?
- How do you read a certificate of analysis?
Ask better questions.
More questions about LL-37
Is LL-37 approved by the FDA?
- No. No LL-37-based product holds FDA approval, and there is no EMA marketing authorisation.
Has LL-37 been tested in people?
- Once. A randomized, double-blind, placebo-controlled trial in 34 people with hard-to-heal leg ulcers was published in 2014. It was the first trial in people, and it was small.
Does the body make LL-37?
- Yes. The record calls it the only cathelicidin-family antimicrobial peptide the human body makes, in immune cells and skin cells. That says nothing about a vial sold under the name.
Does LL-37 break down in wounds?
- Yes, on this record. A study found LL-37 degraded or inactivated in chronic wound fluid, and the record says native LL-37 degrades quickly in wound environments.
Is LL-37 banned in sport?
- It is not named on WADA's list. The record gives no sport source for that. If you compete, check the current List.
Record checked on . Each source shows the date it was checked.