LL-37

Key points

• LL-37 is a human host defence peptide, part of the cathelicidin family, that the body produces naturally.
• It can kill microbes directly and also help steer the immune response.
• Nearly all the evidence is preclinical, from laboratory and animal studies.
• It is not a licensed medicine in the UK and is sold only for research use.

Quick facts

What it is

Natural antimicrobial host defence peptide (cathelicidin)

Studied for

Antimicrobial and immune effects

UK status

Not a licensed medicine; sold for research use

Human evidence

Very limited; mostly laboratory studies

How it works

LL-37 can break up the membranes of bacteria and other microbes, and it also influences immune signalling, helping to coordinate the body's response to infection and injury. Most of what is known comes from laboratory work. Its role is complex, and in some settings it can promote as well as calm inflammation.

What the evidence shows

The evidence is preclinical, describing antimicrobial and immune effects in the laboratory and in animals. There is no human trial evidence of benefit or safety as a treatment, and no established dose.

What it does not settle

• There are no human trials of benefit or safety.
• Its complex effects mean outcomes could cut both ways, which is not well understood in people.
• There is no established human dose.

Side effects

Less common but serious

• Because its effects on inflammation are complex, the results of giving it to people are not predictable.
• Because there is no licensed product, the dose, purity and contents of material bought online cannot be verified.

Report any suspected side effect through the MHRA Yellow Card scheme.

UK legal status and access

LL-37 has no UK marketing authorisation, so it is not a licensed medicine and is not offered by registered clinics or pharmacies. It is sold online as a research chemical.

Common questions