LL-37

Immune In trials Human trials

Also called Cathelicidin, CAP-18 fragment

The only cathelicidin antimicrobial peptide humans make. White blood cells and skin release it to kill bacteria directly by disrupting their membranes. It also directs immune cells and supports wound closure. Too much of it is tied to conditions such as rosacea and psoriasis.

Evidence at a glance

Evidence: Human trials — Studied in people
Status: Reached clinical trials
Dosing: A dose has been tested in humans

Too much LL-37 drives rosacea and psoriasis flares, so more is not better.

What studies report

Direct killing of bacteria, including some resistant strains, in lab tests
Improved healing of hard-to-heal venous leg ulcers in a phase 2 topical trial

How it works

Carries a positive charge and a water-repelling face, so it inserts into the negatively charged membranes of bacteria and breaks them open. It also signals to immune cells and supports wound closure — which is why too much of it drives inflammatory skin disease.

Binds a receptor on the cell surface and signals inward

Where it acts

Thymus

The library groups this compound under Immune. The diagram shows that target, not every tissue it reaches.

Illustrated

A neutral microscopic arrangement of a human innate immune cell beside a few rod-shaped bacteria.

AI-generated subject illustration; not a depiction of the compound or evidence of its effects.

Why people take it

Antimicrobial defenceChronic wounds and ulcersBiofilm research

Reasons people seek it out — not a list of proven effects.

In practice Unapproved use

A niche choice in the chronic infection and biofilm community

Reported real-world use, not evidence and not a recommendation.

Dosing

What was tested Evidence

0.5–1.6 mg/mL topical, twice daily4 weeksPhase 2 in hard-to-heal venous leg ulcers→ Improved healing at lower concentrations; higher ones did worse

What people report using Not evidence

Niche use in chronic infection and biofilm circles

The trial found the lower concentration worked better than the higher — more was worse.

Reported for reference, not as instruction. Nothing here is a recommendation to take anything, and most of these compounds are not approved for human use.

Status: Small trials for hard-to-heal leg ulcers. Not approved.

Route: Subcutaneous injection, from reconstituted lyophilised powder
Sequence: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
Formula: C205H340N60O53
Molecular weight: 4493.3 g/mol
CAS: 154947-66-7
Available as: 4 mg

View on PubChem →

Search PubMed for LL-37 → We link a live search rather than a fixed citation list, so it stays current and nothing here is a reference we have not checked.

Educational information only. Nothing here is medical advice, a dosing protocol, or a recommendation to use any compound. Most entries describe substances not approved for human use. Talk to a licensed clinician before acting on anything you read here. How to read these entries.