Immune & inflammation · Tissue repair
LL-37
A human antimicrobial peptide studied topically for wound healing, now marketed for unrelated systemic uses.
- How settled this rating is:
- very-low confidence in the current evidence rating
- Routes studied:
- Not established · Topical, Subcutaneous injection, Nasal (marketed but never approved)
- Also known as:
- cathelicidin, hCAP-18 fragment, antimicrobial peptide
- Last reviewed:
- 2026-09-06
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Evidence passport
Last reviewed 2026-09-06
A one-screen summary of what is known about this compound. Every field describes the evidence and legal status — not how safe or effective it is, and not a recommendation. The 0-100 figures are evidence-strength ratings, not percentages.
- Evidence level (type of study, not a quality rating)
- L3Early human studies
- How settled this rating is
- Very low confidence in rating
- Human efficacy evidence
- 22 of 100 evidence strength
- Human safety evidence
- 18 of 100 evidence strength
- Regulatory status
- Not approved for this use
- Development
- Stalled
- Routes
- Topical· unapprovedSC injection· unapprovedNasal· unapproved
- Evidence base
- Mostly animal and lab studies
- Furthest stage
- Phase II
- Source curation
- Sources fully curated
- How far human research has progressed
- Phase II/IIb topical wound studies completed; primary outcome not met in the larger study
Most of this evidence comes from animals and cells
Overview
Higher = more and better-quality human evidence. It does not mean the effect is bigger or that the compound works for you.
Higher = more animal, tissue or cell research. Preclinical results are a starting point, not proof of a human benefit.
Higher = more mature, better-documented human safety data. It does not mean the compound is safer than one with a lower number.
How to read these scores
Every number here rates the evidence, not the compound. They are editorial 0-100 strength ratings, not percentages, and not a rating out of five stars.
- Human efficacy evidence strength — Higher = more and better-quality human evidence. It does not mean the effect is bigger or that the compound works for you.
- Preclinical evidence strength — Higher = more animal, tissue or cell research. Preclinical results are a starting point, not proof of a human benefit.
- Human safety evidence strength — Higher = more mature, better-documented human safety data. It does not mean the compound is safer than one with a lower number. A score of 80 does not mean “80% safe”.
- Evidence level (L0-L5) — the strongest type of study behind the compound, from anecdote (L0) to large replicated human trials (L5). It is a description of the study evidence, not a quality, safety or recommendation rating.
- Confidence — how likely we think it is that this rating changes as new research lands. Low confidence means the picture is unsettled, not that the compound is bad.
None of these ratings is medical advice, a safety guarantee, or a recommendation to use anything. How we grade evidence.
How far human research has progressed: Phase II/IIb topical wound studies completed; primary outcome not met in the larger study
Routes & formulations
Marketed / research routes — never approved
Human trials used topical application to wounds. Injectable and nasal products sold online are a different proposition entirely — a topical wound result says nothing about systemic dosing.
Route availability is not evidence of efficacy, and evidence from one route does not transfer to another. The Registry never provides dosing or sourcing information.
Peptide lifecycle
Discovery
Preclinical
Phase I
Phase II
Development stopped here — a programme status, not a safety verdict.
Phase III
Approved
A Phase IIb study in hard-to-heal leg ulcers did not show a significant overall benefit, after earlier smaller work reported signals. Our record does not establish an active late-stage programme.
Why development stopped: Did not meet endpoints. Trials failed to show the benefit they were designed to detect.
Last documented development: Phase IIb topical leg-ulcer study published 2021
What it is
A naturally occurring human cathelicidin peptide with antimicrobial and immune-signalling activity, produced as part of innate defence in skin and mucosa.
What people claim
- Heals chronic wounds
- Treats resistant infections
- Resets or boosts the immune system when injected
What the evidence actually says
There are two completely different LL-37 stories, and they get blended online. One is a legitimate topical wound-healing research programme: earlier small work showed encouraging signals, then a Phase IIb study in hard-to-heal leg ulcers did not show a significant overall benefit. The other is systemic biohacking use, which has no supporting human trials at all. A peptide being part of human immunity is not evidence that injecting it helps anything.
Related evidence
Useful next reads based on this compound — not recommendations.
- Related compound
KPV
A three-amino-acid fragment of alpha-MSH marketed for gut healing and inflammation, with no human clinical studies identified by the FDA.
- Compare
LL-37 vs KPV
Same questions, same fields, side by side — including how much human evidence exists.
- Context
Dark Peptides archive
Why development programmes stop — and why stopped does not automatically mean dangerous.
- Context
Muscle growth evidence
What the human evidence does and does not show for growth and recovery claims.
Human evidence
- Phase IIb randomised study of topical LL-37 in hard-to-heal venous leg ulcers did not demonstrate a significant overall benefit (2021).
- Earlier smaller topical work reported healing signals that the larger study did not confirm.
- No adequate human evidence for systemic, injectable or nasal use.
Preclinical evidence
- Extensive laboratory work on antimicrobial membrane activity, chemotaxis and immune modulation.
- Animal wound and infection models with mixed translation to human outcomes.
Animal and cell findings are Level 1–2 evidence.
Mechanism and pathways
- Direct antimicrobial activity through microbial membrane disruption.
- Host immune signalling, chemotaxis and angiogenesis effects — dose- and context-dependent, and pro-inflammatory in some settings.
Safety and unknowns
- Local irritation reported with topical use; systemic human safety data are absent.
- LL-37 has been implicated in inflammatory skin disease biology, so 'more is better' reasoning is not safe reasoning.
Cancer relevance
This section covers questions raised by how the compound works in the body, plus anything regulators and trial teams keep an eye on. It is not a statement that this compound causes cancer — for most compounds here, no human data exist in either direction.
Theoretical / mechanistic concern only
Regulatory status
Not an approved medicine. Its clinical study history is topical, in hard-to-heal wounds. Injectable or systemic use for infections, 'immune reset' or biohacking purposes is unstudied. Compounding-nomination status has changed during 2026 and should be read cautiously.
Evidence grade
Small, short or uncontrolled studies in people. A hint worth following up, not a conclusion you can rely on.
What would change our rating?
- A positive, adequately powered topical wound trial.
- Any human safety or pharmacokinetic data for systemic administration.
References and sources
- Peer-reviewedPhase IIb randomised study of topical LL-37 in hard-to-heal leg ulcers (PubMed 34687253)
- Regulatory / labelFDA — Nominations for bulk drug substances for use in compounding (updated 22 April 2026)
Source hierarchy: regulatory documents and trial registries first, peer-reviewed work next, sponsor material flagged as non-independent. We never use supplier or clinic marketing as evidence, and where a verified source has not yet been curated we say so rather than inventing one.
Evidence change history
These entries record changes to our assessment of the published evidence — not changes to the compound itself.
No recorded changes yet. Baseline position set on 2026-09-06.