Compound record · Immune
LL-37
Also Cathelicidin LL-37 · hCAP18 (precursor) · CAMP peptide · Ropocamptide (topical analogue)
Human cathelicidin antimicrobial peptide (37 amino acids)
Human antimicrobial peptide: topical wound trials only, injected use untested
Record reviewed 1 September 2026 · 5 references
In the AERVYN range
1 pen carries LL-37
- Class
- Human cathelicidin antimicrobial peptide (37 amino acids)
- Route studied
- Topical gel on chronic ulcers; injected use untested in humans
- Human trials
- Two topical trials (n = 34 and n = 148); phase IIb negative overall
- Authorised
- Nowhere
- WADA
- Not on the Prohibited List
01 Overview
What LL-37 is
Summary
LL-37 is the only human cathelicidin, a 37-amino-acid antimicrobial peptide released from the precursor hCAP18 by skin, airway and immune cells. In the laboratory it kills bacteria, fungi and some viruses and promotes wound closure, which led to topical trials in chronic venous leg ulcers: a 34-patient phase I/II study showed faster healing at low concentrations, but a 148-patient phase IIb trial missed its primary endpoint. Injected or systemic LL-37 — the form sold online — has never been tested in humans, and the peptide is implicated in the autoimmunity of psoriasis and lupus. It is not authorised anywhere.
Mechanism
Disrupts microbial membranes directly and modulates innate immunity: it binds and neutralises bacterial lipopolysaccharide, recruits immune cells, promotes keratinocyte migration and angiogenesis in wounds, and can form complexes with self-DNA that activate dendritic cells — the pathway thought to drive inflammation in psoriasis. Its effects are strongly dose- and context-dependent.
02 Evidence by goal
What has been shown, for which goal
Grades follow one scale across the site. Preliminary overall means: early-phase human data or case series; findings need replication.
Injury & recovery support
PreliminaryEvidence is for topical application to chronic venous leg ulcers only. A phase I/II trial (n = 34) found roughly six-fold faster healing at 0.5 mg/mL, but the phase IIb trial (n = 148) showed no benefit overall, with an effect only in a post-hoc subgroup of large ulcers. There is no human evidence for tendon, ligament, muscle or joint injury, and none for injected use.
General wellbeing
Insufficient'Immune support' claims rest on in-vitro antimicrobial activity. No human trial has tested systemic LL-37 for infections, immunity or wellbeing, and high local concentrations increased inflammation rather than helping.
03 Regulatory status
Where it is authorised, and for what
Status is recorded per jurisdiction from regulator sources and reviewed by hand. It is never inferred from another region's decision.
United Kingdom
Not authorisedNot authorised as a medicine; sold only as an unregulated 'research chemical'.
04 Dosing research
What the evidence says about exposure
Published human studies and the doses, routes and durations they used — reported as research information, not a recommendation.
Research information — not a recommendation. These are the exposures used in published human studies, reported so you can see what has been tested. They are not dosing instructions and do not apply to any individual.
Study 01
Topical LL-37 in hard-to-heal venous leg ulcers — first-in-human phase I/II
Grönberg A et al., Wound Repair Regen 2014;22:613–621 · Source
- Design
- Randomised, double-blind, placebo-controlled, dose-ranging after a 3-week open placebo run-in
- Population
- Adults with chronic venous leg ulcers (Sweden)
- Participants
- n = 34
- Duration
- 4 weeks of treatment, 4 weeks follow-up
- Route
- Topical
- Doses studied
- LL-37 gel at 0.5, 1.6 or 3.2 mg/mL applied to the ulcer twice weekly, versus placebo gel
- Outcome at this exposure
- Healing-rate constants were about six-fold (0.5 mg/mL; P = 0.003) and three-fold (1.6 mg/mL; P = 0.088) higher than placebo, with mean ulcer area falling 68% and 50% respectively. The highest concentration (3.2 mg/mL) produced no improvement.
- Adverse events observed
- No systemic safety concerns. More local wound reactions in the 3.2 mg/mL group; the two lower concentrations were well tolerated.
Study 02
HEAL LL-37 — topical LL-37 in venous leg ulcers, phase IIb
Mahlapuu M et al., Wound Repair Regen 2021;29:938–950 · Source
- Design
- Multicentre, randomised, double-blind, placebo-controlled (Poland and Sweden), with compression therapy
- Population
- Adults with hard-to-heal venous leg ulcers (mean age 68; median ulcer duration 20 months)
- Participants
- n = 148
- Duration
- 13 weeks of treatment, 4 months follow-up
- Route
- Topical
- Doses studied
- LL-37 gel at 0.5 or 1.6 mg/mL applied twice weekly, versus placebo gel
- Outcome at this exposure
- No significant improvement in healing versus placebo in the full population (confirmed complete closure 26.5% vs 24.7% vs 25.3%). A post-hoc analysis suggested benefit with 0.5 mg/mL in ulcers of at least 10 cm². The developer's later programme (ropocamptide) has not led to an authorised product.
- Adverse events observed
- Well tolerated at both strengths; 12 serious adverse events in 11 patients, none judged related to treatment.
Both human trials applied a low-concentration gel directly to chronic skin ulcers; these concentrations are not comparable to any injected dose. No human study has given LL-37 by injection, nasally or orally, so the 'research chemical' vials sold online (typically 50–125 µg subcutaneous 'protocols') represent an entirely untested exposure. Higher local concentrations were less effective and more irritating, so 'more' is not better.
05 Safety
Adverse effects and contraindications
Common effects seen in trials or reports, serious effects that warrant urgent review, and conditions under which use is not appropriate or needs assessment.
Common adverse effects
- Local wound irritation or inflammation at higher topical concentrations
- Injection-site reactions (anecdotal; no trial data for injected use)
- Dermatitis (reported in the phase IIb trial)
Serious adverse effects
- Triggering or worsening of autoimmune or inflammatory disease (theoretical, mechanism-based)
- Immune reactions to peptide impurities in unregulated products (flagged by the FDA)
- Injection-related infection with non-sterile products
- Unknown systemic effects — no human data for any non-topical route
Contraindications
- Autoimmune conditionCaution
LL-37 complexed with self-DNA is a recognised trigger of dendritic-cell activation in psoriasis and is implicated in lupus and rheumatoid arthritis. Exogenous LL-37 in anyone with an autoimmune or inflammatory skin condition is a theoretical risk with no safety data.
- Active infectionCaution
Despite antimicrobial claims, LL-37 is not a substitute for assessment and treatment of an active infection; there is no human evidence for infection control.
- CancerCaution
LL-37 has been reported to promote growth of some tumour types (for example ovarian, lung and breast cancer cells) and to suppress others in laboratory studies; effects in people with cancer are unknown.
Do not use = should not be used · Caution = needs assessment
06 Interactions
Medicine classes that need review
Grouped by how seriously the combination should be taken. Class labels match the medicines questionnaire in the assessment.
- Major
- Moderate
- Minor
Moderate
Monitoring or dose review is usually advised.
Immunosuppressant / biologic
Methotrexate, tacrolimus, adalimumab
Interactions are unstudied. An innate-immune activator alongside immunosuppressants or biologics for autoimmune disease could counteract treatment or provoke flares — a theoretical concern.
Minor
Generally compatible; awareness is sufficient.
Corticosteroid
Prednisolone, dexamethasone, hydrocortisone
Interactions are unstudied; corticosteroids may blunt any immune effect. Listed for completeness.
07 Pregnancy & breastfeeding
Status in pregnancy
No human or animal reproductive safety data; use in pregnancy or breastfeeding cannot be assessed.
08 Monitoring
What is usually monitored
Parameters that trials and product information track. A clinician decides what applies to an individual.
- 01Wound size and appearance if used topically under professional supervision
- 02Skin for new or worsening psoriasis-like or inflammatory lesions
- 03Autoimmune symptoms (joint pain, rashes, fatigue), particularly with any autoimmune history
- 04Signs of infection at wounds or injection sites
09 Combinations
What is known about combining it
Notes on pairing with other compounds in the directory: whether the combination has been studied in people, and where mechanisms overlap.
Thymosin alpha-1
No human studies
Overlap · Both are immune-modulating peptides.
Marketed together as 'immune stacks'; no human data on the combination, and systemic LL-37 has no human trials at all.
BPC-157
No human studies
Overlap · Both are promoted for wound and tissue healing.
No human data on the combination; BPC-157 lacks human efficacy data and LL-37's evidence is topical only.
TB-500
No human studies
Overlap · Both are promoted for healing and recovery.
No human data on the combination; TB-500 has no human efficacy data.
GHK-Cu
No human studies
Overlap · Both are promoted for skin and wound repair.
No human data on the combination.
Discuss any proposed combination with a qualified healthcare professional.
10 Source considerations
Supply, quality and legitimacy
How the compound reaches people in practice, and what that means for product quality.
- 01Every product available is an unregulated 'research chemical'; the FDA has flagged immunogenicity and impurity risks for LL-37.
- 02The trial material was a pharmaceutical-grade gel formulated for wounds; injectable vials sold online have no human safety data and no independent quality assurance.
- 03The 37-amino-acid sequence is prone to aggregation and degradation, so labelled potency of stored vials is unreliable.
11 Questions for your clinician
Take these to your appointment
Specific to this compound. The personal assessment adds questions drawn from your own history and medicines.
- 01Is my injury the kind of wound (chronic skin ulcer) that LL-37 has actually been studied for, or a tendon, muscle or joint problem where there is no evidence?
- 02Given that injected LL-37 has never been tested in people, what is realistically known about its safety?
- 03Do I have any autoimmune or inflammatory skin condition that this peptide could plausibly aggravate?
- 04What evidence-based options — physiotherapy, load management, authorised wound care — should be optimised first?
- 05How would we monitor for benefit or for an inflammatory reaction?
The personal assessment tailors this list to your responses.
12 Alternatives
Compounds with stronger evidence or firmer regulatory footing
Listed for overlapping goals. Whether any is appropriate depends on your history — the assessment maps that for you.
13 References
Sources behind this record
Regulator documents and peer-reviewed publications used to derive every grade and statement above.
- 01Grönberg A et al. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers. Wound Repair Regen 2014
- 02Mahlapuu M et al. Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: multicentre randomised placebo-controlled trial. Wound Repair Regen 2021
- 03Lande R et al. Plasmacytoid dendritic cells sense self-DNA coupled with antimicrobial peptide (LL-37) in psoriasis. Nature 2007
- 04FDA — Bulk drug substances that may present significant safety risks (503A Category 2)
- 05WADA 2026 Prohibited List
The Peptide Checkup provides educational information and a structured summary of published research and regulatory status. It is not medical advice, does not diagnose or treat any condition, and does not replace a consultation with a qualified healthcare professional.
Personal assessment
Check LL-37 against your history
Seven minutes of structured questions about your goal, history and medicines, mapped against this record by a deterministic, clinician-reviewable rules engine. The report tells you when not to buy.