LL-37
Human Cathelicidin | Antimicrobial & Immune Support
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What is LL-37?
LL-37 is the only antimicrobial peptide the human body makes on its own (called a cathelicidin), and researchers study a lab-made version for its effects on wound healing and microbial activity. Clinical research has tested topical formulations on chronic wounds, reported here as third-party study findings. Research-grade LL-37 sold here is intended for laboratory study only, not for human use.
Key terms:
LL-37 is a synthetic cathelicidin antimicrobial peptide.
LL-37 is the only human cathelicidin, a class of antimicrobial (germ-killing) peptides. It is a 37-amino acid cationic peptide derived from hCAP18. It is active against a broad range of bacteria, viruses, and fungi. Researchers study it for immune-modulating and wound-healing effects.
Key research areas
- Studied for topical wound-healing effects in clinical trials
- Researched for local antimicrobial activity
- Studied for tissue-regeneration effects
- Broad-spectrum antimicrobial activity against bacteria, viruses, and fungi (in vitro research)
- Studied for immune-response modulation
- Researched for effects on keratinocyte migration and angiogenesis
Researched dosing
This table reflects the topical-application concentrations and schedules used in published LL-37 clinical trials, presented as research methodology, not a personal treatment plan.
| Phase | Dose | Frequency | Route |
|---|---|---|---|
| Chronic venous ulcer studies | 0.5 mg/mL | Twice weekly | Topical gel application |
| Diabetic foot ulcer studies | 0.5-1.6 mg/mL | Daily application | Topical cream |
| Acute wound-healing models | 1.6 mg/mL | Once daily | Topical gel or cream |
| Pressure ulcer studies | 0.5-1.0 mg/mL | Twice daily | Hydrogel delivery system |
| Burn-wound studies | 1.0 mg/mL | Once to twice daily | Topical gel application |
Commonly cycled 8 weeks on, 0+ weeks off.
How it works
At the cell level, LL-37 research looks at how this peptide reaches wound tissue directly when applied topically, helping skin cells migrate and new blood vessels form while also acting against microbes, the terms below name those processes.
Topical application provides direct access to wound sites, promoting keratinocyte migration, angiogenesis, and antimicrobial protection without systemic exposure
Pharmacokinetics
This chart shows how quickly LL-37 clears in the limited pharmacokinetic data available, because most research studies it as a topical (skin-applied) treatment, systemic absorption data is sparse.
- Peak
- 0.05 hr
- Half-life
- 0.5 hrs
- Cleared
- ~2.5 hrs
Limited human data
What the studies report
This section lists the research areas, chronic wound healing and antimicrobial activity chief among them, that scientists have studied for LL-37 in clinical trials, a summary of what's been published in the literature, not medical claims about people.
Wound Healing
Clinical trials report a 68% ulcer-area reduction at 0.5 mg/mL concentration in chronic venous leg ulcers, along with increased granulation tissue formation and healing rate in diabetic foot ulcer studies. Chitosan hydrogel delivery systems showed faster healing in animal models of pressure ulcers.
Immunity
Broad-spectrum antimicrobial activity against bacteria, viruses, and fungi including antibiotic-resistant strains. A CDC biofilm reactor study reported higher antimicrobial efficacy against MRSA biofilms compared to controls.
Skin Health
Studied for effects on keratinocyte migration and angiogenesis relevant to skin regeneration in chronic wound research.
Dosage reference
- Doses used in research
- 0.5-1.6 mg/mL
- Frequency in studies
- Daily to twice weekly based on wound type
- Handling
- Reconstituted solution, research use only; not for administration
- Timeline reported in studies
- Initial response: 1-2 weeks; Significant healing: 4-6 weeks; Complete healing: varies by wound
- Storage
- Refrigerate 2-8°C, protect from light, use within expiration
- Cycle length
- 2-8 weeks depending on wound healing progress
- Break between cycles
- Continue until complete healing achieved
Interactions
This list shows which other wound-care and antimicrobial compounds researchers have studied alongside LL-37, and why.
Reconstitution & storage
LL-37 is studied primarily as a topical gel or cream rather than an injectable powder, this section notes storage and handling for that research form.
- Store the reconstituted solution refrigerated (2-8°C), labeled with the date and concentration, for laboratory research use only.
Lyophilized: 2-8°C, use within Per manufacturer expiry; protect from light
Reconstituted: 2-6°C, use within Per expiration date; protect from light
Open the LL-37 reconstitution calculatorQuality indicators
These are the formulation and storage checks researchers use to confirm an LL-37 preparation hasn't degraded or become contaminated before use in a study.
Sterile formulation - Topical LL-37 should be sterile with preservatives appropriate for wound care
Appropriate gel base - Compatible gel or cream base that doesn't interfere with peptide activity
Proper concentration - Clinical-grade concentrations (0.5-1.6 mg/mL) with verified potency
Cold storage maintenance - Maintained at 2-8°C throughout storage and transport
Contaminated products - Any signs of microbial contamination or non-sterile preparation
Improper pH formulation - pH outside physiological range that could irritate wound tissue
Homemade formulations - DIY topical preparations may lack sterility and proper formulation
What to expect
This timeline reflects what published clinical trials have reported at each stage of wound-healing research, research context for comparing studies, not a personal-results promise.
Trials reported reduced bacterial load with initial wound-bed preparation
Trials reported increased granulation-tissue formation and epithelial migration
Trials reported substantial reductions in wound size and improved healing quality
Trials reported continued progress toward complete wound closure
Safety notes
This section covers handling cautions for LL-37 research use, sterile-technique and contamination-prevention notes drawn from the clinical trial literature, not medical safety advice.
- Applied only to clean, debrided wound beds in the published studies
- Monitor for signs of wound infection or delayed healing
- Discontinue if signs of hypersensitivity or allergic reactions develop
- Use sterile technique for application to prevent contamination
Regulatory status
- Not approved by the FDA for any indication.
- Supplied and described for laboratory research use only, not for human or veterinary use.
What is not known
The limits of the published work on LL-37, stated plainly. Research use only: none of this is guidance for a person.
The larger trial did not repeat the smaller one. A phase two b study in 148 people with slow healing ulcers on the lower leg found no significant improvement over placebo across the whole group. Only a subgroup with the largest wounds separated out, and that came from an analysis run after the results were in.
So the encouraging first in man result stands beside a bigger negative one. Any page quoting the first without the second is quoting half the record.
The germ killing results are from dishes and from bacteria grown on surfaces. Killing bacteria in a dish does not show a wound heals faster in a body.
LL-37 is a natural human peptide with roles in both calming and driving inflammation. What extra amounts do to that balance is not known.
There is no published work on giving it by any route other than onto the skin, so what it does by any other route is not known.
The terms, in plain words
Every technical term this page leans on, said again in ordinary words.
- Cathelicidin
- A family of germ killing peptides the body makes itself. LL-37 is the only human one.
- Antimicrobial peptide
- A short protein that can kill bacteria, and sometimes fungi and viruses, on contact.
- Biofilm
- A slimy mat of bacteria stuck to a surface, which is much harder to kill than loose bacteria.
- MIC
- Minimum inhibitory concentration, the smallest amount that stops a germ growing in a dish.
- Post hoc analysis
- A comparison decided after the results were in. It can suggest something, but it cannot prove it.
- Venous leg ulcer
- A slow healing wound on the lower leg caused by poor blood return.
Sources
The published work behind this entry. Each link was opened and each note says what that paper reports, not what it suggests.
- Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial Wound Repair and Regeneration, 2014The first in man trial. Thirty four people, topical LL-37 against placebo. Reports faster healing at the middle doses.
- Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial Wound Repair and Regeneration, 2021The larger follow up. 148 people, two doses against placebo. No significant difference across the whole group; a benefit appeared only in the largest wounds, in an analysis run after the fact.
- Antimicrobial peptide LL-37 is bactericidal against Staphylococcus aureus biofilms PLOS ONE, 2019Laboratory work on bacteria grown as a mat on a surface, compared with silver nanoparticles. A dish, not a wound.
How it is studied
In the published studies listed below. Each one names the species it was run in, the dose, how long it ran, and what it reported.
CDC biofilm reactor study reporting LL-37 achieved greater antimicrobial efficacy against Staphylococcus aureus biofilms compared to conventional antibiotics and silver nanoparticles (>4 log reduction in biofilm).
Comprehensive antimicrobial profile study against human pathogens including antibiotic-resistant strains, demonstrating broad-spectrum activity and potential as alternative to conventional antibiotics.
First-in-man randomized, placebo-controlled trial in 34 participants with chronic venous leg ulcers. Demonstrated significant wound healing improvement with 6-fold higher healing rate constants for optimal doses and 68% ulcer area reduction at 0.5 mg/mL.