LL-37 (Cathelicidin)
Human cathelicidin antimicrobial peptide (37 amino acids); one small randomised trial of topical LL-37 in venous leg ulcers; FDA compounding-risk list: immunogenicity, possible male reproductive harm, possible tumour promotion in nonclinical studies.
60-Second Scientific Briefing
LL-37 is the only human cathelicidin, a 37-amino-acid antimicrobial peptide made by skin and immune cells as part of the body's natural defences. It is not approved as a medicine. The only randomised human trial tested it as a topical treatment for hard-to-heal venous leg ulcers in 34 people (2014): the two lower concentrations improved healing measures, the highest did not, and no safety concerns were seen. The FDA cites risks including immunogenicity, possible harm to male fertility and possible tumour promotion seen in nonclinical studies.
What is LL-37 (Cathelicidin)?
Pharmacological Classification & Molecular IdentityLL-37 is a 37-amino-acid human cathelicidin, an antimicrobial host-defence peptide produced by skin and immune cells. The tested product is a synthetic version of the human peptide. [1] Wound Repair Regen, 2014 ↗
Verified Chemical & Regulatory Registry Identifiers
Mechanism of Action & Receptor Targets
Biological Pathway and Target BindingReceptor Selectivity: Acts directly on microbial membranes and also modulates inflammation and wound repair; the 2014 trial tested whether these effects speed the healing of chronic leg ulcers. [1] Wound Repair Regen, 2014 ↗
Regulatory & FDA Approval Status
Legal and Regulatory ClassificationsNot approved by the US FDA or any other regulator. In its 2026 compounding-risk list the FDA cites, for cathelicidin LL-37, a risk of immunogenicity, possible male reproductive harm and possible tumour-promoting effects in some tissues in nonclinical studies. [1] U.S. Food and Drug Administration, 2026 ↗
LL-37 (Cathelicidin) is not approved for commercial sale, prescription therapy, or compounded medication distribution. It exists strictly within authorized scientific and clinical research frameworks.
Human Evidence & Clinical Trials
Clinical Study Readouts and Evidence SynthesesFirst-in-human randomised trial (Wound Repair Regen 2014): 34 people with hard-to-heal venous leg ulcers, a 3-week placebo run-in, then 4 weeks of twice-weekly topical LL-37 at three concentrations or placebo, and 4 weeks of follow-up. Healing rate constants were about six- and threefold higher than placebo for the two lower concentrations (P=0.003 and P=0.088), mean ulcer area fell by 68% and 50%, and the highest concentration did not differ from placebo. No other randomised trial has been published. [1] Wound Repair Regen, 2014 ↗
Clinical Evidence
First-in-human randomised trial (Wound Repair Regen 2014): 34 people with hard-to-heal venous leg ulcers, a 3-week placebo run-in, then 4 weeks of twice-weekly topical LL-37 at three concentrations or placebo, and 4 weeks of follow-up. Healing rate constants were about six- and threefold higher than placebo for the two lower concentrations (P=0.003 and P=0.088), mean ulcer area fell by 68% and 50%, and the highest concentration did not differ from placebo. No other randomised trial has been published.
Safety Profile & Clinical Limitations
Documented Adverse Events and Known UncertaintiesIn the 2014 topical trial there were no safety concerns regarding local or systemic adverse events. The FDA cites immunogenicity, possible male reproductive harm and possible tumour promotion in some tissues in nonclinical studies. [1] U.S. Food and Drug Administration, 2026 ↗ [2] Wound Repair Regen, 2014 ↗
Human data come from one small, short topical trial. The safety of injected LL-37, long-term effects and any benefit for other conditions are unknown. [1] U.S. Food and Drug Administration, 2026 ↗
Dose Approval Status
Commercial Dosing Status and Policy DirectivesNo dose is approved or established. The amounts used in the published studies are part of each study's design and are described in the linked papers; they are not a recommendation. [1] U.S. Food and Drug Administration, 2026 ↗
Under Egypt Peptides medical governance policies, no personal dosages, titration intervals, cycles, stacking recommendations, or self-injection instructions may be provided for unapproved investigational compounds. Clinical study protocols represent controlled experimental research parameters exclusively.
What is Known vs. What is Unknown
Evidence Comparison and Clinical Evidence Boundaries✓ Confirmed Scientific Evidence
- LL-37 is a 37-amino-acid human cathelicidin, an antimicrobial host-defence peptide produced by skin and immune cells. The tested product is a synthetic version of the human peptide.
- Targets & Selectivity: Acts directly on microbial membranes and also modulates inflammation and wound repair; the 2014 trial tested whether these effects speed the healing of chronic leg ulcers.
- First-in-human randomised trial (Wound Repair Regen 2014): 34 people with hard-to-heal venous leg ulcers, a 3-week placebo run-in, then 4 weeks of twice-weekly topical LL-37 at three concentrations or placebo, and 4 weeks of follow-up. Healing rate constants were about six- and threefold higher than placebo for the two lower concentrations (P=0.003 and P=0.088), mean ulcer area fell by 68% and 50%, and the highest concentration did not differ from placebo. No other randomised trial has been published.
- Safety considerations: In the 2014 topical trial there were no safety concerns regarding local or systemic adverse events. The FDA cites immunogenicity, possible male reproductive harm and possible tumour promotion in some tissues in nonclinical studies.
? Unknown / Under Ongoing Investigation
- Human data come from one small, short topical trial. The safety of injected LL-37, long-term effects and any benefit for other conditions are unknown.
Verified Questions & Answers
10 Verified scientific answers with permanent anchor keysLL-37 is the only human cathelicidin, a natural 37-amino-acid antimicrobial peptide made by skin and immune cells. It is not an approved medicine.
It damages microbial membranes and also modulates inflammation and wound repair.
No. LL-37 is not approved anywhere. The FDA cites risks of immunogenicity, possible male reproductive harm and possible tumour promotion seen in nonclinical studies.
- Certain bulk drug substances for use in compounding that may present significant safety risks (U.S. Food and Drug Administration, 2026-04-22)
One randomised trial (2014): 34 people with hard-to-heal venous leg ulcers treated topically for 4 weeks. The two lower concentrations improved healing (ulcer area −68% and −50%); the highest did not differ from placebo.
Wound Repair Regen 2014: a first-in-human trial in 34 participants with venous leg ulcers, with a 3-week open-label placebo run-in, then a 4-week randomised double-blind phase of twice-weekly topical applications at three concentrations or placebo, and 4 weeks of follow-up. Healing rate constants for the two lower concentrations were about six- and threefold higher than placebo (P=0.003 and P=0.088); mean ulcer area fell by 68% and 50%; the highest concentration did not differ from placebo. No local or systemic safety concerns were seen. The authors called for further studies.
No local or systemic safety concerns were seen in the small topical trial. The FDA cites immunogenicity, possible male reproductive harm and possible tumour promotion in nonclinical studies.
- Certain bulk drug substances for use in compounding that may present significant safety risks (U.S. Food and Drug Administration, 2026-04-22)
- 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 Regen, 2014-09-01)
Human data come from one small, short topical trial. The safety of injected LL-37, long-term effects and benefits for other conditions are unknown.
- Certain bulk drug substances for use in compounding that may present significant safety risks (U.S. Food and Drug Administration, 2026-04-22)
No dose is approved or established. The amounts used in the published studies are part of each study's design and are described in the linked papers; they are not a recommendation.
- Certain bulk drug substances for use in compounding that may present significant safety risks (U.S. Food and Drug Administration, 2026-04-22)
There is no approved product label, so no official storage instructions exist.
It is not named individually on the 2026 WADA Prohibited List. Under section S0 (non-approved substances), any pharmacological substance without a current approval by a government health authority for human therapeutic use is prohibited at all times. Athletes should confirm with their national anti-doping organisation.
- WADA Prohibited List (World Anti-Doping Agency)
Egypt Peptides publishes reviewed scientific reference monographs for documentation and research. The site does not give individual medical advice, preparation or injection instructions, combination protocols or off-label use instructions. Decisions about any medicine belong to the treating physician.
Authoritative Sources & Literature Registry
Regulatory dossiers, clinical trial registries, and published studiesCertain bulk drug substances for use in compounding that may present significant safety risks ↗
https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial ↗
https://pubmed.ncbi.nlm.nih.gov/25041740/