LL-37: what it is, what the studies show and where it stands
LL-37 is a naturally occurring 37-amino-acid peptide that is part of the innate immune system in human skin. A synthetic version has been tested in people on leg and foot ulcers and, in one very small trial, injected into melanoma tumours.
At a glance
US Not approved
Canada Not authorized
Group Immune
Sources 10
Checked 10 Oct 2026What is LL-37?
LL-37 is a naturally occurring 37-amino-acid peptide that is part of the innate immune system in human skin. A synthetic version has been tested in people on leg and foot ulcers and, in one very small trial, injected into melanoma tumours. [1]
Other names: LL37, cathelicidin LL-37.
How it has been given to people: Applied to the surface of leg and foot ulcers (topical), and injected directly into melanoma tumours in one small Phase 1 trial. No human study of injection under the skin was found.
Looking for doses? LL-37 dosage chart and vial math
Is LL-37 approved in the US and Canada?
United States: Not FDA approved. FDA lists cathelicidin LL-37 among bulk substances that were in compounding category 2 until the nominations were withdrawn, and says it lacks the safety information to know whether it would cause harm in humans. [7]
Canada: Not authorized in Canada. Health Canada lists LL-37 among unauthorized injectable peptide drugs seized from an online seller (advisory of 1 August 2025). [10]
Both were checked on 10 Oct 2026 against the regulators' own product databases.
Which approved products contain LL-37?
No approved medicine containing LL-37 was found in the US or Canada. Anything sold under this name is not a regulated product, so there is no label to check a dose against.
What human studies of LL-37 exist?
The 6 findings listed here: 5 from randomized human trials and 1 from smaller or observational human studies.
In the first human trial (34 people with hard-to-heal venous leg ulcers), the two lower strengths cut mean ulcer area by 68% and 50%. [2]
In that trial the highest strength, 3.2 mg/mL, healed no better than placebo. [2]
The larger follow-up trial (148 patients) found no significant healing benefit over placebo in the full study population. A benefit was seen only in an after-the-fact analysis of patients with large ulcers. [3]
In a randomized double-blind trial in diabetic foot ulcers with mild infection, LL-37 cream twice a week for 4 weeks increased granulation tissue more than placebo cream but did not lower inflammatory markers or bacterial counts. [4]
An open-label randomized trial called Oral LL-37 in 238 inpatients with COVID-19 used a bacterium (Lactococcus lactis) engineered to make LL-37. It did not give the peptide itself. [5]
In the melanoma trial, 3 participants are in the posted results: 2 at 250 mcg per tumour and 1 at 500 mcg per tumour, injected weekly for up to 8 weeks. No serious adverse events are recorded. [6]
What are the side effects of LL-37?
Reported in human studies or on a label:
- In the 34-person leg ulcer trial there were no safety concerns about local or systemic adverse events. [2]
- In the 148-patient leg ulcer trial the topical drug was well tolerated at both strengths. [3]
- Case report from the melanoma trial: a 63-year-old woman who had 8 weekly LL-37 tumour injections developed multiple wart-like bumps and a blistering lesion on the trunk and limbs about 45 days after starting. [1]
- In that case all skin lesions cleared within 2 months of stopping the injections. [1]
- Non-serious adverse events listed in the posted melanoma trial results include squamous cell carcinoma (1 of 2 participants at 250 mcg), actinic keratosis, anaemia, skin hypopigmentation and hypothyroidism. [6]
- FDA says nonclinical research suggests harm to male reproduction and that LL-37 can promote tumours in some tissues. [7]
- FDA says compounded LL-37 may carry a risk of immune reactions for some routes of administration. [7]
How does LL-37 compare with others in its group?
These are the peptides filed under immune. The last column says whether a randomized human trial is on record for each.
| Peptide | US | Canada | Half-life | Randomized human trial |
|---|---|---|---|---|
| Thymosin Alpha-1 | Not approved | Not authorized | Less than 3 hours after injection under the skin in healthy volunteers, with the peak blood level at 1 to 2 hours and no build-up over 5 days of dosing. | Yes |
| LL-37 | Not approved | Not authorized | Not found | Yes |
| Vilon | Not approved | Not authorized | Not found | No |
What could not be found
These were searched for and did not turn up. They are listed so a missing number is not mistaken for a hidden one.
- Any human study of LL-37 injected under the skin. PubMed searches for LL-37 or cathelicidin with subcutaneous, injection, patients and volunteers, and for LL-37 clinical trials, found only the topical, intratumoral and oral-bacterium studies listed here.
- A human half-life or any human pharmacokinetic figure.
- An approved product or label in the US or Canada, so no official dose, contraindications or storage instructions.
- A full published report of the melanoma trial NCT02225366. Only the registry results [6] and one case report [1] were found.
- The strength of the LL-37 cream in the diabetic foot ulcer trial [4]: not stated in the abstract.
- How often and for how long LL-37 was applied in the Phase 2b leg ulcer trial [3]: not stated in the abstract.
- LL-37 is not named on the WADA 2026 Prohibited List [9]. The list was searched for LL-37 and cathelicidin. Section S0 of the list prohibits any pharmacological substance with no current approval by a governmental health authority; the list does not say whether that covers LL-37.
LL-37 questions
Is LL-37 approved in the US?
Not FDA approved. FDA lists cathelicidin LL-37 among bulk substances that were in compounding category 2 until the nominations were withdrawn, and says it lacks the safety information to know whether it would cause harm in humans.
Is LL-37 authorized in Canada?
Not authorized in Canada. Health Canada lists LL-37 among unauthorized injectable peptide drugs seized from an online seller (advisory of 1 August 2025).
Has LL-37 been tested in a randomized human trial?
Yes. At least one randomized human trial is listed on this page.
Sources
Each one was opened on 10 Oct 2026 and matched to the line it supports.
- Dolkar T et al. Dermatologic toxicity from novel therapy using antimicrobial peptide LL-37 in melanoma: A detailed examination of the clinicopathologic features. J Cutan Pathol 2018. PubMed 29665030.
- Gronberg A et al. 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. PubMed 25041740.
- Mahlapuu M et al. Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial. Wound Repair Regen 2021. PubMed 34687253.
- Miranda E et al. Efficacy of LL-37 cream in enhancing healing of diabetic foot ulcer: a randomized double-blind controlled trial. Arch Dermatol Res 2023. PubMed 37480520. Trial NCT04098562.
- Zhao Y et al. Efficacy and safety of Oral LL-37 against the Omicron BA.5.1.3 variant of SARS-COV-2: A randomized trial. J Med Virol 2023. PubMed 37605995.
- Intratumoral Injections of LL37 for Melanoma ClinicalTrials.gov 2015. clinicaltrials.gov. Trial NCT02225366.
- Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks US Food and Drug Administration 2026. fda.gov.
- Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act US Food and Drug Administration 2026. fda.gov.
- World Anti-Doping Code International Standard Prohibited List 2026 World Anti-Doping Agency 2026. wada-ama.org.
- Unauthorized injectable peptide drugs seized and sold by Canada Peptide may pose serious health risks Health Canada 2025. recalls-rappels.canada.ca.
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LL-37 dosageImmuneStatus in Canada
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