LL-37

Also known as Cathelicidin, hCAP18 peptide

Human trials

Human antimicrobial peptide from the cathelicidin family. Tested topically in randomised trials for hard to heal venous leg ulcers with mixed results.

Not an approved medicine. LL-37 is not an approved medicine for this use in Australia or the United States. This page summarises published research for information only. It is not a recommendation to use LL-37, and VialOwl does not sell or supply it.

Background

LL-37 is the only human member of the cathelicidin family of antimicrobial peptides. It is the 37 amino acid tail cut from a larger protein called hCAP18, which is made by white blood cells and skin and lining cells. It was identified in the mid 1990s, and a Swedish company, Promore Pharma, later developed a topical version for wound healing under the name ropocamptide.

How it is thought to work

LL-37 can punch holes in bacterial membranes and also acts as a signalling molecule that recruits immune cells and influences inflammation and tissue repair. Depending on the tissue, it has been shown in lab studies to either promote or suppress tumour growth.

What is claimed, and the evidence

Claim	Evidence	Notes
Healing of hard to heal venous leg ulcers (topical)	Human trials	Phase IIb randomised trial in 148 patients found no significant healing benefit over placebo overall; a post hoc subgroup with large ulcers looked better, which needs confirming.
Antimicrobial and antibiofilm activity against infections	Animal studies only	Well shown in lab and animal studies; no approved human treatment.
Immune support, gut healing or general recovery when injected	No published evidence	Marketed claims for injected LL-37; no published human trials of injected use.
Anti cancer effects	Animal studies only	Lab evidence is contradictory: LL-37 promoted some cancers (ovarian, lung, breast) and suppressed others (colon, gastric) in experimental studies.

Side effects

Effect	How often	Notes
Local skin or wound reactions with topical use	Uncommon	The venous ulcer trial reported topical LL-37 as well tolerated at both strengths tested.
Effects of injected use	Frequency unknown	No published human safety data for injected LL-37. FDA found insufficient information to know whether it would cause harm when given to humans.
Possible promotion of tumour growth Serious	Frequency unknown	Based on lab and animal findings that LL-37 can be protumorigenic in some tissues; not studied in humans.
Effects on male reproduction Serious	Frequency unknown	FDA cited nonclinical findings suggesting detrimental effects on male reproduction.
Immune reactions to the product Serious	Frequency unknown	FDA flagged a risk of immunogenicity and problems with peptide impurities in compounded products.

Warnings

FDA notes nonclinical findings that LL-37 may promote tumours in some tissues and harm male reproduction.
The only published human trials are of a topical wound product; injected use has no published human safety data.
Unapproved products are not assessed by the TGA for quality, safety or efficacy and may be contaminated, non-sterile, underdosed, overdosed or contain a different substance altogether.

Regulatory status

Australia: Not included on the ARTG (unapproved). Not specifically listed in the Poisons Standard (June 2026).
United States: Not FDA approved. Nomination withdrawn and removed from 503A Category 2 in April 2026; FDA previously noted preclinical findings suggesting reproductive and tumour promoting effects.

Sources

Also in Immune

From the VialOwl library, reviewed 26 September 2026. For education and general information. It is not medical advice and not a recommendation to use LL-37.