Human antimicrobial peptide
LL-37
ClinicalAlso known as Cathelicidin, hCAP18 (37-residue fragment)
Your own antimicrobial peptide, now tested on wounds that won’t close.
- Cited sources
- 5
- Human-tested claims
- 2 of 3
- Best evidence
- Tier 2 · Clinical
- Status
- Research-only
The only human cathelicidin, a 37-residue peptide cut from the hCAP18 precursor in skin, airways and immune cells. It kills microbes, recruits immune cells and promotes vessel growth. As a topical drug it has been through a Phase 2b trial in venous leg ulcers that missed its primary endpoint and a small diabetic-foot trial that did not.
How it works
LL-37 is an amphipathic helix that disrupts bacterial membranes directly and, at lower concentrations, signals to host cells: it is chemotactic for neutrophils and monocytes, drives angiogenesis and keratinocyte migration, and modulates inflammation in both directions depending on context. That breadth is why it is studied for wounds, infection and, experimentally, cancer.
Sequence: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTESResidues 134–170 of the CAMP gene product hCAP18 (UniProt P49913).
What it's studied for
One claim per card, each with its own tier and source. Tiers 1 and 2 are human data. Tiers 3 and 4 are not yet.
- [1]Mahlapuu et al., 2021 (Wound Repair Regen, Phase 2b)(opens in a new tab)
Did not improve healing of hard-to-heal venous leg ulcers versus placebo in the full population of a Phase 2b RCT; a post-hoc subgroup with large wounds improved.
Clinical - [2]Miranda et al., 2023 (Arch Dermatol Res)(opens in a new tab)
Increased granulation tissue in mildly infected diabetic foot ulcers versus placebo cream in a small double-blind RCT.
Clinical - [3]Dürr et al., 2006 (Biochim Biophys Acta review)(opens in a new tab)
Kills bacteria by membrane disruption and acts as a chemoattractant and angiogenic signal in vitro and in animals.
Preclinical
Safety & limitations
Topical LL-37 was tolerated across a 148-patient placebo-controlled trial without a safety signal that stopped development.
[1]Mahlapuu et al., 2021 (Wound Repair Regen, Phase 2b)(opens in a new tab)A Phase 1 intratumoral program in melanoma produced a detailed case report of widespread blistering skin toxicity, a reminder that an immune-activating peptide can activate immunity where you did not intend.
[4]Dolkar et al., 2018 (J Cutan Pathol)(opens in a new tab)Excess LL-37 is implicated in rosacea and psoriasis, so systemic or high-dose use carries a plausible pro-inflammatory risk. No systemic human safety data exist.
[3]Dürr et al., 2006 (Biochim Biophys Acta review)(opens in a new tab)Regulatory & legal status
Not approved in any jurisdiction. A topical formulation has reached Phase 2b; intratumoral injection has been in Phase 1.
[1]Mahlapuu et al., 2021 (Wound Repair Regen, Phase 2b)(opens in a new tab)Frequently asked
Did LL-37 work for leg ulcers?
Not on the trial's primary endpoint. Across all 148 patients healing was no better than placebo. A post-hoc look at the largest wounds found an effect, which is a reason to run another trial, not a result.
Is injectable LL-37 sold online the same thing?
Chemically it may be. The human data are for a topical cream on chronic wounds and for intratumoral injection in a trial setting. Systemic injection has no human evidence at all.
References
- [1]Mahlapuu et al., 2021 (Wound Repair Regen, Phase 2b) (opens in a new tab)
- [2]Miranda et al., 2023 (Arch Dermatol Res) (opens in a new tab)
- [3]Dürr et al., 2006 (Biochim Biophys Acta review) (opens in a new tab)
- [4]Dolkar et al., 2018 (J Cutan Pathol) (opens in a new tab)
- [5]UniProt – cathelicidin / hCAP18 (P49913) (opens in a new tab)
Written by Twenty Residues editorial. Medical review: pending; a named reviewer is being assigned.
Last updated October 1, 2026.
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Update history
- 2026-10-01 — Entry added.