Overview
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In plain language
LL-37 is a 37-amino-acid fragment of the human cathelicidin precursor hCAP18. It participates in host defense, with both antimicrobial and immune-modulating actions; those biological roles do not by themselves establish a treatment. (Morizane & Gallo, 2012)
A laboratory study found reduced bacterial biofilm formation. A separate randomized human wound trial found no statistically significant overall healing improvement. These studies asked different questions. (Overhage et al., 2008) (Mahlapuu et al., 2021)
For students
The CAMP gene encodes hCAP18. Processing depends on the tissue: proteinase 3 releases LL-37 in neutrophils, while kallikreins participate in cathelicidin processing in skin. LL-37 is a positively charged, amphipathic α-helical peptide. (Morizane & Gallo, 2012)
LL-37 can modify host immune responses as well as act against microbes. Complexes with self-DNA can activate plasmacytoid dendritic-cell responses implicated in psoriasis; antimicrobial activity is not a reason to assume that more LL-37 is always beneficial. (Morizane & Gallo, 2012)
For researchers and instructors
Clinical design. The 2021 HEAL LL-37 report describes a randomized, double-blind, placebo-controlled phase IIb venous-leg-ulcer trial alongside compression therapy: 149 participants were randomized and 148 received treatment. (Mahlapuu et al., 2021)
Outcome. No statistically significant overall healing improvement was found versus placebo. The larger-ulcer subgroup finding was post hoc; the trial was not designed or powered to establish subgroup efficacy. (Mahlapuu et al., 2021)
Evidence category. Controlled trials describes the available study design, not proven benefit, a regulatory approval or a recommended clinical use. In-vitro biofilm activity and a clinical wound-healing endpoint are not interchangeable. (Overhage et al., 2008) (Mahlapuu et al., 2021)
Molecular identity
- Amino acids
- 37
- Molecular weight
- ~4,493 Da
- Formula
- Form-dependent; verify
- Sequence
- LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
Sequence map
Hydropathy
Kyte–Doolittle score per residue. Positive values are water-repelling.
Origin and history
Agerberth and colleagues reported the human precursor research under the name FALL-39 in 1995. The mature LL-37/hCAP18 system was subsequently studied in host defense, inflammation, laboratory biofilms and wound healing; these are distinct research contexts. (Agerberth et al., 1995) (Morizane & Gallo, 2012)
The 2008 biofilm experiment and the 2021 randomized wound trial illustrate why a laboratory mechanism should not be presented as proof of clinical success. (Overhage et al., 2008) (Mahlapuu et al., 2021)
Human evidence
The randomized 2021 trial did not show statistically significant healing improvement in the full population. Its exploratory larger-ulcer subgroup does not establish efficacy. The evidence category records a controlled trial, including a null trial, rather than confirmed patient benefit. (Mahlapuu et al., 2021)
Explore the free LL-37 case study to compare that result with the separate in-vitro biofilm experiment. (Overhage et al., 2008)
Safety and regulatory status
See every compound on the regulatory tracker.
Not FDA-approved as a therapeutic LL-37 peptide.
Long-term risks, formulation differences, and human safety evidence require careful review. Educational content only; not medical advice.
Editorial update · November 9, 2026
Changed the evidence category from Early human to Controlled trials to reflect the randomized wound trial, not a finding of proven benefit. Added its overall null result, separated exploratory subgroup findings, and clarified precursor processing and the research date.
Sources
- Mahlapuu et al., 2021https://pmc.ncbi.nlm.nih.gov/articles/PMC9298190/
- Overhage et al., 2008https://pubmed.ncbi.nlm.nih.gov/18591225/
- Morizane & Gallo, 2012https://pmc.ncbi.nlm.nih.gov/articles/PMC3527011/
- Agerberth et al., 1995http://www.ncbi.nlm.nih.gov/pmc/articles/PMC42844
Hernandez Gener, E. (2026, November 9). LL-37: molecular data, research history and evidence. VALREXA Biosciences. https://valrexa.com/peptides/ll-37.html
APA style · Editorially updated November 9, 2026 · Our editorial standardsEditorially updated November 9, 2026. Trial and regulatory status can change; confirm in the linked registries. This profile is educational and is not medical advice, a treatment recommendation, or dosing or sourcing guidance. Report an error · Corrections policy