C tier · mixed
It is a genuine endogenous human peptide with an enormous mechanistic literature and one small but properly randomised, placebo-controlled human ulcer trial, yet development stopped there and FDA has noted nonclinical findings suggesting detrimental effects.
ll-37
LL-37 is the only human cathelicidin, a 37-residue cationic amphipathic host-defence peptide released from the hCAP18 precursor, with broad antimicrobial and immunomodulatory activity. A small randomised placebo-controlled trial in hard-to-heal venous leg ulcers showed a significant benefit at the lowest concentration tested, but no larger confirmatory trial has followed.
// we supply this one
available as a research reagent
≥ 99% HPLC · lyophilised powder · batch certificate published. Grade C above is our own and is not adjusted because we stock it.
the explanation
LL-37 is a natural antibacterial molecule the human body makes as part of its own immune defences, and it also helps skin repair itself. One small but properly designed trial in stubborn leg ulcers showed real benefit at low doses, though the higher doses did not work and no bigger trial has been done since.
regulatory status
not approved for human use
No marketing approval in any jurisdiction; reached only small early-phase clinical testing for venous leg ulcers, and was nominated for the FDA 503A compounding bulks list with immunogenicity concerns and a note that nonclinical research findings suggest detrimental effects, before the nomination was withdrawn. FDA has scheduled a Pharmacy Compounding Advisory Committee meeting before the end of February 2027 to consider whether this substance should be added to the section 503A bulks list. A committee recommendation is non-binding and confers no approval; implementation would require notice-and-comment rulemaking, which the FDA bar estimates at twelve to twenty-four months or longer.
how it works · proposed mechanism
LL-37 is genuinely bifunctional, acting as a direct antimicrobial at high concentration and as an immune signalling molecule at low concentration.
Membrane-disrupting antimicrobial
Its cationic amphipathic helix inserts into and permeabilises negatively charged bacterial membranes, giving broad-spectrum activity. This action is concentration-dependent and largely lost in high-salt or serum-rich environments.
Chemotaxis via FPR2
At sub-antimicrobial concentrations it signals through the formyl peptide receptor 2 to recruit neutrophils, monocytes and T cells. This links the peptide to wound-site immune cell recruitment.
Wound re-epithelialisation
It promotes keratinocyte migration and angiogenesis in skin repair models, and cathelicidin deficiency impairs wound closure. This underpins the venous leg ulcer trial rationale.
Pro-inflammatory double edge
LL-37 complexes with self-DNA and RNA and presents it to scavenger receptors and intracellular sensors, driving interferon responses. Overexpression is causally implicated in psoriasis, rosacea and lupus pathology.
what’s reported
evidence shape
5 sourcesThe composition of the cited literature by study type. This describes the shape of the evidence, not its quality — and it does not by itself set the grade.
⚠ the catch
The single supporting human trial enrolled 34 patients and produced an inverted dose-response, with the lowest concentration significantly effective and the highest indistinguishable from placebo - a pattern that demands replication before it can be believed. More than a decade later no confirmatory trial has been published, and the same peptide is causally implicated in driving psoriasis and lupus inflammation.
key published findings
- Randomised placebo-controlled clinical trial in hard-to-heal venous leg ulcers (Wound Repair and Regeneration, 2014, n=34): at 0.5 mg/mL, LL-37 produced roughly a sixfold higher healing rate than placebo (p=0.003) with 68% mean ulcer area reduction; at 1.6 mg/mL roughly threefold (p=0.088, 50% reduction); at 3.2 mg/mL no significant difference from placebo.
- The same trial used a 3-week open-label placebo run-in followed by a 4-week double-blind treatment phase and reported no safety concerns regarding local or systemic adverse events.
- LL-37 is the sole human cathelicidin, a 37-residue peptide (4,493 Da) cleaved from the hCAP18 precursor encoded by the CAMP gene, and functions as an amphipathic cationic host-defence peptide.
- In vitro work shows LL-37 acts as a TLR2 and TLR4 signalling inhibitor while separately presenting self-RNA to scavenger receptors to promote inflammation, establishing a documented dual pro- and anti-inflammatory role.
- FDA's compounding review recorded both immunogenicity risk and nonclinical research findings suggesting detrimental effects for cathelicidin LL-37.
limitations of the evidence
- The only randomised human evidence is a single trial of 34 patients with a non-monotonic dose-response that has never been replicated.
- Antimicrobial potency in vitro is strongly attenuated by physiological salt and serum concentrations, limiting extrapolation to in vivo activity.
- The peptide's established causal role in psoriasis, rosacea and lupus inflammation represents an unresolved mechanistic safety concern for systemic administration.
identity
| full name | Human cathelicidin antimicrobial peptide LL-37 (CAMP gene product, hCAP18 C-terminal fragment) |
| category | Healing & Repair |
| modality | peptide |
| formula | C205H340N60O53 |
| molar mass | 4493.26 g/mol |
| cas | 154947-66-7 |
| sequence | LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES |
laboratory handling
| storage | Lyophilised powder is typically stored at -20 °C, with supplier stability data supporting up to three years; stock solutions are held at -80 °C for up to a year or at -20 °C for about a month, avoiding repeated freeze-thaw. |
| solubility | Highly water-soluble in laboratory settings, with supplier data reporting 50-100 mg/mL in water; commonly prepared in sterile water or low-ionic-strength buffer since activity is salt-sensitive. |
| co-studied with | Most often co-studied with other host-defence peptides such as defensins, and in wound research alongside standard compression and antimicrobial dressings. |
Handling information describes laboratory practice for a research reagent. It is not a preparation guide for use in humans.
the receipts
6 citedUS Food and Drug Administration · 2026 · official
Wound Repair and Regeneration · 2014 · peer-reviewed
BioMed Research International · 2020 · review
Journal of Biological Chemistry · 2021 · preclinical
U.S. Food and Drug Administration · 2026 · regulatory
Wikipedia · 2026 · tertiary
Sources marked tertiary or press release are the weakest citations on this page.
others in Healing & Repair