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LL-37

Cathelicidin LL-37 — Host Defense Peptide

Half-life: Short (minutes-hours, rapidly degraded by proteases)

LL37hCAP-18 fragmentFALL-39

Research Profile

Research Depth
80
Potency
50
Half-Life Score
10
Selectivity
70
Stability
60

Relative research assessments — educational reference only.

Target Receptors

FPR2/ALXP2X7EGFR (transactivation)

Critical Research Warning

Research chemical — not for human consumption. Potent host-defense peptide with dual pro- and anti-inflammatory effects; doses that are too high can be cytotoxic.

PeptidePlaza Entry #028

"The only human cathelicidin host-defense peptide. Kills bacteria, modulates inflammation, promotes wound healing, and is being studied for infections, sepsis, and tissue repair."

Full Description

LL-37 is the C-terminal 37-amino-acid active fragment of human cathelicidin (hCAP-18), the only cathelicidin family member expressed in humans. It is a multifunctional host-defense peptide: it has direct antimicrobial activity against bacteria, fungi, and enveloped viruses; it modulates innate immune responses by chemoattracting immune cells and regulating cytokine production; and it promotes wound healing and angiogenesis. Because of rising antimicrobial resistance, LL-37 and its analogs are under active investigation as novel anti-infective and immunomodulatory therapeutics, including for sepsis, skin infections, and even as a potential antiviral (including against SARS-CoV-2).

Mechanism of Action

Disrupts microbial membranes (cationic amphipathic alpha-helix); activates multiple receptors (FPR2/ALX, P2X7, EGFR transactivation) to modulate inflammation; induces chemokine and antimicrobial peptide expression; promotes keratinocyte migration and angiogenesis for wound repair.

Reported Benefits

  • Broad-spectrum antimicrobial activity (bacteria, fungi, viruses)
  • Modulates inflammation and recruits immune cells
  • Promotes wound healing and angiogenesis in models
  • Studied as adjunct in sepsis and resistant infections

Potential Side Effects

  • Protease degradation limits stability
  • Cytotoxicity at high concentrations in vitro
  • Potential pro-inflammatory effects in some contexts
  • Limited human safety data

Frequently Asked Questions

What does LL-37 do in the body?
LL-37 is part of the innate immune system. It kills microbes directly, recruits immune cells, modulates inflammation, and helps wounds heal — acting as both an antimicrobial and an immunomodulator.
Why is LL-37 being studied as a drug?
With antibiotic resistance rising, LL-37 is attractive because it kills bacteria by membrane disruption (harder to develop resistance against) and also modulates the host immune response. It has been studied for sepsis, skin and lung infections, and even COVID-19.
How is LL-37 used in research?
In vitro and animal studies use it topically or via injection at microgram-to-milligram doses. It is very unstable in serum (protease degradation), which is a major formulation challenge.

For Research Reference Only

Not medical advice. Peptides may be regulated or restricted in your jurisdiction.

References

  1. 1.LL-37: Cathelicidin-related antimicrobial peptide with pleiotropic activity.. PubMed (2016). Fabisiak A, et al.. pubmed.ncbi.nlm.nih.gov/27117377/
  2. 2.Cathelicidin peptide LL-37: A multifunctional peptide involved in heart disease.. PubMed (2024). Miao S, et al.. pubmed.ncbi.nlm.nih.gov/39615616/
  3. 3.Therapeutic Potential of Cathelicidin Peptide LL-37, an Antimicrobial Agent, in a Murine Sepsis Model.. PubMed (2020). Nagaoka I, et al.. pubmed.ncbi.nlm.nih.gov/32825174/

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