LL-37
From PeptidePlaza, the free peptide reference · Entry #028 · Recovery · Hand-curated entry · Editorial standards
LL-37 (also known as LL37, hCAP-18 fragment, FALL-39) is a recovery research peptide. The only human cathelicidin host-defense peptide. Kills bacteria, modulates inflammation, promotes wound healing, and is being studied for infections, sepsis, and tissue repair.
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).
1 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.
Primary targets: FPR2/ALX · P2X7 · EGFR (transactivation)
2 Reported effects
Effects below are those reported in the published literature cited on this page. They are not claims of clinical benefit and not medical advice.
2.1 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
2.2 Side effects
- Protease degradation limits stability
- Cytotoxicity at high concentrations in vitro
- Potential pro-inflammatory effects in some contexts
- Limited human safety data
3 Chemical and physical properties
| CAS number | 154947-66-7 |
|---|---|
| Molar mass | 4493.3 g/mol |
| Purity (typical) | >98% |
| Half-life | Short (minutes-hours, rapidly degraded by proteases) |
| Storage | −20 °C, lyophilised powder, desiccated |
| Solubility | Sterile water / bacteriostatic water |
| Receptors / targets | FPR2/ALX, P2X7, EGFR (transactivation) |
3.1 Amino acid sequence
LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
4 Research dosages
In vitro: 1–50 μg/mL. Animal models: 1–10 mg/kg. No validated human protocol.
5 Research studies (4)
- LL-37: Cathelicidin-related antimicrobial peptide with pleiotropic activity.
Pharmacological reports : PR (2016) · ReviewAntimicrobial peptides (AMPs) is a large family of compounds serving as natural antibiotics, widely distributed across the organism, mainly in mucus layers. - Unique features of human cathelicidin LL-37.
BioFactors (Oxford, England) (2015) · ReviewCathelicidins are antimicrobial peptides produced by humans and animals in response to various pathogenic microbes. - The human cathelicidin LL-37--A pore-forming antibacterial peptide and host-cell modulator.
Biochimica et biophysica acta (2016) · ReviewThe human cathelicidin hCAP18/LL-37 has become a paradigm for the pleiotropic roles of peptides in host defence. - Human cathelicidin LL-37 exerts amelioration effects against EHEC O157:H7 infection regarding inflammation, enteric dysbacteriosis, and impairment of gut barrier function.
Peptides (2023) · ReviewEnterohaemorrhagic Escherichia coli (EHEC) O157:H7 infection impairs intestinal barrier function, causing intestinal inflammation and enteric dysbacteriosis.
6 Safety and risk profile
6.1 Regulatory status
LL-37 is currently classified as Investigational. It has no approved human indication in the United States; availability elsewhere does not imply demonstrated safety or efficacy.
Safety score: 48/100 — moderate concern. Derived from clinical data volume, known risks and regulatory status.
6.2 Contraindications
Conditions and populations in which use is contraindicated:
- Pregnancy or lactation (insufficient data)
- Known hypersensitivity to cationic peptides
6.3 Drug interactions
| Drug or class | Interaction | Risk |
|---|---|---|
| Cationic antimicrobials (polymyxins) | Potential synergistic membrane disruption. | Low |
| Protease inhibitors | May extend LL-37 half-life by reducing degradation. | Low |
6.4 Long-term risks
- Unknown chronic toxicity
- Immunomodulatory effects could be double-edged in chronic disease
6.5 Research best practices
- Store lyophilized at −20 °C, desiccated
- Highly protease-labile — use fresh solutions, avoid serum-rich buffers in vitro
- Dose-response studies recommended given biphasic effects
7 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.
8 References
- LL-37: Cathelicidin-related antimicrobial peptide with pleiotropic activity. PubMed (2016). Fabisiak A, et al.. View source
- Cathelicidin peptide LL-37: A multifunctional peptide involved in heart disease. PubMed (2024). Miao S, et al.. View source
- Therapeutic Potential of Cathelicidin Peptide LL-37, an Antimicrobial Agent, in a Murine Sepsis Model. PubMed (2020). Nagaoka I, et al.. View source
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