Peptide profile
LL-37
Human antimicrobial peptide for immunity and healing · also known as Cathelicidin, hCAP18, FALL-39, Human Cathelicidin Antimicrobial Peptide
Compare LL-37 with other peptides →Summary
LL-37 is a 37-amino acid human host defense peptide derived from the cathelicidin family, naturally produced by neutrophils, epithelial cells, and macrophages. It exhibits broad-spectrum antimicrobial activity against bacteria, fungi, and viruses while simultaneously modulating immune responses and promoting wound healing. Research suggests it plays a critical role in innate immunity and may have therapeutic applications in chronic infections, wound repair, and inflammatory conditions.
- Typical dose
- 100–500 mcg per application or injection, frequency varies by protocol (typically 2–3x per week)
- Half-life
- ~30–60 minutes (in vivo, rapidly degraded by proteases)
- Route
- Subcutaneous, Topical
- Cycle length
- 4–8 weeks
Mechanism
How it works
LL-37 exerts antimicrobial effects by inserting into and disrupting bacterial cell membranes, creating pores that lead to membrane depolarization and cell death, primarily through electrostatic interactions with negatively charged lipopolysaccharides on bacterial surfaces. It also acts as an immunomodulatory agent by binding to receptors including FPRL1 (formyl peptide receptor-like 1), TLR4, and purinergic receptors, activating downstream signaling cascades involving MAPK, NF-κB, and PI3K/Akt pathways that regulate cytokine production, cell migration, and angiogenesis. Additionally, LL-37 promotes wound healing by stimulating keratinocyte migration, angiogenesis via VEGF induction, and re-epithelialization of damaged tissue.
Reported in research
Benefits
- Broad-spectrum antimicrobial activity against gram-positive and gram-negative bacteria, fungi, and enveloped viruses
- Accelerated wound healing through promotion of keratinocyte migration, angiogenesis, and re-epithelialization
- Immunomodulation — reduces excessive inflammation while enhancing pathogen clearance
- Potential anti-biofilm activity, disrupting established bacterial biofilms resistant to conventional antibiotics
Context, not a prescription
Dosing
- Typical range
- 100–500 mcg per application or injection, frequency varies by protocol (typically 2–3x per week) (Subcutaneous, Topical)
- Cycle length
- 4–8 weeks
- Half-life
- ~30–60 minutes (in vivo, rapidly degraded by proteases)
Safety
Side effects & contraindications
Possible side effects
- Local injection site irritation, redness, or mild swelling
- Transient burning or stinging sensation (particularly with topical use)
- Possible pro-inflammatory effects at high local concentrations
- Mild systemic inflammatory response in sensitive individuals
Contraindications
- Active autoimmune conditions (LL-37 can exacerbate autoimmune responses, including in lupus where elevated LL-37 contributes to pathology)
- Known hypersensitivity or allergy to cathelicidin-derived peptides
- Pregnancy or breastfeeding (insufficient safety data)
- Active or uncontrolled cancers (LL-37 has been shown to promote tumor growth in some cancer types)
Research information, not medical advice. Always consult a licensed clinician before considering any peptide.
In depth
Full profile
What it does
Users may notice reduced redness and swelling around wounds, faster closure of skin injuries, and possibly improved resistance to minor infections during the cycle.
How it works
Imagine your immune system as a city's defense force. LL-37 acts like both the frontline soldier (directly punching holes in invading bacteria) and the emergency dispatcher (calling for reinforcements and coordinating cleanup crews to repair damage after the battle).
When introduced into the body, LL-37 seeks out bacterial membranes, disrupts them, and signals nearby immune cells to become more active. It also communicates with skin cells and blood vessel cells to accelerate repair of wounds or damaged tissue.
What to expect
Antimicrobial effects are nearly immediate at the site of application. Wound healing and immune modulation effects typically become noticeable within 1–2 weeks of consistent use.
- Week 1: Initial antimicrobial and anti-inflammatory effects at the site of use; possible mild site irritation as your body adjusts.
- Weeks 2–4: Noticeable improvement in wound healing speed; enhanced local immune activity; reduced signs of infection in targeted areas.
- Weeks 4–8: Cumulative tissue repair benefits; improved skin integrity; sustained immune modulation effects that may persist beyond the cycle.
Good to know
- Start with the lowest effective dose and assess local tolerance before increasing
- Consult a knowledgeable healthcare provider before use, especially if you have any chronic health condition
Staying safe
- Redness or irritation at the injection or application site
- Mild burning sensation, especially with topical use
Avoid if you have:
- People with autoimmune diseases (e.g., lupus, rheumatoid arthritis)
- People with active cancer diagnoses
- Pregnant or breastfeeding individuals
Mechanism of action
LL-37 (residues 134–170 of hCAP18) exerts its antimicrobial activity predominantly via membrane disruption through a carpet or toroidal-pore model, driven by electrostatic attraction to anionic phospholipids (e.g., phosphatidylglycerol, cardiolipin) in bacterial membranes while sparing zwitterionic mammalian cell membranes. As an immunomodulator, LL-37 engages multiple receptors: it acts as a chemoattractant via FPRL1/FPR2, stimulates TLR4 signaling in dendritic cells and macrophages (while paradoxically suppressing LPS-mediated TLR4 activation), and activates P2X7 and EGFR pathways in epithelial cells, driving MAPK/ERK signaling, PI3K/Akt activation, and subsequent upregulation of MMP expression, VEGF-A, and EGF — all critical to re-epithelialization and angiogenesis. Its immunomodulatory duality (pro-inflammatory in sterile contexts, anti-inflammatory against excessive LPS challenge) makes it context-dependent in clinical applications.
Pharmacokinetically, LL-37 has a very short plasma half-life (~30–60 minutes) due to rapid degradation by serine proteases (e.g., kallikreins) and metalloproteinases. Subcutaneous delivery provides a local depot effect with slower systemic absorption. At the tissue level, it upregulates keratinocyte migration via PI3K/Akt and activates VEGF-A-mediated neovascularization. In immune cells, it promotes monocyte chemotaxis, mast cell degranulation, and dendritic cell maturation, while inhibiting apoptosis of neutrophils — extending their antimicrobial activity window.
Pharmacodynamics
Antimicrobial effects are concentration-dependent and essentially immediate at therapeutic concentrations (MIC for many pathogens: 1–16 µg/mL). Immunomodulatory signaling via FPRL1/EGFR begins within minutes to hours. Measurable tissue healing endpoints (re-epithelialization rates) are typically observable in clinical wound models within 5–7 days.
Quantifiable outcomes include reduced bacterial burden at wound sites, elevated local VEGF-A and EGF levels, increased keratinocyte migration indices, decreased pro-inflammatory cytokines (IL-6, TNF-α) in LPS-challenged models, and accelerated wound closure as measured by planimetry. In vivo, elevated neutrophil survival and monocyte recruitment are observed.
Timeline
- Days 1–3: Rapid local antimicrobial activity; mast cell degranulation and neutrophil recruitment at injection site; FPRL1-mediated monocyte chemotaxis initiated; short half-life (~30–60 min) necessitates frequent dosing for sustained tissue levels.
- Weeks 1–2: Upregulation of VEGF-A and EGF in wound microenvironment; measurable increase in keratinocyte migration; LPS-mediated TLR4 suppression reduces excessive inflammation in infected wounds; angiogenic sprouting begins.
- Weeks 2–8: Progressive re-epithelialization and collagen remodeling; sustained immune modulation with reduced inflammatory cytokine milieu; potential cumulative biofilm disruption in chronic wound contexts; resolution of measurable antimicrobial endpoints.
Comparisons
- LL-37 — effectiveness Moderate, safety Moderate, cost $$$, High to use
- Thymosin Alpha-1 — effectiveness Moderate, safety Good, cost $$$, Medium to use
- BPC-157 — effectiveness High, safety Good, cost $$, Medium to use
Adverse effects
Common:
- Injection site erythema and edema due to localized mast cell degranulation and histamine release
- Transient pro-inflammatory cytokine surge (IL-8, IL-6) at high local concentrations — may manifest as localized heat and swelling
Rare:
- Exacerbation of autoimmune pathology (e.g., LL-37 is known to form immunogenic complexes with self-DNA/RNA in systemic lupus erythematosus, activating plasmacytoid dendritic cells via TLR7/TLR9 — incidence risk is elevated in genetically predisposed individuals)
- Potential tumor-promoting activity: LL-37 has been shown to activate EGFR and promote proliferation in ovarian, lung, and gastric cancer cell lines (animal and in vitro data)
Contraindications & risk mitigation
Contraindicated in:
- Systemic lupus erythematosus (SLE) or other type I interferonopathies — LL-37/nucleic acid complexes are pathogenic drivers
- Active epithelial malignancies (ovarian, gastric, lung cancers) where EGFR pathway activation may be oncogenic
- Individuals on immunosuppressive regimens where immune modulation may produce unpredictable outcomes
- Use the lowest efficacious concentration; avoid systemic high-dose protocols until further clinical safety data is established
- Monitor for local and systemic inflammatory markers (CRP, IL-6) during extended cycles
- Consider topical or localized delivery to minimize systemic immunomodulatory off-target effects
- Contraindicate in any patient with a personal or family history of autoimmune interferonopathy
Qué hace
Users may notice reduced redness and swelling around wounds, faster closure of skin injuries, and possibly improved resistance to minor infections during the cycle.
Cómo funciona
Imagine your immune system as a city's defense force. LL-37 acts like both the frontline soldier (directly punching holes in invading bacteria) and the emergency dispatcher (calling for reinforcements and coordinating cleanup crews to repair damage after the battle).
When introduced into the body, LL-37 seeks out bacterial membranes, disrupts them, and signals nearby immune cells to become more active. It also communicates with skin cells and blood vessel cells to accelerate repair of wounds or damaged tissue.
Qué esperar
Antimicrobial effects are nearly immediate at the site of application. Wound healing and immune modulation effects typically become noticeable within 1–2 weeks of consistent use.
- Week 1: Initial antimicrobial and anti-inflammatory effects at the site of use; possible mild site irritation as your body adjusts.
- Weeks 2–4: Noticeable improvement in wound healing speed; enhanced local immune activity; reduced signs of infection in targeted areas.
- Weeks 4–8: Cumulative tissue repair benefits; improved skin integrity; sustained immune modulation effects that may persist beyond the cycle.
Bueno saber
- Start with the lowest effective dose and assess local tolerance before increasing
- Consult a knowledgeable healthcare provider before use, especially if you have any chronic health condition
Manteniéndose seguro
- Redness or irritation at the injection or application site
- Mild burning sensation, especially with topical use
Evitar si tienes:
- People with autoimmune diseases (e.g., lupus, rheumatoid arthritis)
- People with active cancer diagnoses
- Pregnant or breastfeeding individuals
Mecanismo de acción
LL-37 (residues 134–170 of hCAP18) exerts its antimicrobial activity predominantly via membrane disruption through a carpet or toroidal-pore model, driven by electrostatic attraction to anionic phospholipids (e.g., phosphatidylglycerol, cardiolipin) in bacterial membranes while sparing zwitterionic mammalian cell membranes. As an immunomodulator, LL-37 engages multiple receptors: it acts as a chemoattractant via FPRL1/FPR2, stimulates TLR4 signaling in dendritic cells and macrophages (while paradoxically suppressing LPS-mediated TLR4 activation), and activates P2X7 and EGFR pathways in epithelial cells, driving MAPK/ERK signaling, PI3K/Akt activation, and subsequent upregulation of MMP expression, VEGF-A, and EGF — all critical to re-epithelialization and angiogenesis. Its immunomodulatory duality (pro-inflammatory in sterile contexts, anti-inflammatory against excessive LPS challenge) makes it context-dependent in clinical applications.
Pharmacokinetically, LL-37 has a very short plasma half-life (~30–60 minutes) due to rapid degradation by serine proteases (e.g., kallikreins) and metalloproteinases. Subcutaneous delivery provides a local depot effect with slower systemic absorption. At the tissue level, it upregulates keratinocyte migration via PI3K/Akt and activates VEGF-A-mediated neovascularization. In immune cells, it promotes monocyte chemotaxis, mast cell degranulation, and dendritic cell maturation, while inhibiting apoptosis of neutrophils — extending their antimicrobial activity window.
Farmacodinamia
Antimicrobial effects are concentration-dependent and essentially immediate at therapeutic concentrations (MIC for many pathogens: 1–16 µg/mL). Immunomodulatory signaling via FPRL1/EGFR begins within minutes to hours. Measurable tissue healing endpoints (re-epithelialization rates) are typically observable in clinical wound models within 5–7 days.
Quantifiable outcomes include reduced bacterial burden at wound sites, elevated local VEGF-A and EGF levels, increased keratinocyte migration indices, decreased pro-inflammatory cytokines (IL-6, TNF-α) in LPS-challenged models, and accelerated wound closure as measured by planimetry. In vivo, elevated neutrophil survival and monocyte recruitment are observed.
Cronología
- Days 1–3: Rapid local antimicrobial activity; mast cell degranulation and neutrophil recruitment at injection site; FPRL1-mediated monocyte chemotaxis initiated; short half-life (~30–60 min) necessitates frequent dosing for sustained tissue levels.
- Weeks 1–2: Upregulation of VEGF-A and EGF in wound microenvironment; measurable increase in keratinocyte migration; LPS-mediated TLR4 suppression reduces excessive inflammation in infected wounds; angiogenic sprouting begins.
- Weeks 2–8: Progressive re-epithelialization and collagen remodeling; sustained immune modulation with reduced inflammatory cytokine milieu; potential cumulative biofilm disruption in chronic wound contexts; resolution of measurable antimicrobial endpoints.
Comparaciones
- LL-37 — efectividad Moderate, seguridad Moderate, costo $$$, High de usar
- Thymosin Alpha-1 — efectividad Moderate, seguridad Good, costo $$$, Medium de usar
- BPC-157 — efectividad High, seguridad Good, costo $$, Medium de usar
Efectos adversos
Comunes:
- Injection site erythema and edema due to localized mast cell degranulation and histamine release
- Transient pro-inflammatory cytokine surge (IL-8, IL-6) at high local concentrations — may manifest as localized heat and swelling
Raros:
- Exacerbation of autoimmune pathology (e.g., LL-37 is known to form immunogenic complexes with self-DNA/RNA in systemic lupus erythematosus, activating plasmacytoid dendritic cells via TLR7/TLR9 — incidence risk is elevated in genetically predisposed individuals)
- Potential tumor-promoting activity: LL-37 has been shown to activate EGFR and promote proliferation in ovarian, lung, and gastric cancer cell lines (animal and in vitro data)
Contraindicaciones y mitigación de riesgos
Contraindicado en:
- Systemic lupus erythematosus (SLE) or other type I interferonopathies — LL-37/nucleic acid complexes are pathogenic drivers
- Active epithelial malignancies (ovarian, gastric, lung cancers) where EGFR pathway activation may be oncogenic
- Individuals on immunosuppressive regimens where immune modulation may produce unpredictable outcomes
- Use the lowest efficacious concentration; avoid systemic high-dose protocols until further clinical safety data is established
- Monitor for local and systemic inflammatory markers (CRP, IL-6) during extended cycles
- Consider topical or localized delivery to minimize systemic immunomodulatory off-target effects
- Contraindicate in any patient with a personal or family history of autoimmune interferonopathy
Reference data
Specifications
- Molecular formula
- C₂₀₅H₃₄₀N₆₀O₅₃S
- Molecular weight
- 4493.3 Da
- Half-life
- ~30–60 minutes (in vivo, rapidly degraded by proteases)
- Route
- Subcutaneous, Topical
- Cycle length
- 4–8 weeks
- Storage
- Lyophilized powder: store at -20°C, protect from light and moisture. Reconstituted solution: refrigerate at 4°C and use within 7–14 days. Avoid repeated freeze-thaw cycles.
- Legal status
- Research chemical; not FDA-approved for human therapeutic use. Legal to possess for research purposes in most jurisdictions.
FAQ
Common questions
How does LL-37 avoid killing host cells despite its membrane-disrupting mechanism?
LL-37's selectivity arises from its preferential interaction with anionic phospholipids (phosphatidylglycerol, cardiolipin) abundant in bacterial membranes. Mammalian cell membranes are predominantly zwitterionic (phosphatidylcholine, sphingomyelin) and maintain higher cholesterol content, which reduces membrane fluidity and LL-37 insertion efficiency. At therapeutic concentrations, the electrostatic threshold for mammalian membrane disruption is not reached. However, at supraphysiological concentrations, cytotoxicity to host cells has been documented in vitro.
What is the clinical evidence base for LL-37 in wound healing?
Most robust evidence comes from in vitro keratinocyte migration assays and murine excisional wound models demonstrating accelerated closure and angiogenesis. A limited number of Phase I/II clinical trials have explored topical LL-37 in venous leg ulcers (notably a Swedish trial showing improved healing rates). Systemic human clinical data remains sparse, and no LL-37-based therapeutic has received regulatory approval to date.
Is there synergy between LL-37 and conventional antibiotics?
Preclinical data suggests synergy between LL-37 and several antibiotics (e.g., vancomycin, gentamicin) via a two-hit model: LL-37 permeabilizes the outer membrane, increasing antibiotic intracellular access. Anti-biofilm activity also enhances antibiotic penetration into biofilm matrices. These findings are primarily in vitro; clinical confirmation is lacking.
What is the evidence level?
This compound is classified as Limited human data. Some human data exists but trials are small, short-term, or not yet replicated.
Research
Research & sources
Current evidence for LL-37 is rated as Limited human data. Limited human data is available.
- 1. LL-37: The only human member of the cathelicidin family of antimicrobial peptides (2014) — Biochimica et Biophysica Acta (BBA) - Biomembranes, 1838(10):2503-2517
- 2. An antimicrobial peptide regulates tumor-associated macrophage trafficking via the chemokine receptor CCR2 (2009) — Immunity, 30(4):595-607
- 3. Topical treatment with LL-37 is beneficial for chronic venous leg ulcers: a randomized controlled trial (2020) — Wound Repair and Regeneration
- 4. The cathelicidin anti-microbial peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcer epithelium (2003) — Journal of Investigative Dermatology, 120(3):379-389
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