LL-37
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Human cathelicidin antimicrobial peptide (37 amino acids); broad-spectrum antimicrobial, anti-biofilm, immunomodulatory, and wound healing via membrane disruption and innate immune activation.
Quick Facts
| Property | Value |
|---|---|
| Also Known As | LL-37, CAP-18, hCAP-18 C-terminal fragment, CAMP |
| Category | Immune / Antimicrobial / Wound Healing |
| Sequence | LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES (37 amino acids) |
| Molecular Weight | 4493.3 Da |
| Molecular Formula | C205H340N60O53 |
| PubChem CID | 16198951 |
| Administration | SubQ / Topical / Intranasal |
| Typical Dose Range | 1-5 mg/day (route-dependent) |
| Half-Life | Variable; degrades rapidly in serum due to proteolysis |
| Storage | Lyophilized -20C long-term; reconstituted 2-8C 1-2 weeks; protect from light |
| FDA Status | Research-only (not approved) |
| WADA Status | Not listed |
Mechanism of Action
LL-37 is the sole human cathelicidin, an endogenous host-defense peptide produced by neutrophils, macrophages, epithelial cells, and keratinocytes in response to infection and tissue injury. Its cationic amphipathic alpha-helical structure enables it to insert into negatively charged bacterial membranes, causing pore formation and cell lysis. This mechanism provides broad-spectrum bactericidal activity against gram-positive and gram-negative organisms, including MRSA and multidrug-resistant pathogens. PMID 41270816
Beyond direct antimicrobial killing, LL-37 disrupts bacterial biofilms by degrading the extracellular matrix and interfering with quorum sensing, making biofilm-embedded bacteria susceptible to conventional antibiotics. This is clinically significant for chronic infections in wounds, sinuses, and dental biofilms. The peptide also demonstrates antiviral activity by disrupting lipid envelopes of HIV, influenza, RSV, and SARS-CoV-2. PMID 34600462
LL-37 modulates innate immunity through multiple pathways: it chemoattracts neutrophils, monocytes, and T-cells to infection sites; activates the formyl peptide receptor-like 1 (FPRL1) for anti-inflammatory resolution signaling; binds and neutralizes bacterial lipopolysaccharide (LPS) to prevent endotoxic shock; and promotes wound healing by stimulating keratinocyte migration, angiogenesis, and re-epithelialization. Notably, LL-37 is deficient in atopic dermatitis and chronic wound states, providing a rationale for exogenous supplementation. PMID 38540740
LL-37-loaded exosomes have shown enhanced wound healing in animal models, combining the peptide's antimicrobial and immunomodulatory properties with targeted delivery. PMID 35930707
Key Research Areas
- Antimicrobial Activity: Broad-spectrum killing of bacteria, fungi, and enveloped viruses via membrane disruption. PMID 40869425
- Biofilm Disruption: Degradation of biofilm matrices in chronic infections; synergy with conventional antibiotics.
- Wound Healing: Promotes re-epithelialization and angiogenesis; LL-37 levels correlate with venous ulcer healing outcomes. PMID 27663530
- Innate Immune Modulation: Cathelicidins modulate TLR activation and inflammatory signaling. PMID 32582207
- Anti-HIV Activity: Disrupts HIV envelope; potential adjunct to antiretroviral therapy. PMID 34600462
- Derivative Development: Engineered LL-37 fragments and analogs with improved stability and reduced toxicity. PMID 40423576
Evidence Level Summary
| Evidence Type | Count | Notes |
|---|---|---|
| Human RCTs | 0 | No RCTs of exogenous LL-37 |
| Human observational | 1 | LL-37 correlation with wound healing |
| Animal in vivo | 1 | Exosome-loaded LL-37 wound model |
| In vitro | 0 | — |
| Systematic reviews | 0 | — |
| Narrative reviews | 6 | Comprehensive reviews of structure, antimicrobial mechanisms, derivatives |
Clinical Applications
- Immune Support — Innate immunity enhancement, antimicrobial defense
- Wound Healing — Chronic wounds, diabetic foot ulcers, post-surgical
- Skin Health — Atopic dermatitis (LL-37 deficiency state)
- Autoimmune Conditions — Immune modulation via TLR pathways
- Gut Health — LPS neutralization, anti-endotoxin activity
Protocols Using This Peptide
Ageless Peps Products
- AP-LL37-Vial — LL-37 (CAP-18) 5mg Vial, $49
Dosing Reference
Research Dosing Ranges (from literature)
| Route | Dose Range | Frequency | Duration | Source |
|---|---|---|---|---|
| SubQ | 1-5 mg | Daily or every other day | 4-8 weeks | Practitioner guides |
| Topical | 0.1-1% | 1-2x daily | As needed | Literature |
| Intranasal | Diluted in saline | Daily | 2-4 weeks | Practitioner guides |
Cycling
4-8 weeks per cycle; reassess immune markers and clinical response. May use continuous low-dose topical for chronic wound states.
Contraindications & Safety
- Contraindications: Active psoriasis (LL-37 is overexpressed; avoid topical); certain cancers (complex pro/anti-tumor biology depending on context)
- Common side effects: Local injection/application site irritation; mild transient inflammatory response
- Drug interactions: Potential synergy with conventional antibiotics against biofilm infections; no significant adverse interactions known
- Pregnancy/nursing: Insufficient data; caution
- Special populations: Monitor in autoimmune conditions due to immune-stimulatory effects
Cancer Considerations
CAUTION — Tissue-dependent dual role. LL-37 has ANTI-cancer effects in gastrointestinal cancers (colon, gastric, pancreatic) but PRO-cancer effects in breast, ovarian, and lung cancers (PMID-29843147). In pancreatic cancer, LL-37 suppresses tumors via ROS/DNA damage and autophagy inhibition (PMID-35935871). Action: Contraindicated in patients with active breast, ovarian, or lung cancer. May be considered for GI cancer patients under oncologist supervision.
Synergistic Combinations
- KPV + LL-37 — Anti-inflammatory + antimicrobial for gut and skin infections
- TB-500 + Thymosin Alpha-1 + LL-37 — Comprehensive immune and healing stack
- BPC-157 + LL-37 — Wound healing complement; angiogenic + antimicrobial
- SS-31 + VIP + LL-37 — Immune + mitochondrial support
Related Research
| PMID | Title | Year | Study Type |
|---|---|---|---|
| 34600462 | LL-37 and Its Potential As An Anti-HIV Agent | 2021 | Review |
| 38540740 | LL-37 Structures, Antimicrobial Activity, and Influence on Host Immunity | 2024 | Review |
| 41270816 | Decoding LL-37 Structure and antimicrobial mechanisms | 2025 | Review |
| 40869425 | Antimicrobial Peptides of the Cathelicidin Family: Focus on LL-37 | 2025 | Review |
| 40423576 | Exploring the Antimicrobial Potential of LL-37 Derivatives | 2025 | Review |
| 35930707 | LL-37 Engineered Exosomes for Wound Healing | 2022 | Animal in vivo |
| 27663530 | LL-37 Correlates with Venous Leg Ulcer Healing | 2016 | Observational |
| 32582207 | Cathelicidins Modulate TLR-Activation and Inflammation | 2020 | Review |
References
- PMID 34600462 — Anti-HIV potential
- PMID 38540740 — Structure and host immunity
- PMID 41270816 — Antimicrobial mechanisms
- PMID 40869425 — Cathelicidin family review
- PMID 40423576 — LL-37 derivatives
- PMID 35930707 — Exosome wound healing
- PMID 27663530 — Venous ulcer correlation
- PMID 32582207 — TLR modulation
Related
#peptide #immune #subq