Peptide Profile

LL-37

Antimicrobial Peptide

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Overview

Composition

37-amino-acid cationic antimicrobial peptide (AMP) derived from the C-terminal cleavage product of human cathelicidin (hCAP18), the only cathelicidin found in humans

Mechanism of Action

Disrupts microbial membranes through electrostatic interactions and membrane insertion, leading to cell lysis; modulates immune responses by recruiting/activating immune cells, neutralizing endotoxins (LPS), promoting wound healing, and exhibiting anti-biofilm properties

Primary Effects

Studied for antimicrobial activity against bacteria, fungi, and viruses; immune signaling; wound-repair biology; and context-dependent inflammatory effects

Discovery & Background

Identified in 1995 during research on innate immune defense mechanisms as the active antimicrobial domain of human cathelicidin (hCAP18), expressed primarily in neutrophils, epithelial cells, and skin

1990s: Discovery and initial characterization. 2000s: Expanded research into antimicrobial, immunomodulatory, and wound-healing properties. 2010s-present: Exploration in infectious diseases, chronic wounds, biofilm-related infections, and inflammatory conditions

Not FDA-approved for therapeutic use; remains investigational/research compound, explored in preclinical and early clinical studies

Research Overview

Preclinical research describes LL-37's antimicrobial, immunomodulatory, and wound-healing properties across multiple models

01
Broad-spectrum antimicrobial activity has been reported against MRSA, Pseudomonas, E. coli, Candida, and others
02
Anti-biofilm research reports disruption of established biofilms and reduced formation in experimental systems
03
Wound-healing models show effects on closure, angiogenesis, cell recruitment, and re-epithelialization
04
Immunomodulation: balances cytokine production, neutralizes endotoxins (LPS), recruits immune cells
05
Antiviral activity has been demonstrated against influenza, HIV, and herpes viruses in vitro
06
Cancer-cell findings are limited to selected cell-line models and should not be treated as clinical evidence
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Dysregulation linked to conditions: low levels in chronic infections/wounds; elevated in psoriasis, rosacea (context-dependent)
08
Generally well-tolerated in preclinical safety studies

No FDA approval; lacks large-scale human RCTs for therapeutic claims. Human data limited to small exploratory studies and in vitro/animal models

Safety Considerations

Monitoring

Infection markers (cultures, inflammatory markers)
Wound healing progress (size, appearance, closure rate)
Immune function indicators
Tolerance and side effects
Symptom tracking

Side Effects

Generally Well-Tolerated

Human tolerability data remain early and indication-specific
Rare local irritation (topical)
Preclinical safety studies show minimal systemic toxicity

Context-Dependent

Potential for dysregulation in inflammatory skin conditions (psoriasis, rosacea)—LL-37 may be elevated in these contexts
Unknown long-term effects in humans due to limited data

Contraindications

Hypersensitivity to LL-37 or components
Caution in inflammatory dermatological conditions where LL-37 is already elevated (e.g., psoriasis, rosacea)
Limited human safety data—use with medical supervision
Variable quality in compounded forms

Educational Notice

LL-37 is an investigational antimicrobial and immunomodulatory peptide with most support coming from preclinical and early exploratory research. It is not FDA-approved for therapeutic use, and human safety and efficacy data remain limited and indication-specific. Compounded formulations vary in quality and purity. LL-37's role in inflammatory skin conditions is complex and context-dependent, so clinical decisions require qualified medical oversight.

References