LL-37
Also known as: Human Cathelicidin, hCAP18-derived peptide
Human Cathelicidin | Antimicrobial Peptide
Overview
LL-37 is the only human cathelicidin antimicrobial peptide, a 37-amino acid cationic peptide derived from hCAP18 that exhibits broad-spectrum antimicrobial activity against bacteria, viruses, and fungi while modulating immune responses.
Key benefits
- Direct wound healing acceleration
- Broad-spectrum antimicrobial activity
- Activity against resistant bacteria (MRSA, MDRPA)
- Enhanced tissue regeneration
- Immune modulation
- Local antimicrobial protection
Mechanism of action
Provides direct antimicrobial activity through membrane disruption, promotes wound healing by enhancing keratinocyte migration and angiogenesis, and modulates immune responses without systemic exposure when used topically.
Molecular data
- Type
- Cationic antimicrobial peptide
- Half-life
- Short (rapid proteolytic degradation)
Indications
What the research community uses this compound for, with self-reported effectiveness.
Wound Healing
Chronic Venous Leg Ulcers
Most effective68% ulcer area reduction demonstrated with 0.5mg/mL concentration in clinical trials.
Diabetic Foot Ulcers
EffectiveEnhanced granulation tissue formation and wound closure.
Pressure Ulcers
EffectiveAccelerated healing demonstrated in animal models.
Immunity
Innate Immune Enhancement
EffectiveBoosts natural immune defenses against pathogens.
Antimicrobial Resistance
EffectiveActive against MRSA and multi-drug resistant bacteria with >4 log reduction in biofilms.
Immunomodulation
EffectiveBalances immune responses without causing immunosuppression.
Skin Health
Epithelial Cell Proliferation
ModerateStimulates skin cell growth and regeneration.
Angiogenesis Promotion
ModeratePromotes new blood vessel formation for tissue repair.
Collagen Synthesis
ModerateSupports collagen production for wound healing.
Dosing protocols
Common protocols by delivery method. Adjust the curve below to model accumulation in your own cycle.
Topical
Topical application is the most established route, providing direct access to wound sites with minimal systemic exposure.
| Protocol | Dose | Frequency | Route / duration |
|---|---|---|---|
| Wound healing - Standard | 0.5mg/mL gel/cream | Daily to twice weekly | Direct wound application |
| Wound healing - Intensive | 1.6mg/mL gel/cream | Daily | Direct wound application |
Preparation
Steps
- Clean and debride wound area
- Apply thin layer directly to wound surface
- Cover with sterile dressing if needed
- Change per clinical protocol (daily to twice weekly)
- Monitor healing progress and adjust frequency
- Document wound measurements and progression
Work out the water volume and syringe units in the reconstitution calculator →
Injectable
Subcutaneous injection provides systemic distribution for immune modulation. Limited clinical data compared to topical.
| Protocol | Dose | Frequency | Route / duration |
|---|---|---|---|
| Systemic immune support | 100-150mcg | Once daily | SubQ |
Preparation
You will need
- LL-37 lyophilized powder
- Bacteriostatic water
- Insulin syringes
- Alcohol swabs
Steps
- Allow vial to reach room temperature
- Add bacteriostatic water slowly to peptide
- Gently swirl (don't shake vigorously)
- Calculate dose based on final concentration
- Use sterile injection technique
- Rotate injection sites daily
Work out the water volume and syringe units in the reconstitution calculator →
Interactions
Pairwise interactions with other compounds you might be cycling — the same data behind the cycle builder's safety check.
Amino Acid Solutions
AvoidPhysical incompatibility, especially with IV formulations.
Physiological Salt Solutions
MonitorHigh salt concentrations may reduce antimicrobial activity.
BPC-157
SynergisticEnhanced wound healing through complementary mechanisms.
TB-500
SynergisticCombined anti-inflammatory and healing effects.
Conventional Antibiotics
SynergisticFICI values 0.25-0.5 against resistant bacteria when combined.
Vitamin D3
SynergisticActs as cofactor for endogenous LL-37 production.
Lactoferrin
CompatibleSafe combined use with no negative interactions.
Timeline
Typical week-by-week effects reported in clinical and observational data.
- Week 1-2
Reduced bacterial load, initial wound bed preparation
- Week 2-4
Increased granulation tissue formation, epithelial migration
- Week 4-6
Significant wound size reduction
- Week 6-8
Continued healing toward wound closure
Safety
Reported adverse effects, contraindications, and what to monitor on cycle.
Common side effects
- Generally well-tolerated
- Mild injection site reactions (injectable)
- Local irritation at application site (topical)
Stop signs — stop and seek advice
- Severe injection site reactions with spreading inflammation
- Allergic reaction signs (rash, difficulty breathing, swelling)
- Persistent flu-like symptoms
- Signs of wound infection (increased redness, warmth, drainage)
- Worsening wound condition or delayed healing
- Unusual pain or irritation at application site
Contraindications
- Pre-existing hypersensitivity to peptides
- Compromised immune status (relative contraindication)
- Non-sterile wound environments
Monitoring
- Injection site reactions and excessive irritation
- Signs of wound infection
- Allergic reactions or contact dermatitis
- Wound healing progress
Quality checks
What a legitimate product looks like, what should give pause, and what should make you stop.
Good signs
- Sterile, clear formulation
- ≥98% purity by HPLC
- White to off-white lyophilized powder
- Proper cold chain maintenance (2-8°C)
- Appropriate gel base compatible with peptide activity
- Clinical-grade concentrations (0.5-1.6mg/mL)
Warning signs
- Brief room temperature exposure acceptable if promptly refrigerated
- Homemade topical formulations may lack sterility
Stop signs — don't use
- Discolored or cloudy solutions
- Yellow discoloration or visible particles
- Pre-mixed liquid formulations (LL-37 unstable long-term)
- Non-sterile preparations
- Microbial contamination
Recent research
Newer papers and trial readouts on file for this compound, with source and date.
2025 · International Journal of Antimicrobial Agents
LL-37: Master Antimicrobial Peptide Review
Comprehensive review of broad functions from infection to cancer immunity.
References
Primary literature and clinical-trial data informing this entry.
Venous Leg Ulcer Trial - Grönberg et al.
Wound Repair and Regeneration · 2014
68% ulcer area reduction demonstrated at optimal doses in chronic venous leg ulcers.
Melanoma Phase I Trial
2015
Intratumoral LL-37 in melanoma patients demonstrated safety and immune stimulation (NCT02225366).
MRSA Biofilm Study - Noore et al.
PLOS ONE · 2019
>4 log reduction in MRSA biofilms compared to conventional antibiotics.
Structural Analysis - Wang et al.
Journal of Biological Chemistry · 2008
NMR spectroscopy determining 3D structure of LL-37.
Last updated . How this page was sourced is described in the methodology.