About LL-37
Human cathelicidin antimicrobial peptide; disrupts bacterial membranes and modulates innate immune response via TLR signaling
LL-37 is the mature human cathelicidin antimicrobial peptide, a 37-amino-acid cationic peptide generated by proteolytic cleavage of the hCAP18 precursor protein, constitutively expressed in neutrophil granules and inducibly expressed in keratinocytes and epithelial cells of the skin, lung, and gastrointestinal tract as a component of innate antimicrobial defense. LL-37 disrupts bacterial and fungal membranes through electrostatic interaction with anionic lipopolysaccharide and membrane phospholipids, and also modulates inflammatory responses through formyl peptide receptor 2 (FPR2/ALX) activation, promotes wound healing via EGFR transactivation, and contributes to neutrophil extracellular trap formation and antiviral defense. Human studies have documented LL-37 expression in the context of severe soft tissue infections caused by Streptococcus pyogenes, and biochemical characterization of the hCAP18/LL-37 prosequence has identified antimicrobial and protease-inhibitory functions relevant to human skin defense biology. LL-37 is a research compound with no FDA approval for any indication; exogenous synthetic LL-37 administration is investigational with no completed human clinical trials establishing safety or efficacy for wound healing, antimicrobial, or immunomodulatory applications. LL-37 dosage and administration: No human clinical trial has established a dosage protocol for exogenous LL-37. Preclinical and in vitro studies have used LL-37 at concentrations ranging from 1–50 µg/mL in cellular models. Animal models have employed weight-based dosing via subcutaneous or intravenous delivery. Topical formulations for wound healing and antimicrobial applications have been investigated at varying concentrations, with interest in hydrogel delivery systems for sustained local release. LL-37 is rapidly degraded by host proteases in vivo, which limits systemic bioavailability following subcutaneous injection; this degradation susceptibility has driven research into protease-resistant LL-37 analogues and encapsulated formulations. LL-37 is a research compound with no approved human dosing guidelines for any indication.
LL-37 Benefits & Research Areas
Research Signals
Population research notes
These signals reflect research interest areas, not treatment indications.
Regulatory & Evidence
Risk Profile
Moderate risk profile in research contexts. Review contraindications and administration guidelines before use.
Regulatory Status
- Availability Status
- Research Only
- FDA Status
- Investigational
Human cathelicidin antimicrobial peptide. Phase 1/2 trials for wound healing. No FDA approval, no NDA. Early investigational stage only. Not commercially available in US.
Regulatory status reflects publicly available information and may change. This is not legal or medical advice.
Research Sources
7 sources cited · 7 moderate
5 Cohorts · 1 Review · 1 In vitro
A protease-sensing circuit links neutrophil inflammation to virulence regulation in Streptococcus pyogenes.
bioRxiv · 2026
# Summary Research found that LL-37, an antimicrobial peptide released by neutrophils, normally represses virulence factor expression in *Streptococcus pyogenes*, but neutrophil proteases released during inflammatory cell death (NETosis) counteract this effect by degrading a bacterial repressor protein, thereby reactivating virulence gene expression. This study demonstrated a feedback loop where host inflammation paradoxically amplifies bacterial virulence, explaining the hyperinflammatory nature of group A streptococcal infections.
Evaluation of the antibacterial activity of stem cells from apical papilla and their conditioned medium against Escherichia coli and Staphylococcus aureus.
Arch Microbiol · 2026
# Summary Research found that stem cells from apical papilla (SCAPs) and their secreted factors demonstrate potent antibacterial activity against both *Escherichia coli* and *Staphylococcus aureus*, with LL-37 peptide identified as one of the key antimicrobial compounds responsible for this effect. This study demonstrated that SCAP-conditioned medium exhibited significantly greater antibacterial efficacy than fibroblast-derived medium, suggesting these stem cells represent a promising source of natural antimicrobial factors.
Overcoming LPS-mediated resistance in gram-negative pathogens: a review of LL-37 analogs and computational design strategies.
Arch Microbiol · 2026
# Summary Research found that LL-37 analogs, developed through structural modifications and computational design strategies, show promise in overcoming antimicrobial resistance in Gram-negative bacteria by improving their ability to penetrate and disrupt bacterial membranes while reducing toxicity to human cells. This study demonstrated that computational techniques such as molecular docking, simulations, and artificial intelligence can accelerate the optimization of these peptide analogs to effectively target multidrug-resistant pathogens.
Show 4 more sources ↓
Serine protease HtrA promotes Campylobacter jejuni intestinal colonization through degrading antimicrobial peptide LL-37.
Sci Adv · 2026
# Summary Research found that *Campylobacter jejuni* bacteria evade the antimicrobial peptide LL-37—produced by intestinal cells as part of innate immunity—by using a serine protease called HtrA to degrade and inactivate the peptide at a specific cleavage site. This study demonstrated that HtrA expression is activated in response to LL-37 exposure, allowing resistant bacterial strains to survive intestinal colonization and establish infection.
Optimized LL-37-Derived Peptides Exhibit Antitubercular Activity, Induce Membrane Disruption, and P-Type ATPase Transcriptional Responses in Mycobacterium tuberculosis.
Biomolecules · 2026
# Summary Research found that optimized LL-37-derived peptides, particularly a modified variant called D-LL37, demonstrated antimycobacterial activity against *Mycobacterium tuberculosis* through partial membrane disruption and activation of bacterial stress-response genes involved in ion transport. This study demonstrated that D-LL37 induced structural damage to the bacterial envelope while triggering coordinated upregulation of P-type ATPase genes, suggesting a mechanism combining direct membrane perturbation with cellular stress responses.
Cathelicidin LL-37 in severe Streptococcus pyogenes soft tissue infections in humans
Infection and Immunity · 2008
Research in human biopsy specimens from patients with severe streptococcal soft tissue infections found large amounts of LL-37 at infection sites with neutrophils as the primary source, and demonstrated colocalization of LL-37 with bacteria and the streptococcal cysteine protease SpeB, providing in vivo evidence for LL-37 as a frontline innate immune effector subject to bacterial resistance.
Antimicrobial and protease inhibitory functions of the human cathelicidin (hCAP18/LL-37) prosequence
Journal of Investigative Dermatology · 2003
Research in recombinant protein systems found that the cathelin-like prosequence of hCAP18/LL-37 inhibited cysteine protease activity and killed bacterial pathogens including E. coli and methicillin-resistant Staphylococcus aureus at 16 to 32 μM concentrations, identifying dual antimicrobial and protease-inhibitory functions complementary to the C-terminal LL-37 peptide.
LL-37 Side Effects & Safety Considerations
Moderate risk profile. Review all reported considerations carefully before use.
Reported contraindications & considerations
Consult a qualified healthcare professional before making any health decisions. This information is educational only and does not constitute medical advice.
Research Stacks
Browse all →Where to Buy LL-37 — Providers & Availability
38 providersClinics
9 providersFlorida Regenerative
United StatesView →Mind Body Reset Functional Medicine
United StatesView →Optimize by JaeNix
United StatesView →Revitalize IV Solutions & MedSpa
Chicago, United StatesView →Sage Wellness and Health
United StatesView →CORE IV
Herndon, United StatesView →Functional Medicine Las Vegas
United StatesView →Pura Vida Body & Mind Spa
United StatesView →The Stockbridge Clinic
United KingdomView →
Online Vendors
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Questions to Ask Your Provider
Frequently Asked Questions — LL-37
LL-37 is the mature human cathelicidin antimicrobial peptide, a 37-amino-acid cationic peptide generated by proteolytic cleavage of the hCAP18 precursor protein, constitutively expressed in neutrophil granules and inducibly expressed in keratinocytes and epithelial cells of the skin, lung, and gastrointestinal tract as a component of innate antimicrobial defense. LL-37 disrupts bacterial and fungal membranes through electrostatic interaction with anionic lipopolysaccharide and membrane phospholipids, and also modulates inflammatory responses through formyl peptide receptor 2 (FPR2/ALX) activation, promotes wound healing via EGFR transactivation, and contributes to neutrophil extracellular trap formation and antiviral defense.
antimicrobial, immune modulation, wound healing, anti-biofilm.
Research on LL-37 primarily documents effects related to antimicrobial and immune modulation and wound healing and anti-biofilm. These are areas covered in preclinical and clinical literature — individual response varies and effects depend on context of use.
Reported contraindications and considerations for LL-37 include sepsis risk (may be pro-inflammatory at high doses). This is educational information only — consult a qualified healthcare professional before use.
38 providers in the directory currently offer LL-37.
# Summary Research found that LL-37, an antimicrobial peptide released by neutrophils, normally represses virulence factor expression in *Streptococcus pyogenes*, but neutrophil proteases released during inflammatory cell death (NETosis) counteract this effect by degrading a bacterial repressor protein, thereby reactivating virulence gene expression. This study demonstrated a feedback loop where host inflammation paradoxically amplifies bacterial virulence, explaining the hyperinflammatory nature of group A streptococcal infections.
LL-37 is featured in the following research stacks on PeptideBase: Thymosin Alpha-1 + LL-37: Immune Support.