What Is LL-37? Benefits, Research & Safety
The only human cathelicidin antimicrobial peptide, with broad-spectrum antimicrobial activity and important immunomodulatory functions.
UK summary: Not a licensed UK medicine. Endogenous antimicrobial peptide investigated for chronic infections, wound healing, and inflammation. Substantial preclinical literature; human therapeutic use is essentially absent.
Quick Facts
Overview
LL-37 — evidence and risk at a glance
Twenty standard modules scored against the Peptide Authority evidence grading methodology. Missing modules indicate the field has not yet been characterised editorially — treat absences as uncertainty rather than reassurance.
01Evidence snapshot
Not a licensed UK medicine. Endogenous antimicrobial peptide investigated for chronic infections, wound healing, and inflammation. Substantial preclinical literature; human therapeutic use is essentially absent.
02Human evidence grade
03Preclinical evidence grade
04Regulatory status
- UK: Not licensed for human use. Research compound only.
- EU: Not approved for therapeutic use.
- Notes: LL-37 is a research compound with no regulatory approvals. Therapeutic development continues but the peptide's complexity presents challenges.
05Approved medical uses
None in the UK or EU as a finished medicine. (Or: not yet documented; treat as absence rather than approval.)
06Unapproved / promotional claims
- Treats antibiotic-resistant infections.
- Cures chronic Lyme or biofilm-based infections.
- Heals wounds faster than standard NHS care.
- Safe and effective long-term antimicrobial therapy.
07Common internet claims
- Marketed by 'functional medicine' clinics for chronic Lyme / biofilm infections.
- Sold by online retailers as a research-only antimicrobial peptide.
- Promoted as the natural answer to antibiotic resistance.
08Claim vs evidence
| Claim | Evidence | Human evidence? | Regulatory concern | Safer wording |
|---|---|---|---|---|
| “Treats chronic infections antibiotics can't” | D | No | High | Mechanistic and animal-model evidence; no human RCT support for antibiotic-resistant infection treatment. |
| “Heals wounds faster than standard care” | D | No | High | Animal wound-healing data exist; no human RCT vs standard care. |
09Safety uncertainty score
Limited human safety data; meaningful uncertainty about rare or long-term effects.
10Known adverse signals
- Pro-inflammatory and immunomodulatory effects — can amplify inflammation.
- Theoretical risk in autoimmune disease.
- Injection-site reactions.
- Unknown effects of sustained exogenous cathelicidin exposure.
11Drug-interaction uncertainty
Interaction picture sparse; meaningful uncertainty when combined with other medicines.
12Anti-doping status
13UK legal position
Not licensed for human use. Research compound only.
14EU legal position
Not approved for therapeutic use.
15What this page cannot tell you
- Whether a UK-purchased vial contains LL-37 at the labelled concentration.
- Whether the antimicrobial mechanism translates from petri dish to human infection.
- Long-term effects of sustained antimicrobial peptide elevation.
- Whether it interacts with prescribed antibiotics or immunosuppressants.
16Last reviewed
17Citation quality score
18Research gaps
- No registered Phase 2 or 3 trials in humans for any indication.
- Antimicrobial in vitro activity does not equal clinical effectiveness.
- Long-term safety entirely unstudied.
- Combination with conventional antibiotics uncharacterised.
19Safer alternatives / established care pathways
- GP and infectious-diseases referral for suspected chronic infection.
- NHS antimicrobial-stewardship pathway for resistant infections.
- NHS wound clinic for non-healing wounds — substantial evidence-based options exist.
20Doctor discussion prompts
Questions to ask a qualified clinician
These are starter questions you can adapt for a GP, specialist, pharmacist, or anti-doping advisor. The aim is to help you have a better-informed conversation — not to replace one.
- Is LL-37 a licensed UK medicine?
- What licensed treatments exist for the infection or wound concern I have?
- Why is mechanistic plausibility not the same as proven benefit here?
Discovery & History
Mechanism of Action
Researched Benefits
Based on preclinical and clinical research findings:
- 1Broad-spectrum antimicrobial activity against bacteria, viruses, and fungi
- 2LPS neutralisation reducing sepsis-related inflammation
- 3Wound healing promotion
- 4Biofilm disruption
- 5Immunomodulatory effects
- 6Potential applications in infection control
Claim vs Evidence
How popular claims about LL-37 stack up against the current research, graded using our public evidence grading methodology.
| Claim | Evidence | Human evidence? | Regulatory concern | Safer wording |
|---|---|---|---|---|
| “Treats chronic infections antibiotics can't” | D | No | High | Mechanistic and animal-model evidence; no human RCT support for antibiotic-resistant infection treatment. |
| “Heals wounds faster than standard care” | D | No | High | Animal wound-healing data exist; no human RCT vs standard care. |
Theoretical Dosing & Protocols
| Theoretical Dosage | Not established; highly variable in research |
| Frequency | Variable depending on application |
| Duration | Variable |
| Notes | LL-37 is not approved for therapeutic use. Research applications vary widely depending on the condition being studied. The peptide's complex biology makes dosing and application challenging. |
Administration Routes
Routes studied in research settings (educational only):
- Topical (wound healing research)
- Injection (various research applications)
- Inhaled (respiratory research)
| Half-Life | Stability |
|---|---|
| Short; subject to proteolytic degradation in vivo | Requires careful handling; susceptible to degradation |
Safety Profile & Known Risks
Commonly Reported Side Effects
- Limited human safety data
- Potential for local irritation at high concentrations
Rare Risks & Concerns
- Pro-inflammatory effects in certain contexts
- Potential to exacerbate autoimmune inflammation
- Unknown long-term effects
Contraindications
- Psoriasis (LL-37 implicated in pathogenesis)
- Certain autoimmune conditions
- Pregnancy (no safety data)
- Active malignancy (angiogenic effects)
UK & EU Regulatory Context
🇬🇧 United Kingdom
Not licensed for human use. Research compound only.
🇪🇺 European Union
Not approved for therapeutic use.
Clinical Studies Summary
Cationic antimicrobial peptides and periodontal physiopathology: A systematic review.
Data remain inconsistent between the studies for hBDs mainly due to heterogeneity of the results, periodontal disease diagnostic criteria and assaying technique employed. Given their role in innate immunity and their antimicrobial functions, LL-37 and α-defensins may be eligible as periodontal clinical biomarkers and could be an interesting way for therapeutic development.
Acute salivary antimicrobial peptide secretion response to different exercise intensities and durations.
Levels of four salivary antimicrobial peptides increased after exercise dependently or independently of exercise intensity and duration, whereas some salivary antimicrobial peptides did not change after exercise. These findings suggest that the secretory responses to acute exercise with different intensities and durations differ among salivary antimicrobial peptides.
The therapeutic efficacy of Bifidobacterium animalis subsp. lactis BB-12(®) in infant colic: A randomised, double blind, placebo-controlled trial.
Supplementation with BB-12 is effective in managing infant colic. The effect could derive from immune and non-immune mechanisms associated with a modulation of gut microbiota structure and function.
Antimicrobials from human skin commensal bacteria protect against Staphylococcus aureus and are deficient in atopic dermatitis.
Strikingly, reintroduction of antimicrobial CoNS strains to human subjects with AD decreased colonization by S. aureus These findings show how commensal skin bacteria protect against pathogens and demonstrate how dysbiosis of the skin microbiome can lead to disease.
LL-37: Biological Mechanisms and Emerging Therapeutic Applications in Intestinal Disease.
We have further explored new strategies to overcome these challenges in the near future, including peptide engineering, nanocarrier delivery systems, and combined therapy. These findings together position LL-37 at the intersection of intestinal immunity and microbial ecology, providing a theoretical basis for its therapeutic application in IBD, CRC and infectious colitis.
β-Amyloid (Aβ) and Human Cathelicidin LL-37: Two Sides of the Same Coin?
Similarly to Aβ, LL-37 can induce neuroinflammation by stimulating human microglia to release inflammatory cytokines, such as TNF-α and IL-6. Neuroinflammation is essential for protecting the brain from pathogens-when prolonged, it drives pathological processes underlying AD, Parkinson's disease (PD), and other neurodegenerative disorders.
Registered Trials & Regulatory Status
7 of 9 completed trials have never posted results. Unreported trials are not neutral: results that go unpublished are more often negative ones.
Evaluation of 25(OH)D3 and LL-37 Levels in Periimplant Sulcus Fluid
Status: Not Yet Recruiting · 72 participants · Recep Tayyip Erdogan University
Conditions: Peri Implantitis, Peri Implant Mucositis
Cathelicidin LL-37 Relation to Potentially Malignant Lesions
Status: Completed · 45 participants · Fayoum University
Conditions: Oral Potentially Malignant Lesions
Chlorhexidine and Essential Oil Mouthwashes on Human Beta-Defensin 2 (hbD2) and Kathelicidin (LL-37) Saliva Levels
Status: Unknown · 120 participants · Istanbul Medeniyet University
Conditions: Mouth and Tooth Diseases, Periodontal Diseases, Gingivitis
The Role of Anti-inflammatory Cytokines and Antimicrobial Peptide LL-37 Biomarkers in the Treatment of Periodontal Disease.
Status: Completed · 60 participants · Universidad Rey Juan Carlos
Conditions: Periodontal Diseases, Periodontitis
Peri-implant Vitamin D and Cathelicidin (LL-37) Levels
Status: Completed · 33 participants · Altinbas University
Conditions: Peri-Implantitis and Peri-implant Mucositis
Cathelicidin LL-37 Levels in the GCF and the Saliva of Smokers and Non-smokers With Stage III,IV Periodontitis
Status: Completed · 60 participants · Cairo University
Conditions: Smoking Reduction
Efficacy of LL-37 Cream on Bacteria Colonization, Inflammation Response and Healing Rate of Diabetic Foot Ulcers
Status: Unknown · 40 participants · Fakultas Kedokteran Universitas Indonesia
Conditions: Diabetic Foot Ulcer
Salivary TAS, TOS, LL-37 and Dental Status in Passive Smoking Children
Status: Completed · 180 participants · Merve Erkmen Almaz
Conditions: Passive Smoking, Oxidative Stress, Dental Caries
Passive Smoking and LL-37 in Children
Status: Completed · 180 participants · Kırıkkale University
Conditions: Innate Immunity, Periodontal Health
Intratumoral Injections of LL37 for Melanoma
Status: Completed · 4 participants · M.D. Anderson Cancer Center
Conditions: Melanoma
Effects of Smoking and Vitamin D3 on the Levels of Human Cathelicidin Peptide LL-37
Status: Completed · 60 participants · Gazi University
Conditions: Periodontitis
Effects of Vitamin D and Omega-3 Fatty Acids on Infectious Diseases and hCAP18 (VITAL Infection)
Status: Active Not Recruiting · 25,874 participants · Brigham and Women's Hospital
Conditions: Infections, Human Cathelicidin Antimicrobial Peptide (hCAP-18)
Adverse event reports (FDA FAERS)
Not applicable: no licensed product contains this peptide, so it is not reported through FAERS. This is an absence of surveillance, not evidence of safety.
Source: ClinicalTrials.gov and openFDA. Updated automatically.
Looking for LL-37?
Source research-grade LL-37 from a trusted UK supplier — third-party tested with certificate of analysis.
View at SupplierFrequently Asked Questions
Questions to ask a qualified clinician about LL-37
These are starter questions you can adapt for a GP, specialist, pharmacist, or anti-doping advisor. The aim is to help you have a better-informed conversation — not to replace one.
- Is LL-37 a licensed UK medicine?
- What licensed treatments exist for the infection or wound concern I have?
- Why is mechanistic plausibility not the same as proven benefit here?
UK regulatory & safety context
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