Skip to content

For Research & Educational Discussion Only. Not Medical Advice

BaselineForum

LL-37

Human cathelicidin antimicrobial peptide

Also known as Cathelicidin, hCAP-18, CAMP

The only human cathelicidin, with a very large basic-science literature and a small clinical one. Its dual role, antimicrobial and immunomodulatory, is also why its effects are hard to predict.

Guide updated Sep 2, 2026Literature checked Sep 2, 20262 curated studies37 literature recordsBaseline editorial
SequenceLLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES

Overview

In shortThe active piece of the only antimicrobial peptide of its kind humans make. It is part of your built-in immune defence and does two jobs that are not obviously related: it kills microbes by tearing their membranes, and it steers the immune response. A real clinical programme exists, mostly in wound healing, but it is small next to how much is known in a dish.

LL-37 is the active fragment of hCAP-18, the only cathelicidin found in humans. It is part of innate immunity, expressed by neutrophils and epithelial cells, and it does two jobs that are not obviously related: it kills microbes directly by disrupting membranes, and it modulates the immune response by recruiting cells and altering cytokine signalling.

The literature is large, more than two thousand papers, and overwhelmingly mechanistic and preclinical. There is a real clinical programme, mostly in wound healing, but it is small relative to how much is known about the molecule in a dish.

Mechanism

In shortIt kills bacteria by sticking to their outer membranes and punching holes in them. That is a physical mechanism rather than a receptor one, which is why resistance develops differently from resistance to normal antibiotics. Separately it recruits immune cells and can be either calming or inflammatory depending on tissue and concentration.

Direct antimicrobial activity through electrostatic interaction with negatively charged bacterial membranes, causing permeabilisation. This is a physical mechanism rather than a receptor-mediated one, which is why resistance to it develops differently from resistance to conventional antibiotics.

Separately, immunomodulation via formyl peptide receptor 2 and other pathways: chemotaxis of neutrophils, monocytes and T cells, effects on wound angiogenesis, and both pro- and anti-inflammatory activity depending on context and concentration.

That context dependence is the honest caveat. A molecule that is anti-inflammatory in one tissue at one concentration and pro-inflammatory in another is not well described by either label.

Evidence

In shortExtensive lab and animal work. Clinical work exists and is registered, concentrated in leg ulcers and hard-to-heal wounds, at early stage and small scale. Raised levels of it have also been described in several inflammatory and autoimmune conditions including psoriasis, where it appears to help drive the disease. That is worth knowing before treating it as straightforwardly beneficial.

Extensive in vitro and animal work. Clinical work exists and is registered, concentrated in venous leg ulcers and hard-to-heal wounds, at early phase and small scale.

Elevated LL-37 has also been described in several inflammatory and autoimmune conditions including psoriasis, where it appears to act as an autoantigen. That is a finding worth knowing before treating it as straightforwardly beneficial: the same peptide is implicated in driving disease in some contexts.

Safety

In shortHuman safety data is limited to small early trials and to use on the skin. Injecting it is not well characterised. The specific concerns follow from the biology: it can damage your own cells and red blood cells at higher concentrations, because the membrane-punching mechanism is not perfectly selective, plus the autoimmune association above.

Human safety data is limited to the small early trials and to topical use. Systemic administration is not well characterised.

The specific concerns that follow from the biology: haemolysis and cytotoxicity to host cells at higher concentrations, since the membrane-disrupting mechanism is not perfectly selective, and the autoimmune association above.

Regulatory status

In shortNot approved for anything. Investigational in registered trials, and sold elsewhere as research-use-only material. Synthetic versions vary in purity and in whether they are the full sequence or a fragment, and fragments do not necessarily do what the parent does.

Not approved for any indication. Investigational in registered trials, sold elsewhere as research-use-only material.

Synthetic peptides sold under this name vary in purity and in whether the sequence is the full 37 residues or a fragment, and fragments do not necessarily share the parent's activity.

The literature

2 studies indexed. Findings and limitations get equal weight, on purpose.

Always check the primary source

Members area

The LL-37 literature needs an account

Everything above is free to read. What an account opens is the evidence underneath it: 2 studies with their limitations, and the regimen each trial actually reported.

  • Every study, with what it found and what it cannot show
  • The limitations, given the same weight as the findings
  • The dose each named trial administered, where recorded
Create a free accountI already have one

Free to create. A membership is separate, and you can decide about that later.

Reading is free, an account is not the same as paying. 43 compound guides, every study with its limitations written underneath, and the regimens those trials actually used. A free account opens all of it. A membership is a separate decision, and it opens the forum. What membership costs.

The wider literature

16 indexed papers and 21 registered trials mentioning LL-37, straight from PubMed and ClinicalTrials.gov. 5 of 21 administer it; the rest measure it. These have not been read by us. Unlike the studies above, they carry no findings and no limitations written by anyone here, because writing either would mean claiming a reading nobody has done. They are a starting point for yours.

Registered trials (21)

  1. Using the Babble Boot Camp© Speech Therapy Approach With Babies Born Prematurely

    Murdoch Childrens Research Institute2026NCT07738224

    interventionalnanot yet recruitingn=86

  2. Evaluation of 25(OH)D3 and LL-37 Levels in Periimplant Sulcus Fluid

    Recep Tayyip Erdogan University2025NCT07280754

    observationalnot yet recruitingn=72

  3. Life Skills Boot Camp Study (LEVELUP2)

    University of Cyprus2023NCT05713747

    observationalunknownn=120

  4. Cathelicidin LL-37 Relation to Potentially Malignant Lesions

    Fayoum University2023NCT06219330

    observationalcompletedn=45

  5. Chlorhexidine and Essential Oil Mouthwashes on Human Beta-Defensin 2 (hbD2) and Kathelicidin (LL-37) Saliva Levels

    Istanbul Medeniyet University2021NCT04946617

    observationalunknownn=120

  6. Peri-implant Vitamin D and Cathelicidin (LL-37) Levels

    Altinbas University2021NCT06867250

    observationalcompletedn=33

  7. The Role of Anti-inflammatory Cytokines and Antimicrobial Peptide LL-37 Biomarkers in the Treatment of Periodontal Disease.

    Universidad Rey Juan Carlos2021NCT04404335

    observationalcompletedn=60

  8. Cathelicidin LL-37 Levels in the GCF and the Saliva of Smokers and Non-smokers With Stage III,IV Periodontitis

    Cairo University2021NCT04861493

    observationalcompletedn=60

  9. Association of Cathelicidin and Vitamin D Levels With the Category and Course of COPD

    Karaganda Medical University2020NCT05431218

    interventionalphase4completedn=120

  10. Efficacy of LL-37 Cream on Bacteria Colonization, Inflammation Response and Healing Rate of Diabetic Foot Ulcers

    Fakultas Kedokteran Universitas Indonesia2019NCT04098562

    interventionalphase2unknownn=40

  11. Effect of High-Dose Vitamin D3 in Smokers and Non-Smokers With and Without HIV

    Emory University2018NCT03270709

    interventionalphase1terminatedn=7

  12. FreeStyle Libre FGM During Summer Camp for Children With Type 1 Diabetes

    University of Ljubljana, Faculty of Medicine2017NCT03182842

    interventionalnacompletedn=45

  13. Salivary TAS, TOS, LL-37 and Dental Status in Passive Smoking Children

    Merve Erkmen Almaz2016NCT04292548

    observationalcompletedn=180

  14. Evaluation of the Inhibitory Effects of Topical Ivermectin on Markers of Rosacea Specific Inflammation.

    University of California, San Diego2016NCT02806414

    interventionalphase1phase2completedn=25

  15. Passive Smoking and LL-37 in Children

    Kırıkkale University2016NCT03639376

    observationalcompletedn=180

  16. Cathelicidin and Vitamin D: Impact on Populations At-Risk and With COPD

    University of North Carolina, Chapel Hill2015NCT02464059

    interventionalphase2completedn=23

  17. Effects of Smoking and Vitamin D3 on the Levels of Human Cathelicidin Peptide LL-37

    Gazi University2011NCT03923218

    observationalcompletedn=60

  18. Effects of Aminocaproic Acid (ACA) on Rosacea-specific Inflammation

    University of California, San Diego2011NCT01398280

    interventionalearly_phase1completedn=15

  19. Effect of Pimecrolimus Cream on Cathelicidin Levels in Subjects With Eczema

    University of California, San Diego2009NCT00946478

    interventionalnacompletedn=40

  20. Vitamin D in Active Tuberculosis (TB) Study

    Atlanta VA Medical Center2008NCT00788320

    interventionalnawithdrawnn=0

  21. Comparison of Cathelicidin Expression in Skin and Saliva in Patients With Atopic Dermatitis and Psoriasis

    National Institute of Allergy and Infectious Diseases (NIAID)2005NCT00407979

    observationalcompletedn=80

Papers (16)

  1. Immune Modulatory Effects of Vitamin D on Herpesvirus Infections.

    Galdo-Torres D, et al.International journal of molecular sciences2025PMID 40004230

    journal articlereview

  2. Cathelicidin regulates goblet cell mucus secretion and mucus-associated proteins in Citrobacter rodentium-induced colitis.

    Mirzadzare N, et al.Gut microbes2025PMID 40735968

    journal articleresearch support, non-u.s. gov't

  3. Vitamin D triggers hCAP18/LL-37 production: Implications for LL-37-induced human osteoblast cytotoxicity.

    Aidoukovitch A, et al.Biochemical and biophysical research communications2024PMID 38642493

    journal articleresearch support, non-u.s. gov't

  4. Antibiofilm properties of cathelicidin LL-37: an in-depth review.

    Memariani H, et al.World journal of microbiology & biotechnology2023PMID 36781570

    reviewjournal article

  5. Role of antimicrobial peptide cathelicidin in thrombosis and thromboinflammation.

    Zhang Q, et al.Frontiers in immunology2023PMID 37090695

    journal articlereviewresearch support, non-u.s. gov't

  6. Dissecting the relationship between antimicrobial peptides and mesenchymal stem cells.

    Silva-Carvalho AÉ, et al.Pharmacology & therapeutics2022PMID 34637839

    journal articlereviewresearch support, non-u.s. gov't

  7. LL-37, a Multi-Faceted Amphipathic Peptide Involved in NETosis.

    Radic M, et al.Cells2022PMID 35954305

    editorial

  8. Cathelicidin LL-37 in Health and Diseases of the Oral Cavity.

    Tokajuk J, et al.Biomedicines2022PMID 35625823

    journal articlereview

  9. Psoriasis and Antimicrobial Peptides.

    Takahashi T, et al.International journal of molecular sciences2020PMID 32947991

    journal articlereview

  10. Antiviral Activities of Human Host Defense Peptides.

    Brice DC, et al.Current medicinal chemistry2020PMID 31385762

    journal articlereview

  11. Nanoantibiotics containing membrane-active human cathelicidin LL-37 or synthetic ceragenins attached to the surface of magnetic nanoparticles as novel and innovative therapeutic tools: current status and potential future applications.

    Wnorowska U, et al.Journal of nanobiotechnology2020PMID 31898542

    journal articlereview

  12. Cathelicidins Modulate TLR-Activation and Inflammation.

    Scheenstra MR, et al.Frontiers in immunology2020PMID 32582207

    journal articleresearch support, non-u.s. gov'treview

  13. Cathelicidin LL-37 (an antimicrobial peptide)-induced colistin dependence in Acinetobacter baumannii.

    Lee JY, et al.Diagnostic microbiology and infectious disease2020PMID 32019695

    journal article

  14. Cationic antimicrobial peptide resistance mechanisms of streptococcal pathogens.

    LaRock CN, et al.Biochimica et biophysica acta2015PMID 25701232

    journal articleresearch support, n.i.h., extramuralresearch support, non-u.s. gov'treview

  15. The human cathelicidin hCAP-18.

    Sørensen OEDanish medical bulletin2005PMID 16009068

    journal articlereview

  16. Cathelicidins, multifunctional peptides of the innate immunity.

    Zanetti MJournal of leukocyte biology2004PMID 12960280

    journal articleresearch support, non-u.s. gov'treview

Discussion

LL-37 has its own forum, split by the same six categories as the rest of the site.

All threads
Research & Literature1Peptide Science0Experiences & Logs0Protocol Discussion0Safety & Harm Reduction0General Community0
Research & LiteratureDiscussion

Some of the LL-37 trials stopped early. That is data too

LL 37 is a Human cathelicidin antimicrobial peptide. 2 of 28 records administer it, and at l…

Members only. Join to read the rest

@baselineAdmin000

Membership

Peptides is free. The argument is for members.

The guide above is open to everyone, and the literature underneath it opens with a free account. That is the educational half of this site. Reading and joining the discussion around LL-37, and every other entry, is what membership pays for.

Unlock membershipSign in

From $3.33 a month, billed annually. Cancel anytime.

For Research & Educational Discussion Only. Not Medical Advice

This guide is educational reference material compiled from published literature. It is not medical advice, not a recommendation, and not a substitute for a clinician who knows your history. Nothing here should be used to make a decision about your own health without one.

Talk to a licensed healthcare professional.