LL-37
Also known as: Cathelicidin, hCAP18 fragment, CAP-18
LL-37 (also called Cathelicidin or hCAP18 fragment) is a research peptide in the Cathelicidin class. LL-37 is the only human cathelicidin, released by proteolytic cleavage of the hCAP18 precursor stored in neutrophil granules and produced by epithelial cells.
For research use only.
Key Facts
- CAS
- 154947-66-7
- Molecular Weight (MW)
- 4493 Da
- Half-life
- ~1-2 hours
- FDA status
- Not Approved
- Evidence level
- Limited Human Evidence
- Human dose established
- Yes
- Administration Route
- Topical (both controlled wound-healing trials) · Intratumoral (phase 1 melanoma programme) · Oral, as a recombinant Lactococcus lactis product rather than the free peptide
- Frequency
- Varies by study: daily to twice-weekly topical application, or weekly intratumoral injection
- Last updated
- Sep 6, 2026
- Reviewed
- Aug 30, 2026
- Targets
- Microbial membranesInnate immune receptors
Vendor price snapshot
Each vendor counts once, at the median price per mg of its own listings; the typical range is the middle half of vendors. From public vendor listings collected between Dec 2025 and Sep 2026, so confirm the live price on the vendor site. Peptide Library does not sell peptides.
- Vendors listing this peptide
- 17
- Listed offers
- 18
- Median price per mg
- $14.50/mg
- Typical $10.75–$15.99/mg
Research summary
Human host-defense peptide (cathelicidin) with antimicrobial and immunomodulatory activity. Not FDA-approved as a drug; excess LL-37 is implicated in rosacea/psoriasis biology.
Peptide Library's LL-37 profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.
LL-37 dosage chart
LL-37 has published human dosing, but only for topical and intralesional use, and the dosing is expressed as a concentration applied to a wound rather than as a systemic dose. The largest study, the phase IIb HEAL LL-37 trial, applied 0.5 or 1.6 mg/mL topically to hard-to-heal venous leg ulcers in 148 patients; both strengths were safe and well tolerated, and neither improved healing over placebo on the primary analysis. No human study has given LL-37 by subcutaneous injection, which is how it is generally sold.
| Human dosing established | Yes |
|---|---|
| Route | Topical (both controlled wound-healing trials) · Intratumoral (phase 1 melanoma programme) · Oral, as a recombinant Lactococcus lactis product rather than the free peptide |
| Frequency | Varies by study: daily to twice-weekly topical application, or weekly intratumoral injection |
| Duration studied | 4 weeks in the diabetic foot ulcer trial; longer in the venous leg ulcer programme |
| Evidence level | Limited Human Evidence |
| Last reviewed | 2026-09-05 |
Research-reported dosing
Doses as studied, one row per regimen. Different trials used different regimens; they are listed separately rather than averaged.
| Study / context | Population | Dose | Route | Frequency | Duration | Outcome studied | Source |
|---|---|---|---|---|---|---|---|
| HEAL LL-37 — phase IIb, completed, publishedClinical trial · Phase IIb double-blind randomised placebo-controlled trial, published with results | 148 patients with hard-to-heal venous leg ulcers, mean age 67.6 years | 0.5 mg/mL or 1.6 mg/mL, applied topically to the wound alongside compression therapy | Topical | Per the trial protocol, in combination with compression therapy | Full trial course; median ulcer duration at entry was 20.3 months | Wound healing. The primary analysis found no significant improvement over placebo; a post-hoc subgroup with wounds of at least 10 cm2 did show improvement. Both strengths were safe and well tolerated. | Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial. Wound Repair Regen. 2021. |
| Diabetic foot ulcer cream — randomised double-blind trial, publishedClinical trial · Randomised double-blind controlled trial, registered as NCT04098562 | Adults with diabetic foot ulcer with mild infection | LL-37 cream; the report does not state the concentration of the cream | Topical | Twice a week | 4 weeks, with wounds measured on days 7, 14, 21 and 28 | Granulation index improved consistently versus placebo. IL-1 alpha, TNF-alpha and aerobic bacterial colonisation were not significantly reduced. | Efficacy of LL-37 cream in enhancing healing of diabetic foot ulcer: a randomized double-blind controlled trial. Arch Dermatol Res. 2023. |
| NCT04098562 — phase 2, registry entry for the diabetic foot ulcer creamClinical trial · Registered phase 2 trial; registry status listed as unknown | Planned 40 participants with diabetic foot ulcer | LL-37 cream; the registry record does not disclose the concentration | Topical | — | — | Bacterial colonisation, inflammation response and wound healing | NCT04098562 — Efficacy of LL-37 Cream on Bacteria Colonization, Inflammation Response and Wound Healing in Diabetic Foot Ulcer |
| Intratumoral LL-37 in melanoma — phase 1 programme, toxicity case reportClinical trial · Case report of dermatologic toxicity arising within a phase 1 clinical trial | Patient with stage IIIC cutaneous melanoma, within a phase 1 trial of intratumoral LL-37 | Weekly intratumoral injection; the amount per injection is not stated in this report | Intratumoral | Once weekly | 8 injections | Injected lesions shrank. Widespread verrucous and keratoacanthoma-like skin lesions developed around day 45 and resolved within 2 months of stopping treatment. | Dermatologic toxicity from novel therapy using antimicrobial peptide LL-37 in melanoma: A detailed examination of the clinicopathologic features. J Cutan Pathol. 2018. |
Preclinical and analog research
Not human dosing evidence. Listed for completeness and never extrapolated to a human dose.
| Study / context | Population | Dose | Route | Frequency | Duration | Outcome studied | Source |
|---|---|---|---|---|---|---|---|
| Oral LL-37 for COVID-19 — delivered by a live bacterial vector, not as the peptideClinical trial · Open-label randomised placebo-controlled single-centre trial of a live bacterial vector expressing LL-37, not of the peptide itselfStudied an analog, not LL-37 itself | 238 adult inpatients with Omicron BA.5.1.3 infection | Recombinant LL-37 Lactococcus lactis given by mouth; the peptide amount delivered is not quantified in the report | Oral | — | From confirmation of infection through hospitalisation | Shorter time to SARS-CoV-2 RNA negative conversion (9.80 vs 14.04 days) when started within 6 days. No severe adverse events reported. | Efficacy and safety of Oral LL-37 against the Omicron BA.5.1.3 variant of SARS-COV-2: A randomized trial. J Med Virol. 2023. |
Where sources disagree
- LL-37 is sold as a lyophilised vial for subcutaneous injection, commonly with protocols in the hundreds of micrograms daily. No human study has given LL-37 subcutaneously. Every published human dose is topical, intralesional or delivered by an engineered bacterium, and a wound concentration in mg/mL does not convert into an injected microgram dose.
- The largest and best-controlled human study, the phase IIb HEAL LL-37 trial in 148 patients, did not meet its primary endpoint: LL-37 was no better than placebo for healing across the whole cohort. The positive finding was a post-hoc subgroup analysis in patients with wounds of at least 10 cm2, which the authors themselves describe as warranting a further adequately powered study.
- The oral COVID-19 trial is frequently cited as evidence for oral LL-37. The product studied was Lactococcus lactis engineered to express LL-37, not the peptide, and the amount of peptide delivered was not quantified — so it supports nothing about swallowing or dissolving LL-37 itself.
- The compound in the venous leg ulcer programme is being developed under the non-proprietary name ropocamptide. Material sold as research LL-37 is not that product and has not been through its manufacturing or characterisation.
Reconstitution
Common research vial sizes: 5 mg, 10 mg.
| Vial | Bacteriostatic water | Concentration | Per 0.01 mL |
|---|---|---|---|
| 5 mg | 2 mL | 2.5 mg/mL | 25 mcg per 0.01 mL |
| 10 mg | 2 mL | 5 mg/mL | 50 mcg per 0.01 mL |
These figures are arithmetic only — they convert a vial and a volume into a concentration. They are not a recommendation to take any dose.
Calculate reconstitution & dose →Handling & administration
- Reconstitution Guide
- 3 mL BAC for 5 mg vial
- Injection Sites
- AbdomenNear site
- Concentration Example
- 5 mg / 3 mL = ~1.67 mg/mL
- Timing Notes
- Morning or near affected area
- Expected Onset
- 1-3 days
How to reconstitute LL-37
- Check the vial size and diluent volume. The profile example for LL-37 is: 3 mL BAC for 5 mg vial.
- Swab both vial stoppers and draw the bacteriostatic water into a sterile syringe.
- Add the water slowly down the inside wall of the peptide vial so it does not jet onto the powder, then swirl gently until the solution is clear. Do not shake.
- Record the resulting concentration: 5 mg / 3 mL = ~1.67 mg/mL.
- Label the vial with the date and concentration, refrigerate it (see Storage & stability below), and use the calculator preset to convert a dose in mcg into syringe units.
Sequence & molecular data
| Amino acid sequence | LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES |
|---|---|
| Molecular formula | C205H340N60O53 |
| Molecular weight | 4493 Da |
| CAS number | 154947-66-7 |
| Half-life | ~1-2 hours |
| Appearance | White lyophilized powder |
| Formulation | Lyophilized Powder |
| PubChem CID | 16198951 |
| FDA UNII | 3DD771JO2H |
| ChEMBL | CHEMBL530345 |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
LL-37 is the only human cathelicidin, released by proteolytic cleavage of the hCAP18 precursor stored in neutrophil granules and produced by epithelial cells. It folds into an amphipathic helix with cationic and hydrophobic faces on opposite sides, which lets it bind the anionic surface of bacterial membranes and permeabilise them — a physical mechanism that makes classical resistance difficult. Beyond direct antimicrobial action it is an immune signalling molecule: it neutralises lipopolysaccharide, modulates Toll-like receptor responses, and promotes chemotaxis and wound angiogenesis. Its transcription is driven by vitamin D through a response element in the CAMP gene promoter, which links vitamin D status to innate immune capacity. Sustained overexpression is proinflammatory and has been implicated in rosacea and psoriasis.
Origin
C-terminal fragment of hCAP18.
Targets
Studies
- Human cathelicidin antimicrobial protein 18 (hCAP18/LL-37) is increased in foetal membranes and myometrium after spontaneous labour and delivery
- Role of antimicrobial peptide cathelicidin in thrombosis and thromboinflammation
- Antibiofilm properties of cathelicidin LL-37: an in-depth review
- The LL-37 domain: A clue to cathelicidin immunomodulatory response?
- Renovation as innovation: Repurposing human antibacterial peptide LL-37 for cancer therapy
Regulatory & research status
LL-37 is not an FDA-approved product. It is sold for laboratory research and has no approved medical use.
| FDA status | Not Approved |
|---|---|
| Availability | Research-Only |
| WADA (sport) | Unknown / Not Listed |
| Library classification | Research-Only |
Benefits
LL-37 side effects
LL-37 has only limited human data, so the list below is incomplete and its side-effect profile is not well established.
Side Effects
- Proinflammatory at high local levels
- Cytotoxicity in vitro at high dose
Contraindications
- Autoimmune flares
Stacking
Common stacking partners
Combinations that include LL-37, with the proposed rationale, an evidence grade and what is not established, are catalogued in the peptide stacks directory.
Storage & stability
Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.
Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.
Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.
Cosmetic peptides in this library are formulated into topical products; follow the product label rather than the reconstitution guidance above.
Read the full guide: how to store peptides before and after reconstitution →
Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.
LL-37: frequently asked questions
What is LL-37?
Human host-defense peptide (cathelicidin) with antimicrobial and immunomodulatory activity. Not FDA-approved as a drug; excess LL-37 is implicated in rosacea/psoriasis biology.
How does LL-37 work?
LL-37 is the only human cathelicidin, released by proteolytic cleavage of the hCAP18 precursor stored in neutrophil granules and produced by epithelial cells. It folds into an amphipathic helix with cationic and hydrophobic faces on opposite sides, which lets it bind the anionic surface of bacterial membranes and permeabilise them — a physical mechanism that makes classical resistance difficult.
Is LL-37 FDA approved?
No. LL-37 is not approved by the FDA for any indication and is categorised as research-only. It has not been reviewed for safety or efficacy as a medicine, and published research should be read as investigation rather than established use.
What is the half-life of LL-37?
Reported half-life for LL-37 is ~1-2 hours. Half-life describes how long the compound persists in circulation, not how long any effect lasts, and published figures vary with route of administration, formulation and the population studied.
What is the amino acid sequence of LL-37?
LL-37 has the sequence LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES. Its molecular formula is C205H340N60O53.
What peptides are similar to LL-37?
Compounds most often compared with LL-37 include KPV, Thymosin Alpha-1, Tuftsin and Bonomarlot. They are grouped by shared mechanism or research area rather than by equivalence, and their regulatory status and evidence base differ.
References
- Human cathelicidin antimicrobial protein 18 (hCAP18/LL-37) is increased in foetal membranes and myometrium after spontaneous labour and delivery — J Reprod Immunol, 2015External reference
- Role of antimicrobial peptide cathelicidin in thrombosis and thromboinflammation — Front Immunol, 2023External reference
- Antibiofilm properties of cathelicidin LL-37: an in-depth review — World J Microbiol Biotechnol, 2023External reference
- The LL-37 domain: A clue to cathelicidin immunomodulatory response? — Peptides, 2023External reference
- Renovation as innovation: Repurposing human antibacterial peptide LL-37 for cancer therapy — Front Pharmacol, 2022External reference
Related research, comparisons & guides
Related peptides
Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Sep 6, 2026 · Version 2
This LL-37 profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error
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