LL-37

The 37-residue human cathelicidin host-defense peptide.

Human trialsPeptide research profile

Also known as: hCAP18-derived cathelicidin, CAP-18

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Dosing & scaling, explained

The 100 mcg twice-daily calculator row is not the regimen used in human wound trials, which applied topical LL-37 at defined concentrations. This is educational source context, not a protocol or recommendation.

How sourced amounts are organized

  1. Starting pointNot clinically establishedNo validated titration window

    There is no regulator-approved starting dose for this research use. A low-looking number is not automatically safe.

  2. Recorded preset100 mcg twice dailyCalculator library reference

    This is the range represented in the in-app protocol library. It describes the source record; it does not validate the regimen.

  3. Higher exposureNo systemic ceiling establishedRisk and uncertainty increase

    Higher exposure is not established as more effective. Human pharmacokinetic and long-term safety data may be absent.

Concentration applied to a wound (mg/mL) is not convertible to an injected whole-body dose using the calculator.

Patterns described in source material

  • Twice daily in the recorded preset

    The cadence represented by the recorded calculator presets.

  • Twice-weekly topical application in early wound trials

    Published experiments may use a different route, formulation, timing, or population and should not be treated as interchangeable.

  • No universal schedule

    No single schedule has been validated across products or research contexts.

Clinical context
  • 0.5-3.2 mg/mLTopical, twice weeklyFirst-in-human venous-ulcer trialNot a systemic dose

Human evidence is route-specific: 0.5 and 1.6 mg/mL topical solutions showed early signals, while later results were mixed.

Storage, handling and interpretation

Lyophilized material

Keep cold, dry, and protected from light according to the manufacturer certificate or validated lab SOP.

After reconstitution

Use sterile technique, refrigerate as validated, and avoid repeated freeze-thaw cycles.

Traceability

Record lot, concentration, preparation date, and the identity/purity documentation used by the lab.

Reported protocols for LL-37

What published studies and recent community write-ups report about amounts, timing and course length. 4 clinical, 1 preclinical and 2 community-reported rows, each linked to its source. These are descriptions of what others report, not instructions, and nothing here is medical advice.

ContextDoseFrequencyRouteCourseSource
Clinical4 rows
Phase I/IIa venous leg ulcer trial, dose-ranging34 adults with hard-to-heal venous leg ulcers recruited in Sweden0.5, 1.6 or 3.2 mg/mL applied to the wound bedTwice weeklyTopical, under compression dressings4 weeks of blinded treatment after a 3-week open-label placebo run-in, then 4 weeks of follow-upNot applicableWound Repair and Regeneration (PubMed)2014
Healing rate constants were about six times those of placebo at 0.5 mg/mL (p = 0.003) and three times at 1.6 mg/mL (p = 0.088), with mean ulcer area down 68% and 50% in those groups, while 3.2 mg/mL healed no faster than placebo. No local or systemic safety concern was recorded, and this inverted dose-response is the result that later write-ups quote most often.
Phase IIb HEAL LL-37 trial148 treated adults (149 randomized) with hard-to-heal venous leg ulcers at 15 sites in Poland and Sweden, mean age 67.6 and median ulcer duration 20.3 months0.5 or 1.6 mg/mLTwice weekly, timed to routine dressing changesTopical, combined with compression therapy13 weeks of blinded treatment after a 3-week placebo run-in, with follow-up to 4 monthsNot applicableWound Repair and Regeneration (PubMed)2021
Across the whole cohort the trial found no difference from placebo: an estimated 26.5% of target ulcers closed on 0.5 mg/mL against 25.3% on placebo. A post hoc analysis reported better healing in patients with large ulcers, both strengths were described as safe and well tolerated, and the 12 serious adverse events in 11 patients were all non-fatal; several authors were employees of the sponsor, Promore Pharma.
Diabetic foot ulcer cream trial25 adults aged 18-60 in Jakarta with uninfected or mildly infected diabetic foot ulcers (13 on LL-37, 12 on placebo)0.5 mg/mL LL-37 creamTwice weeklyTopical cream on the wound bed4 weeks, with wound measurement on days 7, 14, 21 and 28Not applicableArchives of Dermatological Research (PubMed)2023
The granulation index rose more in the LL-37 group at every weekly measurement, while the change in wound area favored LL-37 at days 7 to 21 and placebo at day 28 without reaching significance. One treated participant developed mild irritant dermatitis from wound exudate that settled once a foam dressing was added; the trial is small and single-city, and it is the only published human study outside the Swedish program.
Intratumoral melanoma study, phase I/II4 adults with metastatic melanoma and injectable skin lesions at MD Anderson Cancer Center (36 planned)250 mcg per tumor in the first cohort, 500 mcg per tumor in the secondOnce weekly, into 2 to 4 tumorsIntratumoral injectionUp to 8 weeksNot applicableClinicalTrials.gov2020
The study ran from 2015 to 2020 and closed after four patients, far short of its 36-patient design, so no optimal biological dose or response rate was established. The posted results list no serious adverse events and eight other event types; this is the only human injection study of LL-37 and it placed the peptide inside tumors, not under the skin.
Preclinical1 row
Rat sepsis modelsAdult male Wistar rats in three models of gram-negative sepsis, including cecal ligation and puncture1 mg/kgSingle doseIntravenousSingle treatment with survival and bacterial-count follow-upNot applicableAntimicrobial Agents and Chemotherapy (PubMed)2006
LL-37 at 1 mg/kg was compared with polymyxin B 1 mg/kg, imipenem 20 mg/kg and piperacillin 60 mg/kg; every agent reduced lethality and bacterial growth, LL-37 matched polymyxin B on antimicrobial and antiendotoxin measures, and plasma endotoxin was lower with LL-37 and polymyxin B than with the conventional antibiotics. This is the systemic animal study that injectable community pages lean on, and it has no human counterpart.
Community-reported2 rows
Community subcutaneous block100-250 mcg per day, with some write-ups quoting up to 500 mcgOnce daily, often 5 days on and 2 days offSubcutaneous from a 5 mg vial reconstituted with 2 mL bacteriostatic water (2.5 mg/mL, so 250 mcg is 10 units)2-4 weeksA break after each block; no length validatedCommunity resource2026
This protocol page, reviewed in August 2026, keeps the topical trial concentrations and the community subcutaneous figures on separate tabs and states that no human trial has tested injected LL-37, so the subcutaneous structure is unverified practice. It plans vial counts around a 250 mcg daily draw and advises against reconstituting more than can be used quickly because the peptide degrades in solution.

How a course is commonly described

  1. Run-in: 3 weeksClinical

    Both venous leg ulcer trials began with three weeks of placebo under standard compression, so that only ulcers still failing to heal on good wound care were randomized. This selection step is part of why the trial populations are described as hard-to-heal.

  2. Weeks 1-4: twice-weekly topical dosingClinical

    The first-in-human study applied 0.5, 1.6 or 3.2 mg/mL to the wound twice a week for four weeks at dressing changes. The lowest concentration healed fastest and the highest was no better than placebo, which is the dose-response every later source refers back to.

  3. Weeks 5-13: extended courseClinical

    The phase IIb trial extended twice-weekly 0.5 or 1.6 mg/mL applications to 13 weeks with compression and followed patients to four months. Closure rates were close to placebo across the whole cohort, with a possible benefit confined to large ulcers in a post hoc analysis, and tolerability stayed good through the longer exposure.

  4. Community injectable blockCommunity-reported

    Community write-ups describe a 2-4 week block of 100-250 mcg subcutaneous injections once a day, often five days on and two off, from a vial mixed at 2.5 mg/mL. No human study has tested this route, dose or duration, and the pages that list it say so.

  5. BreakCommunity-reported

    Community cycles pause after each block, a convention carried over from other research peptides rather than anything specific to LL-37. One vendor guide argues that the inverted dose-response in the ulcer trial makes short, low-dose and non-escalating use the only defensible reading of the data.

  • Every human course on record is topical or intratumoral and clinician-administered. No pharmacokinetic, dose-finding or safety study of subcutaneous LL-37 exists, and the FDA's published assessment flags a risk of immunogenicity for certain routes, complexities with peptide-related impurities, and nonclinical signals of protumorigenic activity and effects on male reproduction.
  • The dose-response in the 34-patient ulcer trial was inverted: the lowest concentration healed fastest and the highest was no better than placebo. That finding, plus the peptide's concentration-dependent switch between anti-inflammatory and pro-inflammatory signaling, is the main argument community pages make against longer or higher injectable courses.
  • LL-37 has no approval anywhere. It left the FDA's active Category 2 list around April 22, 2026 only because the nomination was withdrawn, is not on the 503A bulks list, and is due for Pharmacy Compounding Advisory Committee discussion before the end of February 2027; it is not named on the WADA list, though a 2026 editorial notes it would fall under the S0 catch-all for unapproved substances.
Sources for this section (10)
  1. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trialWound Repair and Regeneration (PubMed)2014Clinical
  2. Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trialWound Repair and Regeneration (PubMed)2021Clinical
  3. Efficacy of LL-37 cream in enhancing healing of diabetic foot ulcer: a randomized double-blind controlled trialArchives of Dermatological Research (PubMed)2023Clinical
  4. Intratumoral Injections of LL37 for Melanoma (NCT02225366)ClinicalTrials.gov2020Clinical
  5. LL-37 protects rats against lethal sepsis caused by gram-negative bacteriaAntimicrobial Agents and Chemotherapy (PubMed)2006Preclinical
  6. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety RisksU.S. Food and Drug Administration2026Clinical

Plus 4 community resources (dosing guides, forum threads and vendor write-ups), reported above but not linked.

Overview

LL-37 is the only cathelicidin antimicrobial peptide that humans produce: a 37-residue, strongly cationic alpha-helix that proteases release from the C-terminus of the precursor protein hCAP18 (also written CAP-18), which neutrophils carry in their granules and skin, airway and gut epithelium secrete. It kills bacteria by disrupting their membranes and also signals to immune cells, which is why it is studied for wound healing, infection and cancer, and why its effects can switch from anti-inflammatory to pro-inflammatory as the concentration rises. The only human trials applied it topically to chronic venous leg ulcers (a 34-patient dose-ranging study and the 148-patient phase IIb HEAL LL-37 trial sponsored by Promore Pharma under the INN ropocamptide), tested a 0.5 mg/mL cream on 25 diabetic foot ulcers, and injected it into melanoma nodules in four patients; no human study of injected systemic LL-37 has been published. It is approved nowhere, and in April 2026 the FDA moved cathelicidin LL-37 from its active Category 2 compounding list to the withdrawn-nomination table because the nominator pulled out, while keeping its written assessment that the peptide may be immunogenic by some routes and protumorigenic in some tissues.

What researchers are exploring

These themes describe recurring questions in published research. They are not claims of effectiveness or recommendations for use.

  • 1

    Innate host defense

    Laboratory studies cover bacteria, fungi, viruses, biofilms, and membrane interactions.

  • 2

    Immune modulation

    LL-37 can act in pro- or anti-inflammatory directions depending on context.

  • 3

    Wound healing

    Topical trials evaluate hard-to-heal venous and diabetic ulcers.

  • 4

    Cancer biology

    Expression and signaling can be context-dependent and potentially bidirectional.

What the current evidence can support

Study models remain visible so laboratory and animal findings are not mistaken for established human outcomes.

  • Human

    Topical venous-ulcer trials

    A small phase I/II trial showed dose-dependent healing signals; a larger phase IIb study was negative overall.

  • Human

    Route-specific wound research

    Clinical evidence concerns local topical concentrations, not systemic injection.

  • Review

    Pleiotropic biology

    Reviews emphasize antimicrobial, chemotactic, angiogenic, and inflammatory effects that vary by environment.

Amounts recorded for LL-37

These amount records are independent from vial strength, reconstitution volume and measuring device. A recorded source is not the same as study backing, and these values are not recommendations.

  • 1
    Recorded referenceSign in for schedule, duration and source context.
    100 mcg
  • 2
    Dose · upper endpointSign in for schedule, duration and source context.
    500 mcg

Chemistry identifiers

Sequence, synonyms and registry identifiers as recorded in PubChem, the National Library of Medicine's open chemistry database. Formula, mass and CAS number are summarized at the top of the page.

Sequence

Leu-Leu-Gly-Asp-Phe-Phe-Arg-Lys-Ser-Lys-Glu-Lys-Ile-Gly-Lys-Glu-Phe-Lys-Arg-Ile-Val-Gln-Arg-Ile-Lys-Asp-Phe-Leu-Arg-Asn-Leu-Val-Pro-Arg-Thr-Glu-Ser

Also listed as

Ropocamptide (INN), CAP-18, hCAP18/LL-37, Cathelicidin LL-37, FA-LL-37, UNII 3DD771JO2H, CHEMBL530345, LL 37

InChIKey

POIUWJQBRNEFGX-XAMSXPGMSA-N

Origin / design

Proteolytic product of the hCAP18 cathelicidin precursor

IUPAC name

(4S)-5-[[(2S)-6-amino-1-[[(2S,3S)-1-[[2-[[(2S)-6-amino-1-[[(2S)-1-[[(2S)-1-[[(2S)-6-amino-1-[[(2S)-1-[[(2S,3S)-1-[[(2S)-1-[[(2S)-5-amino-1-[[(2S)-1-[[(2S,3S)-1-[[(2S)-6-amino-1-[[(2S)-1-[[(2S)-1-[[(2S)-1-[[(2S)-1-[[(2S)-4-amino-1-[[(2S)-1-[[(2S)-1-[(2S)-2-[[(2S)-5-carbamimidamido-1-[[(2S,3R)-1-[[(2S)-4-carboxy-1-[[(1S)-1-carboxy-2-hydroxyethyl]amino]-1-oxobutan-2-yl]amino]-3-hydroxy-1-oxobutan-2-yl]amino]-1-oxopentan-2-yl]carbamoyl]pyrrolidin-1-yl]-3-methyl-1-oxobutan-2-yl]amino]-4-methyl-1-oxopentan-2-yl]amino]-1,4-dioxobutan-2-yl]amino]-5-carbamimidamido-1-oxopentan-2-yl]amino]-4-methyl-1-oxopentan-2-yl]amino]-1-oxo-3-phenylpropan-2-yl]amino]-3-carboxy-1-oxopropan-2-yl]amino]-1-oxohexan-2-yl]amino]-3-methyl-1-oxopentan-2-yl]amino]-5-carbamimidamido-1-oxopentan-2-yl]amino]-1,5-dioxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-3-methyl-1-oxopentan-2-yl]amino]-5-carbamimidamido-1-oxopentan-2-yl]amino]-1-oxohexan-2-yl]amino]-1-oxo-3-phenylpropan-2-yl]amino]-4-carboxy-1-oxobutan-2-yl]amino]-1-oxohexan-2-yl]amino]-2-oxoethyl]amino]-3-methyl-1-oxopentan-2-yl]amino]-1-oxohexan-2-yl]amino]-4-[[(2S)-6-amino-2-[[(2S)-2-[[(2S)-6-amino-2-[[(2S)-2-[[(2S)-2-[[(2S)-2-[[(2S)-2-[[2-[[(2S)-2-[[(2S)-2-amino-4-methylpentanoyl]amino]-4-methylpentanoyl]amino]acetyl]amino]-3-carboxypropanoyl]amino]-3-phenylpropanoyl]amino]-3-phenylpropanoyl]amino]-5-carbamimidamidopentanoyl]amino]hexanoyl]amino]-3-hydroxypropanoyl]amino]hexanoyl]amino]-5-oxopentanoic acid

Limitations and unknowns

Important limitations

  • LL-37 can be cytotoxic or pro-inflammatory at some concentrations and contexts.
  • Proteolysis and formulation strongly influence local activity.
  • Topical mg/mL trial concentrations cannot validate injectable microgram dosing.
  • A calculator preset is a recorded research convention, not a recommendation or evidence of clinical benefit.
  • Identity, purity, sterility, and stability can vary substantially outside regulated manufacturing.
  • Route, formulation, and population can make results from one study inapplicable to another use.

Sources

3 curated references, each with its journal, year and study model, plus 4 community resources reported but not linked.

  1. A comprehensive summary of LL-37, the factotum human cathelicidin peptideCellular Immunology2013Review
  2. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcersWound Repair and Regeneration2014Human
  3. Evaluation of LL-37 in healing of hard-to-heal venous leg ulcersWound Repair and Regeneration2021Human

Guides that go deeper