Peptide Health Lab

Immune & defense

LL-37

FOR RESEARCH PURPOSES ONLY

Also known as: Cathelicidin LL-37, Ropocamptide

Regulatory status
Research only
Evidence grade
Anecdotal reports only

Last reviewed September 1, 2026 · 17 sources

What LL-37 is and how it works

LL-37 is a peptide the human body already makes. It is 37 amino acids long, it begins with two leucines, and it is the cleaved carboxy-terminal fragment of hCAP18, the protein encoded by the CAMP gene — the only cathelicidin humans have. It was cloned from a human bone-marrow library in 1995 and named FALL-39 after its first four residues — a 39-residue peptide, on a processing site the authors postulated at the time — with the clone encoding a cathelin-like precursor protein of 170 amino acids and expression detected mainly in bone marrow and testis.[1] The name LL-37 belongs to the 37-residue mature peptide the cleavage actually yields, and it is the name used throughout the later literature and on this page.

That paragraph contains the first identity boundary this page has to hold. hCAP18 is the precursor; LL-37 is the mature peptide released from it. They are measured together in much of the literature, written as hCAP18/LL-37, and they are not the same molecule. The second boundary matters more. The mouse does not make LL-37. Mice make CRAMP, encoded by a similar gene, and the landmark cathelicidin-knockout experiment showing that these peptides are a native component of innate defence against necrotic Group A streptococcal skin infection was done in mice, on CRAMP.[3] Any cathelicidin-knockout result is a result about a different peptide.

Two mechanisms are described for the human peptide, and they are separable. The first is direct and physical: the peptide is membrane-active against bacteria. The second is signalling. LL-37 is chemotactic for human neutrophils, monocytes and T lymphocytes, and induces calcium mobilization in monocytes and in cells transfected with formyl peptide receptor-like 1, which the authors propose as its receptor for recruiting those cells to sites of microbial invasion.[2] That second mechanism is where the popular "immune peptide" framing comes from, and it is entirely cell-culture work about the endogenous molecule.

Production is regulated by vitamin D. The CAMP gene is a direct target of the vitamin D receptor, induced by 1,25-dihydroxyvitamin D3 in myeloid, keratinocyte and colon cell lines and in normal human bone-marrow-derived macrophages — through a response element carried in a primate-specific repeat element that is absent from the mouse, rat and dog genomes, with no induction observed in murine cells.[6] So the regulation of this peptide is one of the places where rodent biology does not transfer even in principle.

This page rests on seventeen verified sources. Five of them administered LL-37, or a preparation expressing it, to people. The other twelve describe the molecule as the body makes it — in human tissue, in cultured human cells, or in mice. That ratio is the honest shape of the literature, and holding the two halves apart is the main thing this page is for.

What the research actually shows

Administered, topically, in venous leg ulcers. A first-in-man randomized, double-blind, placebo-controlled trial enrolled 34 patients with hard-to-heal venous leg ulcers, ran a three-week open-label placebo period, then applied 0.5, 1.6 or 3.2 mg/mL LL-37 or placebo twice weekly for four weeks. Healing-rate constants were about six-fold and three-fold higher than placebo at the two lower strengths (p = 0.003 and p = 0.088), mean ulcer area fell by 68% and 50% in those groups, and the highest strength was indistinguishable from placebo. The authors reported no safety concerns for local or systemic adverse events and concluded that the effect on healing predictors at the two lower strengths warranted further investigation.[10]

That further investigation happened, and it is the load-bearing result on this page. A phase IIb multicentre randomized placebo-controlled trial gave 0.5 or 1.6 mg/mL alongside compression therapy to 148 patients with hard-to-heal venous leg ulcers. The efficacy analysis performed on the full study population did not identify any significant improvement in healing compared with placebo. A post hoc analysis found improvement in several interrelated healing parameters in the subgroup whose target wounds were at least 10 square centimetres, and the authors present that as an interesting observation warranting a further study adequately powered to assess it — not as a result. The peptide was well tolerated at both strengths.[15]

Administered, topically, in diabetic foot ulcer. A randomized double-blind controlled trial in Jakarta allocated 25 adults with mildly infected diabetic foot ulcers — 13 to LL-37 cream, 12 to placebo cream — applied twice weekly for four weeks. The cream strength of 0.5 mg/mL and those group sizes are reported in the paper's full text rather than in its abstract. The increase in granulation index was consistently greater in the LL-37 group at days 7, 14, 21 and 28 (p = 0.031, 0.009, 0.006 and 0.037). The mechanistic endpoints did not follow: interleukin-1α and tumour necrosis factor-α rose in both groups, and the reduction in aerobic bacterial colonization was not significant at any timepoint. The authors' own conclusion states both halves — the cream enhanced healing rate, and it did not reduce those cytokines or that colonization.[17]

Administered, by mouth, as a live recombinant bacterium. In an open-label, randomized, placebo-controlled single-centre trial, 238 hospitalized adults with Omicron BA.5.1.3 COVID-19 received either placebo or a recombinant Lactococcus lactis strain expressing LL-37, taken orally. Time to a negative SARS-CoV-2 RNA result was shorter with the intervention when it began within six days of case confirmation (9.80 ± 2.67 versus 14.04 ± 5.89 days, p < 0.01), and no severe adverse events were seen during hospitalization or follow-up.[16] Read the preparation carefully: a live engineered bacterium expressing a peptide in the gut is not the same intervention as a topical solution of synthetic peptide, and it is not the same intervention as an injection.

Administered, intratumorally. The only PubMed-indexed clinical output of the intratumoral melanoma work is a case report by pathologists on a single 63-year-old woman with stage IIIC melanoma. Her injected lesions shrank clinically across eight weekly injections; about 45 days after starting, she developed multiple verrucous papules and a vesiculo-bullous lesion, and 11 of 12 biopsies showed atypical squamous proliferation with verrucous and keratoacanthoma-like features. All of it resolved within two months of stopping.[14]

Endogenous, and this is where the wound programme came from. In human skin, hCAP18/LL-37 is produced upon wounding, peaks around 48 hours after injury and declines as the wound closes; in chronic ulcers, levels are low and immunoreactivity is absent from ulcer-edge epithelium; and in organ-cultured human skin, affinity-purified antibodies against LL-37 inhibited re-epithelialization in a concentration-dependent manner.[4] That is a coherent argument for running a trial. It is not the trial.

Endogenous, and the vitamin D chain breaks in people. In 19 patients with venous leg ulcers, serum LL-37 correlated strongly with healing rate, 25-hydroxyvitamin D did not correlate with healing at all despite every patient being below the normal range, and the two showed no association with each other.[13] Intervening on the vitamin does not reliably move the peptide either: a pilot double-blind randomized trial in 31 mechanically ventilated intensive-care patients gave enteral vitamin D3 totalling 250,000 or 500,000 IU, met its primary endpoint by raising 25-hydroxyvitamin D into the sufficient range by day 7, and reported no statistically significant change in plasma LL-37 — a secondary endpoint — by group over time.[12]

Where the evidence is weak

The two literatures are not the same literature, and only one of them is about administering anything. A search for this peptide returns thousands of papers about what it does in the body that makes it — in psoriatic skin, in lupus serum, in rosacea, in melanoma tissue, in cultured macrophages. Twelve of the seventeen sources on this page are that kind of evidence. None of it is a result about giving the peptide to someone, and a low endogenous level in a disease population is a description of that disease, never a reason to administer anything.

More is not better, and that is not a hypothetical here. The only dose-ranging data that exists is inverted: the lowest strength tested produced the best healing-rate constant, and the highest strength performed no differently from placebo.[10]

The largest trial did not find what the first one suggested. The phase IIb efficacy analysis in the full population found no significant improvement, and the positive finding lives in a post hoc subgroup that the authors themselves frame as needing a further powered study.[15] A page that reported only the subgroup would be describing a different trial.

The mechanism endpoints keep failing even where the healing endpoints move. The diabetic foot ulcer trial improved granulation index without reducing interleukin-1α, tumour necrosis factor-α or bacterial colonization.[17] Whatever is happening, the proposed antimicrobial and anti-inflammatory account of it was not confirmed by the study's own measurements.

The oral COVID result is one open-label trial, in one centre, in one country, against one variant, on a virological endpoint, using a preparation nobody else has replicated.[16] A PubMed search on 1 September 2026 for (LL-37[Title/Abstract] OR ropocamptide[Title/Abstract]) AND (clinical trial[pt] OR randomized controlled trial[pt] OR controlled clinical trial[pt]) returned 60 records, and no second trial of that oral recombinant preparation appears among them.

The melanoma programme is a registry entry, not a published result. The ClinicalTrials.gov record for the intratumoral melanoma study (NCT02225366, MD Anderson Cancer Center, phase 1/2) is marked completed with an actual enrolment of four participants and results posted to the registry. A PubMed search on 1 September 2026 for (LL-37[Title/Abstract] OR ropocamptide[Title/Abstract]) AND (clinical trial[pt] OR randomized controlled trial[pt] OR controlled clinical trial[pt]) returned 60 records, and no primary-results publication of that trial appears among them; the only PubMed-indexed clinical output of the programme is the single-patient toxicity case report described above.[14] Registry entries are administrative records, and four participants is not an evidence base.

"It is natural, so it is safe" is contradicted by the peptide's own biology. In culture, LL-37 caused haemolysis of human erythrocytes and DNA fragmentation in cultured human vascular smooth muscle cells, and the authors state that clinical trials have been hampered by indications of toxic effects on mammalian cells and by evidence that its antimicrobial action is inhibited by serum.[5] Endogenously, it is a T-cell autoantigen in two-thirds of patients with moderate-to-severe plaque psoriasis;[11] it appears in neutrophil extracellular traps as part of the self-DNA complexes that activate plasmacytoid dendritic cells in systemic lupus erythematosus, where the therapeutic direction being pursued is inhibiting its immune reactivity rather than supplying more;[9] it is abnormally abundant and abnormally processed in rosacea, and those forms increased inflammation when injected into mouse skin;[7] and it behaves as a putative growth factor for malignant melanoma in cell work.[8]

A result for a fragment is not a result for LL-37. In the same set of experiments, two N-terminally truncated fragments caused less haemolysis and less DNA fragmentation than the full-length peptide and were not inhibited by serum, while a shorter, more hydrophobic 18-mer variant induced severe haemolysis.[5] The shorter derivatives that circulate under their own names are separate molecules with separate properties, and a favourable safety or potency result for one of them says nothing about this one.

Nobody has given it systemically to a healthy person. A PubMed search on 1 September 2026 for (LL-37 OR cathelicidin) AND (subcutaneous OR intramuscular OR intravenous) AND (healthy volunteers OR healthy adults) AND (administration OR injection) returned 0 records, and a search the same day for (LL-37 OR ropocamptide) AND (subcutaneous injection OR intramuscular injection OR intravenous infusion) AND human returned 9 records, none of which gave the peptide to a person by any of those routes. Every administered study on this page treated a diagnosed disease.

Why the badge above reads "anecdotal reports only" when randomized human trials exist. This library grades the compound-level badge on the claim a reader typically arrives with, not on the compound's best claim, and it grades down rather than up when the two disagree. The claim people bring to this peptide is that taking it supports the immune system of an otherwise healthy adult. No study on this page gave the peptide to a healthy adult for that purpose. What stands where that evidence would be is receptor and chemotaxis work in cultured human cells — LL-37 attracting human neutrophils, monocytes and T cells through formyl peptide receptor-like 1.[2] That is a mechanism in a dish. This library's stated rule is that a grade of "animal studies only" has to have a primary animal study behind it, and that a claim standing on cell-culture work alone takes the residual bottom grade instead — which is what the immune-support claim here does. The badge deliberately does not reach for the mouse cathelicidin literature to clear that bar: those experiments were done on CRAMP, and as the top of this page says, a cathelicidin-knockout result is a result about a different peptide. The randomized trials that do exist are graded human_rct individually in the evidence table above, where they are labelled by route and population. Read the table, not the badge.

Legal and regulatory status

LL-37 is not approved by the FDA for any indication, and human evidence for it is small and confined to specific diseases. Searches of Drugs@FDA, FDA approved labeling and the National Drug Code directory on 1 September 2026 — each run alongside a positive control query of the same shape that returned records — found no approved product under the names LL-37, LL37, cathelicidin, hCAP18, CAP18 or ropocamptide. The National Drug Code directory returned four records for LL-37, and all four are registered under the marketing category BULK INGREDIENT, as powder, with no route of administration and no application number attached. A bulk-ingredient registration records that a facility registered an active ingredient; it is not an approval, and reading it as one is a common error.

Two separate FDA compounding documents bear on this peptide and say different things. It appears in none of the three 503A bulk drug substance nomination categories, checked in the FDA category lists document updated 14 May 2026 with in-document positive controls that did fire. It does appear by name on FDA's page listing certain bulk drug substances for use in compounding that may present significant safety risks — a page stamped as current to 22 April 2026 — in the table of substances nominated but withdrawn, substances previously placed in category 2 of FDA's interim policies whose nominations the nominators then withdrew. FDA's entry there states that compounded drugs containing cathelicidin LL-37 may pose a risk for immunogenicity for certain routes of administration and may involve complexities regarding peptide-related impurities and characterization of the active ingredient; that the agency lacks sufficient safety-related information to know whether the drug would cause harm when administered to humans; and that nonclinical findings suggest detrimental effects on male reproduction and that the drug can be "protumorigenic in some tissues". A withdrawn nomination accompanied by an agency safety statement is not an approval, not a compounding authorization and not a clearance.

The peptide is in pharmaceutical development. The phase IIb report discloses that its sponsor is developing LL-37 under the non-proprietary name ropocamptide, and that several of the authors were employees or shareholders of that sponsor.[15] Outside the United States, Health Canada's Drug Product Database was searched on 1 September 2026 for LL-37, cathelicidin and ropocamptide and returned empty results against a working control query; no other national regulator was checked, and this page asserts nothing about jurisdictions it did not search.

On anti-doping status: the 2026 WADA International Standard Prohibited List, in force from 1 January 2026, was retrieved on 1 September 2026 through the United States Anti-Doping Agency's prohibited-list page, which links the WADA-hosted PDF. A full-text search of that document for cathelicidin, LL-37, LL37, hCAP18 and ropocamptide returned no hits, and the same search of the 2026 Monitoring Program returned no hits. Absence from the List is never a statement that a substance is permitted. Section S0, non-approved substances — prohibited at all times, in and out of competition, with everything in the class classified as a Specified Substance — prohibits any pharmacological substance not addressed by another section of the List that has no current approval by any governmental regulatory health authority for human therapeutic use, and names drugs under pre-clinical or clinical development as an example of what it covers. On the regulatory searches described above, LL-37 has no approved product in the United States or Canada and is a peptide in active clinical development, which is the situation S0 describes. It is not named in S2, the section covering peptide hormones, growth factors, related substances and mimetics, which carries a reach clause extending to substances of similar chemical structure or similar biological effect. An athlete's own governing body is the place to settle any of this.

PHL does not sell peptides and does not tell anyone where to obtain anything. What the regulatory position means for a reader is narrower and more useful: there is no label, no approved manufacturer, no assigned indication and no regulated standard behind anything carrying this name.

Questions to bring to a provider

Most people arrive at this page with a specific problem — a wound that will not close, recurrent infections, a skin condition, or a general sense that their immune system needs help. That problem, not the peptide, is where a useful conversation starts. Questions worth raising:

  • What is the actual diagnosis, and what does standard care offer for it? Both chronic-wound trials of this peptide were run on top of compression therapy or standard wound care rather than instead of it.[15]
  • Given that the largest randomized trial found no significant improvement in its full population, what would have to be true for this to be worth considering at all?[15]
  • Does a history of psoriasis, lupus, rosacea or melanoma change the calculus? Each of those conditions involves this peptide in a direction that argues against supplying more of it.[11][8]
  • Every published human study administered it to the wound or the tumour, or gave a live engineered bacterium by mouth. What is the reasoning behind any other route, and what evidence sits behind that reasoning?[14]
  • If low vitamin D is the underlying concern, what is the evidence that correcting it changes this peptide at all, given that a randomized trial raising 25-hydroxyvitamin D into the sufficient range did not move it?[12]
  • What would be measured, and on what schedule, to distinguish a real change from the natural course of the problem? The trials on this page tracked wound area, a healing-rate constant and a granulation index at fixed timepoints, which is a very different standard of proof from noticing you feel better.[10][17]

A clinician who answers "the human evidence here is four small randomized trials in specific diseases, plus one case report, and none of it is about you" is describing the literature accurately, not dismissing the question.

Evidence by claim

Grades describe how strong the evidence is; the line under each grade describes what kind of studies it is. How we grade evidence.

Administered topically for hard-to-heal venous leg ulcers
Human RCT evidence human RCT

The best-developed administered-drug claim, and it is mixed. A first-in-man randomized placebo-controlled trial in 34 patients found healing-rate constants roughly six-fold and three-fold higher than placebo at 0.5 and 1.6 mg/mL — significant at the lower strength (p = 0.003) and not at the higher one (p = 0.088) — and no difference at all between 3.2 mg/mL and placebo. The larger phase IIb trial in 148 patients then reported that its efficacy analysis on the full study population did not identify any significant improvement in healing versus placebo; a benefit appeared only in a post hoc subgroup with wounds of at least 10 square centimetres, which the authors present as an observation warranting a further adequately powered study rather than as a result.

[10] [15]

Administered topically as a cream for diabetic foot ulcer
Human RCT evidence human RCT

The trial set out to test four things at once, and one of the four came out. In 25 randomized adults in Jakarta, LL-37 cream applied twice weekly for four weeks produced a consistently greater increase in granulation index than placebo cream on days 7, 14, 21 and 28. The other three objectives were missed: interleukin-1α and tumour necrosis factor-α rose in both groups, and the reduction in aerobic bacterial colonization did not reach significance at any timepoint. The authors state exactly that split in their own conclusion — the cream enhanced the healing rate and did not reduce those cytokines or that colonization.

[17]

Administered by mouth as a recombinant bacterium in acute COVID-19
Human RCT evidence human RCT

The one administered study outside wound care, and the preparation is not the same molecule as a vial of peptide: an oral recombinant Lactococcus lactis strain expressing LL-37, given to 238 hospitalized adults in an open-label, randomized, placebo-controlled single-centre trial. The stated primary endpoints were negative conversion time of SARS-CoV-2 RNA and adverse events. The first was met in the early-intervention comparison — 9.80 ± 2.67 days against 14.04 ± 5.89 on placebo, p below 0.01 — and no severe adverse events were observed. Open-label, one centre, one country, one variant, and a virological rather than a clinical endpoint.

[16]

Administered by intratumoral injection in cutaneous melanoma metastases
Anecdotal reports only human observational

The only PubMed-indexed clinical output of this line of work is a single-patient case report describing dermatologic toxicity. The injected lesions shrank clinically over eight weekly injections, and the same patient then developed multiple atypical squamous and keratoacanthoma-like skin lesions that resolved within two months of stopping. One patient, reported by pathologists, is not an efficacy result and the report does not present it as one.

[14]

Administered for general immune support in a healthy adult
Anecdotal reports only in vitro

Unestablished, and searched. A PubMed search on 1 September 2026 for LL-37 or cathelicidin combined with subcutaneous, intramuscular or intravenous administration in healthy volunteers or healthy adults returned no records, and a search the same day for LL-37 or ropocamptide combined with immune support or immunity in healthy subjects restricted to randomized or trial publication types returned twelve records, none of which administered the peptide to anyone. What exists in place of that evidence is receptor work in human cells: LL-37 is chemotactic for human neutrophils, monocytes and T lymphocytes and induces calcium mobilization through formyl peptide receptor-like 1. That is a mechanism, in cells, for the peptide the body makes.

[2]

Raising the body's own cathelicidin with vitamin D
Human RCT evidence in vitro · human RCT · human observational

Endogenous-induction evidence, not administered-drug evidence, and it does not carry. The CAMP gene is a direct target of the vitamin D receptor, but the response element sits in a primate-specific repeat that is absent from the mouse, rat and dog genomes, and induction was not seen in murine cells. In people the chain then breaks twice. A pilot double-blind randomized trial in 31 ventilated intensive-care patients met its primary endpoint — plasma 25-hydroxyvitamin D at day 7, raised into the sufficient range by 250,000 or 500,000 IU of vitamin D3 — and reported no statistically significant change in plasma LL-37, which was a secondary endpoint. And in a proof-of-concept series of 19 patients with venous leg ulcers, serum LL-37 correlated with healing rate while 25-hydroxyvitamin D did not, with no association between the two.

[6] [12] [13]

The endogenous peptide's role in wound repair
Anecdotal reports only human observational

This is the observation the whole wound programme was built on, and it is about the molecule the body makes. In human skin, hCAP18/LL-37 rises after injury, peaks around 48 hours and declines as the wound closes, while levels are low in chronic ulcers with no immunoreactivity in ulcer-edge epithelium; in organ-cultured human skin, antibodies against LL-37 inhibited re-epithelialization in a concentration-dependent way. Uncontrolled human tissue observation plus an ex vivo model — a rationale for a trial, never a substitute for one.

[4] [13]

The endogenous peptide's role in autoimmune and inflammatory disease
Anecdotal reports only human observational

Consistent across three diseases, and it points the opposite way from an immune-support framing. LL-37 is a T-cell autoantigen in two-thirds of patients with moderate-to-severe plaque psoriasis; in systemic lupus erythematosus, self-DNA complexed with neutrophil-derived antimicrobial peptides in neutrophil extracellular traps activated plasmacytoid dendritic cells, and the authors of that work hold a patent on inhibitors of LL-37-mediated immune reactivity to self nucleic acids; and in rosacea the peptide is present at abnormally high levels in abnormally processed forms, with those forms increasing inflammation when injected into mouse skin. Observational human work with animal experiments attached.

[11] [9] [7]

Cancer biology of the peptide
Animal studies only in vitro

Human malignant melanoma cell lines overexpressed hCAP-18/LL-37 compared with keratinocyte and chronic myelogenous leukaemia lines, staining was strong in malignant melanoma tissue, and LL-37 added to a melanoma cell line stimulated proliferation, migration and invasion. The authors frame the peptide as a putative growth factor for malignant melanoma. Cell culture and tissue staining, with no clinical outcome attached to it in either direction.

[8]

FOR RESEARCH PURPOSES ONLY

Typical protocol range in the research

  • Adults with hard-to-heal venous leg ulcers in a first-in-man randomized, double-blind, placebo-controlled dose-ranging trial of 34 participants, following a three-week open-label placebo run-in; administered topically to the ulcer twice weekly for four weeks

    0.5, 1.6 and 3.2 mg/mL, each against placebo. The dose-response was inverted: the lowest strength produced the highest healing-rate constant and the highest strength was indistinguishable from placebo. [10]

  • Adults with hard-to-heal venous leg ulcers in a phase IIb multicentre randomized, double-blind, placebo-controlled trial of 148 patients; administered topically alongside compression therapy

    0.5 and 1.6 mg/mL, each against placebo. The efficacy analysis in the full study population found no significant improvement in healing over placebo at either strength. [15]

  • Adults with mildly infected diabetic foot ulcers in a randomized double-blind controlled trial in Jakarta; 25 participants randomized, 13 to LL-37 cream and 12 to placebo cream, administered to the wound twice weekly for four weeks. The strength and the group sizes come from the paper's full text, not from its abstract

    0.5 mg/mL as a cream, against a placebo cream. The full text gives the strength and the schedule; neither the abstract nor the full text reports an amount of cream applied per application. [17]

  • Hospitalized adults with Omicron BA.5.1.3 COVID-19 in an open-label, randomized, placebo-controlled single-centre trial of 238 inpatients. The administered product was a recombinant Lactococcus lactis strain expressing LL-37, taken by mouth — not synthetic LL-37 peptide, and not the topical peptide used in the wound trials

    The report describes the intervention and its timing, treating early intervention within six days of case confirmation as the comparison of interest. It does not state an administered amount or a schedule in milligrams. [16]

  • A single patient with stage IIIC cutaneous melanoma treated inside a phase 1/2 intratumoral trial and reported afterwards as a case report

    Eight weekly intratumoral injections. The case report states the route and the schedule; it does not state the amount given per injection. [14]

Every figure above is a topical strength in a wound-care trial, an oral live-bacterium preparation, or a schedule in a single-patient case report. None is a systemic amount and none came from a study in healthy adults. A PubMed search on 1 September 2026 for LL-37 or cathelicidin combined with subcutaneous, intramuscular or intravenous administration in healthy volunteers or healthy adults returned no records, and a search the same day for LL-37 or ropocamptide combined with subcutaneous injection, intramuscular injection or intravenous infusion in humans returned nine records, none of which gave the peptide to a person by any of those routes.

Ranges are what published research reports, not a recommendation. PHL does not prescribe, and nothing here is personalized to you.

Side effects & safety signals

  • Haemolysis and toxicity to normal human cells in culture

    Reported consistently in cell-culture work; not quantified as an event rate in any human study · In culture, LL-37 caused haemolysis of human erythrocytes and DNA fragmentation in cultured human vascular smooth muscle cells, and N-terminally truncated fragments of the peptide caused less of both. The same authors state plainly that clinical trials of LL-37 have been hampered by indications of toxic effects on mammalian cells and by evidence that its antimicrobial activity is inhibited by serum. Against that, the first-in-man topical trial reported no safety concerns regarding local or systemic adverse events at the strengths it used. Both things are true, and the difference between them is route and exposure.

    [5] [10]

  • Dermatologic toxicity after intratumoral injection

    One published patient from a phase 1/2 melanoma trial · Roughly 45 days after beginning eight weekly intratumoral injections, a 63-year-old woman with stage IIIC melanoma developed multiple verrucous papules and a vesiculo-bullous lesion on the trunk and extremities. Eleven of twelve skin biopsies showed a lichenoid inflammatory infiltrate with an overlying atypical squamous proliferation carrying verrucous and keratoacanthoma-like features. All lesions resolved within two months of stopping the injections. This is one patient in one report, which is neither a frequency nor a reassurance.

    [14]

  • A pro-tumour signal in melanoma laboratory work

    Reported in cell lines and tissue staining; never measured as a clinical outcome · Human malignant melanoma cell lines overexpressed hCAP-18/LL-37 messenger RNA and peptide relative to keratinocyte and leukaemia lines, immunohistochemistry showed strong expression in malignant melanoma, and adding LL-37 to a melanoma cell line stimulated proliferation, migration and invasion in vitro. The authors describe the peptide as a putative growth factor for malignant melanoma. This is laboratory work about the molecule the body makes and about the molecule added to a dish; it is not an observed outcome in a treated person.

    [8]

  • Autoimmunity and inflammation are part of this peptide's own biology

    Reported in patient cohorts across three separate diseases; not an effect of administration · Two-thirds of patients with moderate-to-severe plaque psoriasis carry T cells specific for LL-37, and the presence of circulating LL-37-specific T cells correlated significantly with disease activity. In systemic lupus erythematosus, complexes of neutrophil-derived antimicrobial peptides and self-DNA released in neutrophil extracellular traps activated plasmacytoid dendritic cells, and patients developed autoantibodies against both components. In rosacea, facial skin carries abnormally high and abnormally processed cathelicidin. These are findings about the endogenous peptide, and they are the strongest available argument against reading it as a simple immune booster.

    [11] [9] [7]

  • No characterized human safety profile for systemic use

    Not established · Unknown, which is an absence of data rather than a finding of safety. A PubMed search on 1 September 2026 for LL-37 or ropocamptide combined with subcutaneous injection, intramuscular injection or intravenous infusion in humans returned nine records, none of which administered the peptide to a person by those routes. The human safety information that does exist comes from topical wound trials, which reported the peptide to be well tolerated and safe at the strengths tested, and from a single intratumoral case report. Neither speaks to what repeated systemic exposure would do.

    [10] [15]

  • Unverified identity and purity of unapproved material

    Not quantified · The peptide behind every published human result was made and supplied inside a sponsor's own development programme, by authors employed by that sponsor. Nothing outside such a programme establishes what material carrying this name actually contains. That is a category-level risk sitting on top of whatever the molecule itself does.

    [15] [10]

Published lists are never exhaustive, so report anything unexpected to a licensed provider.

Storage, handling & reconstitution

Lyophilized storage
Lyophilized short peptides are conventionally kept refrigerated at 2–8 °C and protected from light, with freezing used for long-term holding. That is a general convention rather than a fact about this peptide: searches of Drugs@FDA, FDA approved labeling and the National Drug Code directory on 1 September 2026 returned no approved LL-37 product, so there is no manufacturer label, no assigned beyond-use date and no regulated stability standard behind any storage figure for material carrying this name. The peptide used in the published human studies was made and handled inside a sponsor's own development programme, under conditions those reports do not describe.
Reconstituted storage
Once in solution, peptides are conventionally refrigerated at 2–8 °C, protected from light, and treated as short-dated rather than indefinitely stable. Note that the published human work did not use a reconstituted vial in the way a reader might picture: the wound studies applied a topical solution or a cream prepared by the sponsor, and the one oral study administered a live recombinant bacterium rather than the peptide itself. A PubMed search on 1 September 2026 pairing LL-37 and ropocamptide with lyophilis*, lyophiliz* and "freeze-dried" returned no study describing a freeze-dried presentation of this peptide, so the published record does not say how a reconstituted solution of it behaves in a vial.
Reconstitution diluent
Bacteriostatic water is the conventional diluent for lyophilized research peptides; it is sterile water preserved with 0.9% benzyl alcohol. Sterile water without a preservative is used where a preservative is contraindicated and is treated as single-use. A PubMed search on 1 September 2026 pairing LL-37 and ropocamptide in title or abstract with diluent, reconstitution, reconstituted, "bacteriostatic water" and "sterile water" returned seven records, none of which describes a diluent for a lyophilized preparation of this peptide — which is unsurprising, because none of the human studies reconstituted a powder.
Reconstitution & handling
Conventional handling: sanitize the stopper before piercing it, add the diluent slowly down the inside wall of the vial rather than directly onto the powder, and let it dissolve on its own. Swirl gently if needed; never shake. A properly reconstituted solution is clear, and anything cloudy, discolored or carrying visible particulate is discarded. PHL does not publish volume or unit calculations, because those are dosing decisions and dosing decisions belong with a licensed clinician.
Handling notes
Handling conventions are the only thing this field can honestly carry. Nothing about the composition or impurity profile of material sold under this name outside a sponsor development programme is independently established, which is a category-level uncertainty sitting underneath every storage question.

The how-to guides cover the conventions behind these fields, and what the published stability data does and does not establish: Storage, Reconstitution, Handling.

Questions for your provider

Bring this page to a licensed provider. A provider can order labs, review your medications and history, and tell you whether anything here is relevant to your situation. This page can't. Peptide Health Lab does not prescribe and does not sell peptides.

Want a structured starting point for that conversation? The Stack Builder turns your goals into a research-cited outline you can review together.

Citations

17 sources · every identifier checked against PubMed

Before you act on any of this

This page is educational only and is not medical advice. It does not diagnose, treat, or prescribe. Review it with a licensed provider before making any health decision. Peptide Health Lab does not sell peptides.

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