Name: LL-37
Brand: PeptidesDirect
SKU: PD-LL37-5MG
Price: 57.99 EUR
Availability: InStock

Question 1

What is LL-37?

Accepted Answer

LL-37 is a 37-amino-acid cathelicidin-derived antimicrobial peptide produced by human immune and epithelial cells. It is a key component of innate immunity, widely studied for its antimicrobial, immunomodulatory, and wound-healing properties.

Question 2

How should I store LL-37?

Accepted Answer

Store lyophilized LL-37 at -20°C for long-term storage or at 2-8°C for short-term use. After reconstitution with bacteriostatic water, keep refrigerated at 2-8°C and use within 14 days. Protect from light and avoid repeated freeze-thaw cycles.

Question 3

What purity is your LL-37?

Accepted Answer

Every batch of LL-37 ships with a certificate of analysis from Janoshik Analytical, an independent third-party laboratory, at a minimum purity of 98%. We do not run a lab ourselves: the manufacturer commissions this test, and we pass the report on unchanged, with an online verification link on the product page.

Question 4

What research is LL-37 used in?

Accepted Answer

LL-37 is widely used in antimicrobial, immunomodulation, wound-healing, and innate immunity research. It is also studied in cancer biology, skin barrier function, and chronic inflammation models.

Question 5

How does LL-37 actually kill bacteria and help wounds close, according to the published research?

Accepted Answer

LL-37 is a cationic peptide that inserts into and permeabilizes bacterial membranes: it disrupted both the outer and inner membrane of E. coli and bound bacterial LPS (endotoxin) with high affinity in a classic 1998 assay paper (Turner et al., PMID 9736536). Separately, in human HaCaT skin cells, LL-37 triggered a distinct wound-repair pathway, activating keratinocyte migration through actin remodeling, focal adhesion kinase and paxillin phosphorylation, the Snail/Slug transcription factors, and MAPK/PI3K-Akt signaling via EGFR and FPRL-1 receptor activation (Carretero et al., PMID 17805349). These are two separate, independently studied mechanisms, direct membrane killing and a receptor-driven repair signal, not one unified pathway.

Question 6

What did the LL-37 studies actually find, and how quickly did the effect appear?

Accepted Answer

In a MRSA-infected mouse wound model, untreated wounds carried 7.8x10^7 CFU/g bacteria after 14 days, while combined topical-plus-intraperitoneal LL-37 cut that to 6.9x10^2 CFU/g over the same 14-day treatment period (Simonetti et al., PMID 34680791). In a mouse sepsis model, a single intravenous dose given right after surgery raised 7-day survival from 6.7% to 36.4%, with cytokine and bacterial-load changes already measurable at 15 hours (Hu et al., PMID 26746575). In the first human trial, twice-weekly topical application to venous leg ulcers produced a measurably faster healing rate within the 4-week treatment phase (Grönberg et al., PMID 25041740). The larger confirmatory trial, however, found no significant difference in healing over its full treatment course (Mahlapuu et al., PMID 34687253).

Question 7

What dose did the LL-37 trials use (species, route, frequency, duration), and is there a published human dosing protocol?

Accepted Answer

In the mouse MRSA-wound study, mice received 1 mg/kg LL-37 topically and/or intraperitoneally, starting 24 hours after infection, daily for 14 days (Simonetti et al., PMID 34680791). In the mouse sepsis study, mice received a single 2-microgram intravenous dose immediately after surgery; body weight wasn't reported, so no reliable mg/kg figure exists for that study (Hu et al., PMID 26746575). The two published human trials used LL-37 only as a topical wound solution, 0.5 to 3.2 mg/mL applied twice weekly directly to leg ulcers (Grönberg et al., PMID 25041740; Mahlapuu et al., PMID 34687253), which is a local wound concentration, not a systemic dose. No systemic human dosing protocol, oral, injected or otherwise, has been published for LL-37.

Question 8

What side effects or adverse events were actually reported in the LL-37 studies?

Accepted Answer

In the mouse MRSA-wound study, intraperitoneal LL-37 was reported as safe with no toxic side effects observed over the 14-day treatment (Simonetti et al., PMID 34680791), and the mouse sepsis study reported no adverse effects at its single 2-microgram dose (Hu et al., PMID 26746575). Both human trials reported no local or systemic safety concerns at 0.5 and 1.6 mg/mL (Grönberg et al., PMID 25041740; Mahlapuu et al., PMID 34687253). The one documented risk signal: at the highest tested concentration, 3.2 mg/mL, LL-37 showed no healing benefit over placebo at all, a pattern consistent with LL-37 becoming cytotoxic to cells at higher concentrations, a known limitation of this peptide (Grönberg et al., PMID 25041740). All of this safety data comes from two small, sponsor-run human trials and short-duration rodent studies, not a large or independent population.

Question 9

What is not known about LL-37's long-term safety, the honest evidence gap?

Accepted Answer

There is no long-term human safety data for LL-37: the first human trial ran a 4-week treatment phase plus 4-week follow-up, and the larger confirmatory trial extended treatment to 13 weeks with up to 4 months of follow-up, both in patients with chronic venous leg ulcers, not healthy volunteers (Grönberg et al., PMID 25041740; Mahlapuu et al., PMID 34687253). The larger and better-powered of the two trials, 148 patients, failed its primary healing endpoint, so the strongest available human evidence for LL-37's benefit did not hold up (Mahlapuu et al., PMID 34687253). No trial has tested LL-37 at systemic or injected doses in humans, only topical wound application. The in-vitro antifungal data come from a single laboratory with no mammalian-cell cytotoxicity testing at all, a gap the study's own authors flag as needing future work (Rather et al., PMID 35205958).

Question 10

Is LL-37 approved by the FDA, EMA, or any regulator, or is it strictly an unapproved research compound?

Accepted Answer

LL-37 is not approved by the FDA, EMA, or any other regulator for any use. It has been developed as an investigational drug under the nonproprietary name ropocamptide by Promore Pharma (formerly Pergamum), tested in a first-in-man Phase I/IIa trial (Grönberg et al., PMID 25041740) and a larger Phase IIb confirmatory trial (Mahlapuu et al., PMID 34687253) for venous leg ulcers. That confirmatory trial did not meet its primary endpoint, and no regulatory filing has followed. It remains strictly a research compound with no approved indication anywhere.

Question 11

How much bacteriostatic water should be used to reconstitute a vial of LL-37, and does the ratio matter?

Accepted Answer

A volume of 2 to 3 mL of bacteriostatic water, added slowly down the inside wall of the vial and swirled rather than shaken, is the reconstitution convention used across our catalogue for a vial this size; our LL-37 vial is labeled 5 mg, with a CoA-confirmed content of 5.11 mg. LL-37 sits in our 'high' pH-sensitivity handling tier, but its own chemistry is neutral: unlike acidic peptides such as IGF-1 LR3 or cagrilintide, it dissolves normally in standard bacteriostatic water (USP pH 5.7) and does not need an acidic diluent. The water volume changes the final concentration, not the peptide's stability; a vial that stays cloudy after several minutes of gentle swirling points to the water's own pH or quality, not necessarily a defect in the peptide.

Question 12

What does our own third-party CoA show for LL-37, and how can a batch be verified?

Accepted Answer

Our current LL-37 batch, color-coded 'Clear', tested at 99.15% purity with 5.11 mg content in a vial labeled 5 mg, tested by Janoshik Analytical. That report is one of the majority of our lab reports commissioned by the manufacturer rather than run by us directly or by an independent lab we paid for ourselves, and we publish the figures unchanged. The formal tested-item list on this specific report covers identity and purity, not a separately audited microbial or endotoxin panel for this batch. You can check the batch yourself through the Janoshik verification link on the product page and on our lab-reports page, rather than take our word for the numbers.

Question 13

How does LL-37 compare to BPC-157 in mechanism and evidence, since both are studied for tissue repair?

Accepted Answer

LL-37 and BPC-157 work through different mechanisms: LL-37's primary studied action is direct antimicrobial membrane disruption and LPS neutralization, with wound-repair signaling (keratinocyte migration, angiogenesis) as a secondary effect (Carretero et al., PMID 17805349), while BPC-157 has no antimicrobial action and is studied mainly for angiogenesis and growth-factor signaling in gut and tendon models. LL-37 also has a larger human clinical footprint: two published randomized trials in leg-ulcer patients (Grönberg et al., PMID 25041740; Mahlapuu et al., PMID 34687253), one of which failed its primary endpoint, versus a BPC-157 evidence base that, in our own vetted research record, is rat, mouse and rabbit studies with no published human trial. Neither compound has a published systemic human dosing protocol.

Question 14

Why did the larger confirmatory human trial fail to reproduce the earlier positive result?

Accepted Answer

There is no single confirmed reason, but one documented difference stands out: the first-in-man trial (n=34) found a clear bell-shaped dose response, the two lower topical concentrations, 0.5 and 1.6 mg/mL, improved healing significantly, while the highest concentration, 3.2 mg/mL, showed no benefit at all, a pattern consistent with LL-37 becoming cytotoxic to cells at higher concentrations (Grönberg et al., PMID 25041740). The larger, better-powered Phase IIb trial (n=148) tested only the two lower concentrations that had worked before, yet still found no significant improvement over placebo across the full study population (Mahlapuu et al., PMID 34687253). A post hoc subgroup of patients with larger ulcers (at least 10 cm2) did show a significant benefit in that second trial, but this was not the prespecified primary endpoint, so it needs its own dedicated, adequately powered study before it counts as confirmed. Both trials were run by the same sponsor lineage, Promore Pharma and its predecessor Pergamum.

Question 15

Is LL-37 effective against antibiotic-resistant bacteria and fungi like MRSA and Candida auris in the published research?

Accepted Answer

Yes, with a documented limitation: in vitro, LL-37 killed MRSA, Proteus mirabilis and Candida albicans in low-salt medium, but that activity was lost at a physiological 100 mM NaCl concentration, while activity against other pathogens like Pseudomonas aeruginosa and vancomycin-resistant enterococci held up even at that salt level (Turner et al., PMID 9736536). In vivo, combined topical and intraperitoneal LL-37 reduced MRSA counts in infected mouse wounds from 7.8x10^7 to 6.9x10^2 CFU/g over 14 days (Simonetti et al., PMID 34680791). Against multidrug-resistant Candida auris, LL-37 alone showed a minimum inhibitory concentration of 25 to 100 micrograms/mL, and combining it 1:1 with antifungals produced synergy with no antagonism in a single-lab in vitro study: 70% of the 10 tested strains synergized with fluconazole, and 100% with both amphotericin B and caspofungin (Rather et al., PMID 35205958). No human trial has tested LL-37 against MRSA or Candida auris infection specifically.

Question 16

Is the LL-37 in a research vial the same molecule the human body naturally produces, or a lab-made variant?

Accepted Answer

It is the same 37-residue sequence: LL-37 is the mature peptide cleaved from the human hCAP-18 precursor in neutrophils, keratinocytes and epithelial cells, and the synthetic peptide used in every study cited here, and in our own vial, is manufactured to match that native sequence, not an altered analog. Our own CoA confirms this at the identity level, listing identity as a tested and passed item, with a molecular weight consistent with the 4493.26 g/mol mass expected for the full 37-amino acid sequence. The peptide itself does not change once synthesized: what differs between a lab reagent and the body's own supply is production method, not sequence.

Question 17

Has LL-37 been studied for anything beyond topical wound application, such as inhaled or intravenous use?

Accepted Answer

Yes: outside topical wound use, LL-37 has been tested intravenously in a mouse sepsis model, where a single 2-microgram dose improved 7-day survival from 6.7% to 36.4% (Hu et al., PMID 26746575), and combined with intraperitoneal dosing in a mouse MRSA-wound model (Simonetti et al., PMID 34680791). The original 1998 potency paper also raised inhaled use as a possibility, based on LL-37's activity against Pseudomonas aeruginosa including antibiotic-resistant strains, suggesting it or related molecules 'might have utility as topical bronchopulmonary microbicides in cystic fibrosis' (Turner et al., PMID 9736536). That inhaled application was a hypothesis proposed by the study authors themselves, not something the study tested in the lungs. No published trial has since evaluated LL-37 by inhalation in humans or animals.

Question 18

How long does reconstituted LL-37 stay stable, and does it need the fridge or the freezer?

Accepted Answer

Refrigerate reconstituted LL-37 at 2 to 8°C and treat it as one of the shortest-window peptides in our catalogue: use it within a few days rather than the longer windows typical of more stable peptides. LL-37 is a cationic, amphipathic peptide known to adsorb to glass and plastic surfaces and lose activity faster in solution than many other research peptides, so keep the vial cold, swirl rather than shake or vortex it, and protect it from light. Do not freeze the reconstituted solution or refreeze it once thawed. No peer-reviewed shelf-life study exists for reconstituted LL-37 specifically, so this is conservative handling guidance, not a validated result.

Question 19

Do you sell LL-37 as a topical cream or gel, or only as lyophilized powder for reconstitution?

Accepted Answer

We ship LL-37 only as lyophilized powder in a sealed vial, the same form used across our catalogue; we do not sell a pre-mixed topical cream, gel, or spray. The two human trials that studied LL-37 for wound care applied it as a topical solution the study team prepared themselves at defined concentrations (Grönberg et al., PMID 25041740; Mahlapuu et al., PMID 34687253), not a finished commercial product. If a researcher wants a solution from our vial, that is a standard lab reconstitution step with bacteriostatic water, covered in our reconstitution FAQ above. We do not provide instructions for applying anything to a person.

Question 20

Does vitamin D naturally raise the body's own LL-37, and is that different from using the research peptide?

Accepted Answer

Yes, and it is a separate pathway from using the exogenous peptide. Published research shows that vitamin D's active hormone form binds the vitamin D receptor and upregulates the CAMP gene, the same gene that encodes hCAP-18, the precursor that neutrophils, keratinocytes and epithelial cells cleave into mature LL-37. Raising vitamin D status is a way of prompting the body to make more of its own precursor through that receptor pathway. Reconstituting and using our synthetic LL-37 vial supplies the mature 37-residue peptide directly, bypassing gene expression entirely. This describes the published mechanism only, it is not a recommendation to take vitamin D for any purpose.

Question 21

Is LL-37 linked to inflammatory conditions like psoriasis and rosacea rather than being a simple 'natural antibiotic'?

Accepted Answer

Published research points the other way: LL-37 is implicated as a driver of inflammation in both conditions, not a therapy for either. In psoriasis, LL-37 released by damaged skin cells binds self-DNA, and that complex activates plasmacytoid dendritic cells through TLR9, driving the type-I-interferon and inflammatory signaling seen in psoriatic plaques (Lande et al., Nature, 2007). In rosacea, abnormally high LL-37 processing in skin, driven by elevated kallikrein-5 protease activity, has been linked to the inflammation and vascular changes seen in the disease (Yamasaki et al., Nature Medicine, 2007). This is a caution about LL-37's role in disease biology, not a promotional angle or a use case for our research-grade peptide.

Question 22

Has LL-37 been studied for antiviral activity, e.g. against influenza or SARS-CoV-2?

Accepted Answer

There is published laboratory and observational research on this, but none of it amounts to a protection or treatment claim. In-vitro studies have examined how LL-37 interacts with the SARS-CoV-2 spike protein and ACE2 receptor, with some conditions showing interference with spike-ACE2 binding, the effect varying with peptide concentration and assay setup. Separate observational studies have looked at circulating LL-37 and vitamin D status alongside COVID-19 severity, finding correlations, not a demonstrated protective effect. Older cell-culture work documented LL-37 activity against enveloped viruses such as influenza, though its antiviral effect is context-dependent, not consistent across all viruses studied. This is early-stage in-vitro and correlational research only, not clinical evidence, and not a basis for any protection claim from us.

Question 23

Is LL-37 combined with KPV and BPC-157 in research protocols, the way GHK-Cu/BPC-157/TB-500 are combined in GLOW?

Accepted Answer

Not as a published combination. LL-37, KPV and BPC-157 each have their own separate literature: LL-37's antimicrobial and wound-repair data cited throughout this page, KPV's anti-inflammatory NF-kB and MAP-kinase work, and BPC-157's angiogenesis and tissue-repair studies, but no trial we have found has dosed the three together and measured a combined effect. Stacking them is a research-market practice, the same category as the BPC-157/TB-500 pairing or the GHK-Cu/BPC-157/TB-500 blend in GLOW: common in the peptide-research community, not something any single study has tested or validated as a combination. We apply the same honesty standard here as we do to GLOW, KLOW and WOLVERINE: real ingredients, no invented shared trial.

Question 24

Has LL-37 been studied for cancer, and does the evidence show it fights tumors or promotes them?

Accepted Answer

Both, and the published preclinical literature does not resolve it either way: this is an open, model-dependent research question, not a demonstrated benefit. In some in-vitro and animal models, notably certain ovarian and lung cancer cell lines, LL-37 has been reported to promote tumor cell proliferation, migration and invasion. In others, including gastric and colon cancer models, it has instead been reported to trigger cancer-cell apoptosis and suppress tumor growth. Researchers describe this as a context-dependent, double-edged effect that depends on cancer type, receptor expression and peptide concentration. No human cancer trial of LL-37 has been conducted, and none of this preclinical work supports using it for cancer prevention or treatment in either direction.

Question 25

Is it legal to buy and possess LL-37 in the EU as a research chemical?

Accepted Answer

LL-37 is not a scheduled or controlled substance and is not an approved prescription medicine in the EU, unlike GLP-1 drugs such as semaglutide or tirzepatide. We sell it strictly as a research chemical for in-vitro laboratory use, under our research-use terms: not for human or animal use, and not as a supplement, cosmetic or medicine. That general status can still vary by country, and import or customs rules differ by member state. We cannot give personalized legal advice for your specific situation: if you have doubts, check with your own national regulatory authority (in Germany, for example, the BfArM) before ordering.

Question 26

Does unrefrigerated shipping affect the quality of this product?

Accepted Answer

No. This product ships as a lyophilized (freeze-dried) powder in a sealed vial. Freeze-drying removes the water that drives peptide degradation, so the dry powder remains stable at room temperature for extended periods, longer than any normal parcel transit. Ambient shipping is standard practice across the peptide industry, and a peer-reviewed study reported months of room-temperature stability for a lyophilized therapeutic peptide (teriparatide, PMID 26620825). For comparison, FDA labeling allows an Ozempic (semaglutide) pen, after first use, to be kept out of the fridge for 56 days at 15 to 30°C, and a Mounjaro (tirzepatide) pen for up to 21 days at up to 30°C, even though these are ready-mixed solutions rather than sealed dry powder. Store the sealed vial in the fridge or freezer for long-term storage, and always refrigerate after reconstitution.

Question 27

What is documented about sudden severe reactions right after an injection, such as flushing, a racing heart, or throat tightness?

Accepted Answer

The unambiguous part first: rapid-onset flushing, a racing heart and throat tightness after an exposure are warning signs compatible with a serious allergic reaction (the formal criteria are multi-part clinical criteria, PMID 16461139), and the standard emergency guidance is to call emergency services immediately, even if symptoms seem to ease; in the EU that number is 112, free, from any phone. Nothing about a research compound changes that. What the literature documents around it: for injected peptide-class drugs that went through approval, hypersensitivity is a formally counted category (the tesamorelin label reports hypersensitivity reactions in 4 percent, with rash and urticaria); for research peptides like LL-37 or Thymosin Alpha-1 no verified incidence data were found. Distinguishing a fainting-type vasovagal episode from an allergic emergency is a clinical assessment, not something to attempt from a checklist at home. On the 'hit a vein' worry: a drop of blood or small bruise from nicking a capillary is common and self-limiting, and current immunization practice no longer even recommends aspirating before subcutaneous injections at standard sites because they lack large vessels; that is documented background from immunization practice, not an administration instruction, since our products are sold for in-vitro research and we provide no injection guidance. Any actual incident belongs in front of emergency services or a clinician, immediately and without waiting to see.

LL-37

What is LL-37

How it works

Often studied alongside

Documentation

Storage and stability

Reviews

Frequently Asked Questions

Technical data sheet

Frequently bought together

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Thymalin

BPC-157

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