LL-37 is the only human cathelicidin-derived antimicrobial peptide — a 37-residue cationic fragment released from the C-terminus of the precursor protein hCAP18 (encoded by the CAMP gene) after extracellular cleavage by proteinase 3.1 Its name comes from the two leading leucine residues and its length. Beyond direct antimicrobial activity, researchers have studied LL-37 as a host-defence and tissue-repair molecule, which is why it is catalogued here under healing and recovery.2
This page is for research and educational purposes only. LL-37 is not an approved drug and is supplied in Canada for in-vitro / laboratory research use only. Nothing here is medical advice or a usage direction. Human evidence is limited to two wound-healing trials with mixed results — the larger Phase IIb trial did not meet its primary endpoint4 — so claims should be read with that caveat. Where a value could not be verified it is marked “Not established”.
Sequence & identity
LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES · C205H340N60O53 · 4493 g/mol
Linear 37-residue cationic, amphipathic α-helical peptide. Chemical identity per PubChem CID 16198951 (InChIKey POIUWJQBRNEFGX-XAMSXPGMSA-N).5
Mechanisms studied
Researchers describe LL-37 as a cationic, amphipathic peptide that folds into an α-helix on contact with anionic membranes; this is reported to underlie its direct antimicrobial action through membrane disruption of bacteria.2 In the tissue-repair context, investigators have reported that LL-37 acts largely through the formyl peptide receptor-like 1 (FPRL1 / FPR2), a G-protein-coupled receptor expressed on endothelial cells, neutrophils and other cells. Koczulla and colleagues observed that LL-37 directly activated cultured endothelial cells and induced neovascularisation in the chick chorioallantoic membrane assay and in a rabbit hind-limb ischaemia model, and that mice lacking the murine homologue (CRAMP) showed reduced vascularisation during wound repair.1 Separately, Heilborn and colleagues reported that hCAP18/LL-37 is strongly expressed in healing human skin epithelium (peaking ~48 h after wounding) and that anti-LL-37 antibodies inhibited re-epithelialisation and the proliferation marker Ki67 in an ex-vivo human-skin model, while chronic ulcer edges showed little LL-37.3
Dosing in the research literature
The figures below summarise regimens as reported in published research — they are not recommendations or directions for use.
| Source / model | Regimen reported | Notes |
|---|---|---|
| Grönberg et al. 2014, Wound Repair Regen (first-in-man / Phase I-IIa, 34 patients with hard-to-heal venous leg ulcers)6 | Topical LL-37 at 0.5, 1.6 or 3.2 mg/mL applied twice weekly for 4 weeks (after a 3-week placebo run-in), as reported in the study. | Study-reported, not a usage direction. The 0.5 and 1.6 mg/mL arms showed ~6-fold and ~3-fold higher healing-rate constants vs placebo (p=0.003 and p=0.088); the 3.2 mg/mL arm showed no benefit. Topical, RUO context only — no systemic/injection regimen is established. |
| Mahlapuu et al. 2021, Wound Repair Regen (Phase IIb; 149 patients randomized, 148 treated; randomized placebo-controlled trial)4 | Topical LL-37 at 0.5 mg/mL or 1.6 mg/mL (≈12.5 and 40 µg/cm²) twice weekly (every 3 ± 1 days) for up to 13 weeks, as reported in the study. | Study-reported. The trial did NOT detect a significant difference in venous-leg-ulcer healing versus placebo overall; a post-hoc subgroup (large ulcers ≥10 cm², 0.5 mg/mL) suggested benefit (p≈0.046). Both doses were reported as well tolerated and safe. |
| Koczulla et al. 2003, J Clin Invest (animal / in-vitro angiogenesis)1 | 5 µg LL-37 per pellet/implant used to elicit neovascularisation in animal and membrane assays, as reported in the study. | Preclinical dose for a mechanistic assay only — not a human regimen and not a usage direction. |
Effects observed in research
In laboratory and animal models, studies reported that LL-37 disrupts the membranes of bacteria, fungi and some viruses and modulates innate-immune responses (chemotaxis of neutrophils, monocytes and T cells via FPRL1).2 Researchers observed pro-angiogenic activity — increased endothelial proliferation and vessel-like structure formation in vitro, and neovascularisation in animal ischaemia and wound models.1 In an ex-vivo human-skin wound model, investigators reported that LL-37 was required for normal re-epithelialisation and keratinocyte proliferation, and that it was deficient in chronic ulcer epithelium.3 In humans, a small first-in-man trial reported faster healing of hard-to-heal venous leg ulcers at lower topical doses,6 but a larger Phase IIb trial did not detect a significant overall healing benefit versus placebo, with possible benefit limited to a post-hoc large-ulcer subgroup.4 These are research observations in defined models and human wound-care trials; they are not approved indications and do not describe what the peptide does in a healthy individual.
Strength of evidence
Grade B — limited and mixed human evidence supported by strong mechanistic animal/in-vitro data. The mechanistic and preclinical literature is substantial: well-characterised receptor (FPRL1) pharmacology, in-vitro angiogenesis and antimicrobial data, ex-vivo human-skin re-epithelialisation, and knockout-mouse wound studies.123 Direct human clinical evidence is confined to topical wound-healing: a small first-in-man trial was encouraging at low doses,6 but the subsequent larger Phase IIb randomized placebo-controlled trial (149 patients randomized) did not meet its primary endpoint, with only a post-hoc subgroup signal.4 There are no controlled human data supporting systemic (“anti-aging”, gut, or injected) use, and high LL-37 concentrations can be cytotoxic and have been implicated in inflammatory conditions such as psoriasis and rosacea.2 We have not padded this grade: outside topical wound care the human evidence is best described as not established.
Reconstitution & storage
Reconstitute with bacteriostatic water for laboratory handling. Store lyophilised material frozen and reconstituted material refrigerated. Use Peptigo’s reconstitution calculator and storage cheat sheet for working figures.
References
- Koczulla R, von Degenfeld G, Kupatt C, et al. An angiogenic role for the human peptide antibiotic LL-37/hCAP-18. J Clin Invest. 2003;111(11):1665-1672. doi:10.1172/JCI17545. PMID: 12782669.
- Vandamme D, Landuyt B, Luyten W, Schoofs L. A comprehensive summary of LL-37, the factotum human cathelicidin peptide. Cell Immunol. 2012;280(1):22-35. doi:10.1016/j.cellimm.2012.11.009.
- Heilborn JD, Nilsson MF, Kratz G, et al. The cathelicidin anti-microbial peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcer epithelium. J Invest Dermatol. 2003;120(3):379-389. doi:10.1046/j.1523-1747.2003.12069.x.
- Mahlapuu M, Sidorowicz A, Mikosinski J, et al. 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;29(6):938-950. doi:10.1111/wrr.12977. PMC9298190.
- National Center for Biotechnology Information. PubChem Compound Summary for CID 16198951, LL-37. InChIKey POIUWJQBRNEFGX-XAMSXPGMSA-N; CAS 154947-66-7. https://pubchem.ncbi.nlm.nih.gov/compound/16198951 (accessed 2026-06-03).
- Grönberg A, Mahlapuu M, Ståhle M, Whately-Smith C, Rollman O. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial. Wound Repair Regen. 2014;22(5):613-621. doi:10.1111/wrr.12211.