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Immune & longevity

LL-37

Cathelicidin LL-37Cathelicidin antimicrobial peptidehCAP-18 (C-terminal fragment)CAP-18Ropocamptide (investigational INN)Antimicrobial peptide LL-37

LL-37 is the only human cathelicidin antimicrobial peptide, a 37-residue host-defense peptide studied in research for its broad antimicrobial and immunomodulatory activity, with no approved therapeutic indication.

Sequence fingerprint

LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES

  • Nonpolar16
  • Polar5
  • Acidic (−)5
  • Basic (+)11
  • 37 residues

H-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-OH (37 residues; C-terminal fragment of human hCAP-18 encoded by the CAMP gene)

Overview

LL-37 is the active fragment of the human cathelicidin antimicrobial peptide, encoded by the CAMP gene. The precursor protein hCAP-18 is proteolytically cleaved to release the mature 37-amino-acid peptide, whose name comes from its two N-terminal leucine residues and its length. It is the only cathelicidin found in humans.

Structurally, LL-37 adopts an amphipathic alpha-helix in which cationic and hydrophobic residues segregate to opposite faces. This arrangement lets it associate with and disrupt negatively charged microbial membranes, which underlies the broad antimicrobial activity reported in laboratory studies against bacteria (including some drug-resistant strains), fungi, and enveloped viruses, as well as its reported anti-biofilm activity. Beyond direct microbial killing, in vitro and animal studies describe immunomodulatory roles: LL-37 can act as a chemoattractant for neutrophils, monocytes, and T cells, neutralize bacterial endotoxin (LPS), and influence inflammatory signaling and wound-healing pathways.

Despite this broad activity, translation to the clinic has been limited. Reviews highlight host-cell cytotoxicity, susceptibility to proteolytic degradation, and high manufacturing cost as key obstacles, and much research focuses on engineered analogs (truncated, retro, or D-amino-acid variants) intended to reduce toxicity and improve stability. A synthetic formulation has been studied under the investigational name ropocamptide for hard-to-heal venous leg ulcers; an early trial reported it was well tolerated, but a larger Phase IIb trial did not demonstrate a benefit across the overall study population.

LL-37 is not an approved medicine in the UK, US, or EU and has no authorized therapeutic indication. It is sold only as a research chemical / reference material and is not intended for human or veterinary use.

Mechanism, evidence & status

LL-37 is the sole human cathelicidin antimicrobial peptide, released by proteolytic cleavage from the C-terminus of the hCAP-18 precursor encoded by the CAMP gene. It folds into an amphipathic alpha-helix that inserts into and disrupts microbial membranes, and in laboratory models it also modulates innate immunity by acting as a chemoattractant for neutrophils, monocytes, and T cells and by influencing inflammatory signaling.

Human evidence
Extensive in-vitro and preclinical research; limited early-phase human clinical trials; no approved indication.
Regulatory status
Not an approved medicine. NOT FDA-approved and not authorized by the UK MHRA or EMA for any indication. The endogenous peptide and a synthetic formulation under investigation as ropocamptide (LL-37 for venous leg ulcers) remain investigational. Sold only as a research chemical / reference material; not for human or veterinary use.
Research applications
  • Studied in vitro as a broad-spectrum antimicrobial against bacteria (including drug-resistant strains), fungi, and enveloped viruses, and as an inhibitor of bacterial biofilm formation.
  • Investigated as a model immunomodulatory peptide influencing chemotaxis, inflammation, and wound-healing pathways in cell and animal models.
  • Explored in early-phase research (including as ropocamptide) for hard-to-heal chronic wounds such as venous leg ulcers.
  • Used as a scaffold for engineered analogs (truncations, retro/D-amino-acid variants) aimed at reduced toxicity and improved stability.
Safety considerations
  • Reviews note that host-cell cytotoxicity, low proteolytic stability, and high production cost are major obstacles limiting clinical translation of native LL-37 (Int J Mol Sci, 2025).
  • Dysregulated LL-37 expression has been associated in the literature with inflammatory and autoimmune conditions, underscoring that more is not inherently better.
  • No established safety profile exists for non-clinical/self-administered use; sold strictly as a research material with no approved human dosing.
  • An early-phase topical trial reported the LL-37 formulation (ropocamptide) was well tolerated in venous leg ulcers, but the larger Phase IIb trial did not show a benefit across the overall study population.
References
  1. [1]PubChem Compound 16198951 — LL-37 (cathelicidin antimicrobial peptide)PubChem (NIH/NCBI)
  2. [2]Antimicrobial Peptides of the Cathelicidin Family: Focus on LL-37 and Its Modifications (Int. J. Mol. Sci., 2025)PubMed
  3. [3]Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: a multicentre randomized placebo-controlled trial (Wound Repair Regen., 2021)PMC
  4. [4]Cathelicidin antimicrobial peptide (CAMP) — gene and LL-37 overviewWikipedia