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LL-37

Preclinical

Human cathelicidin antimicrobial peptide

Also known as: Cathelicidin, CAP-18 fragment, hCAP18

Immune

LL-37 is the only human cathelicidin antimicrobial peptide, a key part of innate immunity studied for its direct antimicrobial action, wound healing, and immune-signalling roles.

Molecular & research data

Sequence
LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES (37 aa)
CAS number
154947-66-7
Molecular formula
C205H340N60O53
Molecular weight
≈4493 g/mol
Half-life
Short in circulation; activity is largely local
Primary targets
Microbial membranes, Innate immune signalling
Routes (research)
Subcutaneous, Topical
Storage
Lyophilised: −20 °C. Reconstituted: 2–8 °C, use within weeks.

Overview

LL-37 is the only cathelicidin antimicrobial peptide found in humans, produced by cleavage of the precursor protein hCAP18. It is a core component of innate immunity — a fast, non-specific first line of defence — and is found in immune cells, skin, and mucosal surfaces.

Mechanism of action

LL-37 is amphipathic, meaning it has both water-attracting and fat-attracting regions. This structure lets it:

  • Disrupt microbial membranes directly, killing bacteria, fungi, and some viruses by permeabilising their cell walls
  • Modulate innate immune signalling, recruiting and influencing immune cells
  • Support wound healing and angiogenesis at sites of injury and infection

Because its action is largely local and membrane-based, LL-37 differs fundamentally from the receptor-mediated immunomodulation of Thymosin Alpha-1.

Common research uses

  • Antimicrobial and anti-biofilm research
  • Wound healing and skin-barrier studies
  • Innate-immunity and inflammation research
  • As a template for antimicrobial peptide drug design

LL-37 FAQ

What is LL-37?+

LL-37 is the active fragment of human cathelicidin (hCAP18), the only cathelicidin antimicrobial peptide found in humans. It is a frontline molecule of innate immunity.

How does LL-37 kill microbes?+

Its amphipathic structure lets it disrupt and permeabilise microbial cell membranes directly. It also modulates the immune response and supports wound healing.

Is LL-37 a drug?+

No. It is a naturally occurring human peptide studied in research; it is not an approved therapeutic, though it inspires antimicrobial drug development.

References

  1. [1]Cathelicidin LL-37 — PubChemPubChem
  2. [2]LL-37 antimicrobial peptide and immunity literaturePubMed

Related peptides

Thymosin Alpha-1

In clinical trials

Thymic immunomodulatory peptide

Thymosin Alpha-1 is a naturally occurring thymic peptide and immunomodulator, approved in many countries (as thymalfasin) for hepatitis and as a vaccine adjuvant, studied for its effects on T-cell function.

Immune

Last reviewed: 2026-06-26. Information is provided for research and educational reference only — see our disclaimer.