Explore BioBoost LabsLL-37
The only human cathelicidin antimicrobial peptide, a 37-residue peptide released from the precursor protein hCAP18.
What the name means
The name encodes the peptide’s structure directly. “LL” refers to the two leucine residues at its N-terminus, and “37” is the number of amino acids in the mature peptide.
So LL-37 reads as “the 37-residue peptide that begins Leu-Leu.”
What it actually is
LL-37 is a cationic host-defense (antimicrobial) peptide and the only member of the cathelicidin family found in humans.
The reported sequence is LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES (molecular formula around C205H340N60O53, roughly 4.5 kDa). Its net positive charge and amphipathic helix let it interact with microbial membranes.
Where it came from
LL-37 is a natural human peptide. It is stored as part of the larger precursor protein hCAP18 in cells such as neutrophils and in epithelial tissues, and is liberated by proteolytic processing.
It was characterized in the 1990s as researchers mapped the cathelicidin family; humans, unlike some other species, have just this one cathelicidin.
Why it was created — the thought process
LL-37 was not designed by people; it is a component of innate immunity. Research interest grew from understanding what it does biologically and whether that could be harnessed.
Because it can disrupt microbial membranes and also influences immune signaling and wound processes, it became a template for studying antimicrobial peptides and for designing synthetic analogs aimed at resisting infection.
How it is made
In the body, LL-37 is generated when enzymes such as proteinase 3 cleave the mature peptide from the hCAP18 precursor.
For research, the 37-residue peptide is typically produced by solid-phase peptide synthesis, then purified by HPLC and confirmed by mass spectrometry. At 37 residues it is a relatively demanding synthesis compared with short peptides.
What the research actually shows — honestly
LL-37 is well studied in basic immunology, with documented antimicrobial and immunomodulatory activities in laboratory systems.
Translating this into approved therapies has proven difficult: LL-37 can be cytotoxic to host cells at higher concentrations and its behavior is sensitive to the surrounding environment, so clinical benefit for specific uses is not established. It is provided for research use only (RUO) and is not an approved drug.
Selected research & sources
The items below are drawn from the peer-reviewed literature (PubMed) and describe results observed in research models or reported in the clinical literature. They are listed so the evidence can be examined at its source — not to suggest any use.
- Ju R, et al. J Control Release. 2025. “Polyaminoglycoside nanosystem expressing antimicrobial peptides for multistage chronic wound management.” doi.org/10.1016/j.jconrel.2025.113657
- Ma D, et al. ACS Appl Mater Interfaces. 2024. “Prolonged Immunomodulator Delivery Boosts Monocyte Exosome Secretion and Elevates Cathelicidin/LL-37 Content.” doi.org/10.1021/acsami.4c20695
Regulatory status: Not FDA-approved. Research material, RUO.
◆ A reference, not a recommendation
This page explains what LL-37 is and where it came from — the science and the story — not who should use anything, or how. These are research materials for laboratory research only; nothing here is medical, dosing, or treatment advice.
Research-use-only educational content. Factual overview; claims of clinical benefit are not implied.