LL-37
LL-37 is the sole human cathelicidin antimicrobial host-defense peptide, studied for innate immunity, antimicrobial activity, and tissue repair; research protocols typically use 125 mcg daily subcutaneously.
It has been studied in models of innate immunity, antimicrobial and anti-biofilm activity, endotoxin neutralization, and tissue-repair/wound-healing research.
LL-37 is the only human member of the cathelicidin family of antimicrobial host-defense peptides — a 37-residue, cationic, amphipathic alpha-helical peptide cleaved from the C-terminus of the precursor protein hCAP18 (CAP-18) by proteinase 3. Research has characterized two broad activities. First, direct antimicrobial action: its cationic, amphipathic structure permeabilizes negatively charged bacterial membranes of both Gram-positive and Gram-negative organisms, and studies report it can disrupt biofilms at concentrations well below those needed to kill the constituent bacteria.
Second, immunomodulation: LL-37 signals largely through the G protein-coupled formyl peptide receptor 2 (FPR2/FPRL1), with additional reported interactions at P2X7 purinergic and EGFR pathways, driving chemotaxis of neutrophils, monocytes, T cells and mast cells, and binding/neutralizing bacterial endotoxin (LPS). LL-37 is not FDA-approved; it is handled as a research compound, and AMP-derived therapeutics have not been broadly adopted clinically.
In research settings it has most often been administered by subcutaneous injection on a daily or every-other-day basis, with conservative, individualized dosing; topical and intranasal routes also appear in the antimicrobial and wound literature.
Time-to-effect is not well established in human research; in vitro antimicrobial and biofilm-disruption effects are observed rapidly, while any systemic immunomodulatory effects studied in models are less characterized.
In research discussions it is sometimes grouped with other innate-immune or tissue-repair compounds such as thymosin alpha-1, thymosin beta-4 (TB-500) or BPC-157, though combination data are limited.
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This page is educational reference material about compounds studied in research settings. It is not medical advice, and nothing here is a recommendation to buy, possess, or use any compound. Research findings described are from published literature; individual compounds may not be approved for human use. Talk to a licensed clinician about anything that affects your health.