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.
Best for
It has been studied in models of innate immunity, antimicrobial and anti-biofilm activity, endotoxin neutralization, and tissue-repair/wound-healing research.
What to expect
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.
Pairs with
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.
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.
- How often
- Daily
- When
- Morning
- Route
- Subcutaneous
- Vial & water
- 10 mg vial in 3 mL = 3.33 mg/mL · 125 mcg = 3.75 units on a U-100 syringe
- Cycle
- 50 days on, 4 weeks off (or 4–6 wk cycles)
The same numbers the goodtides app and the Dose Calc use — a research reference, not a prescription. Responses are individual; research protocols start at the low end.
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.
LL-37 is not FDA-approved; it is handled as a research compound, and AMP-derived therapeutics have not been broadly adopted clinically.
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).
- Half-life
- Not well established; reported to have rapid turnover with low systemic levels
- Peak
- Not characterized in human pharmacokinetic studies
- Absorption
- Susceptible to proteolytic degradation; injectable routes used in research
- Bioavailability
- Negligible oral bioavailability (peptide; degraded in GI tract)
References3
- Durr UH et al. - LL-37, the only human member of the cathelicidin family of antimicrobial peptides (Biochim Biophys Acta)
- Svensson D et al. - Human antimicrobial/host defense peptide LL-37 may prevent the spread of a local infection through multiple mechanisms: an update (Inflamm Res)
- PubChem - LL-37 Compound Summary, CID 16198951 (sequence, C205H340N60O53, MW 4,493)
Log every dose, count every vial, and verify your batches — free in the goodtides app.
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.