About LL-37

LL-37 is the human cathelicidin antimicrobial peptide — a 37-amino-acid host-defense peptide produced naturally by neutrophils, mast cells, and epithelial cells as part of the innate immune response. Its name comes from the two leucines at the N-terminus (LL) and the 37-residue length. It has documented antimicrobial activity across bacteria, viruses, and fungi, plus modulating effects on wound healing, angiogenesis, and inflammation.

Research interest in synthetic LL-37 spans antimicrobial protocols (especially for biofilm-associated infections where conventional antibiotics struggle), chronic wound research, and as an immunomodulator. It’s a different class than Thymosin Alpha 1 — LL-37 is more direct antimicrobial; TA1 is more T-cell modulation.

Dosing observed in research literature

Route	Dose range	Frequency	Notes
Topical	~100 mcg/mL solution	Twice daily to wound site	Wound-healing research protocols
Subcutaneous	100–300 mcg	Daily, 2–4 weeks	Systemic immune research protocols
Higher-range research	500 mcg	Daily, short cycle	Less common; reserved for specific research

Research cycles typically run 2–4 weeks. LL-37 is most often used as a short-course intervention rather than chronic administration. Extended-cycle data is limited in published literature.

Typical reconstitution protocols

LL-37 typically ships as a 5 mg lyophilised vial:

Vial size	BAC water	Concentration	200 mcg draw	500 mcg draw
5 mg	2 mL	2500 mcg/mL	8 units (U-100)	20 units
5 mg	2.5 mL	2000 mcg/mL	10 units	25 units
5 mg	5 mL	1000 mcg/mL	20 units	50 units

Half-life and storage

Plasma half-life is short — approximately 1 hour. LL-37 acts primarily at tissue level rather than maintaining a plasma reservoir, so the short half-life doesn’t undermine effect. Once-daily SubQ dosing is standard. Storage: lyophilised at 2–8°C; reconstituted up to 28 days refrigerated. Never freeze.

Frequently asked questions

Is LL-37 an antibiotic?

It’s an antimicrobial peptide rather than a conventional antibiotic. It disrupts bacterial cell membranes directly rather than targeting specific bacterial enzymes the way traditional antibiotics do. This mechanism makes resistance harder to develop and gives broad-spectrum coverage including biofilm-protected bacteria.

Can LL-37 be used topically?

Yes — topical wound application is documented in research literature. The reconstituted solution can be applied to the wound site directly. Topical use is typically twice daily for wound research protocols.

How does it compare to BPC-157 for wound research?

Different mechanisms. BPC-157 promotes tissue regeneration via angiogenesis and growth-factor pathways. LL-37 has antimicrobial and immunomodulatory effects, addressing infection and inflammation. Some research protocols combine them — BPC-157 for repair, LL-37 for antimicrobial coverage in infected wounds.

What injection site is used?

Subcutaneous abdomen for systemic protocols. Topical direct-to-site for wound-healing research.

Related compounds

LL-37 sits in the recovery / healing research category as the antimicrobial host-defense peptide. Adjacent: BPC-157 (tissue repair, often combined for wound research), Thymosin Alpha 1 (T-cell-focused immune modulation), TB-500 (cell migration, recovery). For full category overview: Healing & Recovery Peptides.