LL-37
LL-37 is an endogenous, highly lethal cathelicidin antimicrobial peptide serving as the human immune system's ultimate first line of defense. Vastly superior to traditional isolated antibiotics, LL-37 attacks devastating systemic infections—including severe Lyme disease, rampant Candida overgrowth, and antibiotic-resistant MRSA biofilms. Far beyond basic pathogen destruction, it acts as a hyper-vigilant immune regulator, aggressively mitigating rogue autoimmune responses, suppressing extreme systemic inflammation, and initiating advanced epithelial tissue regeneration.
Quick Stats
Scientific Data
Mechanism of Action
LL-37 (Cathelicidin, hCAP18) is the only human cathelicidin antimicrobial peptide — an endogenous 37-amino-acid α-helical peptide derived from the C-terminus of the hCAP18 protein. It serves as a critical first-line innate immune defense. LL-37 exerts broad-spectrum antimicrobial activity by inserting into microbial lipid bilayers, forming pores that cause rapid membrane disruption and cell lysis — effective against gram-positive and gram-negative bacteria, enveloped viruses, and fungi.
Beyond direct killing, LL-37 acts as an immunomodulator: it activates TLR4 and EGFR signaling, promotes chemotaxis of immune cells (monocytes, neutrophils, T-cells), stimulates angiogenesis, and accelerates wound healing through keratinocyte migration. It disrupts biofilms — a key advantage over antibiotics — and has been studied in chronic Lyme disease, MRSA, and as an adjuvant in cancer immunotherapy.
Source: PMID: 18082616
Background & History
LL-37 is the only known member of the cathelicidin family of antimicrobial peptides in humans, derived from the C-terminus of the hCAP18 protein. It was first described in 1995 by Gudmundsson et al. (PNAS). Beyond its broad-spectrum antimicrobial activity against bacteria, viruses, and fungi, LL-37 also modulates the immune response, promotes wound healing, and shows emerging roles in cancer biology. Its expression is induced by Vitamin D3, exercise, and infection.
Research Use Cases
- ✓Chronic wound healing and biofilm disruption
- ✓Antimicrobial support in antibiotic-resistant infections (research)
- ✓Immune modulation in chronic inflammatory conditions
- ✓Cystic fibrosis (CF) lung infection management research
Dosing Protocol
| Typical Dose | 50-200 mcg/day |
| Frequency | 1× daily |
| Half-Life | ~4 hours (estimated) |
| Common Vial Sizes | 5 mg |
Dosing Protocols
Starting Dose
Standard Protocol
Advanced / Infection
Body-Weight Dosing Reference
Estimated doses extrapolated from the published research range of 50–200 mcg/day (referenced to 70 kg / 154 lb). These are approximations — consult a qualified healthcare provider for personalised guidance.
| Weight | Low Dose | Target Dose | High Dose |
|---|---|---|---|
| 120 lb(54 kg) | 39 mcg | 96 mcg | 154 mcg |
| 140 lb(63 kg) | 45 mcg | 113 mcg | 180 mcg |
| 160 lb(73 kg) | 52 mcg | 130 mcg | 209 mcg |
| 180 lb(82 kg) | 59 mcg | 146 mcg | 234 mcg |
| 200 lb(91 kg) | 65 mcg | 163 mcg | 260 mcg |
| 220 lb(100 kg) | 71 mcg | 179 mcg | 286 mcg |
| 250 lb(113 kg) | 81 mcg | 202 mcg | 323 mcg |
💉 For exact syringe units based on your vial concentration, use the LL-37 Reconstitution Calculator →
Administration
Expected Timeline
Who Is It For?
Antimicrobial / Infection
ModerateBroad-spectrum antimicrobial activity against bacteria, viruses, fungi, and biofilms. Most evidence is preclinical.
Wound Healing
ModeratePromotes keratinocyte migration, angiogenesis, and inflammatory resolution at wound sites.
Chronic Lyme / MRSA
LowPromising but limited human data. Use with medical supervision only.
Reconstitution Example
Safety & Considerations
Naturally occurring human antimicrobial peptide. Research use only — not FDA-approved as a standalone therapeutic. May cause injection site irritation. Start with 50 mcg and titrate. Herxheimer-like reactions are reported in early use.
Regulatory & Legal Status
Not currently on the WADA 2026 Prohibited List. Policies may change — verify before competition.
Research Chemical
US Compounding: Not eligible / not available
⚠️ This information is for educational purposes only and may not reflect the most current regulatory updates. Always verify with official FDA, WADA, and jurisdiction-specific sources before use.
Interactions & Contraindications
LL-37 can cause hemolysis at high concentrations — stay within research dose ranges. Pro-inflammatory at high doses. May interact with the action of topical antibiotics (additive or competitive effects at bacterial membranes). Vitamin D deficiency reduces endogenous LL-37 production.
Synergies & Common Stacks
LL-37 provides antimicrobial protection at wound sites while BPC-157 drives vascular repair. Together supporting infected wound healing.
GHK-Cu enhances dermal matrix while LL-37 clears microbial contamination — comprehensive wound healing support.
Dosing Quick Reference
Frequently Asked Questions
What is LL-37 used for?▼
What is the LL-37 dosing protocol?▼
References
- Agerberth B et al. “"LL-37: The Only Human Member of the Cathelicidin Family".” FEBS Letters (1995). PMID: 7556173
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