LL-37: The Human Cathelicidin and Its Antimicrobial Role
The human cathelicidin antimicrobial peptide, part of the body's first line of defense against infection, studied for wound healing and immune modulation.
What is LL-37?
LL-37 is the human cathelicidin antimicrobial peptide, a 37-residue C-terminal fragment of the hCAP18 precursor protein, named for its first two residues (leucine-leucine) and total length. It's a cationic, amphipathic, alpha-helical peptide that disrupts bacterial cell membranes for broad-spectrum antimicrobial activity, and plays a role in the body's innate immune response at sites of infection and inflammation. It's also studied for wound healing and angiogenesis. No established human clinical dosing protocol exists, nearly all substantive data is preclinical or in-vitro, and it's sold only as a research compound.
Quick facts
- Molecular Formula
- C205H340N60O53
- CAS Number
- 597562-32-8
- Class
- Human cathelicidin antimicrobial peptide
- Brand Names
- No trademarked brand, sold as a research compound
- Legal Status
- Not FDA-approved for human use, research use only (RUO)
- Category
- Antimicrobial / Wound Healing
- Storage
- Store the lyophilized vial refrigerated (2-8°C) or at -20°C, away from light. Once reconstituted, keep refrigerated at 2-8°C and use promptly.
Dosing at a glance
A common research-vendor convention is a 5mg vial reconstituted with 2mL bacteriostatic water = 2500mcg/mL, this reflects vendor convention, not a validated clinical protocol. Run the numbers in the LL-37 reconstitution calculator.
Store the lyophilized vial refrigerated (2-8°C) or at -20°C, away from light. Once reconstituted, keep refrigerated at 2-8°C and use promptly.
LL-37 Mechanism of Action
Broad-Spectrum Membrane Disruption
LL-37 is a cationic, amphipathic, alpha-helical peptide that inserts into and disrupts bacterial cell membranes, giving it broad-spectrum antimicrobial activity against both gram-positive and gram-negative bacteria. As part of the human cathelicidin family, it's produced by immune cells (neutrophils, macrophages) and epithelial cells as a first-line defense at sites of infection or injury.
Beyond Antimicrobial Activity
Beyond directly killing pathogens, LL-37 is studied for roles in wound healing (promoting keratinocyte migration and angiogenesis) and broader immunomodulation, recruiting and activating other immune cells, and influencing inflammatory signaling at injury or infection sites.
LL-37 Dosage and Protocols
No Established Human Protocol
There is no established human clinical dosing protocol for LL-37. Vendors sell it for topical and subcutaneous research use with wide, non-standardized ad hoc dosing conventions, but no formal human pharmacokinetic or dose-finding study has ever been published, treat any specific dose figure circulating in research communities as informal convention, not validated guidance.
LL-37 Side Effects and Safety
Undefined Human Safety Profile
No formal human safety or tolerability study exists for LL-37 administered as a standalone compound. Given its role in immune signaling, active autoimmune conditions are treated as a precautionary contraindication, along with pregnancy.
Contraindications
Reported contraindications: pregnancy, active autoimmune conditions.
LL-37 Research Evidence
Preclinical and In-Vitro Focus
The substantial majority of LL-37 research is preclinical, cell culture, animal models, and structural/biophysical studies of its membrane-disrupting mechanism. It's a well-studied molecule academically, but that depth of preclinical characterization has not translated into human clinical trials or an approved therapeutic use.
Regulatory and Legal Status
LL-37 has no FDA-approved indication and is not approved for human consumption. It is sold exclusively as a research-grade compound (RUO). Researchers and users should verify the legal status of LL-37 in their jurisdiction prior to purchase or use.
LL-37 Stacking and Combinations
Standalone Research Compound
LL-37 doesn't have a well-established peptide-stacking pairing in the research-community sense, it's typically studied and used on its own for wound-healing or antimicrobial research angles, rather than combined into multi-peptide protocols.
LL-37 Pharmacokinetics
No Published Human PK Data
No formal human pharmacokinetic study, absorption, half-life, clearance, has been published for LL-37. Available data comes from in-vitro membrane-interaction studies and animal models rather than human plasma measurements.
Legal status
Not FDA-approved for human use, research use only (RUO)
Regulatory standing is a statement about how a compound may be sold and prescribed, not about whether it works. See how we grade evidence.
Frequently asked questions
What is a typical LL-37 dose?
Published research protocols report No standardized dose, no established human protocol. This is the range described in the literature, not a recommendation.
What is the half-life of LL-37?
No formal human pharmacokinetic data published.
Is LL-37 backed by strong evidence?
LL-37 carries a REGEN research grade of D. REGEN Research Tier D, real topical wound-gel RCTs exist (one small positive, one failed confirmatory), but the injectable form users buy has zero human data.
How is LL-37 administered?
Routes reported in the literature: subcutaneous, topical.
Who should avoid LL-37?
Contraindications noted in the literature include pregnancy, active autoimmune conditions.