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 reconstitution calculator.
Doses shown are those reported in published research, not a recommendation.
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.
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.
Contraindications
- pregnancy
- active autoimmune conditions
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.
References
- Molecular Dynamics Simulations of Human Antimicrobial Peptide LL-37
- Immunomodulatory Functions of the Human Cathelicidin LL-37-Derived Peptides
- Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial · Grönberg A, Mahlapuu M, Ståhle M · 2014