LL-37 — Clinical Reference

**⚠ Educational reference only — not medical advice.** This article is for research and educational reference. Always consult your own physician before considering any peptide protocol. See the full Disclaimer at the end of this article. ## Introduction LL-37 is the sole mature human cathelicidin — a 37-amino-acid amphipathic α-helical cationic peptide cleaved from the inactive precursor hCAP-18 by proteinase 3 in neutrophils and other cells. Central effector of innate immunity at epithelial surfaces. Investigational as a finished therapeutic; not FDA-approved. ## Mechanism of Action Disrupts bacterial membranes via electrostatic interaction with anionic lipids (the "carpet" mechanism), retaining activity against many antibiotic-resistant Gram-negative and Gram-positive organisms. Beyond direct microbicidal activity, LL-37 modulates the host immune response — neutrophil/monocyte chemotaxis, dampening of LPS-driven inflammation, and angiogenic signaling that supports wound healing. ## Research Indications Chronic wounds (venous ulcers, diabetic foot ulcers), antibiotic-resistant skin and soft-tissue infections, biofilm-associated infections, and rosacea (where LL-37 dysregulation is implicated). Immune-modulation research in autoimmune disease. ## Reconstitution Typical 5 mg lyophilized vial: add **2.5 mL of bacteriostatic water**, swirl gently. Final concentration **2000 mcg/mL (2 mg/mL)** — each 0.05 mL (5 units on a U-100 insulin syringe) delivers 100 mcg. ## Dosing Protocol (research literature) Research protocols typically dose **100–500 mcg subcutaneously once daily** for systemic protocols; **higher topical concentrations** (varied vehicle) for wound applications. Cycle length **2–4 weeks** with reassessment; longer durations are not well-characterized for the systemic SC route. ## Administration Subcutaneous into abdominal fat for systemic protocols. Topical application directly to the wound bed in wound-care protocols (typically with a saline or aqueous vehicle). ## Storage & Handling Lyophilized: refrigerate (2–8°C); freeze (–20°C) for long-term storage. Reconstituted: refrigerate; stable approximately **7–14 days** — LL-37 is protease-sensitive and concentration declines noticeably in solution. Protect from light. ## Side Effects Local injection-site reactions most common. Systemic high-dose exposure can produce cytotoxicity and pro-inflammatory effects — dose and concentration matter substantially. LL-37 is implicated as an autoantigen in psoriasis pathophysiology. ## Contraindications Pregnancy, lactation, active autoimmune skin disease (especially psoriasis), and hypersensitivity to cathelicidin-class peptides. ## Monitoring Baseline wound-area measurement (digital photography or planimetry), CBC, CRP for systemic protocols. Re-measure wound endpoints weekly; systemic biomarkers at 4 and 8 weeks. ## Disclaimer **This article is for informational and research-reference purposes only.** Nothing in this document constitutes medical advice, a prescription, or a recommendation from a physician. The reconstitution, dosing, and protocol information above reflects ranges commonly cited in published research and clinician-directed protocols — it is provided as reference material only, not as instructions, an endorsement of off-label use, or a substitute for individualized medical evaluation. **Customers should do their own research and consult their own physician** before considering any peptide protocol. Whether a given compound is appropriate for an individual — and at what dose, for what duration, and alongside what monitoring — is a decision that only a licensed clinician with knowledge of that individual's medical history, current medications, and conditions can make. The platform and the author make no claim that any compound described here is safe, effective, or appropriate for any particular person or purpose, and accept no responsibility for outcomes arising from self-directed use of the information.