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Tissue Repair & Anti-Inflammatory

LL-37 (Cathelicidin)

The body's own vitamin D–driven antimicrobial peptide; studied topically for wounds, used off-label for biofilm infections.

RestrictedEvidence level 3 of 5: Limited human dataAlso: Cathelicidin LL-37, hCAP-18 C-terminal peptide, Ropocamptide

Overview

LL-37 is the only cathelicidin antimicrobial peptide made by humans, produced by white blood cells and epithelial cells and strongly increased by vitamin D. It kills bacteria, fungi and some viruses by disrupting their membranes, can break up biofilms, neutralizes bacterial endotoxin and recruits immune cells to sites of infection and injury. It also promotes new blood vessel growth and re-epithelialization in wounds. These properties have made it of interest for chronic wounds and difficult, biofilm-associated infections. Human data are limited to small topical wound and cancer trials. Because elevated LL-37 contributes to psoriasis, lupus and rosacea, it can aggravate some autoimmune conditions, and initial use in heavily colonized patients may provoke flu-like reactions.

Classification
Endogenous 37-amino-acid human cathelicidin antimicrobial peptide
Route
Subcutaneous, topical or intranasal
Half-life
Short (minutes to hours; protease-degraded)

Mechanism of action

Primary targetMicrobial membranes; FPR2 and P2X7 receptors on immune cells
  1. SC, topical or nasal dosingDelivered systemically or applied directly to wounds or sinuses.
  2. Membrane disruptionAmphipathic helix inserts into microbial membranes, killing bacteria and fungi.
  3. Biofilm breakdownInhibits biofilm formation and penetrates established biofilms.
  4. Endotoxin neutralizationBinds LPS, reducing excessive inflammatory signaling.
  5. Immune recruitment, re-epithelializationChemoattracts immune cells and stimulates keratinocyte migration and angiogenesis.
Downstream effects
  • Broad antimicrobial activity
  • Wound healing
  • Immune modulation

Researched for

  • Chronic venous leg ulcers
  • Biofilm-associated chronic infection
  • Chronic rhinosinusitis / MARCoNS
  • Melanoma (intratumoral, early-phase)
  • Diabetic foot wounds

Research notes

  • Grönberg et al. (2014) Phase I/II: topical LL-37 improved venous ulcer healing rate versus placebo in a small trial.
  • HEAL LL-37 Phase IIb (2020): benefit reported only in a post-hoc subgroup of larger ulcers.
  • LL-37 levels are elevated in psoriatic plaques and implicated in lupus and rosacea pathology.
  • No controlled human data for subcutaneous use in chronic infection, Lyme or CIRS.

Reported side effects

  • Injection-site pain or redness
  • Herxheimer-like flu symptoms early in treatment
  • Flare of psoriasis, rosacea or autoimmune disease
  • Local irritation (topical)

Contraindications & cautions

  • Active autoimmune disease (psoriasis, lupus, rosacea)
  • Pregnancy and breastfeeding
  • Active malignancy (angiogenic effects)
  • Age under 18 without specialist input

Lab monitoring

  • CBC with differential
  • CMP
  • CRP, ESR
  • Vitamin D (25-OH), zinc
  • Quantitative immunoglobulins; CIRS markers if indicated

Dosing and pricing for LL-37 (Cathelicidin)

Dosing references and compound pricing are available to established patients in the secure portal after a medical evaluation.

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