LL-37 for Chronic and Biofilm-Associated Infections

Candidate profile

Adults with chronic, recurrent, or antibiotic-resistant infections where biofilm formation is suspected or documented. Common presentations:

• Chronic sinusitis with culture-positive MARCoNS (multiple antibiotic-resistant coagulase-negative staphylococci) — often in the context of CIRS
• Chronic Lyme disease or post-treatment Lyme disease syndrome with persistent symptoms
• Recurrent urinary tract infections unresponsive to standard antibiotic courses
• Chronic wound infections with suspected biofilm component

Not appropriate for: acute bacterial infections (use antibiotics), viral infections (LL-37 has limited antiviral activity), or as a replacement for appropriate antimicrobial therapy.

Approach

LL-37 is the only human cathelicidin antimicrobial peptide — a 37-amino-acid peptide cleaved from the precursor hCAP-18. It functions as a first-line innate defense molecule with three relevant mechanisms:

1. Direct antimicrobial activity — LL-37 disrupts bacterial membranes through electrostatic interaction with negatively charged lipid bilayers. Effective against gram-positive and gram-negative bacteria, and some fungi
2. Biofilm disruption — LL-37 prevents biofilm formation and disrupts established biofilms at sub-bactericidal concentrations. This is its most clinically interesting property for chronic infections, as biofilm-protected bacteria are 100–1000× more resistant to conventional antibiotics
3. Immune modulation — LL-37 recruits immune cells to infection sites, modulates dendritic cell activation, and promotes wound healing. It serves as a bridge between innate and adaptive immunity

Protocol design

Peptide: LL-37, 100 mcg subcutaneous daily

Route: Subcutaneous (abdominal or deltoid), or intranasal for sinus-targeted applications

Duration: 4–8 weeks

Optional adjunct: Thymosin alpha-1, 1.6 mg subcutaneous 2–3 times weekly (for comprehensive immune support alongside LL-37's antimicrobial action)

For MARCoNS/sinus infections:

• Nasal spray formulation: LL-37 combined with EDTA-based biofilm disruptor
• BEG spray (Bactroban/EDTA/Gentamicin) is the conventional approach; LL-37 nasal spray is an emerging adjunct or alternative

Expected timeline

Week 1–2: Minimal clinical change. Biofilm disruption is gradual, not immediate.

Weeks 3–4: Possible increase in symptoms ("die-off" or Herxheimer-like reaction as biofilm-protected organisms are exposed). Some patients experience temporary worsening before improvement.

Weeks 5–6: Progressive improvement in chronic infection symptoms. For MARCoNS, repeat nasal culture at 4 weeks may show reduced colony counts.

Weeks 7–8: Consolidation. Repeat cultures to assess microbial clearance. Symptom improvement should be progressive.

Monitoring

• Microbial cultures (baseline, 4 weeks, 8 weeks): nasal culture for MARCoNS, urine culture for UTI, wound culture as appropriate
• Inflammatory markers: CRP, ESR, white blood cell count
• Symptom tracking: Infection-specific symptoms (sinus pain, urinary symptoms, wound appearance)
• For CIRS context: MARCoNS culture status, VCS testing, and upstream CIRS markers

Important caveats

• LL-37 has dual roles — antimicrobial and pro-inflammatory. In some contexts (psoriasis, rosacea), LL-37 is pathologically elevated and contributes to disease. Exogenous LL-37 in patients with LL-37-mediated conditions could theoretically worsen inflammation
• Human clinical data for exogenous LL-37 administration is very limited. Most evidence is in-vitro and animal models
• LL-37 is being developed for wound healing applications (topical formulations) with clinical trials underway, but injectable use for chronic infections is not supported by published clinical trials
• Biofilm-associated infections are complex. LL-37 may be one component of a comprehensive strategy that includes appropriate antibiotics, biofilm disruptors, and immune support — not a standalone cure
• Product quality and stability of LL-37 preparations vary significantly between compounding sources