LL-37

Overview

LL-37 is the only human cathelicidin antimicrobial peptide, produced naturally by skin, immune cells and mucosal surfaces as part of innate defense. It has broad-spectrum antimicrobial and anti-biofilm activity and also signals to host cells in ways linked to inflammation, angiogenesis and wound healing. It is more clinically advanced than most research peptides — multiple human trials exist — but the results are mixed and cut both ways. A small Phase I/IIa study in chronic venous leg ulcers reported reduced ulcer area with topical LL-37, but the larger HEAL Phase IIb trial (148 patients) found NO significant healing benefit over placebo. A 3-patient Phase 1 study injected LL-37 into melanoma lesions, and separate research has raised the concern that LL-37 may actually promote tumor invasion in some contexts. It is not FDA-approved for any indication, and the most rigorous wound-healing trial was negative.

Commonly Reported Uses

These are uses commonly discussed or marketed by users and vendors — not a list of proven or approved benefits, and not a recommendation.

• Chronic wound and ulcer healing (marketed claim; positive small trial but a larger Phase IIb RCT was negative)
• Antimicrobial / anti-biofilm and immune support (marketed claim; mechanism established, clinical benefit unproven)
• Anti-cancer / intratumoral immunotherapy (investigational only; tiny early study, and possible tumor-promoting effects reported)

What to Track

Data points you and your clinician might monitor. For observation only — not a diagnostic protocol.

• Subjective — wound size, healing progress and pain for a tracked wound or ulcer; standardized photos
• Labs — white-cell count and hs-CRP if a clinician is monitoring infection/inflammation
• Skin — local irritation, redness or unexpected lesion changes (dermatologic toxicity has been reported with intratumoral use)
• Subjective — energy and general recovery
• WHOOP — recovery and resting heart rate as a general well-being signal during an infection-recovery goal

Sources & References

1. [1]Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: a multicentric prospective randomized placebo-controlled clinical trial — PMC
2. [2]The Human Cathelicidin Antimicrobial Peptide LL-37 as a Potential Treatment for Polymicrobial Infected Wounds — PMC
3. [3]LL-37 Might Promote Local Invasion of Melanoma by Activating Melanoma Cells and Tumor-Associated Macrophages — PMC