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All peptides

Immune · Investigational

LL-37

No lawful US pathway

Tell me if this changesRead the free 2026 Peptide Safety Checklist →
Written by Peptide Association Editorial TeamLast reviewed Editorial policy

01 · Overview

The only human cathelicidin antimicrobial peptide, a 37-amino acid cationic peptide cleaved from the precursor protein hCAP18 (PMID 40869425). LL-37 has broad antimicrobial, antiviral, and antifungal activity along with immunomodulatory functions, but clinical use is limited by low proteolytic stability, cytotoxicity, and production costs (PMID 40869425).

It is produced in skin upon wounding and appears to contribute to re-epithelialization (PMID 12603850).

02 · Research summary & key findings

In a first-in-human randomized, placebo-controlled trial in 34 patients with hard-to-heal venous leg ulcers, topical LL-37 at the two lower doses improved healing and was well tolerated, while the highest dose did not differ from placebo (PMID 25041740). LL-37 is absent from the epithelium at the edge of chronic ulcers, which may impair wound closure (PMID 12603850). Rosacea skin shows abnormally high cathelicidin levels and abnormally processed peptides that promote inflammation (PMID 17676051). Some MRSA strains show clonotype-specific resistance to LL-37 (PMID 35709124).

03 · Regulatory status

LL-37 is in the investigational stage. While preclinical and early-phase data exist, it has not received regulatory approval for clinical use in the United States.

No lawful pathway today

LL-37 is not FDA-approved and does not currently have a lawful prescription or compounding pathway in the United States, so we do not sell it and will not book a consultation for it. That can change: in 2026 FDA began reviewing several peptides for compounding.

See the 1 FDA-approved compound in Immune

Tell me if the status changes

One email, only if this compound's regulatory standing actually moves. Not a newsletter, not a sales sequence.

04 · Administration routes

  • Subcutaneous injection
  • Topical

References

  1. [1]The cathelicidin anti-microbial peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcer epithelium J Invest Dermatol, 2003. PMID 12603850
  2. [2]Increased serine protease activity and cathelicidin promotes skin inflammation in rosacea Nat Med, 2007. PMID 17676051
  3. [3]Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial Wound Repair Regen, 2014. PMID 25041740
  4. [4]Multilocus sequence type-dependent activity of human and animal cathelicidins against community-, hospital-, and livestock-associated methicillin-resistant Staphylococcus aureus isolates J Anim Sci Technol, 2022. PMID 35709124
  5. [5]Antimicrobial Peptides of the Cathelicidin Family: Focus on LL-37 and Its Modifications Int J Mol Sci, 2025. PMID 40869425

Primary literature

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Disclaimer: This information is provided for educational and research purposes only. It is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting any peptide therapy. The Peptide Association does not endorse or recommend any specific treatment protocol. See our editorial policy for how this content is produced and reviewed. Clinicians: join the network.