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LL-37

LL-37 is a 37-amino-acid peptide that the human body makes as part of its first-line defense against infection. It is cut from a larger protein called cathelicidin and is found in skin, the gut, the airways and white blood cells. In lab studies it kills many microbes and affects inflammation and wound repair. It is not approved as a medicine anywhere.

Not approved · research onlyWADA Not named; as an unapproved drug it falls under S0 (prohibited at all times)Checked October 2026
Open the LL-37 calculatorSources

Approval status

Not approved as a medicine anywhere. A drug version, ropocamptide, was tested in phase 2 trials as a topical treatment for leg ulcers. FDA had listed it among compounding substances that may pose significant safety risks. It came off that list in April 2026 after its nomination was withdrawn, but it is still not a substance pharmacies may compound with. FDA plans to ask its advisory committee about it before the end of February 2027.3456713

What it’s used or studied for

  • Human studies

    Hard-to-heal venous leg ulcers: a small first trial suggested faster healing, but a larger placebo-controlled trial in 148 patients found no overall benefit.83

  • Human studies

    Diabetic foot ulcers: one randomized trial reported faster healing with an LL-37 cream than with a placebo cream over four weeks.9

  • Human studies

    Melanoma: injected into skin tumors in a small early-phase trial with 4 patients.1011

  • Animal & lab only

    Fighting bacteria, viruses and fungi, and calming inflammation: shown in lab studies, reflecting its natural role in the immune system.12

Each label shows how strong the evidence is: an approved use, human studies, animal or lab studies only, or a popular claim with no published studies. Being studied is not the same as being proven safe or effective.

Side effects

Serious or rare

  • Wart-like skin growths that looked like skin cancer after tumor injections; they cleared after stopping (one case)

Applied to leg ulcers, LL-37 was well tolerated in two trials. The few effects judged possibly related to it, such as skin irritation at the treated area, wound infection and leg swelling, each occurred in single patients. The skin growths were reported in a melanoma patient given repeated tumor injections.381110

Cautions

  • FDA notes animal findings suggesting harm to male reproduction, and that LL-37 may promote tumors in some tissues.4
  • FDA warns that compounded LL-37 may trigger immune reactions and may contain peptide-related impurities.4

Sources

  1. UniProt: Cathelicidin antimicrobial peptide, human (P49913)
  2. PubChem: LL-37 (ropocamptide) (CID 16198951)
  3. Mahlapuu et al. (2021). Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: a multicentric randomized placebo-controlled trial. Wound Repair Regen
  4. FDA: Bulk drug substances used in compounding that may present significant safety risks (current as of April 2026)
  5. FDA: Bulk drug substances nominated for compounding under section 503A, categories 1 to 3 (updated May 14, 2026)
  6. FDA guidance: Interim policy on compounding using bulk drug substances under section 503A (January 2025)
  7. FDA: Upcoming Pharmacy Compounding Advisory Committee meeting, before the end of February 2027
  8. Grönberg et al. (2014). Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled trial. Wound Repair Regen
  9. Miranda et al. (2023). Efficacy of LL-37 cream in enhancing healing of diabetic foot ulcer: a randomized double-blind controlled trial. Arch Dermatol Res
  10. ClinicalTrials.gov: Intratumoral injections of LL37 for melanoma (NCT02225366)
  11. Dolkar et al. (2018). Dermatologic toxicity from novel therapy using antimicrobial peptide LL-37 in melanoma. J Cutan Pathol
  12. Dürr, Sudheendra & Ramamoorthy (2006). LL-37, the only human member of the cathelicidin family of antimicrobial peptides. Biochim Biophys Acta
  13. World Anti-Doping Agency: 2026 Prohibited List (in force from January 1, 2026)

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