PeptideFederation

Human antimicrobial peptide

LL-37

Also known as Cathelicidin, hCAP18 (precursor), CAMP

Human RCTs

Summary

LL-37 is the only human cathelicidin, an antimicrobial peptide made by skin, gut and immune cells. It kills bacteria by disrupting their membranes and also signals to immune cells. An early trial found it improved healing of hard-to-heal leg ulcers, but a larger follow-up trial did not meet its primary endpoint.

Structure

  1. L1
  2. L2
  3. G3
  4. D4
  5. F5
  6. F6
  7. R7
  8. K8
  9. S9
  10. K10
  11. E11
  12. K12
  13. I13
  14. G14
  15. K15
  16. E16
  17. F17
  18. K18
  19. R19
  20. I20
  21. V21
  22. Q22
  23. R23
  24. I24
  25. K25
  26. D26
  27. F27
  28. L28
  29. R29
  30. N30
  31. L31
  32. V32
  33. P33
  34. R34
  35. T35
  36. E36
  37. S37

HydrophobicGly / ProPolarBasic (+)Acidic (−)

The only cathelicidin in humans, cleaved from the precursor hCAP18. Named for its first two leucines and its length.

How it works

LL-37 is cationic and amphipathic, so it inserts into negatively charged bacterial membranes. It also binds lipopolysaccharide, recruits immune cells, and promotes angiogenesis and re-epithelialization.

Research use cases

Areas where LL-37 has been studied. Inclusion here does not mean it works for that purpose.

  • Chronic wound healing
  • Antimicrobial and anti-biofilm research
  • Innate immunity and autoimmunity (psoriasis, lupus) research

What the research found

Venous leg ulcers, phase 1/2

In 34 patients, topical LL-37 at the lower and middle concentrations significantly improved the healing rate of venous leg ulcers over four weeks compared with placebo.1

Venous leg ulcers, phase 2b

A larger multicentre trial did not show a significant overall difference in healing versus placebo, although subgroup analyses were reported.2

Biology review

Reviews describe LL-37’s dual roles in host defence and in inflammatory disease, where excess LL-37 can contribute to psoriasis and rosacea.3

Safety and open questions

Topical use was well tolerated in trials. LL-37 can be cytotoxic to human cells at high concentrations and has been linked to inflammatory skin disease when overexpressed.

Regulatory status

Not approved. Tested in phase 1/2 and phase 2b trials for venous leg ulcers. Not included in the 2026 compounding changes.

Status was accurate when this page was last reviewed on October 26, 2026. Regulations change; check with the relevant authority before relying on it.

LL-37: common questions

Is LL-37 an antibiotic?

It has antibiotic activity, but it is also an immune signal. It is being studied for wounds and infections, not approved as an antibiotic.

Is LL-37 approved for human use?

Not approved. Tested in phase 1/2 and phase 2b trials for venous leg ulcers. Not included in the 2026 compounding changes.

References

  1. Grönberg A, Mahlapuu M, Ståhle M, Whately-Smith C, Rollman O. (2014). 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 and Regeneration.
  2. Mahlapuu M, Sidorowicz A, Mikosinski J, et al. (2021). Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial. Wound Repair and Regeneration.
  3. Dürr UHN, Sudheendra US, Ramamoorthy A. (2006). LL-37, the only human member of the cathelicidin family of antimicrobial peptides. Biochimica et Biophysica Acta.

Links open a PubMed search for the exact title, or the original source where one is given.