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LlHuman trials

LL-37

LL-37 is a natural germ-fighting peptide made by the body. In people it has been tested only as a gel on leg ulcers that would not heal. It is not an approved medicine, and we found no trial of injected LL-37.

Not approved as a medicine by the US FDAHuman trials: gel on leg ulcers (phase 1/2 and phase 2b)No trial of injected LL-37 found
OverviewDosingMixingResearchCommunitySafetyFAQSources

LL-37 quick reference

TypeHuman cathelicidin peptide (37 amino acids)
Studied forChronic wounds, infection
EvidenceGel trials in people
RouteGel (trials); injection (community)
Half-lifeNot established

What is LL-37?

The body's own germ-fighting peptide, made by skin and immune cells.

People use it hoping to fight stubborn infections and aid repair.

Tested in people only as a wound gel; injection is untested.

How LL-37 works

Germ membranes (lab)

Disrupts germ cell membranes in lab tests.

Biofilm block (lab)

Stopped Pseudomonas biofilm forming at doses far below killing level.

Wound repair signal

Made at skin-wound edges; missing in chronic ulcers.

Immune trigger

Calls in immune cells; excess can fuel autoimmune skin disease.

What LL-37 is studied for

PeopleLeg ulcers

Gel shrank ulcers 68% at 0.5 mg/mL in 34 people.

PeopleLarger ulcer trial

148 people: no significant healing gain overall.

PeopleSkin wound healing

Higher at healing wound edges; absent in chronic ulcers (human skin).

AnimalsRosacea

Rosacea-type LL-37 fragments inflamed mouse skin.

Lab / cellsBiofilms

Blocked Pseudomonas biofilm formation in dishes.

Lab / cellsPsoriasis

LL-37 plus self-DNA switched on human immune cells.

LL-37 dosing protocol

TrialAmount and schedule
Human injection doseNot established
Phase 1/2, venous leg ulcers (34 people)Gel at 0.5, 1.6 or 3.2 mg/mL, applied twice a week for 4 weeks
Phase 2b, venous leg ulcers (148 people)Gel at 0.5 or 1.6 mg/mL, together with compression bandaging

Grönberg 2014 and Mahlapuu 2021. Both were gels applied to the wound, not injections. The phase 2b abstract does not state how often the gel was applied.

GEL TRIAL (PHASE 1/2)0.5–3.2 mg/mL gel, twice weekly, 4 weeksTrial
GEL TRIAL (PHASE 2B)0.5 or 1.6 mg/mL with compressionTrial
COMMUNITY RANGE100–200 mcg daily under the skinCommunity
CYCLEShort, targeted coursesCommunity

Label and trial amounts come from the sources below. Community amounts are what people report; they have not been tested.

Mixing

Vial5 mg
+
BAC water2 mL
=
Strength2.5 mg per mL

Bacteriostatic water. Swirl, refrigerate. Trial gels were topical, not injected.

Open the peptide calculator

What the research found

Phase 1/2 trial, 34 people with hard-to-heal venous leg ulcers, 4 weeks of treatment. What was measured: how much the ulcer shrank.

68%average ulcer shrinkage at 0.5 mg/mL
50%average ulcer shrinkage at 1.6 mg/mL
Nonedifference from placebo at 3.2 mg/mL
148people in the larger phase 2b trial, which found no significant healing gain overall

Grönberg A et al. Wound Repair Regen 2014 (PMID 25041740); Mahlapuu M et al. Wound Repair Regen 2021 (PMID 34687253). In the phase 2b trial a later subgroup look suggested a benefit for ulcers of 10 cm2 or more; that was not the main result.

LL-37 community experience

What users report. Not tested in trials.

Positive reports

  • Stubborn problems Some report better recovery from persistent skin or immune issues.
  • Short courses Many prefer brief, targeted use over continuous use.
  • Biofilm and gut interest These goals drive many of the reports.

Negative & mixed

  • Injection-site burning Burning, swelling and itching are common.
  • Flu-like days Aches, tiredness, low fever and malaise are reported.
  • Hard to read Some see no benefit; flares are hard to interpret.

LL-37 stacking

LL-37 + BPC-157

Germ-fighting plus repair idea. Not studied together.

LL-37 + thymosin alpha-1

Innate plus adaptive immunity idea. Not studied together.

LL-37 + antibiotics

Lab synergy only. Never change prescribed treatment.

LL-37 side effects & safety

Common

  • Gel trials found no safety concerns; injections are untested.
  • The gel was well tolerated in the larger trial.
  • User reports: burning, redness or itching where injected.
  • User reports: tiredness, aches or low fever.

Less common

  • May flare psoriasis, rosacea, lupus or other inflammatory disease.
  • High amounts damaged human cells in lab tests.
  • Long-term injected safety is unknown.

Precautions

  • Avoid with psoriasis, rosacea, lupus or other autoimmune disease.
  • Avoid in pregnancy or breastfeeding; no data.
  • Active infection needs proper medical treatment.
  • Immunosuppressant drugs: possible interaction, unstudied.

Our verdict on LL-37

Real biology and a modest gel signal. Injected LL-37 is unstudied and could inflame some conditions.

LL-37 FAQ

Is LL-37 proven for infections?

No. The germ-killing data are lab-only.

Has injected LL-37 been tested in people?

Not that we found. Human trials used a wound gel.

Does LL-37 help wounds?

The early gel trial said yes at low strength. The larger trial missed its main goal.

Who should avoid LL-37?

People with autoimmune or inflammatory skin disease.

Sources

  • Grönberg A et al. Wound Repair Regen 2014 (phase 1/2), PMID 25041740
  • Mahlapuu M et al. Wound Repair Regen 2021 (phase 2b, HEAL LL-37), PMID 34687253
  • Drugs@FDA / openFDA search: no LL-37 product
  • Overhage J et al. Infect Immun 2008 (LL-37 blocks biofilm formation), PMID 18591225
  • Heilborn JD et al. J Invest Dermatol 2003 (LL-37 in human skin wounds), PMID 12603850
  • Lande R et al. Nature 2007 (LL-37, self-DNA and psoriasis), PMID 17873860
  • Yamasaki K et al. Nat Med 2007 (cathelicidin and rosacea), PMID 17676051
  • Svensson D et al. Biochem J 2016 (LL-37 toxicity to human cells), PMID 26508735