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Peptide profile

LL-37: FDA Status, Research and Uses

By Living+. Updated October 25, 2026.

Key takeaway

LL-37 is a 37 amino acid antimicrobial peptide that the human body makes from its only cathelicidin gene. It is an investigational drug, and FDA lists it among compounding substances with safety concerns. Small human trials tested it as a topical treatment for leg and foot ulcers, with mixed results [7, 6, 1, 10].

At a glance

Where it stands

Checked

  • FDA approvedNoNo approved product
  • Pharmacy compounding (503A)WithdrawnNot in category 1, 2 or 3 on FDA's 503A list updated May 14, 2026; FDA's safety page (current as of April 22, 2026) lists cathelicidin LL-37 as previously in category 2 with the nomination withdrawn. Not discussed at the July 2026 PCAC meeting.
  • Outsourcing facilities (503B)Not nominatedNot listed in any 503B category on FDA's 503B list updated March 21, 2025.
  • WADA (sport)UnclearNot named on the 2026 or 2027 List. S0 (non-approved substances) may apply, since it covers substances no government has approved for human use. The 2027 List, in force January 1, 2027, adds peptides as an S0 example.
Same data as the Status Tracker. Checked against 7 sources

Key facts

Class
Human cathelicidin antimicrobial peptide (host defense peptide) [6, 7]
Length
37 amino acids [7]
Half-life
Not established in humans [1]
Route in studies
Topical solution or cream on ulcers in human trials; injection into tumors in one small melanoma trial [9, 11, 12]
First studied
1995 (predicted as FALL-39), mature LL-37 isolated in 1996 [5, 6]

How it works

LL-37 was first predicted in 1995 from a human bone marrow gene as a longer peptide called FALL-39, which killed some bacteria in lab tests [5]. In 1996 researchers found that white blood cells release the mature 37 amino acid form, named LL-37. Its gene is the only cathelicidin gene in the human genome [6, 7].

LL-37 forms a helix with one water-loving side and one fat-loving side. This shape lets it disrupt the membranes of many microbes [7]. It is made in skin, gut and airway lining cells and in several kinds of white blood cells. It also binds bacterial toxins, draws immune cells to wounds and infection sites, and supports skin regrowth over wounds [7].

The active form of vitamin D turns on the cathelicidin gene in human skin and immune cells, which raises LL-37 levels [8]. Higher LL-37 is not always good. A 2023 study found that LL-37 raised signals linked to tumor invasion and blood vessel growth in human melanoma cells, and its mouse version did the same in mice [13]. FDA also notes that animal research suggests harm to male reproduction and possible tumor growth in some tissues [1]. FDA says it lacks enough safety information to know whether LL-37 would cause harm in people [1].

What the research shows

4 human trials1 animal study1 lab study

  1. 2023Human trial

    Diabetic foot ulcer cream trial (Miranda et al.)

    Adults with mildly infected diabetic foot ulcers Randomized, double-blind, placebo cream twice a week for 4 weeks

    Granulation scores rose more with LL-37 cream on days 7 to 28. Inflammation markers and bacteria counts did not differ significantly [11].

    Read the study
  2. 2021Human trial

    Phase 2b venous ulcer trial (Mahlapuu et al.)

    Studied for venous leg ulcers

    148 adults with long-lasting venous leg ulcers Phase 2b, randomized, double-blind, placebo-controlled, topical plus compression

    No significant benefit over placebo in the full group. A post hoc look suggested benefit in large ulcers [10].

    Read the study
  3. 2015Human trial

    Intratumoral LL-37 for melanoma (NCT02225366)

    Studied for immune response in melanoma

    4 adults with melanoma Phase 1/2 dose-finding study of injections into tumors

    The study is listed as completed in 2020, with results posted on the registry [12].

    Read the study
  4. 2014Human trial

    First-in-human venous ulcer trial (Gronberg et al.)

    34 adults with venous leg ulcers Randomized, double-blind, placebo-controlled, 4 weeks of topical dosing twice a week

    Ulcer area fell 68% at 0.5 mg/mL and 50% at 1.6 mg/mL. The 3.2 mg/mL dose did no better than placebo. No safety concerns were seen [9].

    Read the study
  5. 2023Animal study

    LL-37 and melanoma invasion (Ohuchi et al.)

    Mice, human melanoma cells and tissue samples Tissue staining, mouse melanoma model and cell culture

    LL-37 in human cells, and its mouse version CRAMP in mice, raised pro-invasion and blood vessel growth signals. Authors suggested it might promote local melanoma invasion [13].

    Read the study
  6. 1995Lab study

    Discovery of FALL-39 (Agerberth et al.)

    Human bone marrow gene library (lab) Gene cloning and lab antibacterial tests of the synthetic peptide

    Identified a 39 residue precursor peptide that was highly active against E. coli and B. megaterium in lab tests [5].

    Read the study

Doses used in studies

No human dose of LL-37 has been established, and no dose by injection under the skin or by mouth has been tested in a published trial we found. Published human trials used LL-37 on the skin of chronic ulcers. A first-in-human trial applied 0.5, 1.6 or 3.2 mg/mL twice a week for 4 weeks [9]. The phase 2b trial used 0.5 or 1.6 mg/mL [10].

A diabetic foot ulcer trial applied LL-37 cream twice a week for 4 weeks [11]. A small melanoma trial tested injections into tumors to find a dose, with 4 people enrolled [12].

Dosing is set by a licensed provider.

Side effects and safety

FDA says compounded LL-37 may cause immune reactions for some routes, may contain peptide impurities, and that it lacks enough safety information to know whether it would cause harm in people [1]. FDA also notes that animal research suggests harm to male reproduction and that LL-37 can promote tumors in some tissues [1].

In the topical ulcer trials, LL-37 raised no local or systemic safety concerns over 4 weeks [9], and the phase 2b trial reported it was well tolerated at both strengths [10]. These trials were short and applied LL-37 to wounds, so they do not show safety for injected or long-term use [9, 10].

Lab research on LL-37, and a mouse study of its mouse version, linked it to signals that may help melanoma invade nearby tissue [13]. There is no FDA label or boxed warning for LL-37 [1].

Common questions

What is LL-37?

LL-37 is a 37 amino acid antimicrobial peptide. It is the only cathelicidin peptide made by humans [7, 6].

Is LL-37 FDA approved?

No. It has only been tested in small trials. One developer was testing it under the name ropocamptide [10]. FDA lists it among compounding substances with safety concerns [1].

Can a US pharmacy compound LL-37?

It is not on FDA's 503A categories list as of May 14, 2026. FDA lists it as previously in category 2, with the nomination withdrawn [2, 1].

Was LL-37 discussed at the July 2026 FDA advisory meeting?

No. The July 23 to 24, 2026 meeting covered BPC-157, KPV, TB-500, MOTS-c, emideltide, Semax and Epitalon, not LL-37 [14].

Does vitamin D raise LL-37?

Lab research shows the active form of vitamin D turns on the cathelicidin gene in human skin and immune cells [8].

Can LL-37 promote cancer?

FDA says animal research suggests it can promote tumors in some tissues [1]. A 2023 study linked it to melanoma invasion signals [13].

Has LL-37 been tested in people?

Yes, in small trials on venous leg ulcers and diabetic foot ulcers, and a 4 person melanoma study [9, 10, 11, 12].

Is LL-37 banned by WADA?

Unclear. LL-37 is not named. WADA's S0 class bans any drug substance with no current government approval for human use, but WADA has not said whether that covers LL-37, which the body also makes [4].

Sources

  1. FDA: Certain bulk drug substances for use in compounding that may present significant safety risks
  2. FDA: Bulk drug substances nominated for use in compounding under section 503A (updated May 14, 2026)
  3. FDA: Bulk drug substances nominated for use in compounding under section 503B (updated March 21, 2025)
  4. WADA: 2026 Prohibited List
  5. Agerberth et al. 1995, PNAS (PubMed)
  6. Gudmundsson et al. 1996, Eur J Biochem (PubMed)
  7. Durr et al. 2006, Biochim Biophys Acta, review (PubMed)
  8. Wang et al. 2004, J Immunol (PubMed)
  9. Gronberg et al. 2014, Wound Repair Regen (PubMed)
  10. Mahlapuu et al. 2021, Wound Repair Regen (PubMed)
  11. Miranda et al. 2023, Arch Dermatol Res (PubMed)
  12. ClinicalTrials.gov: NCT02225366, Intratumoral injections of LL37 for melanoma
  13. Ohuchi et al. 2023, Cancers (PubMed)
  14. FDA: July 23-24, 2026 meeting of the Pharmacy Compounding Advisory Committee

Updated October 25, 2026. Educational information, not medical advice.