Peptides / Immune and antimicrobial

Natural fragment · 37 amino acids · 4,493.3 Da

LL-37

Not approvedBanned in sport

LL-37 is a natural antimicrobial peptide from the human immune system, cut from a larger protein called hCAP18. It was tested as a skin drug in leg ulcer trials and is not approved, and most studies are in lab cells, on infection. PepBank shows 24 results on LL-37 from 5 studies in people, and 166 from animal and lab studies. The strongest evidence is a randomized trial in people. Data as of 2026-10-30.

Also known as CAP18, hCAP18, Antibacterial peptide LL-37, Cathelicidin LL-37, LL37, Ropocamptide

37 amino acids, from first to last0 changed amino acids

Evidence level: Some studies in people24 of 190 results come from studies in people.

Results in people

13% of 190 results

Results in animals

24% of 190 results

Results in lab cells

121

64% of 190 results

From computer models

0% of 190 results

Overview

LL-37 at a glance

What it is	Natural fragment, 37 amino acids
Approval	Not approved for any use
In sport	Banned in sport (WADA S0)
Studies	147 studies with results. 49 of them gave LL-37, with 190 results. 24 in people45 in animals121 in lab cells
Best study in people	Randomized controlled trial with 238 people (2023)
Clinical trials	2 registered: 0 active or planned, 1 with posted results
Community use	General immune support and chronic infections, including Lyme disease claims; Gut problems such as SIBO and dysbiosis, often stacked with BPC-157; Biofilm disruption claims (based on lab data)

The science

What is LL-37?

Human antimicrobial peptide (37 residues) cut from the cathelicidin precursor hCAP18. Tested as a topical drug (ropocamptide) in leg ulcer trials; not approved.

Amino acids in one chain

The history of LL-37

1996
The oldest paper on LL-37 in PepBank is from 1996.
2015July
A registered trial of LL-37 started (NCT02225366).

LL-37 structure and chemistry

The key facts about the molecule. Long codes are in the closed section below.

Sequence, 37 amino acidsFrom the first amino acid to the last

L1LG−DF5F+R+KS+K10−E+KIG+K15−EF+K+RI20VQ+RI+K25−DFL+RN30LVP+RT35−ES

Darker means more water-repelling+ and − show charge in the body

Structure

LL-37 is a natural fragment of 37 amino acids, with no ring, no changed amino acids.

Formula

C₂₀₅H₃₄₀N₆₀O₅₃

Molecular weight

4,493.3 g/mol

CAS number

154947-66-7

Target

N-formyl peptide receptor 2 (FPRL1) (gene FPR2): agonist (chemotaxis, Ca2+ mobilisation)Evidence: primary literature (human monocytes, neutrophils, T cells and FPRL1-transfected HEK293 cells, 2000)

Development

Promore Pharma AB (ropocamptide, topical, venous leg ulcers). Highest phase: phase 2.

Identifiers

PubChem 16198951, ChEMBL CHEMBL530345, UNII 3DD771JO2H, DrugBank DB16532, UniProt P49913, PDB 2K6O

Full sequence, SMILES and InChIKey

Three-letter sequence
H-Leu-Leu-Gly-Asp-Phe-Phe-Arg-Lys-Ser-Lys-Glu-Lys-Ile-Gly-Lys-Glu-Phe-Lys-Arg-Ile-Val-Gln-Arg-Ile-Lys-Asp-Phe-Leu-Arg-Asn-Leu-Val-Pro-Arg-Thr-Glu-Ser-OH

InChIKey
POIUWJQBRNEFGX-XAMSXPGMSA-N

SMILES
CC[C@H](C)[C@@H](C(=O)NCC(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CC1=CC=CC=C1)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CCCNC(=N)N)C(=O)N[C@@H]([C@@H](C)CC)C(=O)N[C@@H](C(C)C)C(=O)N[C@@H](CCC(=O)N)C(=O)N[C@@H](CCCNC(=N)N)C(=O)N[C@@H]([C@@H](C)CC)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CC(=O)O)C(=O)N[C@@H](CC2=CC=CC=C2)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CCCNC(=N)N)C(=O)N[C@@H](CC(=O)N)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](C(C)C)C(=O)N3CCC[C@H]3C(=O)N[C@@H](CCCNC(=N)N)C(=O)N[C@@H]([C@@H](C)O)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CO)C(=O)O)NC(=O)[C@H](CCCCN)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@H](CCCCN)NC(=O)[C@H](CO)NC(=O)[C@H](CCCCN)NC(=O)[C@H](CCCNC(=N)N)NC(=O)[C@H](CC4=CC=CC=C4)NC(=O)[C@H](CC5=CC=CC=C5)NC(=O)[C@H](CC(=O)O)NC(=O)CNC(=O)[C@H](CC(C)C)NC(=O)[C@H](CC(C)C)N

See charge, composition and 3D structure on the Scientific page

The evidence

What LL-37 studies show

Results grouped by what the studies measured. Each card shows where its results come from.

Some studies in people24 of 190 results come from studies in people.

Skin, hair and wounds

19 results · 10 in people · 3 animal · 6 lab

In people with hard-to-heal leg ulcers, LL‑37 applied topically did not improve healing more than placebo overall. Wound repair and regeneration, 2021

Top results

In people with hard-to-heal leg ulcers, LL‑37 applied topically did not improve healing more than placebo overall. (Wound repair and regeneration, 2021)
In mice, long-term LL‑37 treatment caused new blood vessel growth in the skin, like rosacea. (Animal models and experimental medicine, 2025)
In adults with hard-to-heal leg ulcers, LL‑37 at 0.5 mg/mL made ulcers heal about six times faster than placebo. (Wound repair and regeneration, 2014)

Infections

44 results · 4 in people · 7 animal · 33 lab

In adults hospitalized with Omicron COVID-19, oral LL‑37 given early shortened the time to a negative virus test versus placebo. Journal of medical virology, 2023

Top results

In adults hospitalized with Omicron COVID-19, oral LL‑37 given early shortened the time to a negative virus test versus placebo. (Journal of medical virology, 2023)
In people with mildly infected diabetic foot ulcers, LL‑37 cream did not clearly reduce bacteria counts compared with placebo cream. (Archives of dermatological research, 2023)
In lab tests, LL‑37 broke open a lot of human red blood cells collected in EDTA. (Journal of immunological methods, 2024)

Immune system and inflammation

80 results · 2 in people · 23 animal · 55 lab

In people with diabetic foot ulcers, LL‑37 cream did not lower the inflammation marker IL-1α in wound fluid. Archives of dermatological research, 2023

Top results

In people with diabetic foot ulcers, LL‑37 cream did not lower the inflammation marker IL-1α in wound fluid. (Archives of dermatological research, 2023)
In rats with sepsis, LL‑37 led to lower blood endotoxin than conventional antibiotics did. (Antimicrobial agents and chemotherapy, 2006)
In infected rabbits, IL-6 was lower with LL‑37 than with cefalexin or saline from day 1. (Orthopaedic surgery, 2020)

Cancer

3 results · 1 in people · 2 lab

In one woman with melanoma, injected skin lesions shrank during 8 weekly LL‑37 injections. Journal of cutaneous pathology, 2018

Top results

In one woman with melanoma, injected skin lesions shrank during 8 weekly LL‑37 injections. (Journal of cutaneous pathology, 2018)
In cells, LL‑37 made breast cancer cells move more. (Breast cancer research, 2009)
In cells, LL‑37 changed the shape of breast cancer cell colonies in a way that suggests a higher chance of spread. (Breast cancer research, 2009)

Survival and serious illness

9 results · 9 animal

In rats with sepsis, LL‑37 given into a vein lowered deaths compared with saline. Antimicrobial agents and chemotherapy, 2006

Top results

In rats with sepsis, LL‑37 given into a vein lowered deaths compared with saline. (Antimicrobial agents and chemotherapy, 2006)
In mice with endotoxin shock, normal LL‑37 prevented illness. (Journal of immunology, 2014)
In young rats with sepsis, lower doses of LL‑37 given with LPS reduced deaths compared with LPS alone. (Pediatric surgery international, 2005)

Bones and joints

5 results · 5 lab

In cells, LL‑37 did not change alkaline phosphatase activity, a marker of cell maturation. Journal of periodontal research, 2012

Top results

In cells, LL‑37 did not change alkaline phosphatase activity, a marker of cell maturation. (Journal of periodontal research, 2012)
In cells, a high dose of LL‑37 strongly reduced the number of cells. (Journal of periodontal research, 2012)
In cells, a high dose of LL‑37 cut DNA synthesis by about 90%, which slows cell growth. (Journal of periodontal research, 2012)

All 5 studies in people

In people

In hospitalized adults with COVID-19, no severe side effects were seen with oral LL‑37 during the hospital stay and follow-up.

2023Journal of medical virology238 people

In people

In people with hard-to-heal leg ulcers, LL‑37 applied topically did not improve healing more than placebo overall.

2021Wound repair and regeneration148 people

In people

In adults with hard-to-heal leg ulcers, LL‑37 at 0.5 mg/mL made ulcers heal about six times faster than placebo.

2014Wound repair and regeneration34 people

In people

In people with diabetic foot ulcers, LL‑37 cream improved granulation tissue formation more than placebo cream.

2023Archives of dermatological research

In people

In one woman with melanoma, new skin growths and a blister appeared about 45 days after starting LL‑37 injections.

2018Journal of cutaneous pathology1 person

All 147 LL-37 studies by area Open the Scientific page

Key LL-37 studies

Studies in people come first, then studies in animals and in the lab.

People
Efficacy and safety of Oral LL-37 against the Omicron BA.5.1.3 variant of SARS-COV-2: A randomized trial
Zhao et al. 2023 · Journal of medical virology · 238 people · cited by 7
4 results
People
Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial
Mahlapuu et al. 2021 · Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society · 148 people · cited by 36
3 results
People
Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial
Grönberg et al. 2014 · Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society · 34 people · cited by 140
8 results
People
Efficacy of LL-37 cream in enhancing healing of diabetic foot ulcer: a randomized double-blind controlled trial
Miranda et al. 2023 · Archives of dermatological research · cited by 27
4 results
People
Dermatologic toxicity from novel therapy using antimicrobial peptide LL-37 in melanoma: A detailed examination of the clinicopathologic features
Dolkar et al. 2018 · Journal of cutaneous pathology · 1 person · cited by 15
5 results

All 147 LL-37 studies

LL-37 clinical trials

ClinicalTrials.gov lists 2 trials of LL-37. 0 are active or planned, and 1 has posted results. PepBank does not show trial results.

Solid bars are dates that happened. Hatched bars are planned dates. Data from ClinicalTrials.gov.

Intratumoral Injections of LL37 for Melanoma

Phase 1/2completed4 people

Efficacy of LL-37 Cream on Bacteria Colonization, Inflammation Response and Healing Rate of Diabetic Foot Ulcers

Phase 2status unknown40 planned

Status and safety

Is LL-37 approved?

FDA

United States

Not approved

No approved medicine contains it.

EMA

European Union

Not approved

No approved medicine contains it.

WADA

Sport

Banned

On the 2026 Prohibited List, section S0.

No. Not approved for any use. Its most advanced trial is in phase 2. The FDA, the EMA and the other sources we use show no approval (as of 8 Oct 2026). Banned in sport (WADA S0).

Laws and labels change, so check the regulator for the current status.

LL-37 side effects and safety

PepBank has 11 safety results from studies of LL-37. 7 of them come from studies in people.

Safety results from studies (11)

In hospitalized adults with COVID-19, no severe side effects were seen with oral LL‑37 during the hospital stay and follow-up. (Journal of medical virology, 2023)
In people with hard-to-heal leg ulcers, topical LL‑37 was reported as well tolerated at both strengths. (Wound repair and regeneration, 2021)
In adults with leg ulcers, topical LL‑37 raised no safety concerns about local or whole-body side effects. (Wound repair and regeneration, 2014)
In one woman with melanoma, new skin growths and a blister appeared about 45 days after starting LL‑37 injections. (Journal of cutaneous pathology, 2018)
In one woman with melanoma given LL‑37, most skin biopsies showed inflammation and abnormal skin cell growth. (Journal of cutaneous pathology, 2018)
In one woman with melanoma given LL‑37, most skin lesions did not show a certain fluid swelling pattern. (Journal of cutaneous pathology, 2018)
In one woman with melanoma, the skin lesions went away within 2 months after LL‑37 injections stopped. (Journal of cutaneous pathology, 2018)
In mice, citrullinated LL‑37 given with endotoxin made sepsis worse. (Journal of immunology, 2014)
In mice, citrullinated LL‑37 given with endotoxin raised blood levels of the inflammation signal IL-6. (Journal of immunology, 2014)
In lab tests, low levels of LL‑37 made two bacterial species more resistant to the antibiotic rifampin. (PLoS pathogens, 2014)
In gum cell cultures, LL‑37 at 2-6 μM did not harm the cells. (Asian Pacific journal of allergy and immunology, 2014)

See every safety result on the Scientific page

Doses studied (15 shown)

The doses that these studies used. They are not recommendations.

Dose as reported	Class	Species	Route	Duration	Design	Source
0.5 or 1.6 mg/mL	Human	human	topical	Not reported	Randomized trial in people · n = 148	Mahlapuu 2021
0.5, 1.6 and 3.2 mg/mL	Human	human	topical	4 weeks	Randomized trial in people · n = 34	Grönberg 2014
0.5 mg/mL	Human	human	topical	4 weeks	Randomized trial in people	Grönberg 2014
1.6 mg/mL	Human	human	topical	4 weeks	Randomized trial in people	Grönberg 2014
3.2 mg/mL	Human	human	topical	4 weeks	Randomized trial in people	Grönberg 2014
1 mg/kg	Animal	rat	intravenous	Not reported	Study in live animals	Cirioni 2006
10-100 µg/ml	Lab	human	Not reported	Not reported	Study on cells in a dish	Bowdish 2005
5 µg/ml	Lab	human	Not reported	Not reported	Study on cells in a dish	Mookherjee 2006
2 µM	Lab	Bacillus subtilis	Not reported	Not reported	Study on cells in a dish	Barns 2013
4 µM	Lab	Bacillus subtilis	Not reported	Not reported	Study on cells in a dish	Barns 2013
0.1 and 1 µM	Lab	human	Not reported	Not reported	Study on cells in a dish	Jönsson 2012
8 µM	Lab	human	Not reported	Not reported	Study on cells in a dish	Jönsson 2012
1 and 8 µM	Lab	human	Not reported	Not reported	Study on cells in a dish	Jönsson 2012
10 µg/mL	Lab	human	Not reported	18 hours	Study on cells in a dish	Suphasiriroj 2013
2-6 μM	Lab	human	Not reported	Not reported	Study on cells in a dish	Montreekachon 2014

From the community

How people use it

What people report online. It comes from forums and guides, not from studies.

Community-reported. Not tested in trials.

Community sources describe LL-37 as an antimicrobial peptide injected under the skin for immune support, chronic infection and gut problems. Reported amounts are small (50 to 400 mcg a day), usually raised slowly because it can cause flu-like symptoms.

Reported routines and cautions

What people use it for

General immune support and chronic infections, including Lyme disease claimsS1
Gut problems such as SIBO and dysbiosis, often stacked with BPC-157S1
Biofilm disruption claims (based on lab data)S1

Reported regimens

Regimens that community sources report for LL-37. Community-reported, not tested in trials.
Context	Route	Amount	How often	How long	Agreement	Sources
General immune support (standard protocol)	subcutaneous injection	100 to 200 mcg per dose	once daily, 5 days on and 2 days off	8 to 12 weeks	2 sources agree on amount, frequency and duration. S2 may copy community text. Both sources carry seller links.	S1S2
Active infection (higher amount)	subcutaneous injection	200 to 400 mcg per dose	once daily	2 to 4 weeks (S2: 8 to 16 weeks)	sources differ: amount agrees (200 to 400 mcg); duration differs (2 to 4 weeks vs 8 to 16 weeks). Both sources carry seller links.	S1S2
Gut repair	subcutaneous injection	100 mcg per dose	once daily	4 to 8 weeks	single source. The source carries seller links.	S1
Slow titration (niche)	subcutaneous injection	50 to 400 mcg per dose	once daily	8 to 16 weeks	single source. The source carries seller links.	S1

Reported side effects

low-grade fever, tiredness and body aches in the first few days, read by users as immune activationS1

Reported benefits (claims, not shown in trials)

fewer respiratory infections, less bloating (with BPC-157), better skin healing (self-reported)S1

Cautions

People with autoimmune conditions report that LL-37 may worsen symptoms.S1
S1 says no established systemic injection protocol exists in the clinical literature, and that the injection route is entirely community-derived.S1
Immune activation effects can be hard to tell apart from illness.S1
Product quality and purity are flagged as critical for an antimicrobial peptide.S1

Status notes

FDA identified LL-37 for removal from its Category 2 list and for later advisory committee review, expected before February 2027. Removal does not by itself make compounding allowed. LL-37 was not among the seven peptides on the July 2026 committee agenda. It is not FDA-approved.S3 S4

Community sources

S1LL-37: Community Protocols & Reportspeptideprotocolwiki.comcarries seller links, not linked
S2LL-37 (Cathelicidin)outliyr.comcarries seller links, not linked
S3FDA Signals Potentially Evolving Stance Toward Compounding of Certain Peptides (opens in a new tab)goodwinlaw.com
S4FDA AdComm recommends adding six peptides to bulk list (opens in a new tab)dlapiper.com

Gaps

Only one non-seller source (S1) gives amounts, and S2 carries affiliate or shop links, so it is marked seller-linked. No forum threads were readable (Reddit is blocked). No harm-reduction page with doses was found. Side-effect frequency is not stated by any source. Topical wound use (the best-studied route) is not covered here.

Questions and more

Ask a question about LL-37

The answer links to every study it uses.

What does the evidence say about LL-37?Is LL-37 tested in people?Compare with Thymosin alpha-1 Compare with Thymogen (oglufanide)

Sources

Database: PepBank data for LL-37 (data version 308560)
Regulator: FDA status record
Regulator: EMA status record
Regulator: WADA status record
Trial registry: ClinicalTrials.gov
Community: community sources (forums and guides), as summarized in the PepBank community file

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

PepBank is a research reference. Talk to a doctor before you use any peptide.

Ask your AI about LL-37

Curo is a peptide shop. PepBank and Curo have the same owner. See the Curo catalog (opens in a new tab).

LL-37

Not approvedBanned in sport

Also known as CAP18, hCAP18, Antibacterial peptide LL-37, Cathelicidin LL-37, LL37, Ropocamptide

What it is

Natural fragment, 37 amino acids

Approval

Not approved for any use

In sport

Banned in sport (WADA S0)

Studies

147 studies with results. 49 of them gave LL-37, with 190 results.
24 in people45 in animals121 in lab cells

Best study in people

Randomized controlled trial with 238 people (2023)

Clinical trials

2 registered: 0 active or planned, 1 with posted results

Community use

General immune support and chronic infections, including Lyme disease claims; Gut problems such as SIBO and dysbiosis, often stacked with BPC-157; Biofilm disruption claims (based on lab data)

Dose as reported

Class

Species

Route

Duration

Design

Source

0.5 or 1.6 mg/mL

Human

human

topical

Not reported

Randomized trial in people · n = 148

Mahlapuu 2021

0.5, 1.6 and 3.2 mg/mL

Human

human

topical

4 weeks

Randomized trial in people · n = 34

Grönberg 2014

0.5 mg/mL

Human

human

topical

4 weeks

Randomized trial in people

Grönberg 2014

1.6 mg/mL

Human

human

topical

4 weeks

Randomized trial in people

Grönberg 2014

3.2 mg/mL

Human

human

topical

4 weeks

Randomized trial in people

Grönberg 2014

1 mg/kg

Animal

rat

intravenous

Not reported

Study in live animals

Cirioni 2006

10-100 µg/ml

Lab

human

Not reported

Study on cells in a dish

Bowdish 2005

5 µg/ml

Lab

human

Not reported

Study on cells in a dish

Mookherjee 2006

2 µM

Lab

Bacillus subtilis

Not reported

Study on cells in a dish

Barns 2013

4 µM

Lab

Bacillus subtilis

Not reported

Study on cells in a dish

Barns 2013

0.1 and 1 µM

Lab

human

Not reported

Study on cells in a dish

Jönsson 2012

8 µM

Lab

human

Not reported

Study on cells in a dish

Jönsson 2012

1 and 8 µM

Lab

human

Not reported

Study on cells in a dish

Jönsson 2012

10 µg/mL

Lab

human

Not reported

18 hours

Study on cells in a dish

Suphasiriroj 2013

2-6 μM

Lab

human

Not reported

Study on cells in a dish

Montreekachon 2014

Context

Route

Amount

How often

How long

Agreement

Sources

General immune support (standard protocol)

subcutaneous injection

100 to 200 mcg per dose

once daily, 5 days on and 2 days off

8 to 12 weeks

2 sources agree on amount, frequency and duration. S2 may copy community text. Both sources carry seller links.

S1S2

Active infection (higher amount)

subcutaneous injection

200 to 400 mcg per dose

once daily

2 to 4 weeks (S2: 8 to 16 weeks)

sources differ: amount agrees (200 to 400 mcg); duration differs (2 to 4 weeks vs 8 to 16 weeks). Both sources carry seller links.

S1S2

Gut repair

subcutaneous injection

100 mcg per dose

once daily

4 to 8 weeks

single source. The source carries seller links.

Slow titration (niche)

subcutaneous injection

50 to 400 mcg per dose

once daily

8 to 16 weeks

single source. The source carries seller links.

LL-37

LL-37 at a glance

What is LL-37?

The history of LL-37

LL-37 structure and chemistry

What LL-37 studies show

Skin, hair and wounds

Infections

Immune system and inflammation

Cancer

Survival and serious illness

Bones and joints

All 5 studies in people

Key LL-37 studies

LL-37 clinical trials

Is LL-37 approved?

LL-37 side effects and safety

How people use it

What people use it for

Reported regimens

Reported side effects

Reported benefits (claims, not shown in trials)

Cautions

Status notes

Community sources

Ask a question about LL-37

Related peptides

Sources

LL-37

LL-37 at a glance

What is LL-37?

The history of LL-37

LL-37 structure and chemistry

What LL-37 studies show

Skin, hair and wounds

Infections

Immune system and inflammation

Cancer

Survival and serious illness

Bones and joints

All 5 studies in people

Key LL-37 studies

LL-37 clinical trials

Is LL-37 approved?

LL-37 side effects and safety

How people use it

What people use it for

Reported regimens

Reported side effects

Reported benefits (claims, not shown in trials)

Cautions

Status notes

Community sources

Ask a question about LL-37

Related peptides

Sources