Peptide dossier, updated Oct 31, 2026

LL-37

Cathelicidin LL-37, a human antimicrobial peptide. LL-37 is the 37-amino-acid fragment of a human protein called hCAP18. The body makes it, and it is widely studied as a marker and mediator in infection, skin and other disease. FDA lists it on its safety-risk page and has published no staff evaluation of it that we found. This page lays out what each source actually says.

See all 10 verified records for LL-37 on the Records page

FDA safety-risk page

Listed

FDA says it lacks sufficient safety information. It adds that nonclinical findings suggest detrimental effects on male reproduction and that the drug can be protumorigenic in some tissues.

HHS enforcement, Oct 30

Not covered

Two law-firm summaries list the six peptides the draft policy covers. LL-37 is not one of them. We could not open the policy attachment itself.

FDA advisory panel, July

Not reviewed

FDA’s Federal Register notice for the July 23–24 meeting lists seven peptides. LL-37 is not among them.

WADA prohibited list

Not named

The 2022 and 2026 lists do not name LL-37. Section S0 covers substances with no approval from any government health authority.

Human evidence

Small trials, topical or injected into tumors

We found trials of topical LL-37 in leg and foot ulcers and a 4-patient melanoma injection study. None tests it as a peptide injected under the skin or taken by mouth.

Human studies

ClinicalTrials.gov returns many records that mention LL-37 as a blood or tissue marker. Two register LL-37 itself as the intervention.

Registry	Study	Sponsor	Status	What the record says
NCT02225366	Phase 1/2: intratumoral injections of LL37 for melanoma	M.D. Anderson Cancer Center	Completed	Dose-finding study: a starting dose of 250 µg per tumor, injected every 7 days for up to 8 weeks. Four participants. Started Jul 8, 2015, completed Nov 24, 2020. Results are posted. The adverse-event table lists, as other (non-serious) events, one case each of squamous cell carcinoma, actinic keratosis, anemia, skin hypopigmentation and hypothyroidism among the four. The record does not say whether they were related to LL37.
NCT04098562	Phase 2: LL-37 cream on diabetic foot ulcers	Universitas Indonesia, Faculty of Medicine	Status unknown	LL37 cream versus standard wound care. Planned 40 participants. Start listed as Oct 2019 (estimated). No results posted. A 2023 paper from Jakarta, under Published research, may report this study; we have not confirmed that.

Registry entries are written by the sponsors and are not reviewed for scientific merit. A registered study is not a result. The phase 2b venous leg ulcer trial below was not among the registry records we pulled.

FDA review

FDA’s safety-risk page (content current Apr 22, 2026) is the one FDA document on LL-37 that we read.

What FDA’s page says

FDA lists “cathelicidin LL-37” among bulk drug substances that were nominated and later withdrawn. The page says these were previously in category 2 under FDA’s interim compounding policies.
It says compounded drugs containing it may pose risk for immunogenicity for certain routes, and may have complexities with peptide-related impurities and API characterization.
It says FDA lacks sufficient safety-related information to know whether the drug would cause harm when administered to humans.
It adds: nonclinical research findings suggest detrimental effects on male reproduction and that the drug can be protumorigenic in some tissues. The page does not cite the studies, and we have not reviewed them.

What we did not find

We found no FDA briefing document or advisory committee evaluation for LL-37. FDA’s notice for the July meeting does not name it, so the safety-risk page entry is the only FDA statement on it that we read.
No route of administration is stated on the page for LL-37.
No statement from FDA on topical products. The two ulcer trials below test topical formulations.

Sources: FDA: bulk substances that may present significant safety risks Federal Register notice of the July meeting

Published research

PubMed returns 2,550 results for “LL-37” in the title or abstract. In the 30 most recent results we looked at, nearly all concern rosacea, antimicrobial-peptide design, or LL-37 as a biomarker. Three randomized trials give it or a product built around it to people.

Human trials

Venous leg ulcers, 2021. Phase IIb, double-blind, placebo-controlled, 148 patients, topical LL-37 at 0.5 or 1.6 mg/mL with compression. The full-population analysis found no significant improvement in healing. A post hoc analysis found improvement in patients whose wounds were at least 10 cm². The authors report it was well tolerated. Wound Repair Regen PubMed
Diabetic foot ulcers, 2023. Randomized, double-blind trial in Jakarta of LL-37 cream versus placebo cream, twice a week for 4 weeks. The abstract reports a greater increase in granulation index in the LL-37 group on days 7, 14, 21 and 28. Arch Dermatol Res PubMed
COVID-19, 2023. 238 inpatients in an open-label randomized trial. The product, which the authors call “Oral LL-37,” is a recombinant Lactococcus lactis preparation, not the peptide itself. The authors report a shorter time to a negative viral test with early treatment and no severe adverse events. J Med Virol PubMed

Read with care

These trials test topical or bacterial-delivery products. None tests it as a systemic injected or oral peptide.
The venous ulcer trial’s main analysis was negative. The positive result is a post hoc subgroup.
FDA’s warning about male reproduction and tumor promotion rests on nonclinical findings it does not cite on the page. We have not reviewed that literature.
We read abstracts only, not full text, funding or author disclosures.

FDA warning letters

We found one FDA warning letter that names LL-37. It is addressed to a compounding pharmacy and is not a finding about LL-37’s safety. This rests on web searches, not a full pull of FDA’s database.

Recipient	Date	Letter	What it says
Tailor Made Compounding LLC, a compounding pharmacy	Apr 1, 2020	Warning letter 594743	FDA says an inspection found the firm compounding with a list of 22 bulk substances that includes LL-37, and that drugs made from them were not eligible for the section 503A exemptions. The letter says none of them is covered by a USP or NF monograph or is a component of an FDA-approved drug, and that the listed substances “have not been nominated” for the bulks list. We read the letter text.

A warning letter is FDA’s statement about one firm’s conduct on one date. It is not a finding about the substance. FDA’s list of letters cannot be searched by peptide, so other letters could exist that we did not find.

SEC filings

We did not find an SEC filing that names LL-37 as a product or program. EDGAR’s full-text search was not available to us, so this rests on web searches of sec.gov.

What a company says in a filing is its own claim about its business. It is not a finding about LL-37.

Timeline

Newest first. Every entry links to the document it comes from.

Government or registry record
Journal

Oct 30, 2026Regulatory
HHS publishes draft policy pausing enforcement on six peptides; LL-37 is not one of them
Per two law-firm summaries the six are BPC-157, TB-500, epitalon, Semax, KPV and MOTS-c. The policy is a draft and not FDA approval. We could not open the policy attachment, so this rests on the summaries.
Federal Register Docket BakerHostetler summary
July 23–24, 2026Regulatory
FDA advisory committee meets on seven peptides; LL-37 is not among them
The committee recommended six of the seven, all nonbinding. FDA’s notice of the meeting does not list LL-37.
Federal Register notice Holland & Knight summary
Apr 22, 2026Regulatory
FDA’s safety-risk page lists LL-37
FDA says it lacks sufficient safety information, and cites nonclinical findings on male reproduction and tumor growth.
FDA page
2023Literature
Two randomized trials: LL-37 cream in diabetic foot ulcers, and a bacterial “Oral LL-37” in COVID-19
See Published research above.
PubMed (ulcer)PubMed (COVID-19)
2021Literature
Phase IIb venous leg ulcer trial finds no overall benefit
A post hoc subgroup of large wounds improved.
PubMed
Apr 1, 2020Enforcement
FDA warning letter to a compounding pharmacy names LL-37 among 22 substances
The letter says drugs the firm compounded from these bulk substances were not eligible for the 503A exemptions.
Warning letter 594743
Jul 2015Trials
Melanoma injection study begins at M.D. Anderson
Four participants, completed Nov 2020, results posted.
NCT02225366

Still not covered

Left off rather than guessed:

Policy coverage: HHS’s list of covered peptides sits in a policy attachment we could not open. That LL-37 is outside it comes from two law-firm summaries, not from the document itself.
FDA review: We found no FDA briefing document or advisory committee evaluation for LL-37. FDA’s notice for the July meeting does not name it, so the safety-risk page entry is the only FDA statement on it that we read.
Patents: not researched for this dossier.
Seller claims and independent lab reports: how it is marketed versus what testing finds. We have not collected testing data.
Venous ulcer trial registration: we did not look up its registry record or sponsor.
Unread items: full text of every paper; WADA lists for years other than 2022 and 2026; EU and other non-US trial registries.
Warning letter and SEC completeness: web searches only.