LL-37’s largest human trial missed its primary endpoint. The peptide was put on wounds, not injected.

Why this note exists

LL-37 is the human body's own cathelicidin, an antimicrobial peptide, and it has a following in the research market as an "immune" or "healing" peptide. In April 2026 it moved in two ways on FDA's pages at once. Its compounding nomination sits in a section for substances "previously in category 2 of the interim policies" whose nominations "were withdrawn by the nominators," and FDA announced it would bring LL-37 before an advisory committee by February 2027.[1][2] That second fact will be read as momentum. This note sets out what the committee will have to work with.

In the index generated on September 8, 2026, 41 of 108 vendors carried an LL-37 listing, 49 listings in all.[20] Where a size is stated, 5 mg is the common vial (31 of 49), followed by 10 mg (12).[20] Two of the 49 are blends. None is named as a cream, gel, solution or other topical product.[20]

A note on what kind of evidence this is: every efficacy figure below is human data and carries its design and participant count. One paragraph reports FDA's summary of nonclinical findings and is labeled as such. pepmg reports doses only as their sources published them and does not convert a topical concentration into an injection.

The regulatory status

What FDA has actually written about LL-37

There is no FDA-approved LL-37 product. A query of FDA's Drugs@FDA data on September 11, 2026 returned no match for cathelicidin, LL-37 or ropocamptide, the name its developer used.[6] The question FDA is weighing is narrower than approval: whether licensed pharmacies may compound drugs from LL-37 bulk substance under section 503A.[3]

FDA's interim policy sorts nominated substances into categories. For category 1, "FDA does not intend to take action against a compounder … provided that the conditions described in the guidance document are met." Category 2 holds substances where "FDA has identified significant safety risks relating to the use of these substances in compounding pending further evaluation," and for which "FDA would consider taking action against a compounder … under its general enforcement policies."[3] LL-37 was a category 2 substance. FDA's significant-safety-risk page now lists it under "[b]ulk drug substances nominated but withdrawn," a section FDA describes as "bulk drug substances previously in category 2 of the interim policies [that] were withdrawn by the nominators."[1]

The entry itself is three sentences, and it is the most specific thing FDA has published about this peptide. It reads in full:[1]

Then the forward step. FDA's early announcement, current as of April 15, 2026, says "FDA will host an advisory committee meeting before the end of February 2027" to consider five substances for the 503A bulks list: cathelicidin (LL-37), GHK-Cu, dihexa acetate, Melanotan II and pegylated mechano growth factor.[2] LL-37 was not among the seven substances the committee took up on July 23–24, 2026.[4] When checked on September 11, 2026, FDA's 2027 meeting-materials page had no agenda, briefing document or date posted.[5] No FDA evaluation of LL-37 has been published yet, so the committee's view of the evidence is not yet public.

The human evidence

Four trials that gave people LL-37, and what each one was

Most human research on "LL-37" measures the body's own levels of it, or gives vitamin D to raise them. A ClinicalTrials.gov search for LL-37 as an intervention on September 11, 2026 returned 20 records, and only two of them administer the peptide itself.[16] The trials that did give people LL-37 are listed below.

Counts are patients treated or analysed as reported by each paper or registry record. A fifth trial, of an engineered oral bacterium rather than the peptide, is described separately below.[7][8][12][14]

The first-in-human trial (2014). Thirty-four people with venous leg ulcers had a three-week open-label run-in on placebo, then four weeks of randomized, double-blind treatment with twice-weekly applications of LL-37 at 0.5, 1.6 or 3.2 mg/mL or placebo, and four weeks of follow-up.[7] The authors report healing rate constants "approximately six- and threefold higher than for placebo" at the two lower strengths, p = 0.003 for 0.5 mg/mL and p = 0.088 for 1.6 mg/mL, and "[n]o difference in healing" between the highest strength and placebo, with "no safety concerns regarding local or systemic adverse events."[7] The first author's listed affiliation is Research & Development at Pergamum AB, a company.[7] Across the three strengths, the strongest result came from the weakest concentration, and the strongest concentration did nothing measurable. Thirty-four people split four ways cannot tell you why.

The phase IIb (HEAL LL-37, 2021). This is the trial that was built to settle the question. It was double-blind, randomized and placebo-controlled, run with compression therapy in 148 treated patients with hard-to-heal venous leg ulcers: mean age 67.6, median ulcer duration 20.3 months, mean wound size 11.6 cm².[8] The full analysis set had 46 patients at 0.5 mg/mL, 48 at 1.6 mg/mL and 50 on placebo, treated twice weekly for 13 weeks.[9] The primary endpoint was "[c]onfirmed complete wound closure of the target ulcer … at any time up to the end‐of‐treatment visit at 13 weeks, which was sustained at the post‐wound closure visit, 2 weeks after the first reported closure."[9] The estimated proportions reaching it were 26.5%, 24.7% and 25.3%.[9] In the authors' words, analysis "on the full study population did not identify any significant improvement in healing in patients treated with LL-37 as compared with the placebo."[8]

The diabetic foot ulcer trial (2023). An academic group in Jakarta randomized 25 people with mildly infected diabetic foot ulcers to LL-37 cream (0.5 mg/g, 13 patients) or placebo cream (12), applied twice a week for four weeks.[11][12] The increase in granulation index, the share of the wound covered by new granulation tissue, was greater on LL-37 at every weekly measurement (p = 0.031, 0.009, 0.006 and 0.037).[11] The reduction in wound area at day 28 was not significantly different between groups, and neither were the inflammatory markers or bacterial counts the trial also measured.[11][12] The registry record had planned 40 participants; the authors attribute the smaller sample to COVID-19 recruitment problems.[13][12] One participant on LL-37 had mild irritant contact dermatitis.[12]

The melanoma study. MD Anderson Cancer Center registered a phase 1/2 study of "LL37 administered intratumorally," starting at 250 µg per tumor weekly and escalating to 500 µg, with a primary outcome defined by toxicity.[14] It enrolled four people; the posted results cover three, two in the first cohort and one in the second. One of the three left the study for "Lack of Efficacy," and the results report no serious adverse events.[14] This was a dose-finding record with three people in it, not an efficacy result.

A fifth trial is often cited as LL-37 evidence and tested something else. A single-centre, open-label, randomized trial in 238 adult COVID-19 inpatients in China gave "Recombinant LL-37 Lactococcus lactis," a bacterium engineered to produce the peptide, by mouth.[15] It reported faster conversion to a negative viral test when treatment started early (9.80 vs 14.04 days, p < 0.01) and no severe adverse events.[15] It is evidence about an engineered probiotic, not about a vial of synthetic peptide.

Read the subgroup, and who announced it, before you read the headline

The result that circulates from HEAL LL-37 is not the primary endpoint. It is a subgroup. In patients whose target ulcer was at least 10 cm² at randomization, confirmed closure was 28.1% on 0.5 mg/mL against 8.1% on placebo (P = 0.0458), and 19.6% on 1.6 mg/mL (P = 0.1393).[9] The paper calls this a "[p]ost‐hoc efficacy analysis," and its authors are direct about its weight: "the trial was not designed or powered to identify significant differences in the subgroups which were small with only 21–24 patients per group."[9]

Their own conclusion keeps the two findings in the right order. The trial "did not detect any significant differences in healing of venous lower leg ulcers in the entire study cohort," and the subgroup is "an interesting observation … exigently warranting a further study adequately powered to statistically assess the treatment outcome in this patient group."[8] The sponsor's announcement of the same trial, in November 2020, was headlined "Promore Pharma announces positive results from Phase IIb study of ropocamptide in the treatment of venous leg ulcers."[10] To its credit, the body of the release does say that "no statistically verifiable differences could be detected for the total study group"; it does not describe the large-ulcer analysis as post hoc.[10]

Two things about who produced this evidence. The trial "was financed by Promore Pharma AB," and three authors were company employees at the time, one a minority shareholder.[9][8] That is normal for a drug-development trial and is disclosed. It also means that both venous leg ulcer trials came out of company research, and the only controlled trial of the synthetic peptide run by an academic group with no declared conflict is the 25-person foot ulcer study.[7][8][11]

The gap

The follow-up trial has not appeared

The "further study adequately powered" that the phase IIb authors called for does not appear in the registry. A ClinicalTrials.gov search for ropocamptide on September 11, 2026 returned nine records, because the registry expands the term to LL-37's other names. None is a ropocamptide trial: the only one that gives LL-37 at all is the melanoma study above, and the rest measure the body's own LL-37 or test vitamin D, probiotics or inhaled drugs.[17] In October 2023 Promore Pharma announced it was initiating voluntary liquidation. The trigger was a different product: trial results showing "the treatment effect of ensereptide was insufficient to justify further investments."[18] In the same announcement the company still described ropocamptide as its leading project, one "recently … evaluated in a clinical phase IIb study with positive results."[18] A January 2024 exchange notice records that the board "had assessed that the opportunities to raise the capital needed to develop the Company's program for ropocamptide were limited," and that the listed company was continuing "under name change to PMD Device Solutions AB" through a reverse takeover.[19]

That leaves the route question, which matters more here than for most peptides. Every controlled trial of the synthetic peptide in people put it on a wound.[7][8][11] The one injection study put it into skin tumors, in three patients.[14] In the literature and registry searches behind this note, we found no human trial of LL-37 given by subcutaneous or intramuscular injection.[16] FDA's concern about immunogenicity is worded as a risk "for certain routes of administration."[1] What the index lists is 5 mg and 10 mg vials, and no topical product.[20]

Nonclinical data, labeled as such: FDA's entry states that "[n]onclinical research findings suggest detrimental effects on male reproduction and that this drug can be protumorigenic in some tissues."[1] Those are FDA's summary of animal and laboratory findings, not human outcomes, and FDA does not cite the underlying studies on that page. pepmg has not reviewed them and reports only that FDA wrote it.

Three things this note is not saying

First, it is not saying LL-37 does nothing. The first-in-human trial and the diabetic foot ulcer trial both reported differences from placebo on healing measures, and the phase IIb found a signal in large ulcers that its authors thought worth a proper trial.[7][11][9] Those are real observations from small studies. They are not an established effect.

Second, it is not saying FDA has found LL-37 dangerous. FDA wrote that it "lacks sufficient safety-related information … to know whether the drug would cause harm when administered to humans."[1] That is a statement of missing evidence, filed under a nomination that was withdrawn, not a finding of harm. The topical trials reported the peptide as well tolerated.[7][8]

Third, it is not predicting the committee's vote. The panel has not met, FDA has not published its evaluation, and a vote either way would be advice on compounding, not an approval of a drug or a finding about any vendor's vial.[2][5]

What it is saying is narrower. The best-designed trial of LL-37 in people missed its primary endpoint. The trial its authors said should come next has not appeared in the registry, and the company that ran it initiated liquidation. And the human evidence that does exist is for a peptide put on a wound, while what the market lists is a vial.[8][17][18][20]

Questions people are asking