Thymosin Alpha-1 + KPV + LL-37

Where the name "Thymosin Alpha-1 + KPV + LL-37" comes from

This is community and market usage. Peptide Health Lab neither coined the name nor endorses it, and this page exists because the phrase is what people search for.

The origin is undocumented in the published literature, and the searches that establish that are worth reading before anything else on this page. A PubMed search for (thymosin alpha 1) AND (KPV) AND (LL-37) on 1 September 2026 returned 0 records. So did (thymosin alpha 1 OR thymalfasin) AND (LL-37 OR cathelicidin OR hCAP18) AND (KPV OR lysine-proline-valine OR alpha-MSH), (KPV) AND (LL-37) AND (combined), and ("thymosin alpha 1") AND ("hCAP18"), each run the same day. No paper proposes this grouping, defines it, or names it. Two of the three two-component searches returned exactly one record each, and the two records are different in kind. (KPV) AND (LL-37) on 1 September 2026 returned 1: a 2025 short review of host defence peptides for inflammatory bowel disease that lists KPV under alpha-melanocyte-stimulating hormone and an LL-37-Talpha1 construct under cathelicidins, in one enumerated sentence, and administers nothing to anything.^[13] (thymosin alpha 1) AND (LL-37) on the same day also returned 1 — and that one is not a study of two peptides but of the fused construct the next section takes apart. (thymosin alpha 1) AND (KPV) returned 0.

But the searches do return something, and it is the reason this page exists rather than being folded into its two-component sibling. Somebody did try to put two of these molecules together. What they built was not a stack. It was a new molecule, and the rest of this page is largely about that distinction.

Dosing and protocol ranges for each component live on the individual compound pages, not here. This page carries none.

What's in it and why people combine them

LL-37 is the component that changes the character of this grouping, and it is the one a reader is most likely to misread. It is a peptide the human body already makes: the mature carboxy-terminal peptide released from hCAP-18, the product of the CAMP gene, and the only cathelicidin humans have. That single fact splits its literature in two. The very large part is about what the body's own peptide does — where it is expressed, what it correlates with, what happens in disease. A much smaller part is about administering a synthetic version to a person, and those are different questions with different answers.

Rodents do not make LL-37, and the landmark mouse result is about a different peptide. The paper that established cathelicidins as a real component of innate skin defence used mice and the mouse peptide CRAMP, encoded by Cnlp; the paper itself sets the human and mouse peptides side by side as similar in structure, spectrum and tissue distribution while being the products of separate genes.^[1] It is a result about mouse cathelicidin in mice. A search for (CRAMP) AND (LL-37) AND (mouse) on 1 September 2026 returned 84 records, which is a fair measure of how routinely the two are handled in one breath. This page does not treat that literature as LL-37 evidence.

Thymosin alpha-1 appears in the relevant literature here as a fragment, not as itself. In the hybrid work described in the next section, what was joined to the LL-37 fragment was the active centre of thymosin alpha-1 — residues 17 to 24 in the first design, and residues 20 to 25 and 20 to 27 in the two redesigns.^[9] The 28-residue peptide sold under this name is not that fragment. Its own randomized evidence is in sepsis and chronic hepatitis in hospital populations, and its largest trial, a multicentre phase 3 in 1,106 adults with sepsis, missed its primary endpoint of 28-day all-cause mortality with a hazard ratio of 0.99 and P=0.93.^[12] The compound page carries the rest; this page does not restate it.

KPV appears in none of the hybrid work at all. It is the carboxy-terminal tripeptide of alpha-melanocyte-stimulating hormone; a PubMed search for (KPV OR lysine-proline-valine) AND (clinical trial[pt] OR randomized controlled trial[pt]) on 1 September 2026 returned 7 records and not one of them studies the tripeptide; and it is on this page because the community name includes it. Its own mechanism carries a finding that sits oddly next to an immune rationale, described further down.

What the evidence says about the combination

The decisive search is (thymosin alpha 1) AND (LL-37) NOT hybrid, which returned 0 records on PubMed on 1 September 2026 — so no indexed study has administered these three peptides together, and the closest thing the index holds is a paper about a different substance. Every indexed record that pairs thymosin alpha-1 with LL-37 is a fusion-construct paper or a review citing one.

The fusion programme is real work and it is worth reading correctly. One laboratory designed eight hybrid peptides, joining active centres of antimicrobial peptides — including LL-37 residues 13 to 36 — to thymopentin or to the active centre of thymosin alpha-1. The best, called LTA, was selected by molecular docking and cell screening and then reduced histological injury and pro-inflammatory cytokines and raised tight-junction protein expression in an LPS-induced murine jejunal model.^[8] A companion paper cloned the fused gene into Pichia pastoris, purified one 3.9 kDa recombinant peptide, and characterised endotoxin binding and reduced LPS-induced cytotoxicity and cytokine release in a mouse macrophage line.^[7] A third redesigned the thymosin fragment three ways and tested the best in immunosuppressed mice.^[9]

That is one engineered molecule, not two peptides taken together. A covalent fusion of a fragment of one peptide to a fragment of another is a new chemical entity with its own folding, its own stability and its own target engagement. Nothing about its behaviour transfers to a person who takes two separate intact peptides, in the same way that nothing about a fusion protein's activity is a property of the two proteins sitting in the same vial. Reading these three papers as evidence for the grouping this page is named after is the single most likely mistake a reader will make here, which is why the page reports them and then disqualifies them.

Two further limits on that work. All three papers list the same laboratory at China Agricultural University in their affiliations, and their author lists overlap: Zhang, Wei, Zhang, Si and Cheng are on the first and the third, and Ahmad is on the second and the third. Nor do the searches turn up anyone else working on it: (thymosin alpha 1) AND (LL-37) on PubMed on 1 September 2026 returned 1 record, and it is the first of these three — there is no reproduction of the hybrid result by an unconnected group to point to. And the mouse experiments dosed a construct containing a human LL-37 fragment into a species that does not make LL-37 — so the molecule-identity problem and the species problem stack rather than cancelling.

The three two-component searches run on PubMed on 1 September 2026 — (thymosin alpha 1) AND (KPV), (KPV) AND (LL-37), and (thymosin alpha 1) AND (LL-37) — returned 0, 1 and 1 records, and the two records they return are the review and the hybrid-design paper described above. Neither reports an additivity test, in either direction. The claim for the grouping on this page is graded anecdotal because there is nothing to grade.

Where the evidence is weak

The trials that administer LL-37 to a person put it on skin or into the gut, and none of them is about immune support. A PubMed search for (LL-37) AND (randomized controlled trial[pt] OR clinical trial[pt]) on 1 September 2026 returned 60 records, and reading the set shows only four in which the peptide was given to anyone: two topical trials in venous leg ulcers, one topical trial in diabetic foot ulcer, and one given by mouth. The other 56 measure the body's own cathelicidin as an outcome of something else, most often vitamin D supplementation — which is a different question, and it is the commonest way this literature gets read as bigger than it is. The first-in-man study applied it topically to venous leg ulcers in 34 participants and reported faster healing at the two lower concentrations, of which only the lower reached significance, and no difference at the highest.^[3] The larger follow-up, a phase IIb trial in 148 patients, did not find any significant improvement in healing in the full study population; the positive result its authors report is a post hoc subgroup analysis in patients with large wounds, and they say themselves that it warrants a properly powered study rather than settling anything.^[10] The one non-topical trial gave a recombinant bacterium by mouth to 238 COVID-19 inpatients and measured a virological surrogate, open-label and at one centre.^[11] A larger, later, better-powered trial of the same indication failing to confirm a small earlier one is the ordinary shape of a therapeutic that does not work as well as the first study suggested, and it belongs on the page next to the first study rather than beneath it.

LL-37's own biology cuts both ways, and the adverse half is a large literature. Two-thirds of patients with moderate-to-severe plaque psoriasis carry T cells specific for the peptide, and the frequency of those cells in blood tracks disease activity — it is an autoantigen in a common inflammatory skin disease.^[4] Melanoma cell lines overexpress it, it is strongly expressed in malignant melanoma tissue, and adding it to melanoma cells increased proliferation, migration and invasion in culture.^[2] A search for (LL-37) AND (psoriasis) AND (autoantigen) on PubMed on 1 September 2026 returned 12 records and (LL-37) AND (tumor OR cancer) AND (promot*) returned 100, so neither is an isolated observation. The single published account of a person given the peptide therapeutically outside a wound trial reports both an effect and a harm: injected melanoma lesions shrank, and about six weeks after starting, the patient developed a widespread verrucous and vesiculo-bullous eruption that resolved only after treatment stopped.^[6] That is one case report and should be read as one. It is also the only one of its kind the index returns: a PubMed search for (LL-37) AND (case reports[pt]) on 1 September 2026 returned 11 records, and this is the single one in which a person was given the peptide — the other ten concern the body's own LL-37 in infection, neutrophil disorders and inflammatory skin disease.

KPV's delivery mechanism and a tumour-promoting mechanism are the same mechanism. The transporter that carries KPV into intestinal cells, PepT1, is upregulated in human colorectal cancer, and in mice its overexpression increased tumour size and burden while its deletion reduced them — in the same paper in which KPV, delivered through it, prevented carcinogenesis in wild-type animals and did nothing in animals lacking the transporter.^[5] Both halves are in one experiment, and neither half has been examined in a person.

Three unapproved compounds taken at once, and no interaction data the index can find. The three-way search (thymosin alpha 1) AND (KPV) AND (LL-37) returned 0 records on PubMed on 1 September 2026, and the three two-component searches run the same day returned 0, 1 and 1 — so nothing in that set addresses what any of these does in the presence of the others, and nothing in it touches prescribed medication either. The nearest thing to a document that holds two of them in one frame is a 2025 review that files KPV under alpha-melanocyte-stimulating hormone and an LL-37-Talpha1 construct under cathelicidins in a single enumerated sentence of candidate molecules, and administers nothing to anything.^[13] A mechanistic story about layering an immunomodulator, an anti-inflammatory tripeptide and an antimicrobial peptide is a story, not a result.

Questions to bring to a provider

• What is the immune problem being described, and does it have a diagnosis? Every trial that has administered LL-37 to a person treated either a hard-to-heal venous leg ulcer^[3] or acute COVID-19 in hospital,^[11] not immune support in a healthy adult.
• LL-37 is a T-cell autoantigen in plaque psoriasis,^[4] and it is overexpressed by malignant melanoma cells and stimulates their proliferation, migration and invasion in culture.^[2] What would a clinician want to know about personal or family history of inflammatory skin disease or skin cancer before this is considered at all?
• A published case report of a woman given eight weekly intratumoral LL-37 injections describes a widespread eruption whose lesions all resolved within two months of stopping.^[6] What would be monitored, and what would trigger stopping?
• KPV's transporter, PepT1, was found upregulated in colonic biopsies from patients with colorectal cancer, and in mice its overexpression produced larger tumours and greater tumour burden.^[5] A PubMed search for (KPV OR lysine-proline-valine) AND (clinical trial[pt] OR randomized controlled trial[pt]) on 1 September 2026 returned 7 records and none studies the tripeptide, so there is no human safety signal either way. How should that be weighed by someone with a personal or family history of colorectal disease?
• What would an objective measure of "immune support" even be here, and over what interval would it be read?

Anti-doping status

None of the three components is named on the World Anti-Doping Agency Prohibited List in force for 2026. The 2026 List, the 2026 Monitoring Program and the 2026 Explanatory Note were retrieved on 1 September 2026 through the United States Anti-Doping Agency's prohibited-list page, which returned HTTP 200 with a browser user-agent string and links the WADA-hosted PDFs; all three PDFs returned HTTP 200. Searching the three documents: "LL-37", "LL37" and "cathelicidin" returned 0 occurrences each; "KPV", "melanocortin", "melanocyte" and "MSH" returned 0 occurrences each; "thymosin" returned 2 occurrences in the List and 0 in the other two documents, and both belong to the same S2.3 entry, "Thymosin-ß4 and its derivatives e.g. TB-500", under growth factors and growth factor modulators. Thymosin beta-4 is a separate gene product from thymosin alpha-1, and neither the intact peptide nor the eight-residue active centre used in the fusion work is a derivative of it.^[8] These statements carry no citation because they were read from the published documents themselves, and a research paper is never a source for what a regulator has done.

What settles nothing is a missing name; what settles something is section S0. S0 reads on "any pharmacological substance which is not addressed by any of the subsequent sections of the List and with no current approval by any governmental regulatory health authority for human therapeutic use". The trigger turns on approval by any government's health authority anywhere, not on United States approval, and that is where the three components separate.

For LL-37 and for KPV the trigger is satisfied as far as this page could check. No approval was found at any regulator searched, and each search was run against a working control: the United States drug-label interface returned HTTP 404 for LL-37, for cathelicidin and for KPV while returning a label for a control compound; DailyMed returned zero total elements for LL-37 against a database published 31 August 2026 while returning hundreds for a control; the Canadian active-ingredient interface returned an empty list for LL-37, for cathelicidin and for KPV against a control that returned results. For KPV there is also a current federal record of non-approval: the Food and Drug Administration's briefing document for the Pharmacy Compounding Advisory Committee meeting of 23–24 July 2026, retrieved at HTTP 200 on 1 September 2026, records that KPV-related bulk drug substances were nominated for the 503A bulks list, that the nomination was withdrawn by the nominator, that the agency elected to present them anyway, and that it proposed KPV free base and KPV acetate NOT be included on that list. The compounds the section prints after "including but not limited to" are illustrations of its sentence rather than the edge of it, and on that sentence's own terms it reaches both.

For thymosin alpha-1 this page cannot settle the question and therefore asserts no S0 conclusion. The Gazzetta Ufficiale della Repubblica Italiana, Parte Seconda number 84 of 18 July 2023, retrieved at HTTP 200 on 1 September 2026, records a Type IB variation to a marketing authorisation for a human medicinal speciality under Italian Legislative Decree 219/2006 — the product ZADAXIN, powder and solvent for injectable solution, holder Sciclone Pharmaceuticals Italy S.r.l., authorisation number A.I.C. 028364026 — granted on that date. That is an approval by a governmental regulatory health authority, verified live in 2023. Whether it remains in force in 2026 could not be verified from any primary source in this session: the Italian medicines agency's live register did not resolve, its documented interface path returned HTTP 404, and the European regulator's product database failed at the network layer. If the authorisation stands, S0's trigger is not met for thymosin alpha-1. This page verified 2023, could not verify 2026, and states both rather than choosing one. The widely circulated claim that the compound is approved in dozens of countries was not confirmed at any primary regulator here and is not repeated.

An athlete subject to testing should treat an unapproved injectable as a question for their national anti-doping organization rather than as a settled absence, and nothing above should be read as saying any of these three compounds is permitted. The List is reissued annually and its sections renumber between editions, so a competing athlete should confirm the current year's list rather than this page.