TB-500 at a glance
TB-500 is a commercial name, and it covers two different things. One is synthetic thymosin beta-4 (Tβ4) at full length: 43 amino acids with an acetylated N-terminus, about 4963 Da. The other is a short piece centred on the part of Tβ4 that binds actin, for instance the acetylated heptapeptide Ac-LKKTETQ at a little under 900 Da. Only the mass printed on the certificate distinguishes them.
The parent peptide came out of calf thymus preparations in the early 1980s, hence the name, but it is no thymus hormone in the narrow sense. Nearly all cell types contain it, platelets and white blood cells in large amounts. It is an actin-binding peptide, usually filed with the repair compounds BPC-157 and GHK-Cu.
- A label, not a molecule: full-length Tβ4 (4963.5 Da) or a fragment under 1,000 Da.
- Evidence: rodent models, plus early human trials of Tβ4 formulations that led to no approval.
- Prohibited in sport under WADA class S2.
How TB-500 works
Actin exists as single units, G-actin, and as the filaments assembled from them. Inside the cell Tβ4 pairs with G-actin one to one and keeps the bound unit out of filaments. That creates a buffer stock: when a cell has to migrate or change shape, monomers are at hand and the actin skeleton can be rebuilt fast. The pairing depends heavily on residues 17–23, the motif LKKTETQ, which is why fragment products are built around it.
The peptide also acts outside cells. Platelets and injured tissue release it, and cell and animal studies connect extracellular Tβ4 with cell migration, new blood vessels, less inflammation and less scarring. The sources name no classical receptor; the documented binding partner is G-actin.
The first four residues can be split off as Ac-SDKP, a small peptide with a literature of its own on fibrosis and on the production of blood cells. Whether a seven-residue fragment keeps much of the whole molecule’s activity is unsettled. The sources give no half-life for either form.
The evidence ladder for TB-500
| Evidence level | Model or trial | Main finding |
|---|---|---|
| Cell culture | Cells exposed to Tβ4 | Links to migration, vessel formation and lower inflammation |
| Animal study | Rat skin wounds, late 1990s; later diabetic and aged mice | Quicker closure and more vessels in the wound bed |
| Animal study | Corneal injury in rodents | The wound findings carried over to the eye |
| Animal study | Mice with a tied-off coronary artery, Bock-Marquette et al. (2004) | More heart muscle cells survived and function held up, partly via integrin-linked kinase |
| Early human trials | Tβ4 eye drops in dry eye and neurotrophic keratopathy; a gel on chronic skin wounds; an intravenous phase 1 safety study in healthy volunteers | Generally well tolerated over short periods; efficacy modest or mixed |
| Trials of products sold as TB-500 | None published | – |
| Licensed use | None | No Tβ4 medicine approved anywhere |
Nearly every rung concerns thymosin beta-4 itself, and in the human trials a defined pharmaceutical formulation of it. Products sold under the TB-500 name have no published controlled human studies. If a vial holds a fragment, even the animal literature applies to it only by assumption.
The heart research remains contested. Follow-up work in mice reported that Tβ4 switched on progenitor cells in the heart’s outer layer and that vessels grew. A further claim, that new heart muscle cells are formed, has been challenged by other groups. On the human side the ladder stops at early-phase trials, none of which produced an approved medicine.
TB-500 doses reported in studies
The table is a reference summary of published study designs, not guidance. The sources report no standard dose: animal papers state amounts per animal or per kilogram, and these differ widely from one model to the next.
| Setting | Material | Route | Note |
|---|---|---|---|
| Rats, skin wounds | Tβ4, full length | Applied to the wound or given intraperitoneally | Closure, vessel growth |
| Mice, heart injury | Tβ4, full length | Intraperitoneal; some studies also directly into heart muscle | Cell survival, heart function |
| Rodents, corneal injury | Tβ4, full length | Eye drops | Epithelial healing, inflammation |
| Humans, early trials | Pharmaceutical Tβ4 formulations | Eye drops, skin gel, intravenous | Short trial periods |
| Products sold as TB-500 | Tβ4 or a fragment | – | No controlled human study published |
Neither Tβ4 nor any of its fragments has a validated dose in humans. The clinical trials ran specific formulations for a short time, which says nothing about a research vial.
Safety findings and open questions
The early Tβ4 trials reported acceptable tolerability over short periods. Those findings belong to the formulations that were tested, not to research products that may hold another molecule. Long chains are also harder to make cleanly than short ones, so the least a buyer needs is an HPLC purity figure and a mass that matches.
- Which molecule is it? Data for full-length Tβ4 do not transfer to a fragment.
- Cell migration and vessel growth also serve tumours, and in experimental cancer models higher Tβ4 expression went together with invasiveness. There is no evidence that Tβ4 causes cancer, but nobody has tested the point properly.
- What does long-term exposure do? The human trials were short, and the question has not been studied.
Bench notes: storing and reconstituting TB-500
The panel on this page specifies −20 °C for the lyophilised powder. Keep the sealed vial dry, and open it only at room temperature so that no water condenses on the peptide.
Reconstitution in research settings is normally done with bacteriostatic water, whose preservative permits several withdrawals from one vial. Add it slowly along the glass and swirl gently instead of shaking. A dissolved peptide is much less stable than the powder: keep it refrigerated, note the lot number and date on the vial, and freeze separate aliquots so that no portion is thawed twice. Storage and Reconstitution: A Bench Protocol gives the full procedure.
Status in the Netherlands, Belgium and Luxembourg
EU marketing authorisations are issued through the European Medicines Agency and apply in all three Benelux countries alike. Neither thymosin beta-4 nor any product sold as TB-500 holds one, and no Tβ4 medicine has been approved elsewhere. Research material comes without a marketing authorisation and is not intended for human use; national and institutional rules on possession and import differ and need checking.
In sport, thymosin beta-4 and its derivatives, TB-500 included, fall under class S2 of the WADA Prohibited List and are prohibited at all times.
Ordering TB-500 for research in the Benelux
King Peptides lists TB-500 (Thymosin Beta-4) 5 mg as a single compound. The product name points to the full-length peptide, which makes 4963.5 Da the expected mass on its certificate. If a certificate reports less than 1,000 Da, the vial holds a fragment regardless of its label. Check too that the lot number matches the vial and that HPLC purity is 99% or higher. The shop supplies a lot-specific certificate with HPLC and mass spectrometry for every lot; Checking a Certificate of Analysis, Line by Line shows how to read one.
TB-500 is also part of two blends: Wolverine Stack - BPC-157 + TB-500 5/5 mg and KLOW-80 Blend - GHK-Cu + BPC-157 + TB-500 + KPV. A blend certificate should name a mass for each ingredient. On such pairings and their evidence gaps, see Peptide Combinations: What Is Studied Together and Why.
Parcels leave the Netherlands with tracking. Delivery usually takes 1–2 business days within the Netherlands and 3–5 business days to Belgium and Luxembourg, and inside the EU there is no customs clearance. The wider checklist is in Buying Research Peptides in the Netherlands, Belgium and Luxembourg.
TB-500: quick answers
Does every vial labelled TB-500 contain thymosin beta-4? No. Some hold the full 43-residue peptide, others a short fragment around LKKTETQ. The mass spectrometry line on the certificate settles it.
What did the human trials actually test? Pharmaceutical formulations of thymosin beta-4, given as eye drops, as a gel on the skin or intravenously. They were short, efficacy was modest or mixed, and no medicine resulted. None tested a product sold as TB-500.
What is Ac-SDKP? A four-residue peptide that can be cleaved from the front end of Tβ4 and is studied in its own right. It is one reason a fragment cannot be assumed to behave like the whole chain.
Why does horse racing come up? TB-500 has featured in doping cases there, and laboratories built dedicated tests to detect it. In human sport it sits in WADA class S2.
Research use only. This page describes TB-500 for laboratory and scientific research. Research material has no marketing authorisation, whatever the status of the molecule as a medicine elsewhere, and is not meant for human or veterinary use. Nothing on this page is medical advice; the doses above are those reported in published studies, not recommendations. Check the rules that apply in your country and at your institution before ordering.