What is TB-500?

Compound Spotlight

TB-500 is usually described as synthetic thymosin beta-4. It is not. Analytical laboratories that have examined TB-500 identify it as a seven-amino-acid peptide copied from one region of thymosin beta-4, with an acetyl group added to one end. That distinction decides which research actually applies to it.

What TB-500 actually is

The clearest descriptions of TB-500 come from anti-doping laboratories, which needed to know exactly what to test for. In 2012 a doping control laboratory at Ghent University analysed a TB-500 product and identified its peptide as the N-terminal acetylated 17–23 fragment of human thymosin beta-4, sequence Ac-LKKTETQ. The same year, the Hong Kong Jockey Club’s racing laboratory described the veterinary preparation sold as TB-500 the same way.

So TB-500 is seven amino acids, not 43. The two independent analytical sources agree on the sequence, even though some research papers still call it “synthetic thymosin beta-4”. A French laboratory that later analysed products sold online as TB500 found their contents did not consistently match those descriptions.

The parent protein: thymosin beta-4

Thymosin beta-4 is a small, ubiquitous 43-amino-acid protein found in essentially all cells and body fluids. Its best-characterized job is sequestering monomeric actin: it holds a reserve of actin subunits that cells draw on when they build filaments to change shape and move.

Reviews of Tβ4 describe several distinct active sites within the molecule. An N-terminal tetrapeptide, Ac-SDKP, is associated with reduced inflammation and fibrosis. The central LKKTETQ region, the actin-binding domain, is linked to angiogenesis, wound healing and cell migration. TB-500 corresponds to that central region only.

Why the actin-binding region drew attention

Much of the case for the fragment rests on a 2003 study from the National Institutes of Health. Philp and colleagues found that a seven-amino-acid actin-binding motif matched full Tβ4 in human endothelial cell migration assays and in vessel sprouting from chick aortic arches, while peptides missing any part of that motif were inactive.

Two cautions apply. The reported activities of this motif belong to its unacetylated form, LKKTETQ, not the acetylated peptide identified in TB-500. And the work measured cell and tissue behaviour in culture, not repair in a living animal. A 2024 study from the Korea Institute of Science and Technology stated plainly that the biological effects of TB-500 itself had not been documented. In fibroblast assays, only one metabolite, Ac-LKKTE, showed significant wound-healing activity, and the authors suggested earlier reported activity might come from that metabolite rather than TB-500 itself.

What research has examined

Nearly everything written about tissue repair under the TB-500 name traces back to full-length Tβ4. Tβ4 has been studied in dermal wound-healing models, and it has reached human trials: a small phase 2 randomized, placebo-controlled trial of Tβ4 eye drops (RGN-259) in nine patients with severe dry eye reported improvements in symptoms and corneal staining compared with vehicle.

None of that is TB-500 research. Direct studies of TB-500 are mostly analytical: how to detect it and its metabolites in horse plasma and urine, and how it is broken down in human serum and in rats.

Animal studies of TB-500 itself are only starting to appear. A 2026 study from Turkey randomized 32 rats with repaired Achilles tendons to control, BPC-157, TB-500 or the combination (eight per group). At four weeks the TB-500 group showed higher load to failure and better histology scores than controls, and the combination did not outperform either compound alone. The authors called it exploratory.

What the evidence supports

The parent protein has a substantial literature: more than a thousand PubMed records mention thymosin beta-4, including cell, animal and small human studies. TB-500 or Ac-LKKTETQ appears in a few dozen, many of them doping-control chemistry or broad reviews. There are no published human trials of TB-500.

The mechanistic link is real: the LKKTETQ region is where Tβ4 binds actin, and in culture that motif reproduced some of Tβ4’s effects on endothelial cells. But a short acetylated peptide is not the 43-amino-acid protein. It lacks Tβ4’s other active sites, it is broken down into shorter metabolites, and its own biological activity rests on a handful of cell and rat studies. Any claim that moves a Tβ4 finding onto TB-500 should say so.

On regulation: TB-500 is not approved for human use by any regulator. WADA’s 2026 Prohibited List names “thymosin-β4 and its derivatives e.g. TB-500” under S2, growth factors, prohibited at all times. The FDA’s list of bulk drug substances that may present significant safety risks in compounding includes “thymosin beta-4, fragment (LKKTETQ)”, citing immunogenicity, aggregation and peptide-impurity concerns, and records it as previously in Category 2 with the nomination later withdrawn. Check the FDA page directly for its current status.

Frequently asked questions

Is TB-500 the same as thymosin beta-4?

No. Tβ4 is a 43-amino-acid protein. TB-500 is a seven-amino-acid synthetic peptide, Ac-LKKTETQ, matching Tβ4’s actin-binding region.

Do thymosin beta-4 studies apply to TB-500?

Not automatically. The fragment lacks the protein’s other active sites and has rarely been studied directly. Results on Tβ4 are evidence about Tβ4.

How is it related to BPC-157?

Only by research interest. The two are unrelated peptides with different origins and proposed mechanisms, often discussed together in tissue-repair research. Our Wolverine Blend breakdown covers both.

How do I know what is actually in the vial?

Every lot we sell has a published Certificate of Analysis from an independent, third-party lab confirming identity and purity. Lot numbers on the vial should match the COA you are referencing.

References

• Esposito S, et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential. Drug Test Anal. 2012;4(9):733–738.
• Ho EN, et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin β4, in equine urine and plasma by liquid chromatography-mass spectrometry. J Chromatogr A. 2012;1265:57–69.
• Sosne G, et al. Biological activities of thymosin beta4 defined by active sites in short peptide sequences. FASEB J. 2010;24(7):2144–2151.
• Philp D, et al. The actin binding site on thymosin beta4 promotes angiogenesis. FASEB J. 2003;17(14):2103–2105.
• Rahaman KA, et al. Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro. J Chromatogr B. 2024;1235:124033.
• Delcourt V, et al. TB500/TB1000 and SGF1000: a scientific approach for a better understanding of misbranded and adulterated drugs. Drug Test Anal. 2023;15(4):458–464.
• Biçer O, et al. Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: a histopathological and biomechanical study. Jt Dis Relat Surg. 2026;37(3):822–837.
• Sosne G, Dunn SP, Kim C. Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. 2015;34(5):491–496.

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For laboratory and research use only. Not for human consumption. TB-500 has no human clinical trial data, is not approved by any regulatory authority, and is prohibited by WADA. This article summarizes published research for informational purposes and is not medical advice, nor a recommendation or protocol for use.

Related research compounds

Arc Peptides supplies these compounds, each third-party tested for purity and identity with a lot-specific Certificate of Analysis:

• TB-500

For laboratory research use only. Not for human consumption.