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TB-500: what the research shows, and what it doesn’t

By Pinnacle Pulse Editorial Team · Status as of 16 October 2026 · Next scheduled update: 14 January 2027

Short answer: TB-500 is a trade name for a synthetic peptide, not an approved medicine. When doping-control chemists analyzed a product sold under that name, they found a seven-amino-acid fragment of the human protein thymosin beta-4. Small clinical trials exist for the full protein, given as eye drops. For TB-500 itself, FDA says it identified no human exposure data.

A name with two meanings

Most of the confusion about TB-500 is a vocabulary problem, so let’s sort that out first.

Thymosin beta-4 is a protein, 43 amino acids long, that your cells make in large amounts. It grabs onto actin, part of the scaffolding inside every cell. In a 2010 review in the FASEB Journal, Gabriel Sosne and colleagues pointed to one short stretch of it, amino acids 17 to 23 (LKKTETQ in the one-letter code), as the actin-binding region and a likely active site.

TB-500 is a sales label. In 2012 the anti-doping laboratory in Ghent got hold of a product called TB-500, worked out what was in it, and made a reference sample. It was that 17-to-23 stretch with an acetyl group stuck on the front (Ac-LKKTETQ). Around the same time, chemists at the Hong Kong Jockey Club’s racing laboratory published a method for spotting it in horse urine and plasma. Which tells you something about where the early demand came from.

So when a website quotes thymosin beta-4 research to sell you on TB-500, it’s borrowing results from a molecule roughly six times longer.

What has been studied

The full protein

The clinical work on thymosin beta-4 is mostly about eyes. A 2015 trial in Cornea tested drops called RGN-259 in nine people with severe dry eye, randomized against a vehicle for 28 days. The authors reported better symptoms and less corneal staining at several time points, with no safety problems. Nine patients. Keep that number in mind.

A bigger phase II trial that year, in Clinical Ophthalmology, randomized 72 people with moderate to severe dry eye. Both primary endpoints came up empty: no significant difference from placebo. Some secondary measures did improve, and the authors’ conclusion was upbeat anyway. That happens a lot in medical publishing, and it’s why we read past the abstract.

Allan Goldstein and Hynda Kleinman, two researchers who have worked on thymosin beta-4 for many years, reviewed its development for wounds, eyes and the heart in 2015. Much of what they describe is animal and lab work.

The fragment

For the acetylated fragment, the literature is mostly analytical chemistry. How do you make it as a reference standard? How do you find it in an athlete’s urine? We ran a PubMed search on 16 October 2026 for TB-500 or LKKTETQ limited to human studies. It returned 22 records. Nine deal with detecting or analyzing the substance in the lab, six are recent reviews of peptide use, three matched only by accident (one is about tuberculosis), and the rest are lab studies. None of them tests TB-500 in people.

FDA is blunter than we are. On its list of substances withdrawn from compounding nominations it names “thymosin beta-4, fragment (LKKTETQ), also known as TB-500” and says it found no human exposure data. Before the July 2026 advisory committee meeting, where TB-500 was looked at for wound healing, FDA staff recommended against adding it to the compounding list.

What the research does not show

There's no clinical trial of TB-500 in people. Not a small one, not an open-label one, none.

The eye-drop trials don’t carry over to an injected fragment of seven amino acids. Different molecule, different route, different tissue. And even for the drops, the larger trial missed both primary endpoints.

Nothing published shows that TB-500 helps people recover from sports injuries, which is what it’s usually sold for. Nothing shows it’s safe, either in the short run or over years.

Since TB-500 is a seller’s label, the analyses describe specific products at specific times. They can’t vouch for what’s in a vial today.

TB-500 is not authorized as a medicine in the EU or the US. WADA’s 2027 Prohibited List puts “thymosin-β4 and its derivatives e.g. TB-500” in class S2, so it is banned in sport at all times. The details are on our page Is TB-500 legal?.

FAQ

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

No. Thymosin beta-4 is a 43-amino-acid protein. The product analyzed by the Ghent anti-doping lab as TB-500 contained a seven-amino-acid fragment of it with an acetyl group added.

Has TB-500 been tested in humans?

Not in published clinical trials. FDA says it identified no human exposure data for the fragment. The human trials that exist used the full thymosin beta-4 protein, mostly as eye drops.

Do the thymosin beta-4 eye-drop trials apply to TB-500?

They don’t. They tested a different molecule applied to the eye, and the larger of the two 2015 trials did not meet its primary endpoints.

Sources

  • Sosne G, et al. Biological activities of thymosin beta4 defined by active sites in short peptide sequences. FASEB J. 2010;24:2144-51. PMID 20179146
  • Esposito S, et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500. Drug Test Anal. 2012;4:733-8. PMID 22962027
  • 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. PMID 23084823
  • 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):491-6. PMID 25826322
  • Sosne G, Ousler GW. Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, phase II clinical trial. Clin Ophthalmol. 2015;9:877-84. PMID 26056426
  • Goldstein AL, Kleinman HK. Advances in the basic and clinical applications of thymosin β4. Expert Opin Biol Ther. 2015;15 Suppl 1:S139-45. PMID 26096726
  • PubMed search “(TB-500 OR LKKTETQ) AND humans[mh]”, run 16 October 2026 via NCBI E-utilities: 22 records.
  • FDA. Certain bulk drug substances for use in compounding that may present significant safety risks. fda.gov
  • FDA. FDA briefing document, Pharmacy Compounding Advisory Committee, July 2026. fda.gov/media/193342/download
  • WADA. 2027 Prohibited List, class S2.3. wada-ama.org

Facts last checked: 16 October 2026.

About this article

Written by: the Pinnacle Pulse Editorial Team, the people who make the Pinnacle Pulse app. We work only from primary sources such as regulators, legal texts, trial registries and PubMed, and we remove claims we can’t check against one.

This article has not been reviewed by a physician. It is general information, not medical advice.

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Change log

  • 16 October 2026: First published.

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