What Is TB-500? Research, Evidence & UK Status

Peptide Guides

What is TB-500?

TB-500 is not the scientific name of a molecule. It is a product name, and the first thing worth understanding about it is what the products carrying that name actually contain.

The name belongs to a preparation whose key ingredient is a very short peptide: seven amino acids copied from the middle of thymosin beta-4, a natural peptide of 43 amino acids found in almost every cell of the human body. A peptide is a short chain of amino acids, the small chemical units the body builds peptides and proteins from, and our introduction to peptides covers the category from the beginning. Picture thymosin beta-4 as a chain of 43 links. TB-500 copies just seven of those links, the short section scientists believe does the molecule's most important work, with one small chemical change added to help it last longer. When anti-doping laboratories analysed vials of TB-500, this short copied section is what they found inside.^1,2

That distinction matters more for TB-500 than for almost any other research peptide, because nearly everything written about it online describes findings from studies of the full-length protein, then presents them as findings about the fragment. They are related molecules. They are not the same molecule, and the research record for one is not the research record for the other.

Where TB-500 came from

TB-500's public profile did not come from human medicine. It came from horse racing.

The preparation was sold as a veterinary product, and its first appearances in the scientific literature are papers from racing laboratories working out how to detect it in horses. In 2012, the Hong Kong Jockey Club's racing laboratory published the first test for detecting TB-500 in horses. To prove the test worked, they gave the product to two horses and traced it in their blood and urine.² Doping-control laboratories in Europe published parallel work characterising the fragment and building tests for it in human samples.^1,3

That origin explains a lot about the compound's reputation. It became known as something injected into racehorses to speed up recovery from injury, and the claims attached to it in fitness circles grew from there. What did not grow alongside the claims was human evidence, a pattern that repeats right across animal versus human peptide research.

What thymosin beta-4 is and does

Thymosin beta-4 is a genuine and well-studied biological molecule. It is one of the most abundant small peptides in human cells, and it is concentrated in platelets and in the fluid of healing wounds. Its main known job is to look after actin, the protein cells use as internal scaffolding. Cells put that scaffolding up and take it down constantly as they move, divide and repair themselves.

Because cell movement is central to wound healing, researchers have studied thymosin beta-4 in laboratory and animal models of injury for decades. Animal and cell studies have reported effects on skin wound closure, corneal repair, blood vessel formation and heart tissue after injury. These are real findings, published in real journals, and they are the reason a pharmaceutical development programme existed at all. The fragment itself has some animal evidence of its own: a 2026 rat study of Achilles tendon repair reported that TB-500 improved tendon strength and tissue structure at four weeks.¹³ All of these are findings in animals and cells, not demonstrations in people. Animal findings frequently do not translate directly to human outcomes.

What Does the Research on TB-500 Show?

Thymosin beta-4 is unusual among research peptides in that genuine human trials of it do exist. What those trials show is the important part.

A pharmaceutical programme ran for around two decades, testing thymosin beta-4 formulations in people for pressure ulcers, venous leg ulcers, the fragile-skin condition epidermolysis bullosa, dry eye, a corneal condition called neurotrophic keratopathy, and heart attack recovery. Registered trials on ClinicalTrials.gov include completed Phase 2 studies in pressure ulcers and venous ulcers, terminated trials in epidermolysis bullosa, a series of dry eye trials running to Phase 3 with several hundred participants each, and eye-drop trials in neurotrophic keratopathy.^4,5,6

The results, reported by the trial teams, are mixed. A Phase 2 dry eye trial in 72 people reported that neither of its two main outcome measures showed a significant difference from placebo, alongside improvements on some secondary measures.⁷ A small Phase 3 trial of thymosin beta-4 eye drops in neurotrophic keratopathy reported that six of ten treated patients healed completely against one of eight on placebo, a difference the authors described as a strong trend that did not reach statistical significance on the primary analysis.⁸ A 2025 Cochrane review judged the evidence for those eye drops to be of low certainty and concluded they may not increase corneal healing.⁹ Larger dry eye trials completed years ago without producing an approved product.

After twenty years, the position is simple. No thymosin beta-4 medicine has been approved by any regulator, several programmes were terminated or withdrawn, and development continues in places, including trials of a recombinant thymosin beta-4 for heart attack patients in China.¹⁰

And the short section actually sold as TB-500? It has never been given to people in any recorded study. When the FDA reviewed TB-500 in July 2026, it stated that it had not identified human exposure data for products containing the TB-500 fragment.¹¹ A registry entry that circulated in 2026 describing a TB-500 heart trial turned out to be a fictional example record, not a real study, and it is not evidence of anything.

What TB-500 has not been shown to do

Given how TB-500 is marketed, what it has not been shown to do in humans matters as much as anything else on this page. There is no controlled human evidence that TB-500 speeds recovery from muscle, tendon or ligament injury. There is no controlled human evidence that it heals anything at all. There is no published human safety data for it either; TB-500 side effects covers what little is known. Claims about flexibility, hair growth and injury prevention trace back to animal studies of the full-length peptide, to anecdote, or to nothing.

None of this means the underlying biology is uninteresting. It means the questions remain open. Reading a peptide study shows how to tell an open question from an answered one.

TB-500 is also sold alongside BPC-157 under the Wolverine Stack name. The Wolverine Stack explained covers that pairing, including the one controlled study of the combination.

How Is TB-500 Supplied for Research?

Research-grade TB-500 is supplied as a freeze-dried powder in sealed vials, labelled by weight of peptide. In a laboratory, the powder is dissolved to make a solution of known strength; reconstituting peptides explains that process step by step.

One caution specific to this compound: because TB-500 is a product name rather than a molecule name, one supplier's vial may contain the short copied section while another's contains the full natural protein, and the label alone does not tell you which. This is exactly the situation a batch-specific certificate of analysis exists for, because an identity test reports what the vial actually contains.

Is TB-500 legal, and is it banned in sport?

In the UK, TB-500 is not listed as a controlled drug and no product containing it holds a marketing authorisation. Genuine laboratory research products may fall outside medicines regulation, but "research use only" labelling does not by itself determine classification; the MHRA considers a product's overall presentation, intended use and pharmacological properties. In sport the position is stricter: the 2026 WADA Prohibited List names thymosin beta-4 and its derivatives, with TB-500 as the named example, under its growth factors category, prohibited at all times.¹² Both positions, including how detection works, are set out in full in TB-500 in the UK.

Common questions about TB-500

What is TB-500?

A product name for a lab-made copy of a small section of thymosin beta-4, a natural healing-associated peptide found throughout the body. It first became known as a veterinary product in horse racing, and most claims about it come from research on the full-length peptide rather than the fragment.^1,2

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

No. Thymosin beta-4 is the full natural peptide, a chain of 43 amino acids. TB-500 copies just seven of those links, with one small chemical change. Because the copied section is the part thought to do the important work, findings about one are routinely presented as findings about the other, which they are not. TB-500 vs thymosin beta-4 sets the two records side by side.

Does TB-500 work?

No controlled human study has tested whether TB-500 as sold speeds healing or improves recovery, so the question has no evidence-based answer. Trials of full-length thymosin beta-4 formulations in people produced mixed results and no approved medicine after two decades. The compound itself has never been given to people in any recorded study; the FDA's 2026 review identified no human exposure data for products containing the fragment.¹¹

Is TB-500 banned in sport?

Yes, at all times, in and out of competition. The WADA Prohibited List names it explicitly, and anti-doping laboratories have published detection methods for it.^3,12

TB-500 Research Specification

The current TB-500 research specification is freeze-dried (lyophilised) powder, purity-tested by HPLC with identity confirmed by mass spectrometry, with a dated certificate of analysis published per batch. We publish what each batch contains and make no claims about what it does. The full range is listed under research peptides.

Supplied for laboratory research use only. Not for human consumption.

References

1. Esposito S, Deventer K, Goeman J, Van der Eycken J, Van Eenoo P. 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):733-8. DOI
2. Ho ENM, Kwok WH, Lau MY, 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. DOI
3. Thomas A, Görgens C, Guddat S, et al. Simplifying and expanding the screening for peptides <2 kDa by direct urine injection, liquid chromatography, and ion mobility mass spectrometry. J Sep Sci. 2015;39(2):333-41. DOI
4. RegeneRx Biopharmaceuticals. Study of Thymosin Beta 4 in Patients With Pressure Ulcers. ClinicalTrials.gov identifier NCT00382174. Completed 2008, results posted. Registry record
5. RegeneRx Biopharmaceuticals. Study of Thymosin Beta 4 in Patients With Venous Stasis Ulcers. ClinicalTrials.gov identifier NCT00832091. Completed 2009, results posted. Registry record
6. Guarnera G, De Rosa A, Camerini R. Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement on healing. Ann N Y Acad Sci. 2007;1112:407-12. DOI
7. Sosne G, Ousler GW. Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial conducted using the controlled adverse environment (CAE) model. Clin Ophthalmol. 2015;9:877-84. DOI
8. Sosne G, Kleinman HK, Springs C, et al. 0.1% RGN-259 (Thymosin ß4) ophthalmic solution promotes healing and improves comfort in neurotrophic keratopathy patients in a randomized, placebo-controlled, double-masked Phase III clinical trial. Int J Mol Sci. 2022;24(1):554. DOI
9. Kruoch Z, Choo AY, Kemp A, et al. Medical and surgical interventions for neurotrophic keratopathy. Cochrane Database Syst Rev. 2025;12:CD015723. DOI
10. Beijing Northland Biotech. Efficacy and Safety Study of Thymosin Beta 4 in Patients With Acute Myocardial Infarction. ClinicalTrials.gov identifier NCT05984134. Completed 2023, no results posted. Registry record
11. US Food and Drug Administration. Pharmacy Compounding Advisory Committee Briefing Document: TB-500. July 2026. FDA briefing document
12. World Anti-Doping Agency. Prohibited List 2026, effective 1 January 2026, category S2.3: Growth Factors and Growth Factor Modulators. WADA
13. Biçer O, Adanir O, Güleryüz Y, 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. DOI