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Peptide profile · Synthetic fragment of thymosin beta-4 (actin-sequestering peptide)

TB-500

Also known as: Thymosin beta-4 fragment, Tβ4 (17-23), TB500, Thymosin beta 4 (marketed form)

A synthetic fragment marketed as thymosin beta-4. The full-length natural peptide has early human trials in wound healing and eye disease; the fragment sold as TB-500 has none.

Preclinical evidenceNot FDA-approved
Abstract peptide-chain illustration for the TB-500 profile

Evidence level

Preclinical

Full-length thymosin beta-4 has animal data and small phase 1/2 human trials for dermal wounds and dry eye. TB-500 as sold has no controlled human trials for any use; its evidence is borrowed from the parent molecule.

Regulatory status (US)

Not FDA-approved

Not FDA-approved. Full-length thymosin beta-4 has been studied in registered clinical trials (investigational); the TB-500 fragment has not. Thymosin beta-4 fragment (LKKTETQ) was placed in category 2 of the compounding interim policies and appears on the FDA withdrawn-nomination list current 22 April 2026. Prohibited in sport by WADA (S2.3, growth factors).

Mechanism (proposed)

Thymosin beta-4 binds G-actin, regulating cytoskeletal dynamics, cell migration and angiogenesis; animal studies report accelerated dermal, corneal and cardiac repair. Whether the marketed fragment reproduces these effects in humans is untested.

Studied for: Dermal wound healing (thymosin β4, human phase 2), Dry eye and neurotrophic keratopathy (thymosin β4, human), Cardiac repair (animal), Muscle and tendon (animal, marketing)

Full research analysis

TB-500 and Thymosin Beta-4: What the Research Actually Studies

TB-500 is sold on the back of thymosin beta-4 research — a different molecule with real but early human trials in wounds and eye disease. We untangle which studies are about what, and what that means for the fragment people actually buy.

Read the analysis

Two molecules, one name

Almost every claim made for TB-500 cites research on thymosin beta-4 (Tβ4), a naturally occurring 43-amino-acid peptide that regulates actin and has been studied for tissue repair for decades[1]. TB-500 is a much shorter synthetic fragment. The assumption that the fragment does what the parent does in humans has not been tested.

What thymosin beta-4 evidence looks like

Full-length Tβ4 has animal data in dermal, corneal and cardiac injury models, and it has reached small human trials: a phase 2 study in venous leg ulcers[2] and trials of Tβ4 eye drops (RGN-259) for dry eye and neurotrophic keratopathy[3]. These are real, registered studies — small, early-phase, and not yet leading to an approval.

What TB-500 evidence looks like

There is none in humans. No registered trial, no published controlled study. The grade is preclinical because the fragment's evidence is at best inferential from Tβ4 animal work.

Regulatory position

Not FDA-approved. Prohibited in sport at all times under WADA's S2.3 (growth factors), which names thymosin-β4 and its derivatives such as TB-500[4]. Sold online as a "research chemical" of unverified identity and purity.

Safety summary

Thymosin beta-4 was reported as well tolerated in early-phase trials of topical and intravenous formulations. No human safety data exist for the fragment sold as TB-500. Because thymosin beta-4 promotes cell migration and angiogenesis, its behaviour in the presence of tumours is a theoretical concern that has not been studied clinically.

Frequently asked questions

Is TB-500 the same as thymosin beta-4?
No. Thymosin beta-4 is a natural 43-amino-acid peptide. TB-500 is a short synthetic fragment marketed as its active region. Human trial data exist only for the full-length molecule.
Has TB-500 been tested in humans?
Not in any controlled trial we can find. Full-length thymosin beta-4 has been through small phase 1/2 trials for wounds and eye conditions.
Is TB-500 approved anywhere?
No. It is not an approved drug in the U.S. or, to our knowledge, any other jurisdiction, and it is prohibited in sport.

References

Numbered in order of first use. Study type is shown for every source; see our methodology for how we rank evidence.

  1. 1.

    Goldstein AL, Hannappel E, Sosne G, Kleinman HK. Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications Expert Opinion on Biological Therapy, 2012.

    Review

    Result: Summarises Tβ4 biology, animal repair models and early clinical trials in wounds and eye disease.

    Limitations: Authors have commercial interests in Tβ4 development.

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  2. 2.

    Guarnera G, DeRosa A, Camerini R. Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement in healing Annals of the New York Academy of Sciences, 2010.

    Randomized controlled trialAdults with chronic venous leg ulcersn = 72

    Result: Topical Tβ4 was well tolerated; healing signals were seen at a middle dose but the trial was small.

    Limitations: Small; dose-response not monotonic; not confirmed in a larger trial.

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  3. 3.

    Clinical trials of thymosin beta 4 (search) ClinicalTrials.gov.

    Trial registry

    Result: Registered phase 1–3 trials of full-length Tβ4 (e.g. RGN-259 eye drops); no registered trials of the TB-500 fragment.

    ↑ back to text
  4. 4.

    The Prohibited List World Anti-Doping Agency, 2026.

    Regulatory source

    Result: Thymosin-β4 and its derivatives (e.g. TB-500) are named under S2.3 Growth Factors; prohibited at all times.

    ↑ back to text

Review status: Editorially reviewed against primary sources. This article was fact-checked against the primary sources listed in the references by our editorial team, and it has not been reviewed by a licensed clinician. It is educational content, not medical advice. Read our editorial policy and methodology. Spotted an error? Tell us.

Profile by Tristen Ta. Published August 15, 2026; updated August 15, 2026.

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