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PeptidesEvidence: Preclinical-dominant

TB-500: Thymosin Beta-4 Fragment Science, Veterinary History & Athlete Bans

Written by
Daniel Reyes, PhD
Medically reviewed by
Dr. Sarah Lindqvist, MD
Published
June 20, 2025
Updated
June 20, 2025
Last medical review
June 20, 2025
Reviewer scope
Metabolic health
3D protein structure render representing TB-500, the synthetic actin-binding fragment of the repair protein thymosin beta-4

TB-500 is a synthetic version of the actin-binding region of thymosin beta-4, a naturally occurring repair-signaling protein. Animal models show enhanced cell migration, angiogenesis, and wound closure; full-length thymosin beta-4 reached early human wound-healing studies. The TB-500 fragment sold online has no published human trials, is not FDA-approved, and is prohibited at all times by WADA.

Fragment vs full protein — a distinction that matters

Clinical-stage work on thymosin beta-4 involved the full 43-amino-acid protein in dermal and corneal healing. TB-500 is the short actin-binding fragment — cheaper to synthesize, pharmacologically related, but not the molecule those studies used. Evidence for one is routinely miscredited to the other.

Sports physiotherapy session — TB-500’s repair reputation comes from animal models and veterinary use, not human trials

The veterinary shadow

TB-500’s notoriety began in racing animals, where it circulated as an unregulated recovery agent long before human biohacking adopted it. That history explains supply chains; it does not create human data.

TB-500 is usually cross-shopped against BPC-157 — the tendon-repair evidence review grades that compound’s data. Calculator questions are answered in TB-500 dosage calculator explained, the compound-by-compound overview in the peptide cheat sheet, and the full profile in our TB-500 monograph.

Risk snapshot

  • No human safety or efficacy trials of the fragment
  • Cell-migration/angiogenesis biology carries theoretical oncologic caution
  • Strict-liability doping violation for tested athletes
  • Unregulated purity, like every gray-market peptide

Frequently asked questions

What is TB-500 used for?
It is sold for injury recovery, but the claims rest on animal models showing enhanced cell migration, angiogenesis, and wound closure — plus early human studies of the full thymosin beta-4 protein, which is not the fragment being sold. The TB-500 fragment itself has no published human trials.
Is TB-500 the same as thymosin beta-4?
No. TB-500 is a synthetic copy of the short actin-binding region of thymosin beta-4 — cheaper to make and pharmacologically related, but not the full 43-amino-acid protein used in clinical-stage wound-healing research. Evidence for one is routinely miscredited to the other.
Is TB-500 banned for athletes?
Yes. TB-500 is prohibited at all times under WADA’s S2 category, and anti-doping violations are strict-liability — a positive test is a violation regardless of intent.

Questions to ask a licensed clinician

  • Is any human evidence route-relevant to my injury?
  • Am I subject to anti-doping rules in any competition?

References

  1. Goldstein AL, Hannappel E, Sosne G, Kleinman HK (2012). Thymosin beta-4: a multi-functional regenerative peptide. Expert Opinion on Biological Therapy. SourceReview
  2. World Anti-Doping Agency (2024). The Prohibited List — S2 peptide hormones, growth factors and related substances. WADA. SourceAgency list
  3. US Food and Drug Administration (2023). Certain bulk drug substances for use in compounding that may present significant safety risks. FDA Human Drug Compounding. SourceAgency notice

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