Overview
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In plain language
TB-500 is a name used for a lab-made peptide based on a small piece of thymosin beta-4, a natural protein found in almost every cell. Most often it refers to a 7-amino-acid fragment.
Researchers have studied the parent protein for wound healing and tissue repair in animals. Those results cannot automatically be applied to the TB-500 fragment. TB-500 is not an FDA-approved medicine, it is banned in sport, and products sold online may not contain what the label says.
For students
TB-500 usually refers to a synthetic fragment based on the actin-binding region of thymosin beta-4, commonly described as residues 17–23 (LKKTETQ), sometimes acetylated. Some products labeled TB-500 instead contain full-length thymosin beta-4, which adds to the confusion.
The actin-binding motif is linked to cell migration in studies of the full protein. Animal studies of the fragment itself are limited, and human data are essentially absent. That is why VALREXA grades it Preclinical.
For researchers and instructors
Evidence attribution. Most cited evidence comes from studies of full-length thymosin beta-4 (43 residues), including clinical trials of eye drops. These cannot be attributed to the fragment.
Sport. Prohibited by WADA; detections have been reported in human and equine anti-doping testing.
Regulatory. Not FDA-approved. Since October 2026, licensed 503A pharmacies may compound it under FDA enforcement discretion, which is not approval.
Molecular identity
- Amino acids
- 7 (fragment)
- Molecular weight
- ~889.0 Da
- Formula
- Variant-dependent
- Sequence
- Sequence must be specified
Origin and history
TB-500 is a name used for synthetic products based on thymosin beta-4, a natural peptide discovered in the thymus research of Allan Goldstein in the 1960s–80s. Many TB-500 products are built around the short actin-binding region of the molecule (the sequence LKKTETQ) rather than the full 43-amino-acid peptide, so what a vial actually contains varies.
TB-500 was first used mainly in horse racing, where it was promoted for recovery, and it has been found in drug tests of racehorses. In human sport it is banned by WADA. It became widely known through the Essendon Football Club scandal in Australia: in 2016 the Court of Arbitration for Sport banned 34 current and former players over a supplement program involving thymosin beta-4.
Key people
- Allan L. GoldsteinBiochemist who discovered the thymosins
Timeline
- 1981
Thymosin beta-4 is isolated and sequenced
- 2000s
TB-500 products appear in the horse-racing world
- 2012
Essendon supplement program begins in Australian football
- 2016
Court of Arbitration for Sport bans 34 Essendon players
- 2026
FDA allows 503A compounding of TB-500 under enforcement discretion
See every peptide on one history timeline.
Human evidence
Clinical studies involving thymosin β4 formulations do not establish the efficacy of products sold as TB-500.
Confirm exact sequence and chemical form before assigning molecular mass, clinical evidence or trial references.
Explore original publications and distinguish preclinical findings from controlled human evidence.
Safety and regulatory status
See every compound on the regulatory tracker.
TB-500 is not FDA-approved as a therapeutic product.
Product identity, purity, sterility, and endotoxin testing address different risks. This profile is educational and does not provide treatment guidance.
Sources
Hernandez Gener, E. (2026, November 7). TB-500: molecular data, research history and evidence. VALREXA Biosciences. https://valrexa.com/peptides/tb-500.html
APA style · Last reviewed November 7, 2026 · Our editorial standardsLast reviewed November 7, 2026. Trial and regulatory status can change; confirm in the linked registries. This profile is educational and is not medical advice, a treatment recommendation, or dosing or sourcing guidance. Report an error · Corrections policy