TB-500 is a synthetic fragment of the natural protein thymosin beta-4 that is marketed for tissue repair, but human evidence for the TB-500 fragment itself is essentially absent; the human trial data that exist are for the separate full-length thymosin beta-4 drug (RGN-259). It is not approved anywhere and is prohibited in sport by WADA at all times.

Is TB-500 approved for medical use?

TB-500 is not approved for medical use and is prohibited in one or more regulatory or anti-doping frameworks. United States (FDA): Not FDA-approved; TB-500 placed on the 503A Category 2 list (barred from compounding). Full-length thymosin beta-4 (RGN-259) is a separate investigational drug in Phase 3 ophthalmic trials. On July 23, 2026, the FDA Pharmacy Compounding Advisory Committee voted 8-6, with one abstention, to recommend TB-500 (for wound healing) for the Section 503A Bulk Drug Substances List; the vote is advisory and non-binding, and the FDA had not made a final decision as of publication. European Union (EMA): No EMA marketing authorisation. Australia (TGA): No registered/approved product; an unapproved therapeutic substance.

Is TB-500 legal in Australia?

TB-500 in Australia (TGA): No registered/approved product; an unapproved therapeutic substance.

Is TB-500 banned in sport?

TB-500 under the World Anti-Doping Agency (WADA) code: Prohibited at all times under S2 (peptide hormones, growth factors and mimetics) since 2011.

Synthetic peptide fragment (Ac-LKKTETQ) corresponding to the actin-binding region of thymosin beta-4; note it is NOT the same molecule as full-length recombinant thymosin beta-4

TB-500

Prohibitedaka Thymosin beta-4 fragment, Tbeta4 fragment, TB4 fragment, LKKTETQ peptide

TB-500 is a short synthetic peptide based on the actin-binding portion of thymosin beta-4. Preclinical studies suggest roles in wound healing, angiogenesis and reduced fibrosis, but robust human trials exist only for full-length thymosin beta-4 (RGN-259), a distinct molecule.

Compare

BPC-157 vs TB-500

Mechanism

The LKKTETQ sequence binds and sequesters actin, influencing cell migration, angiogenesis and tissue remodeling, with reported anti-inflammatory effects and stem/progenitor cell recruitment. Nearly all data derive from full-length thymosin beta-4 or animal models; the mechanism and pharmacology of the TB-500 fragment in humans are not well characterised.

Regulatory Status by Region

United States (FDA)Not FDA-approved; TB-500 placed on the 503A Category 2 list (barred from compounding). Full-length thymosin beta-4 (RGN-259) is a separate investigational drug in Phase 3 ophthalmic trials. On July 23, 2026, the FDA Pharmacy Compounding Advisory Committee voted 8-6, with one abstention, to recommend TB-500 (for wound healing) for the Section 503A Bulk Drug Substances List; the vote is advisory and non-binding, and the FDA had not made a final decision as of publication.
Australia (TGA)No registered/approved product; an unapproved therapeutic substance.
European Union (EMA)No EMA marketing authorisation.
WADAProhibited at all times under S2 (peptide hormones, growth factors and mimetics) since 2011.

See the full regulatory status matrix

Key Studies

Thymosin beta 4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial (opens in a new tab) (Sosne et al., Cornea 2015;34(5):491-6; PMID 25826322 (full-length thymosin beta-4, RGN-259))
0.1% RGN-259 (Thymosin beta-4) Ophthalmic Solution Promotes Healing in Neurotrophic Keratopathy: A Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial (opens in a new tab) (PMCID PMC9820614 (full-length thymosin beta-4))
TB-500: Status, Risks, and Bans in Sport and Military (WADA S2 classification) (opens in a new tab) (BSCG regulatory summary; WADA Prohibited List S2)

Related Clinical Trials

Common Questions

What is TB-500?: TB-500 is a synthetic fragment of the natural protein thymosin beta-4 that is marketed for tissue repair, but human evidence for the TB-500 fragment itself is essentially absent; the human trial data that exist are for the separate full-length thymosin beta-4 drug (RGN-259). It is not approved anywhere and is prohibited in sport by WADA at all times.
Is TB-500 approved for medical use?: TB-500 is not approved for medical use and is prohibited in one or more regulatory or anti-doping frameworks. United States (FDA): Not FDA-approved; TB-500 placed on the 503A Category 2 list (barred from compounding). Full-length thymosin beta-4 (RGN-259) is a separate investigational drug in Phase 3 ophthalmic trials. On July 23, 2026, the FDA Pharmacy Compounding Advisory Committee voted 8-6, with one abstention, to recommend TB-500 (for wound healing) for the Section 503A Bulk Drug Substances List; the vote is advisory and non-binding, and the FDA had not made a final decision as of publication. European Union (EMA): No EMA marketing authorisation. Australia (TGA): No registered/approved product; an unapproved therapeutic substance.
How does TB-500 work?: The LKKTETQ sequence binds and sequesters actin, influencing cell migration, angiogenesis and tissue remodeling, with reported anti-inflammatory effects and stem/progenitor cell recruitment. Nearly all data derive from full-length thymosin beta-4 or animal models; the mechanism and pharmacology of the TB-500 fragment in humans are not well characterised.
Is TB-500 legal in Australia?: TB-500 in Australia (TGA): No registered/approved product; an unapproved therapeutic substance.
Is TB-500 banned in sport?: TB-500 under the World Anti-Doping Agency (WADA) code: Prohibited at all times under S2 (peptide hormones, growth factors and mimetics) since 2011.