Molecule profile · Module 6
TB-500 and thymosin beta-4 — evidence and research limits
This label describes the research context of this profile, not a product-by-product approval determination. It does not mean every use of the molecule lacks approval. Read the existing evidence details and regulatory context for the specific preparation, indication and jurisdiction; no new approval is inferred.
MOLECULE PROFILE
- Evidence summary
- Investigational — profile context
- Esposito and colleagues identified an N-terminally acetylated 17–23 fragment of thymosin beta-4 in material called TB-500. Guarnera and colleagues studied a topical preparation of full-length thymosin beta-4 in venous ulcers. An analytical identification and a trial of a different molecule and route do not establish a subcutaneous TB-500 regimen. The interpretation is specific to the studied molecule, formulation, route, population, and endpoint. Reported commercial regimens are not validated by a study of a different product or outcome.
- Regulatory status varies by jurisdiction
- The academic source does not establish a current authorization for every preparation sold under this name. Product identity, formulation, indication, jurisdiction, and current official labeling must be checked separately. A discussion of compounding or an advisory meeting is not a product approval.
Educational information for healthcare professionals and the general public. Not individual medical advice, diagnosis, treatment, or a recommendation to use a compound.
Identity and mechanism
Full-length thymosin beta-4 participates in actin-related cellular biology. The name TB-500 has also been used for a characterized acetylated fragment; it does not reliably identify every product sold under that name. Analytical identity, full-length peptide studies, and fragment studies must remain separate before discussing repair mechanisms or clinical effects.
What the evidence supports
Esposito and colleagues identified an N-terminally acetylated 17–23 fragment of thymosin beta-4 in material called TB-500. Guarnera and colleagues studied a topical preparation of full-length thymosin beta-4 in venous ulcers. An analytical identification and a trial of a different molecule and route do not establish a subcutaneous TB-500 regimen.
The interpretation is specific to the studied molecule, formulation, route, population, and endpoint. Reported commercial regimens are not validated by a study of a different product or outcome.
Regulatory context
The academic source does not establish a current authorization for every preparation sold under this name. Product identity, formulation, indication, jurisdiction, and current official labeling must be checked separately. A discussion of compounding or an advisory meeting is not a product approval.
Safety and uncertainty
Ambiguity between fragment and full beta-4 thymosin prevents automatic transfer of safety data. Human safety cannot be inferred from a cell result, a product name, or lack of events in a small report. These educational adaptations do not provide an administration protocol.
Sport and anti-doping status
The WADA 2026 Prohibited List names thymosin-β4 and its derivatives, for example TB-500, among growth factors and modulators in section S2.3, prohibited at all times (in and out of competition). This is an anti-doping classification, separate from clinical evidence, product quality and regulatory approval. Medical supervision, a prescription or an approved indication does not by itself permit use in sport; any exemption for a documented medical condition is a separate decision by the competent anti-doping organization. The List is revised each year, so check the List in force on the relevant date.
Continue learning
Explore Module 6 in PEPTIDE Academy for the full evidence discussion.
References
Bibliographic sources shown for transparency. Citation verification pending; no citation is marked verified.
- Guarnera G, DeRosa A, Camerini R, et al. The effect of thymosin treatment of venous ulcers. Ann N Y Acad Sci. 2010;1194:207-12. DOI: 10.1111/j.1749-6632.2010.05490.x. PMID: 20536470.DOI 10.1111/j.1749-6632.2010.05490.x · PMID 20536470
- Safer D, Elzinga M, Nachmias VT. Thymosin beta 4 and Fx, an actin-sequestering peptide, are indistinguishable. J Biol Chem. 1991;266(7):4029-32. PMID: 1999398. · PMID 1999398
- Esposito S, Deventer K, Goeman J, et al. 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: 10.1002/dta.1402. PMID: 22962027.DOI 10.1002/dta.1402 · PMID 22962027
- World Anti-Doping Agency. International Standard: Prohibited List 2026 (in effect from 1 January 2026). Checked 19 October 2026.
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