Checked 2026-11-10. Independent clinical review has not been completed. WADAFUK is independent of WADA and does not provide medical advice or an individual anti-doping determination.
Prohibited at all times
2026: prohibited at all times (S2). [1]
2026 List, S2.3, printed page 8 · 2026 rules apply from 1 January 2026. Any 2027 material below concerns future rules from 1 January 2027; it is not current clearance.
Identity: fragment versus parent molecule
Here TB-500 means the N-acetylated seven-amino-acid fragment corresponding to thymosin-beta-4 positions 17–23. It is distinct from the full 43-amino-acid protein and from the non-acetylated fragment. Findings for those other molecules cannot simply be transferred to this compound. [2]
What has actually been studied
Esposito and colleagues used analytical chemistry to identify the acetylated fragment in a confiscated TB-500 package. This was a product-characterization study, not a human treatment trial. It does not establish the contents of every product now using the name TB-500. [3]
FDA’s 2026 review did not identify human clinical studies establishing effectiveness of this exact fragment for the proposed conditions. It identifies major toxicology, clinical-safety and peptide-quality gaps. Lack of a reported adverse event is not evidence that the product is safe. [2]
Current US policy context
The October 2026 HHS policy describes conditional enforcement discretion for specified TB-500 acetate compounding. This interim nonbinding policy is not FDA approval, validation of recovery claims or permission under anti-doping rules. Conditions and chemical form matter. [4] [5]
What remains uncertain
- No human efficacy or long-term safety conclusion is supported for the exact fragment.
- No worldwide legal conclusion or current retail-product assay was performed.
Check the sources.
These are concise editorial paraphrases of selected sources, not a systematic review or a reproduction of source tables. Access depth is shown for each reference; an abstract-only check cannot resolve details found only in a full paper.
- WADA 2026 Prohibited List ↗Accessed 2026-11-10 · official_full_text_relevant_sections
Effective date; S0 printed page 4; S2 printed pages 7–8
- FDA staff review: thymosin-beta-4 fragment related substances, 15 May 2026 ↗Accessed 2026-11-10 · official_full_text_relevant_sections
Chemical identity; distinction from parent/non-acetylated fragment; clinical and safety evidence
- Esposito et al. 2012: acetylated thymosin-beta-4 fragment identified in TB-500 ↗Accessed 2026-11-10 · full_text_relevant_sections
Accepted manuscript pages 3 and 6–8; DOI 10.1002/dta.1402
- Federal Register: HHS peptide compounding policy notice, 30 October 2026 ↗Accessed 2026-11-10 · official_full_text_relevant_sections
Notice and legal effect of policy
- HHS 503A peptide enforcement-discretion policy and Appendix B ↗Accessed 2026-11-10 · official_full_text_relevant_sections
Policy conditions pages 1–4; BPC-157 acetate and TB-500 acetate entries pages 5–7
Check the current official WADA List and the relevant anti-doping authority for your sport, product, route and circumstances. Do not stop or change necessary treatment based on this page. Ask a qualified clinician about health decisions. Missing evidence does not establish safety.