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 and research context
Full-length thymosin-beta-4 is a 43-amino-acid, actin-binding peptide studied in tissue-repair contexts. It is not the same compound as the acetylated seven-amino-acid TB-500 fragment. Clinical findings must be matched to the molecule and formulation actually studied. [3] [2]
Dry-eye trial: primary versus secondary outcomes
A phase 2, single-centre, randomized, double-masked study tested thymosin-beta-4 eye drops in 72 people with dry eye over 28 days. Neither of the two primary day-29 outcomes, ocular discomfort and inferior corneal staining, showed a significant benefit. Some secondary measures favoured treatment, but they do not turn a negative primary analysis into confirmed efficacy. [3]
Safety and scope
No adverse events were reported in this short trial. That observation cannot rule out uncommon or longer-term harms, and a topical eye-drop study cannot establish the safety or effectiveness of injected products for sports recovery. The authors reported no conflicts of interest. [3]
What remains uncertain
- This review does not cover the complete full-length thymosin-beta-4 development programme.
- No current marketing authorization, injection-use benefit or current consumer-product composition was established.
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
- Sosne and Ousler 2015: thymosin-beta-4 eye drops for dry eye ↗Accessed 2026-11-10 · full_text_relevant_sections
Clinical Ophthalmology 9:877–884; methods, primary/secondary outcomes and safety
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.