Is Thymosin Alpha-1 (Tα1) legal?
Thymosin Alpha-1 (Tα1) is not FDA approved as a finished drug. For drug-tested athletes it is not on the WADA prohibited list. Yes outside the U.S., prescribed by hepatology / oncology providers in countries where Zadaxin is approved.. Legal status depends on your country and changes over time. This reflects US status at the time of writing and is not legal or medical advice.
Regulatory status
- FDA: Not FDA approved in the U.S. Has orphan drug status for some indications. Approved in 35+ countries (sold as Zadaxin) for hepatitis B/C and chemotherapy adjunct.
- WADA: Not listed
- Prescription: Yes outside the U.S., prescribed by hepatology / oncology providers in countries where Zadaxin is approved.
References
- Thymosin alpha 1 in chronic hepatitis B and C — Sherman KE et al., Gut, 2003
- The efficacy and safety of thymosin alpha1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial — Wu J et al., BMJ, 2025
- The efficacy of thymosin alpha 1 for severe sepsis (ETASS): a multicenter, single-blind, randomized and controlled trial — Wu J et al., Critical Care, 2013
Pepdex is an editorial reference, not medical advice. Peptides vary in legal and approval status by country, many are research compounds without full human safety data. Talk to a qualified clinician before starting anything.
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Last updated 2026-06-06.