Peptide Graded

Thymosin alpha-1

Is Thymosin alpha-1 legal in the US?

No. It is not approved and is sold as a research chemical. It is approved in over 35 other countries.

BSome human evidenceNot approvedas of 2026-10-27

Thymosin alpha-1 is not approved by the FDA for any use. It is approved as thymalfasin (Zadaxin) in more than 35 other countries for hepatitis B and C and as an immune adjuvant. In the United States it was taken off the FDA's Category 2 compounding list after its nominators withdrew it, and in December 2024 the Pharmacy Compounding Advisory Committee voted 17 to 4 against adding it to the 503A bulks list; it is sold online as a research chemical.

No. It is approved as thymalfasin (Zadaxin) in over 35 countries, mainly for hepatitis B and as a vaccine adjuvant. The FDA has never approved it. It was taken off the FDA's Category 2 compounding list after its nominators withdrew it. In December 2024 the Pharmacy Compounding Advisory Committee voted 17 to 4 against adding it to the 503A bulks list. So pharmacies cannot legally compound it under that pathway. 1716

Read the full Thymosin alpha-1 page

More on Thymosin alpha-1

Citations

  1. Garaci 2009, Expert Opin Biol Ther: From lab to bedside, emerging clinical applications of thymosin alpha 1 pubmed.ncbi.nlm.nih.gov
  2. Chien 1998, Hepatology: Efficacy of thymosin alpha1 in chronic hepatitis B, randomized controlled trial pubmed.ncbi.nlm.nih.gov
  3. Wu 2013, Critical Care: Thymosin alpha1 in severe sepsis, randomized trial (ETASS) doi.org
  4. Liu 2025, BMJ: Thymosin alpha1 for sepsis (TESTS), phase 3 trial doi.org
  5. Iino 2005, J Viral Hepat: Thymosin alpha-1 in Japanese patients with chronic hepatitis B doi.org
  6. 2025, Front Cell Infect Microbiol: Efficacy of thymosin alpha1 for sepsis, systematic review and meta-analysis doi.org
  7. FDA: Certain bulk drug substances for use in compounding may present significant safety risks fda.gov
  8. Mannherz 2009, Cell Motil Cytoskeleton: The beta-thymosins, intracellular and extracellular activities pubmed.ncbi.nlm.nih.gov
  9. Chan 2004, Expert Rev Anti Infect Ther: Thymalfasin for chronic hepatitis B pubmed.ncbi.nlm.nih.gov
  10. Ren 2011, Microb Cell Fact: Production of N-acetylated thymosin alpha1 in E. coli pubmed.ncbi.nlm.nih.gov
  11. Romani 2006, Blood: Thymosin alpha1 activates dendritic cell tryptophan catabolism pubmed.ncbi.nlm.nih.gov
  12. 2026, Peptides: Thymosin beta 4, an emerging therapeutic candidate for kidney diseases pubmed.ncbi.nlm.nih.gov
  13. Chan 2001, Aliment Pharmacol Ther: Thymosin in chronic hepatitis B, meta-analysis pubmed.ncbi.nlm.nih.gov
  14. Iino 2005, J Viral Hepat: Thymosin alpha-1 in Japanese patients with chronic hepatitis B, randomized trial pubmed.ncbi.nlm.nih.gov
  15. Liu 2025, BMJ: Thymosin alpha1 for sepsis (TESTS), multicentre phase 3 trial pubmed.ncbi.nlm.nih.gov
  16. FDA: Pharmacy Compounding Advisory Committee minutes, December 2024 fda.gov

Reference information only, not medical advice. Drawn from the Thymosin alpha-1 article, fact-checked against the cited sources. No dosing anywhere on this site.