Peptide Graded

Thymosin beta-4

Is Thymosin beta-4 legal in the US?

No. It is not approved and is sold as a research chemical.

BSome human evidenceNot approvedas of 2026-10-27

Thymosin beta-4 is not approved by the FDA for any use. Injectable products sold online, often labeled TB-500 (which the FDA reviewed as a seven-amino-acid fragment), are research chemicals; the FDA found no human exposure data for TB-500, and the agency has not acted on its compounding advisory committee's July 2026 vote to recommend adding TB-500 to the 503A bulks list. RGN-259 eye drops are in a phase 3 trial for neurotrophic keratopathy, and a recombinant intravenous form has been tested in heart attack patients.

No. It is in clinical trials as eye drops and as an intravenous drug for heart attack. None has reached approval. Injectable product sold online, often labeled TB-500, is not approved. The FDA found no human exposure data for TB-500, and it has not acted on its advisory committee's July 2026 vote to recommend adding TB-500 to the 503A bulks list. 3814

Yes. The World Anti-Doping Agency and horse-racing authorities prohibit it. Labs have published methods to detect both the protein and the TB-500 fragment. 6

Read the full Thymosin beta-4 page

More on Thymosin beta-4

Citations

  1. Goldstein 2012, Expert Opin Biol Ther: Thymosin beta4, a multifunctional regenerative peptide doi.org
  2. Guarnera 2007, Ann N Y Acad Sci: Thymosin beta-4 and venous ulcers, European randomized study doi.org
  3. ClinicalTrials.gov NCT03937882: RGN-259 phase 3 in dry eye clinicaltrials.gov
  4. Sosne 2022, Int J Mol Sci: RGN-259 in neurotrophic keratopathy, phase 3 pubmed.ncbi.nlm.nih.gov
  5. 2026, Peptides: Thymosin beta 4, an emerging therapeutic candidate for kidney diseases pubmed.ncbi.nlm.nih.gov
  6. Ho 2012, J Chromatogr A: Doping control analysis of TB-500 in equine urine and plasma pubmed.ncbi.nlm.nih.gov
  7. 2025, Cardiovasc Res: Recombinant human thymosin beta 4 in mice and STEMI patients after reperfusion pubmed.ncbi.nlm.nih.gov
  8. FDA: Certain bulk drug substances for use in compounding may present significant safety risks fda.gov
  9. ClinicalTrials.gov NCT05555589: RGN-259 phase 3 in neurotrophic keratopathy clinicaltrials.gov
  10. Ruff 2010, Ann N Y Acad Sci: Randomized placebo-controlled single and multiple dose study of intravenous thymosin beta4 in healthy volunteers pubmed.ncbi.nlm.nih.gov
  11. 2021, J Cell Mol Med: First-in-human phase 1 study of recombinant thymosin beta4 in healthy Chinese volunteers pubmed.ncbi.nlm.nih.gov
  12. Malinda 1999, J Invest Dermatol: Thymosin beta4 accelerates wound healing pubmed.ncbi.nlm.nih.gov
  13. STAT 2026: FDA panel to discuss broader access to peptides via compounding statnews.com
  14. STAT 2026: FDA peptide compounding panel backs epitalon, rejects emideltide statnews.com

Reference information only, not medical advice. Drawn from the Thymosin beta-4 article, fact-checked against the cited sources. No dosing anywhere on this site.