Peptide Graded

Thymosin beta-4

Is Thymosin beta-4 safe?

Volunteer trials only; no data on injection use

BSome human evidenceNot approvedas of 2026-10-27

The full-length protein was well tolerated in the phase 1 trials and the eye-drop and heart trials. Side effects were similar to placebo. Those data cover use in a vein and on the eye under trial conditions. The courses lasted days to weeks. 471011

No one knows what repeated injection under the skin does. That is how people actually use gray-market product, for injuries. The FDA's compounding assessment found no human exposure data for TB-500, the fragment sold for injury recovery. The FDA lists TB-500 as nominated but withdrawn from Category 2. Its advisory committee voted in July 2026 to recommend adding TB-500 to the 503A bulks list, and the FDA has not acted on that vote. Thymosin beta-4 promotes blood-vessel growth. No one has studied its effect on existing tumors in people. It is on the WADA prohibited list. 6814

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.