TB-500
A synthetic fragment of thymosin beta-4. The parent protein reached phase 2 human trials; the fragment sold as TB-500 has not been trialled in humans.
Healing & Repair
Thymosin Beta-4
The full-length protein that TB-500 is a fragment of. Unlike the fragment, this has reached phase 2 and phase 3 human trials — mostly ophthalmic, with mixed results.
Overview
Thymosin beta-4 is one of the most abundant proteins inside human cells. Its main job is to hold onto actin, the protein scaffold cells use to change shape and move. By managing the pool of available actin it influences how readily cells migrate into damaged tissue, and it also promotes new blood vessel formation and dampens inflammation. That combination is why it has been trialled for wound healing, corneal injury and heart repair.
A 43-amino-acid, 4.9 kDa G-actin sequestering protein binding monomeric actin at 1:1 stoichiometry and buffering the polymerisable pool. Downstream effects include upregulation of laminin-5 and matrix metalloproteinases in corneal and dermal models, promotion of endothelial migration and tubulogenesis, Akt activation in cardiomyocytes after ischaemic injury, and reduced myofibroblast transdifferentiation. Clinical development has focused on topical ophthalmic formulations (RGN-259) in dry eye disease and neurotrophic keratopathy, with phase 2 and phase 3 trials reporting inconsistent results across endpoints. The intravenous cardiac programme (RGN-352) did not complete.
Research areas
Corneal healingDry eyeWound healingCardiac repair
Dosing reported in the literature
Every protocol below is reproduced from a published study or approved labelling, with its source named. These are records of what was studied — not recommendations, and not a suggestion that any of them is appropriate for any person.
| Protocol as reported | Source |
|---|---|
| 0.1% topical ophthalmic solution, six times daily for 28 days in dry eye disease | RGN-259 phase 3 protocol |
| Intravenous thymosin beta-4 phase 1 safety and pharmacokinetic study in healthy volunteers | Ruff et al., Annals of the New York Academy of Sciences 2010 |
Trial status
Phase 2 and phase 3 completed in dry eye and neurotrophic keratopathy with mixed endpoint results. Cardiac and dermal programmes did not complete.
Reported safety signals
- Phase 1 intravenous dosing reported no dose-limiting toxicity, but total systemic human exposure remains limited.
- Pro-angiogenic activity carries a theoretical oncologic concern that has not been directly studied.
- Most human data is from topical ophthalmic use, which does not establish safety for systemic injection.
- Material sold for injection is unregulated and its identity is unverified.
Common questions
Should I read TB-500 evidence as evidence for thymosin beta-4?
It works the other way around, and only partly. Nearly all the published research uses this full-length protein, and TB-500 is a seven-amino-acid fragment of it. Evidence for the protein does not automatically transfer to the fragment, because the fragment has never been separately characterised in humans.
Primary sources
Medical disclaimer
This page is for informational and research purposes only. Nothing here constitutes medical advice. The compounds discussed are research chemicals. Consult a qualified clinician before starting any protocol.
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