Tissue repair

TB-500 (Thymosin Beta-4)

Reviewed 22 October 2026 · How we research

Also known as: TB500, Thymosin Beta-4, Tβ4, TB 500

What is TB-500?

TB-500 is the trade name for a synthetic version of thymosin beta-4 (Tβ4), a 43-amino-acid protein present in almost every human cell. Confusingly, the name is used for two different things: some products contain full-length Tβ4, others contain only the short fragment (Ac-LKKTETQ) thought to carry its actin-binding and wound-healing activity. A good certificate of analysis should tell you which one you have.

Tβ4 has a much stronger research base than BPC-157, including human trials of the full-length protein in eye and skin conditions.

How TB-500 works

Tβ4 is the main actin-sequestering molecule in cells. By controlling the pool of free actin it regulates how cells move, which is central to wound repair. It also promotes new blood-vessel formation, reduces inflammation and was shown in mice to mobilise heart progenitor cells after injury. Its N-terminal fragment Ac-SDKP has separate anti-fibrotic effects.

What the research shows

• Topical and injected Tβ4 accelerated wound closure in rats (Malinda et al., 1999).
• In mice, Tβ4 triggered heart progenitor cells to mobilise and form new blood vessels after injury (Smart et al., 2007).
• Human phase 2 trials of Tβ4 eye drops (RGN-259) showed benefit in dry eye and neurotrophic keratitis.
• A phase 1 study found intravenous Tβ4 well tolerated in healthy volunteers across a wide dose range.

Compare: BPC-157 vs TB-500

TB-500 side effects

In the intravenous phase 1 study, Tβ4 caused no dose-limiting toxicity. Reported effects from non-clinical use include headache, lethargy and injection-site irritation. As with other pro-angiogenic peptides, there is a theoretical concern about effects on existing tumours.

UK legal status

TB-500 is not licensed as a medicine in the UK. It is sold for research use only and is prohibited in sport. It has been the subject of doping cases in horse racing and human sport.

More detail, including current UK research-vial prices: TB-500 UK guide. For the doses used in published studies and the reconstitution maths: TB-500 dosing in the literature.

References

1. Malinda KM, et al. Thymosin β4 accelerates wound healing. J Invest Dermatol. 1999;113:364–368.
2. Smart N, et al. Thymosin β4 induces adult epicardial progenitor mobilization and neovascularization. Nature. 2007;445:177–182.
3. Goldstein AL, Hannappel E, Kleinman HK. Thymosin β4: actin-sequestering protein moonlights to repair injured tissues. Trends Mol Med. 2005;11:421–429.
4. Ruff D, et al. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin β4 in healthy volunteers. Ann N Y Acad Sci. 2010;1194:223–229.