TB-500: research, uses and evidence

TB-500 is the trade name for synthetic thymosin beta-4 or its active fragment. Thymosin beta-4 is a naturally occurring 43-amino-acid protein that binds actin and is involved in cell migration. It accelerated wound healing and cardiac repair in animals, and eye-drop formulations have reached phase 2 and 3 trials for dry eye and corneal injury.

Structure

HydrophobicGly / ProPolarBasic (+)Acidic (−)

Shown: full-length human thymosin beta-4 (43 residues, N-terminally acetylated). “TB-500” is sold as either the full peptide or the short actin-binding fragment Ac-LKKTETQ (residues 17–23). The two are not interchangeable; check the certificate of analysis.

How it works

Thymosin beta-4 sequesters G-actin, regulating how cells reorganize their cytoskeleton to move. It also promotes angiogenesis, reduces inflammation, and in mouse hearts activated integrin-linked kinase and mobilized epicardial progenitor cells. The LKKTETQ motif is the actin-binding region.

Research use cases

Areas where TB-500 has been studied. Inclusion here does not mean it works for that purpose.

Dermal wound healing
Corneal epithelial repair and dry eye
Cardiac repair after infarction in animal models
Hair follicle stem cell activation
Tendon and muscle injury in equine and rodent models

What the research found

Wound healing

Topical or injected thymosin beta-4 increased re-epithelialization by 42% at four days and 61% at seven days in a rat full-thickness wound model, with more collagen deposition and angiogenesis.¹

Cardiac repair

In mice, thymosin beta-4 activated integrin-linked kinase, improved cardiomyocyte survival and reduced scarring after coronary ligation.²

Dry eye in people

In a phase 2 trial of 0.1% thymosin beta-4 eye drops (RGN-259) in severe dry eye, treated eyes showed improvements in some sign and symptom scores versus vehicle. Later phase 3 trials had mixed results on primary endpoints.³

Review

A review by researchers involved in its discovery summarizes thymosin beta-4 as a multifunctional repair molecule, while noting that most evidence is preclinical.⁴

Safety and open questions

Human trials of the full-length protein, mainly topical and ophthalmic, reported tolerability similar to placebo. Systemic injection of research-grade TB-500 has not been studied in controlled human trials. As with other pro-angiogenic peptides, the effect on existing tumours is unknown.

Regulatory status

Not approved. Prohibited by WADA (S2). Full-length thymosin beta-4 has been tested in human trials for eye and skin conditions under the name RGN-259 and RGN-137. Included in the July 2026 FDA advisory committee compounding vote.

Status was accurate when this page was last reviewed on October 26, 2026. Regulations change; check with the relevant authority before relying on it.

TB-500: common questions

Is TB-500 the same as thymosin beta-4?

Sometimes. Suppliers use “TB-500” for both full-length synthetic thymosin beta-4 and the 7-residue fragment Ac-LKKTETQ. Most of the published research uses the full-length protein.

Is TB-500 banned in sport?

Yes. Thymosin beta-4 and its fragments are prohibited by WADA under S2. There have been anti-doping cases in horse racing and human sport.

Is TB-500 approved for human use?

References

Malinda KM, Sidhu GS, Mani H, et al. (1999). Thymosin beta4 accelerates wound healing. Journal of Investigative Dermatology.
Bock-Marquette I, Saxena A, White MD, DiMaio JM, Srivastava D. (2004). Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature.
Sosne G, Dunn SP, Kim C. (2015). Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea.
Goldstein AL, Hannappel E, Sosne G, Kleinman HK. (2012). Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications. Expert Opinion on Biological Therapy.

Links open a PubMed search for the exact title, or the original source where one is given.