TB-500 (Thymosin Beta-4 Fragment)
aka TB4 fragment · Tβ4 17-23
A synthetic fragment of the actin-sequestering protein thymosin beta-4, studied in cardiac repair and corneal/dermal wound healing, and heavily used off-label in veterinary and grey-market human settings.
Mechanism of action
Binds actin monomers to promote cell migration, upregulates laminin-5 and MMPs for extracellular-matrix remodeling, and reduces inflammatory cytokine signaling at injury sites.
Doses used in published studies
Human ophthalmic trials used topical 0.1% Tβ4. Injectable protocols circulating online (2–5 mg/week) have no trial basis.
These figures describe what researchers administered under supervision. They are reported for accuracy and are not a protocol, recommendation, or substitute for clinical guidance.
Reported benefits
- Improved corneal wound closure in controlled human trials of full-length Tβ4
- Reduced scarring and improved cardiac function post-infarct in animal models
- Hair-follicle and dermal repair signals in rodents
Risks & unknowns
- Cell-migration mechanism carries theoretical metastasis concern
- Fragment products differ chemically from the trialed molecule
- Unknown immunogenicity with chronic use
Legal & regulatory status
Full-length thymosin beta-4 (RGN-259) has completed human ophthalmic trials; TB-500 as sold online is not approved anywhere for human use and is WADA-prohibited.
Check status in your state or country →Key studies
- Thymosin Beta 4 in Ocular Surface Repair: Randomized Clinical Data
Journal of Ocular Pharmacology and Therapeutics · 2015