TB-500
Also known as Thymosin Beta-4 fragment · Ac-LKKTETQ
Evidence comes from rodents or other animal models, with no published controlled human trials. Most compounds that look promising in animals do not replicate in people — the attrition rate from animal model to approved drug is well over 90%.
What it is
A seven-residue fragment of thymosin beta-4, a naturally occurring actin-binding protein. TB-500 and full-length thymosin beta-4 are routinely conflated in discussion, but they are different molecules with different evidence behind them.
How it is thought to work
The parent protein sequesters G-actin and influences cell migration. The fragment is proposed to retain some of this activity, though it is far smaller than the protein it derives from.
What the studies found
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Animal work on the parent protein
Full-length thymosin beta-4 has shown effects on wound healing, corneal repair and cardiac repair in animal models.
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Human trials of the parent protein did not lead to approval
Thymosin beta-4 was taken into clinical trials for dry eye disease and wound healing. Development did not result in a licensed product.
What the evidence does not show
- Nearly all supporting evidence concerns full-length thymosin beta-4, not the TB-500 fragment sold under that name.
- There are no published human trials of the fragment itself.
- Claims about tendon and ligament repair in humans are extrapolation from animal work on a different molecule.
Reported risks and adverse effects
- No human safety data for the fragment.
- Prohibited at all times by WADA.
- Because the compound promotes angiogenesis and cell migration in models, theoretical concerns have been raised about effects on existing tumours. This is unstudied rather than established.
This is a summary of what has been reported in the literature, not a complete safety profile. For anything concerning your own health, speak to a doctor.
Regulatory status
Not approved anywhere for any indication.