How it works
Thymosin beta-4 binds G-actin and is involved in cytoskeletal reorganisation, cell migration and angiogenesis. In animal models of cardiac and dermal injury it has shown repair effects.
TB-500 is a fragment of that protein rather than the protein itself. The claims made for it are borrowed from the full-length molecule's animal literature, which is a substitution nobody has validated in people.
What the evidence shows
Full-length thymosin beta-4 has been through small early-phase trials in ophthalmic and cardiac indications. None of them tested the general tissue-repair use that TB-500 is sold for, and TB-500 itself has no human efficacy trials at all.
Typical dosing
No established human dose. Circulating protocols are extrapolated from animal work.
Reported side effects
No human safety profile exists.
Labelled warnings and contraindications
- No human toxicology, no established dose, no label.
- Listed in FDA's Category 2 bulk drug substances review, closing the compounding route.
- Prohibited by the World Anti-Doping Agency. This is one of the more commonly detected substances in anti-doping testing.
- The theoretical concern that gets raised most often is angiogenesis, since promoting new blood vessel growth is not desirable in the presence of an undetected tumour. It is a theoretical concern, not a demonstrated harm, because nobody has looked.
Legal status and sourcing
Not approved as a drug and not a lawful supplement ingredient. Sold under research-use-only labelling.
Prohibited in competitive sport at all times, in and out of competition.
What it costs
Nothing here is sold through a pharmacy, so there is no legitimate price to report. What circulates is research-use material priced by vendors with no regulatory obligation to anyone. We do not reproduce those figures.
How confident anyone can be
Very low. The underlying protein has interesting biology. The fragment being sold has no human evidence behind it.