TB-500 questions left over from the story
Some questions cut across the experiments. These are the ones that the name alone cannot answer.
Is TB-500 a steroid?
No. TB-500 is a synthetic peptide comprising the acetylated LKKTETQ sequence, not a steroid. The equine analytical study identifies the fragment corresponding to residues 17–23 of thymosin beta-4. Sharing the actin-binding region does not make the fragment the full protein. The sequence comparison is the place to start if the names have blurred together.
Are there human clinical trials on TB-500?
There are no completed controlled human trials of the heptapeptide for any indication in this research record. There is a randomized human Phase 1 study of full-length thymosin beta-4. Its healthy volunteers and early tolerability findings do not establish human tissue-repair efficacy for TB-500.
“Human data” strikes me as evasive when it has lost the molecule’s name. A real study can still be the wrong study for the claim being made.
TB-500 injury healing time
No human TB-500 healing time has been established. The often-repeated 42% at 4 days and up to 61% at 7 days describe increased re-epithelialization in rat wounds given full-length thymosin beta-4 versus saline. The healing time for a human tendon, joint or muscle injury remains unestablished by those figures. The repair page describes what the rats actually received and what was measured.
Does TB-500 cause cancer?
The concern comes from preclinical tumor and angiogenesis findings for thymosin beta-4 and human pancreatic cancer cells studied in vitro. Human cancer risk from TB-500 remains unestablished. The same repair-related biology gives the concern a rationale, while the fragment’s missing human safety studies prevent a quantified answer.
I regard both a confident yes and a confident reassurance as too neat for that record. Reported effects and safety concerns deserve separate space.
Is TB-500 FDA approved, or allowed in sport?
TB-500 has no FDA-approved human therapeutic indication. On FDA’s page current as of April 22, 2026, the nomination is shown as withdrawn and the safety concerns remain. The advisory meeting was not approval. TB-500 and thymosin beta-4 are also WADA-prohibited in and out of competition for the relevant classes. The regulatory page separates drug approval, compounding eligibility and the sport ban.
Is there a reliable human TB-500 half-life?
Not in this research record. Full-length thymosin beta-4 pharmacokinetics in healthy volunteers and horse detection of TB-500 and its metabolites do not establish a validated human half-life for the fragment. The dosage and half-life page reports study amounts in their original populations rather than proposing a regimen.