TB-500
Also known as Thymosin beta-4 fragment, Tβ4 17-23, Ac-LKKTETQ
TB-500 is a synthetic peptide based on the actin-binding region of thymosin beta-4, a 43-amino-acid protein found in most human cells. The name is used loosely for both the short fragment and the full protein. Neither is an approved drug.
By [Author name]. Licensed pharmacist review: pending. Last updated .
Identity
- TB-500 fragment
- Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln (Ac-LKKTETQ), residues 17-23 of thymosin beta-4, about 889 g/mol
- Thymosin beta-4 (full)
- 43 amino acids, N-acetylated, about 4,963 g/mol
- Function studied
- Binding of G-actin (the protein's best-characterized role)
What the research covers
Thymosin beta-4 has been studied for decades as an actin-sequestering protein involved in cell migration. Animal studies have looked at wound, cardiac and corneal models.
Full-length thymosin beta-4 (not the TB-500 fragment) has been tested in small clinical trials of topical and eye-drop formulations, for dermal wounds and eye-surface conditions. These were formulation-specific and did not lead to an approved product.
The short TB-500 fragment itself has essentially no published human clinical data. Most of what is said about it online is extrapolated from the full protein.
Summaries describe what studies measured, not what a substance does for anyone. Nothing here is a claim of benefit or a basis for use.
Regulatory status
- Not FDA-approved in either form.
- A 2026 PCAC vote recommended TB-500 for the 503A bulks list; listing requires rulemaking. The October 15, 2026 interim access policy draft names TB-500 among the peptides pharmacies could compound under enforcement discretion. Neither was final as of the review date.
Anti-doping (WADA)
Prohibited at all times. WADA's S2 class names thymosin beta-4 and its derivatives, such as TB-500, explicitly.
Follow changes on the FDA peptide status tracker.
TB-500 questions
Why do TB-500 vials differ so much between sellers?
Because the name covers two molecules with very different sizes, and because research-chemical labels are not verified by any regulator. A mass-spec result is the only way to confirm identity.