TB-500
- Also called
- Thymosin beta-4 fragment (17–23), Ac-LKKTETQ
- Category
- Tissue Research Peptides
- Length
- 7 amino acids, with an acetyl cap on the first one
- Molecular weight
- ≈ 889 Da
- Supplied as
- Lyophilized (freeze-dried) powder in a sealed vial
- Status checked
- October 2026
01What it is
Thymosin beta-4 is a 43-amino-acid protein found in almost every human cell. TB-500, as sold today, is a lab-made copy of just one 7-amino-acid stretch of it (positions 17 to 23), with a small chemical cap (an acetyl group) on one end. That makes it a different molecule from full-length thymosin beta-4, and the two shouldn't be confused. The FDA notes the "TB-500" name isn't standardized, so the COA mass is the way to tell what's in a vial.
02Where it stands legally
| FDA approval | None. It isn't an approved drug for any use, in the US or, per the FDA's 2026 review, in the EU, UK, Canada or Australia. |
| Compounding | Taken off the FDA's "Category 2" list in April 2026 after its nomination was withdrawn. In July 2026 FDA's compounding advisory committee narrowly voted to recommend adding it to the list pharmacies can use, against the advice of FDA's own staff, who found no human data on it. The vote is advisory: pharmacies can't legally compound it unless the FDA adds it through rulemaking. |
| Sport | Prohibited at all times by the World Anti-Doping Agency. The 2026 list names "thymosin-β4 and its derivatives, e.g. TB-500" (S2.3). |
| Sold here as | Research use only. Not for human or animal consumption. |
03Storage
| Sealed vial (powder) | Store sealed at room temperature, away from heat and light. |
04Quality: what a good COA shows
| Identity (mass spectrometry) | A main peak near 889 Da, the 7-amino-acid Ac-LKKTETQ fragment. A peak near 4,960 Da would be full-length thymosin beta-4, a different product. |
| Salt form | Some COAs list the acetate salt (about 949 g/mol). The mass-spec peak should still be the peptide near 889 Da. |
| Purity (HPLC) | 98% or higher, with the chromatogram shown, not just a number. |
| Lot number and date | Matches the vial you have. A COA without a lot number proves nothing. |
| Red flags | No lab name, no chromatogram, the same COA reused for every lot, a "100%" purity claim, or a COA that doesn't say which molecule was tested. |
05Common questions
How much should I take?
We don't give dosing or usage guidance for any research peptide. TB-500 isn't approved for human use, so there's no established safe dose. The only person who can advise you on putting a substance in your body is a licensed clinician who knows your health.
Is TB-500 the same as thymosin beta-4?
No. Thymosin beta-4 is the full 43-amino-acid protein. TB-500 is a 7-amino-acid fragment of it with an acetyl cap. Check the COA mass: about 889 Da for the fragment.
Is it legal to buy?
In the US it can be sold for laboratory research. It can't be sold as a drug, supplement or treatment, and pharmacies can't compound it.
Did the FDA approve TB-500 in 2026?
No. Coming off the Category 2 list and the July committee vote are steps in a review, not approvals. The vote is a recommendation the FDA doesn't have to follow, and FDA's own staff recommended against it.
What's the difference between TB-500 and BPC-157?
They're unrelated molecules from different parent proteins. BPC-157 fact sheet →
06Sources
- FDA, Briefing Document for TB-500-Related Bulk Drug Substances, Pharmacy Compounding Advisory Committee, July 23–24, 2026.
- FDA, Bulk drug substances used in compounding under section 503A (category lists, updated May 14, 2026).
- Committee vote as reported by NCPA and AJMC (July 2026).
- Esposito S et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500. Drug Test Anal, 2012. PMID 22962027.
- World Anti-Doping Agency, Prohibited List 2026, S2.3.