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TB-500 is a synthetic peptide based on a short section of thymosin beta-4, a protein found in almost all human cells. It is not FDA-approved for any use, and no approved medicine in the United States contains it.
Thymosin beta-4 is made of 43 amino acids. It is the main protein inside cells that holds on to actin, the building block of the cell's internal skeleton that cells use to change shape and move. TB-500 is usually described as the seven-amino-acid sequence Ac-LKKTETQ, taken from the central actin-binding region of thymosin beta-4. The FDA refers to it as thymosin beta-4 fragment (LKKTETQ)/TB-500.
TB-500 is a trade-style name rather than a formal drug name, and it is not the same as full-length thymosin beta-4. Products sold under the name are not standardized.
In laboratory research, the LKKTETQ region of thymosin beta-4 has been linked to cell migration, the growth of new blood vessels and wound repair, according to a 2010 review in The FASEB Journal. These findings come from cell and animal experiments. They show what scientists were investigating, not that TB-500 has these effects in people.
Published research related to TB-500 has been done almost entirely in cells and animals. A 2024 study from a doping-control laboratory in South Korea, which mapped how TB-500 is broken down in the body, noted that the biological effects of TB-500 itself had not been documented.
In its compounding review, the FDA stated that it had not identified any human exposure data for drug products containing this thymosin beta-4 fragment.
Full-length thymosin beta-4 has been tested separately in people, mainly as an eye drop called RGN-259. In a phase 3 trial that enrolled 18 patients with neurotrophic keratopathy, a rare corneal condition, complete healing at 4 weeks occurred in 6 of 10 people on RGN-259 and 1 of 8 on placebo, a difference that did not reach statistical significance (International Journal of Molecular Sciences, 2022). RGN-259 is not FDA-approved, and results for an eye drop of the full protein do not apply to TB-500.
Current status: Not FDA-approved.
TB-500 was previously on the FDA's Category 2 list of bulk substances that raise significant safety concerns for compounding. The FDA cited a possible risk of immunogenicity (an unwanted immune response), partly because the peptide can clump together, as well as peptide impurities. As of the FDA's April 2026 update, the nomination is listed as withdrawn by the nominator and TB-500 is no longer in Category 2.
On July 23, 2026, the FDA's Pharmacy Compounding Advisory Committee voted 8 to 6, with 1 abstention, to recommend adding TB-500 to the 503A Bulks List, the list of bulk substances pharmacies may use for compounding, for wound healing. FDA staff had recommended against it. The committee's vote is advisory only. The FDA must still make its own decision and complete formal rulemaking before pharmacies could use the substance, and as of late August 2026 it had not done so. Being placed on that list would allow compounding with a prescription; it would not make a substance an FDA-approved drug.
Products sold online as research chemicals are not approved medicines, and the FDA has not reviewed their contents, purity or quality.
The World Anti-Doping Agency (WADA) 2026 Prohibited List names thymosin beta-4 and its derivatives, such as TB-500, under class S2 (growth factors). They are prohibited at all times, in and out of competition.
Peptide Labs does not sell this compound. This page is general information, not medical advice. Our Peptide Guide exists to explain what these compounds are and how they are regulated, not to supply them.
Anyone with questions about TB-500 should speak with a licensed healthcare provider, who can explain the current evidence and the legal status in plain terms.
See the full list of compound profiles in the Peptide Guide. TB-500 is often discussed alongside BPC-157 and in the blend known as the Wolverine Stack. For the legal background, read whether peptides are legal in the U.S.
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