Is TB-500 legal? FDA status, the July 2026 vote and what the evidence shows

The short version. TB-500 is not FDA approved and is not on the 503A Bulks List. An advisory committee voted for listing it on 23 July 2026, a recommendation the FDA is not bound by. FDA staff recommended against, and wrote that they found no article in which TB-500 was given to a human.

What is TB-500?

TB-500 is a synthetic seven amino acid peptide. The FDA briefing document prepared for the July 2026 Pharmacy Compounding Advisory Committee describes it as a fragment of thymosin beta-4, amino acids 17 to 23, with an acetyl group on the first leucine: Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln. TB-500 is a common name, not a United States Adopted Name, and the FDA says it has encountered multiple salts and derivatives, including different active moieties, sold under that same name. The agency calls that a patient safety risk, because a person may receive a different substance from the one a physician ordered.

The naming problem was serious enough to shape the review itself. The FDA wrote that the nominator gave inconsistent information about whether it meant TB-500 free base or TB-500 acetate, which are different active ingredients, so the agency evaluated both on its own initiative. The committee was then asked two separate questions, one for each form. Many websites also present TB-500 as a synthetic version of thymosin beta-4 and use the two names interchangeably. The FDA is explicit that they are not the same: one is a seven-residue fragment, the other is the full protein it is cut from.

In plain English"TB-500" is a nickname, not a regulated drug name. The FDA says products sold under it are not always the same molecule, and it is not the same thing as the thymosin beta-4 protein it is cut from.

Is TB-500 legal in 2026?

TB-500's legal position rests on three dated facts. First, there is no approved product: the FDA briefing found none in the US, and none in Canada, Australia, the United Kingdom, Belgium, Ireland, France, Norway, Germany, Spain or Italy, or through the European Medicines Agency. Second, TB-500 is not on the 503A Bulks List, and the FDA page on 503A bulk substances, updated 14 May 2026, does not name it. Third, the FDA safety-risk page, updated 22 April 2026, lists "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" among substances that were nominated but withdrawn, which takes it out of the interim categories rather than into Category 1.

The committee vote is the fact most often misreported. On 23 July 2026 the committee voted on whether TB-500 free base and TB-500 acetate should be placed on the list, and the vote was reported as 8 to 6 in favour with one abstention. The FDA's own briefing states that it will not issue a final determination until the advisory process is considered and all reviews are finalised, and adding a substance requires rulemaking. As of 2 October 2026 the FDA meeting page carried no posted minutes and no final determination. A page that calls TB-500 "now legal" or "FDA cleared" is describing a rule that does not exist yet.

In plain EnglishA committee said yes. The FDA has not acted on it. Until it does, TB-500 is in the same legal position it was in before the vote.

The FDA found no article in which TB-500 was given to a human. The July 2026 committee voted to list it anyway.

The Ozemback peptide legal status tracker carries TB-500 in the "recommended, not law" group alongside BPC-157, KPV, MOTS-c, Epitalon and Semax, with the date of each fact. TB-500 was one of six peptides the committee backed over two days in July 2026, and emideltide was the only one voted down. The tracker will change the TB-500 row on the day the FDA proposes or finalises a rule, because that is the event that would actually alter its legal status. For how the same committee overrode its own staff across the July meeting, see our analysis of the vote.

What does the evidence for TB-500 show?

The FDA's answer is short: no clinical studies, no human exposure data and no human pharmacokinetic data for TB-500 by any route.

The FDA reviewers searched PubMed, Embase, ClinicalTrials.gov, FAERS and other databases. They wrote that after conducting a literature search, no articles were found in which TB-500 was administered to humans. The nomination cited three references in support of wound healing, and none were studies of TB-500 given to people. On the animal and laboratory side, the FDA found no in vivo study testing whether TB-500 promotes wound healing. It did find an in vitro study reporting that TB-500 free base, at 50 micrograms per millilitre, did not induce healing in scratch-wounded fibroblast cultures. Pharmacokinetic work in animals showed that the peptide reaches the circulation after injection and is broken down into smaller fragments.

Most human data quoted on TB-500 pages is actually about thymosin beta-4, the full protein. A 2010 phase 1 study in the Annals of the New York Academy of Sciences gave intravenous synthetic thymosin beta-4 or placebo to four cohorts of 10 healthy volunteers and reported infrequent, mild or moderate adverse events over 14 days. An eye-drop form of the full protein, RGN-259, has been in late-stage trials, and in July 2025 Ophthalmology Times reported that the phase 3 SEER-3 trial in neurotrophic keratitis missed its primary endpoint. None of that tests TB-500, and none of it produced an approved product.

In plain EnglishThe FDA found no published study giving TB-500 to people. The human studies you see quoted are about a different, larger molecule, and even that one has not been approved for anything.

What has been reported on safety

The FDA's safety conclusion is that potential risks of TB-500 in humans are unknown. Its search of FAERS through 26 March 2025 returned no reports, and the food and supplement complaint system returned two cases about "blended TB-500 and BPC-157" that did not include safety assessments. The nominator submitted, and FDA found, no genotoxicity, reproductive toxicity or carcinogenicity studies. The concern the FDA spelled out is immunogenicity: an injected peptide with uncharacterised impurities and possible aggregates may provoke an immune response, and the publicly available certificates of analysis did not report tests for impurities, aggregates, microbial quality or bacterial endotoxin. Absence of reports is not evidence of safety, as the FDA itself notes about FAERS.

What is the TB-500 dosage?

There is no approved dose of TB-500, and there is no human study to take one from.

Every dose figure you will find for TB-500 comes from somewhere other than a label or a published human trial, because neither exists. The FDA briefing notes that sellers offer powders in several strengths labelled for research use only, that one website gave reconstitution and administration instructions, and that 22 websites offered a consultation about TB-500 without saying how it would be obtained. Human doses quoted from thymosin beta-4 studies belong to a different molecule given by a different route. We report this because it is the record, and we do not publish a recommended dose, schedule or protocol for TB-500 or any other compound.

What is still unknown about TB-500?

• Whether it does anything in humans. The FDA found no human study of TB-500 for any use, including the wound healing it was nominated for.
• Whether it is safe to inject. The FDA lists immunogenicity, impurities and aggregation as unresolved concerns, with no human safety data to weigh them against.
• What is in a given product. The FDA says multiple salts and derivatives are sold under the same name, and public certificates of analysis lack key tests.
• Whether the FDA will follow the committee. The agency is not bound by the July 2026 vote, and no rule had been proposed as of 2 October 2026.
• Long-term effects. No carcinogenicity, genotoxicity or reproductive studies were identified.

How should you read other pages about TB-500?

Check whether the page separates TB-500 from thymosin beta-4, because evidence for the full protein is routinely borrowed for the fragment. Check whether it reports the July 2026 vote as a recommendation or as a change in the law; only the first is accurate. Check whether it names a single human study of TB-500 itself, with a citation you can open. Check who pays the author: nearly every site ranking for TB-500 dosage or benefits sells it, sells a consultation or links to a seller. This page carries a date at the top, 2 October 2026, so you can tell when it stops being current. Related file: BPC-157, often sold alongside it.

The questions people actually type

Sources