As of October 2026, the FDA and the EMA have not approved any product sold as TB-500. The name is a seller's label for thymosin beta-4 or a piece of it, and sellers use it for different molecules. HHS's October 2026 policy defines one form, TB-500 acetate, by its sequence. No human trial has tested a product sold under this name. WADA bans it in sport at all times. So the label alone cannot tell you what a given vial holds.
Reading up on TB-500? Get the week's peptide and GLP-1 news every Wednesday, with the document behind each line.
What is TB-500?
TB-500 is a seller's name, used loosely for lab-made thymosin beta-4 or for a smaller piece of it. Thymosin beta-4 is a natural protein involved in cell movement and tissue repair, and it has been studied since the 1990s for wound healing. Sellers use the TB-500 label for different molecules, and products sold under it are unregulated. HHS's October 2026 policy defines one form, TB-500 acetate, by its sequence.
Does TB-500 work?
Nobody knows. No human trial has tested a product sold as TB-500, and the registered human trials used full-length, pharmaceutical-grade thymosin beta-4.
What we found. 0 completed randomized trials. 2 completed human trials of pharmaceutical-grade thymosin beta-4, and 1 animal study. The randomized Phase 2 dry-eye trial on the list does not count, because it tested a different, pharmaceutical-grade product.
| Study | Tested in | Status | What it shows |
|---|---|---|---|
| Phase 2 trial of RGN-137, thymosin beta-4 made for skin wounds | People | Completed. Company-sponsored | Company trials explored the healing of skin wounds. The product is not approved by the FDA |
| Phase 2 trial of a thymosin beta-4 eye solution for dry eye, NCT01387347 on ClinicalTrials.gov (opens in new tab) | People | Completed. Randomized, compared with placebo | A signal of benefit was reported. The product was not approved |
| Study of how thymosin beta-4 acts in skin healing | Animals | Published | It supports a role for thymosin beta-4 in cell movement during tissue repair |
Both human trials tested the pharmaceutical-grade protein. Neither tested a vial sold as TB-500.
How we count a trialIs TB-500 safe?
Nobody knows. No human trial has tested a product sold as TB-500, so no trial has measured its safety in people. The trials on this record used pharmaceutical-grade thymosin beta-4, and the record lists no safety results from them. Products sold under the TB-500 name are unregulated and unverified in what they hold. With this name, the safety question starts with what is in the vial, and that section comes after the legal one.
Is TB-500 legal?
- United States
- Not approved by the FDA. Sellers use the name for different molecules, and it is not a formal pharmaceutical product. HHS's October 2026 policy names one form, TB-500 acetate, and defines it by its sequence for compounding.
- Compounding
- On 28 October 2026 HHS said it does not intend to take enforcement action against a US pharmacy or physician who compounds TB-500 acetate for a patient with a prescription. Ten conditions apply. The policy lasts until the FDA decides TB-500 in a final rule. TB-500 is not on the FDA's compounding list and is not approved.
- European Union
- No marketing authorisation from the EMA.
- Sport
- Banned in sport at all times. WADA's Prohibited List names it.
- Trial products
- Company programs tested pharmaceutical-grade thymosin beta-4 in people, and none reached approval.
Not medical advice. Approval and sport status as of . Medical disclaimer
What is in a vial sold as TB-500?
Products sold as TB-500 are unregulated and unverified in what they hold, and sellers use the name for different molecules. None of the trials above tested a product sold under it. A "research use only" label guarantees nothing about purity. A certificate of analysis counts only if it names your lot number, a lab with no stake in the result, and the method used. Purity and identity are separate tests.
Three questions to ask the seller:
- Which lot number is this certificate for?
- Who ran the test, and are they independent of you?
- Does the report confirm identity by mass spectrometry, or purity alone?
What don't we know?
- Whether any product sold as TB-500 does anything in people. No human trial has tested one.
- What chemical a vial sold as TB-500 holds. Sellers use the name for different molecules.
- Whether results from pharmaceutical-grade thymosin beta-4 carry over to products sold as TB-500.
- What is in any given vial with this label.
The other side
A personal result is real to the person who had it. Because sellers use the name for different molecules, it cannot show which chemical was in the vial, or whether the body would have mended on its own.
What would change this record?
- A final FDA rule on the 503A bulks list that adds TB-500 or leaves it off, or HHS narrowing or withdrawing its interim policy of 28 October 2026.
- A published human trial, completed and large enough to give an answer, of a chemically verified, standard peptide identical to what is sold as TB-500.
- A submission to a regulator built on that trial.
Change log
- HHS published an interim enforcement policy that covers TB-500 acetate. A Compounding line and a change trigger were added. Lines that said no chemical identity stands behind the name now say that sellers use it for different molecules and that HHS defines one form. HHS Enforcement Discretion Policy Regarding 503A Compounding Using Certain Peptide Bulk Drug Substances (opens in new tab)
- Record checked. No change logged yet.
Three questions to ask next
- What does 'research use only' actually mean?
- How can you tell if a peptide vendor is legitimate?
- How do you read a certificate of analysis?
Ask better questions.
More questions about TB-500
Is TB-500 the same as thymosin beta-4?
- Not exactly. TB-500 is a seller's name used loosely for lab-made thymosin beta-4 or for a piece of it. Sellers use the name for different molecules, and HHS's October 2026 policy defines one form, TB-500 acetate, by its sequence. The registered human trials used full-length, pharmaceutical-grade thymosin beta-4.
Is TB-500 approved by the FDA?
- No. No product sold as TB-500 has been approved by the FDA, and none has an EMA marketing authorisation.
Is TB-500 banned in sport?
- Yes. WADA's Prohibited List names it, and the ban applies at all times.
Has TB-500 been tested in people?
- Not in a trial. No human trial has tested a product sold under this name. All registered human trials used full-length, pharmaceutical-grade thymosin beta-4 in company programs, and none of those reached approval.
What is TB-500 made of?
- Nobody can say from the label alone. The name is used for lab-made thymosin beta-4 or for a smaller piece of it, and products sold under it are unverified in what they hold.
THE PEPTIDE TABLE
RECORD · TB-500
- Checked
- 29 OCT 2026
- Sources read
- 4
- Approved?
- NO
- Sport (WADA)
- BANNED
- COMPLETED RANDOMIZED TRIALS
- 0
- GRADE
- D
Ask better questions.
thepeptidetable.com/table/tb-500
The record on one slip. Save it as a picture and send it to whoever asked you about TB-500.
Record checked on . Each source shows the date it was checked.
In the same group
Often confused with Thymosin beta-4 (TB4). Thymosin beta-4 is the protein that trials tested in pharmaceutical-grade form, and TB-500 is a seller's name for it or a piece of it. Sellers use the name for different molecules.