TB-500
The short answer: TB-500 is a lab-made fragment of thymosin beta-4, a protein involved in cell movement and wound repair. As of October 17, 2026 it is not FDA-approved, and the human trials people cite tested the full 43-amino-acid protein as eye drops, not the fragment sold as TB-500.
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Based on public sources; we cannot guarantee it is correct. Not medical advice. A doctor should prescribe and confirm. Full disclaimer
What is TB-500?
TB-500 is a short synthetic peptide linked to the LKKTETQ region of thymosin beta-4. Thymosin beta-4 is a 43-amino-acid protein that plays a role in cell movement and wound repair.
A result for full-length thymosin beta-4, tested as eye drops for corneal and dry-eye conditions, does not transfer to an injected fragment. For TB-500 itself, the evidence is animal and lab work.
What is TB-500 claimed to do, and what does the evidence show?
| Use | Claimed | Shown | Grade |
|---|---|---|---|
| Soft-tissue repair | Heals muscle, tendon and ligament injuries | Animal and lab work for the fragment. Human trials exist only for full-length thymosin beta-4 as eye drops, a different product.[4] | Evidence grade D |
| Whole-body recovery | Faster recovery from training | No study measured this. | Evidence grade U |
What are the known risks and side effects of TB-500?
An unapproved product has no required quality testing. In July 2026 FDA staff told the agency's advisers they had concerns about impurities, bacterial toxins and unreliable certificates for several of these peptides, and that nobody knows how often they trigger an immune response.
Thymosin beta-4 has been linked in lab studies to new blood-vessel growth, which tumors also rely on. No study has shown that TB-500 causes or worsens cancer in people, and none has ruled it out.
- People who are pregnant, trying to get pregnant or breastfeeding. There is no human data in pregnancy.
- Anyone under 18. It has not been studied in young people.
- Tested athletes and service members. Check with USADA or your service's rules first. A positive test counts whatever the label said.
- People taking prescription medicines. Interactions have not been studied. Bring the product label to your clinician.
- Swelling of the face, lips or throat, trouble breathing, chest pain, a racing heart or fainting. Call 911.
- Redness spreading from an injection site, warmth, pus or a fever. Get same-day care.
- Unsure what you took or whether a reaction is serious: Poison Control 1-800-222-1222 (free, 24 hours).
- Thoughts of harming yourself: call or text 988.
Is TB-500 legal?
Not FDA-approved for any use.[1,5] Not on the 503A bulks list. FDA advisers recommended it on July 23, 2026; the vote is non-binding and no rule has been proposed.[2,6,7]
Every status change for TB-500 is logged with its date and source in the regulatory tracker entry for TB-500.
Is TB-500 banned in sport?
Prohibited at all times under the 2026 WADA List (S2.3: thymosin beta-4 and its derivatives, e.g. TB-500).[3] Anti-doping rules work on strict liability: a positive test counts whatever the label said.
What don't we know about TB-500?
- Any effect in people: no human trial of the fragment has been published.
- What is actually in products sold online: there is no required quality testing.
- Effects in pregnancy: there is no human data.
What should you tell your doctor if you're using TB-500?
Tell them exactly what you took, for how long, and where it came from, and bring the label. These questions can help the conversation:
- Is there an approved treatment for my goal that has been tested in people?
- What should I watch for, and which symptoms mean I should stop and call you?
- Could it interact with the medicines I already take?
Compare next
- US Food and Drug Administration. 503A bulk drug substances: interim categories, updated April 15, 2026 , 2026-04-15.
- US Food and Drug Administration. Pharmacy Compounding Advisory Committee, meeting of July 23-24, 2026: briefing documents and vote record , 2026-07-23.
- World Anti-Doping Agency. 2026 Prohibited List (sections S0 and S2) , 2026-01-01.
- ClinicalTrials.gov. Thymosin beta-4 (RGN-259) eye-drop trials in neurotrophic keratopathy and dry eye .
- Frier Levitt. FDA peptides 'do not compound' list update 2026 , 2026-04-16. (law-firm or secondary summary)
- DLA Piper. FDA AdComm recommends adding six peptides to bulk list , 2026-07-31. (law-firm or secondary summary)
- McDermott Will & Emery. Bulk list bound? PCAC backs majority of peptides in two-day public meeting , 2026-07-27. (law-firm or secondary summary)