# TB-500

FDA defines TB-500 as a seven-amino-acid fragment of thymosin beta-4, a 43-amino-acid protein involved in cell movement and repair. Sellers also use the name for the whole protein. Every human trial used the full-length protein.

Also called: Thymosin beta-4 fragment, Tβ4 fragment
Source page: https://peplogue.com/peptides/tb-500/
Reviewed: 2026-10-12. Not medical advice.

## How it works

- Where it acts: Thymosin beta-4 binds actin, the protein cells use to move.
- What it changes: In animal and cell studies, cells move into wounds faster and new blood vessels form.
- What people notice: Human trials used the full protein, as eye drops and wound gels. The TB-500 fragment has no human data.

## What the evidence shows

- **Injury recovery**: Lab only. Animal and cell studies only.
- **Wounds and sores (full-length protein)**: Early. Phase 2 trials in pressure sores and leg ulcers finished more than a decade ago with mixed results. No phase 3 trial or approval followed.
- **Eye surface healing (full-length protein)**: Failed. Eye drops (RGN-259) missed their main goal in phase 3 trials for dry eye and, in 2025, for neurotrophic keratitis. Another trial is due to report in November 2026.

## Side effects and risks

- unknown: FDA has found no data on human exposure to the fragment.
- unknown: In lab work the parent protein drives cell movement and blood-vessel growth, which raises an untested question about cancer.
- unknown: FDA cites the risk of immune reactions to injected peptide and its impurities.

Who should avoid it: Anyone with a history of cancer, and athletes.

## How it has been given in studies

No established human dose for TB-500. Trials of the parent protein used 0.1% eye drops five times a day for four weeks.

## Legal status

- United States: undefined. Advisers backed compounding in July 2026. FDA staff opposed it, and FDA had not acted by late September 2026.
- European Union: undefined
- Spain: undefined. Neither AEMPS nor the EMA has approved TB-500 as a medicine (El Confidencial, Aug 2026). Not lawful to sell to the public.
- Germany: undefined. Not approved in Germany. TB-500 is named in the AntiDopG doping annex (thymosin beta-4 derivatives); unapproved sale is a crime under the AMG.
- France: undefined. Not authorised. Named in ANSM's Jul 2026 alert on injectable peptides sold online and on social media. Sale and use outside pharmacies are illegal.
- Italy: undefined. No Italian authorisation found. Thymosin beta-4 derivatives are on the WADA banned list. Research vials sold online are unverified.
- Netherlands: undefined. No Dutch marketing authorisation. Sale as a medicine without one is illegal per IGJ. Banned in sport (WADA S2, as TB-500 and thymosin-beta4).
- United Kingdom: undefined
- Canada: undefined. Named in a 2025 Health Canada advisory on unauthorized injectable peptides.
- Australia: undefined. Schedule 4 and Appendix D of the Poisons Standard: possession without authority is illegal.

## Questions people ask

**Is TB-500 the same as thymosin beta-4?**

Not exactly. FDA defines TB-500 as a seven-amino-acid fragment of thymosin beta-4, a 43-amino-acid protein, but sellers also use the name for the whole protein.

**Does TB-500 work for injuries?**

Only animal and cell studies support it. Every human trial used the full-length protein, as eye drops and wound gels, with mixed or failed results, and the fragment has no human data.

**Is TB-500 safe?**

FDA has found no data on human exposure to the fragment and cites the risk of immune reactions to injected peptide and its impurities. In lab work the parent protein drives cell movement and blood-vessel growth, which raises an untested question about cancer.

**Why is TB-500 taken with BPC-157?**

Users take it with BPC-157 for stubborn injuries, and one in eight documented BPC-157 users also took TB-500. Because it is almost always stacked, nobody can tell which product did what.

**Is TB-500 legal?**

In the US, FDA advisers voted 8 to 6 in July 2026 to back compounding, but FDA staff opposed it and FDA had not acted by late September 2026. In Australia possession without authority is illegal, and Health Canada named it in a 2025 advisory.

## Sources

- FDA: bulk substances that may present significant safety risks: https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
- Ophthalmology Times: SEER-3 misses primary endpoint (1 Jul 2025): https://www.ophthalmologytimes.com/view/hlb-therapeutics-misses-primary-endpoint-in-phase-3-seer-3-trial-of-rgn-259
- American Pharmaceutical Review: ARISE-3 misses primary outcomes: https://www.americanpharmaceuticalreview.com/1315-News/574482-ARISE-3-Dry-Eye-Trial-Does-Not-Meet-Primary-Outcome-Measures/
- McDermott: July 2026 advisory committee votes: https://www.mcdermottlaw.com/insights/bulk-list-bound-pcac-backs-majority-of-peptides-in-two-day-public-meeting/