All peptides / Muscle and bone
TB-500
Synthetic Tβ4 fragment
Also TB500, TB 500, Thymosin beta-4, Thymosin beta 4, Thymosin β4, Tβ4
- Evidence
- CAnimal and cell studies
- FDA status
- Not approvedas of 2026-10-26
- Route
- Injection
- Studies cited
- 0 human2 animal or cell
It is sold as an injection for healing torn muscles and tendons. No study has tested it for injuries in people or animals.
Sold for
TB-500 is sold online as an injectable healing peptide for torn muscles, tendons and ligaments, often paired with BPC-157.
Studies say
Nothing published tests TB-500 for injury in humans or animals; the evidence for its parent protein comes from small trials in wounds and the eye, so the grade is C.
Why grade C. There are no published human trials of TB-500 itself. The only TB-500-specific papers are doping-control chemistry studies that identified the peptide in gray-market and veterinary products and detected it in horses. Human trials exist for full-length thymosin beta-4 (a venous-ulcer safety study planned for 72 patients and an 18-patient eye-drop trial), but those tested a different, larger molecule. 3468
FDA. TB-500 is not approved by the FDA for any use and is sold as a research chemical. In July 2026 an FDA advisory committee voted to recommend it for the list of substances pharmacies may compound, but that recommendation has not become a rule and is not an approval. 710
Written from 10 cited sources. Last refreshed 2026-10-27. Not physician reviewed.
What this means for you
- What people take it for
- Healing muscle, tendon and ligament injuries
- Can a US doctor prescribe it?
- No. It is not approved and is sold as a research chemical.
- Properly tested in people?
- Not properly: animal or lab studies, or small uncontrolled human reports. No human trial of TB-500 exists.
Evidence checklist
- Randomised controlled trial No human trial of TB-500 itselfno
- Human study over 100 people No human trial of TB-500no
- More than one research group Only doping-chemistry papersno
- Clinical outcomes, not surrogate markers No clinical outcomeno
- Human safety data beyond case reports No human exposure datano
Drawn from the cited studies below. A dash means the sources give no information.
What it is
TB-500 is a synthetic seven-amino-acid fragment of thymosin beta-4, a protein found in nearly every human cell. The fragment covers positions 17 to 23 of the parent protein (the sequence LKKTETQ) with an acetyl group added at one end. This stretch is the part of thymosin beta-4 that binds actin, the protein that forms the internal scaffolding of cells. 68
The name TB-500 first appeared on a veterinary product marketed for racehorses. Anti-doping laboratories analyzed it in 2012 and confirmed the contents as the acetylated 17-23 fragment, which is how the compound entered the scientific literature. It is now sold to humans by online vendors labeled for research use. 68
How it works
Full-length thymosin beta-4 holds single actin molecules in reserve, and cells use it to reorganize their skeleton when they move. The 17-23 region is where that binding happens. Sellers extrapolate from this to claim TB-500 drives cell migration, blood-vessel growth and collagen deposition in wounds. Those are properties documented for the whole protein in laboratory and animal work; whether the short fragment on its own does the same thing in a person has not been tested. 158
What human research shows
No human study of TB-500 has been published. The closest data come from thymosin beta-4 itself. A European randomized, placebo-controlled study in venous leg ulcers was designed to enroll 72 patients and test topical thymosin beta-4 for safety and healing; the published report describes the protocol and early enrollment, not final efficacy. 3
A phase 3 trial of thymosin beta-4 eye drops in neurotrophic keratopathy, a condition where the cornea loses sensation and fails to heal, randomized 18 patients. Complete healing at four weeks occurred in 6 of 10 treated patients and 1 of 8 on placebo, a difference that did not reach statistical significance for the primary endpoint. These results concern a topical, full-length protein and cannot be transferred to injected TB-500. 4
A 2025 population study of racehorses measured natural thymosin beta-4 levels in blood and showed that a synthesis impurity could be detected after a dose of a TB-500-type product, confirming the compound circulates and that misuse can be caught. 9
| Study | Model | Finding |
|---|---|---|
| Identification of TB-500 contents (2012) | Chemistry, product analysis | Mass spectrometry identified the acetylated 17-23 fragment of thymosin beta-4 as the active ingredient of a TB-500 product and proposed a detection method. 6 |
| Equine doping-control study (2012) | Horses, single administration | The peptide and its metabolites were detected in urine and plasma after a dose of TB-500. 8 |
| Thymosin beta-4 venous ulcer study | Humans, planned n=72, randomized placebo-controlled | Protocol report for topical thymosin beta-4 in venous ulcers; the report covers design and early safety, not final healing rates. 3 |
| RGN-259 neurotrophic keratopathy trial | Humans, n=18, randomized placebo-controlled phase 3 | Six of 10 treated eyes healed at 4 weeks versus 1 of 8 on placebo, with the primary endpoint not reaching significance. 4 |
Safety
There are no safety data for TB-500 in humans. The FDA's compounding review notes the absence of human exposure data, and the 2026 advisory committee vote was split (reported as 8 to 6 with one abstention), with FDA's own scientists not supporting the easing. Full-length thymosin beta-4 was well tolerated in the small eye and wound trials, but the fragment has not been studied. 2710
TB-500 is prohibited in sport. The World Anti-Doping Agency and equine racing authorities ban it, and detection methods in plasma and urine exist. 89
Questions for your clinician
- Is there any trial of TB-500 itself, rather than full-length thymosin beta-4?
- What does the split advisory committee vote mean for safety?
- Would it count as a banned substance for my sport?
Questions people ask
How does TB-500 relate to thymosin beta-4?
No. Thymosin beta-4 is a 43-amino-acid protein. TB-500 is a synthetic copy of seven of those amino acids, the actin-binding segment, with an acetyl group attached. Studies of the full protein do not automatically apply to the fragment. 68
Is TB-500 FDA-approved or legal?
It is not approved for any use. Selling it as a research chemical is how vendors avoid drug rules, but marketing it for human injection is unlawful. In July 2026 an FDA advisory committee recommended adding it to the list pharmacies may compound from; that still requires FDA rulemaking. 710
Has TB-500 itself been tried in people?
None have been published. The only TB-500-specific papers are analytical chemistry studies for doping control. Human trials exist for the full thymosin beta-4 protein in wounds and the eye, and they are small. 346
Would a doping screen pick up TB-500?
It can. Anti-doping laboratories have published methods that detect the acetylated fragment and its breakdown products in plasma and urine, and it is on the WADA prohibited list. Standard workplace drug panels do not look for it. 89
How does TB-500 differ from BPC-157?
They are unrelated molecules. BPC-157 is a 15-amino-acid fragment derived from a gastric protein; TB-500 is a 7-amino-acid fragment of thymosin beta-4. Both are sold for injury recovery, and neither has a published human efficacy trial. 6
Citations
- Goldstein 2012, Expert Opin Biol Ther: Thymosin beta4, a multifunctional regenerative peptide doi.org
- McDermott Will & Emery 2026: PCAC backs majority of peptides in two-day public meeting mcdermottlaw.com
- Guarnera 2007, Ann N Y Acad Sci: Thymosin beta-4 and venous ulcers, a European randomized study pubmed.ncbi.nlm.nih.gov
- Sosne 2022, Int J Mol Sci: RGN-259 ophthalmic solution in neurotrophic keratopathy, phase 3 pubmed.ncbi.nlm.nih.gov
- Goldstein 2007, Ann N Y Acad Sci: Thymosin beta4 overview doi.org
- Esposito 2012, Drug Test Anal: Synthesis and characterization of the 17-23 fragment identified in TB-500 pubmed.ncbi.nlm.nih.gov
- FDA: Certain bulk drug substances for use in compounding may present significant safety risks fda.gov
- Ho 2012, J Chromatogr A: Doping control analysis of TB-500 in equine urine and plasma pubmed.ncbi.nlm.nih.gov
- 2025, Drug Test Anal: Equine doping controls of thymosin beta 4, a population study pubmed.ncbi.nlm.nih.gov
- STAT 2026: FDA peptide compounding panel backs epitalon, rejects emideltide statnews.com