TB-500 vs Thymosin beta-4
It is sold as an injection for healing torn muscles and tendons. No study has tested it for injuries in people or animals. It is sold as an injection to heal tendon, muscle and joint injuries. No one has tested that use in people; the small human trials are on eye drops, the heart and safety.
Thymosin beta-4 has the stronger evidence, grade B (some human evidence) against grade C for TB-500. Neither is FDA approved.
Evidence
CAnimal and cell studies
BSome human evidence
Human studies cited
Animal or cell studies cited
Why the grade
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.
Thymosin beta-4 has two phase 1 safety trials in healthy volunteers (40 and 84 subjects), an 18-patient phase 3 eye-drop trial, a 96-patient randomized trial after heart attack, and a venous ulcer study. All are small and most tested topical or intravenous full-length protein for specific diseases, not the injected wound-healing use it is sold for. Animal work in rats and mice supports wound and cardiac effects. Grade B for the clinical indications under study; the injury-recovery use sold online has no trial.
FDA
Not approved
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 recommended it for the list of substances pharmacies may compound. On 28 October 2026 HHS issued an enforcement discretion policy covering TB-500 acetate for injection under the skin or into muscle. Licensed pharmacies and physicians may compound it for a named patient if they meet sourcing, testing, labeling and reporting conditions. That is not an approval, and the bulks list decision still needs a rule.
Not approved
Thymosin beta-4 is not approved by the FDA for any use. Injectable products sold online, often labeled TB-500 (which the FDA reviewed as a seven-amino-acid fragment), are research chemicals; the FDA found no human exposure data for TB-500, and the agency has not acted on its compounding advisory committee's July 2026 vote to recommend adding TB-500 to the 503A bulks list. RGN-259 eye drops are in a phase 3 trial for neurotrophic keratopathy, and a recombinant intravenous form has been tested in heart attack patients.
Sold for
TB-500 is sold online as an injectable healing peptide for torn muscles, tendons and ligaments, often paired with BPC-157.
Thymosin beta-4 is sold as a regenerative injection for tendon, muscle and joint injuries and promoted as the full-length version of TB-500.
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.
Small randomized trials show safety and signals of benefit in eye and heart disease, but the injected use for sports injuries has never been tested in people, which is why it grades B for the studied indications and no better.
Class
Synthetic Tβ4 fragment
Actin-regulating peptide
Route
Injection
Several routes