Two names that should not be confused
The TB-500 assessed by the FDA is a short fragment of thymosin beta-4. However, some publications cited in connection with recovery concern the full molecule. In its July 2026 review, the FDA found no clinical data establishing the effectiveness of TB-500 itself. [31]
What was actually studied in the eye?
The RGN-259 study enrolled 18 people with neurotrophic keratopathy, a disease of the eye's surface. It compared drops containing full-length thymosin beta-4 with placebo. It did not study TB-500 injections or sports injuries. [34]
Numbers and an important limitation
After four weeks, complete healing was found in 6 of 10 people receiving the study product. The primary result did not meet the prespecified threshold for statistical significance. The trial stopped before reaching its planned size because recruitment was slow. We reviewed the abstract and available parts of the methods. [34]
Numbers can look encouraging while still leaving considerable uncertainty. Even a convincing result in this specific disease would not automatically prove that a different molecule helps a torn tendon.
Why does the preparation itself also need checking?
Analytical studies of online products show that the names TB500/TB1000 may not describe their contents consistently with earlier literature. Finding a familiar-sounding label is therefore not enough. It is necessary to establish whether the publication and the offered product concern the same substance. [33]
What about reports of changing US rules?
The October 2026 HHS proposal concerns specified compounded products. It does not turn a full-length thymosin beta-4 study into a TB-500-fragment study, and it is not approval of a new medicine. [52]
When reading the next report, check three things: who was studied, exactly what was given and what happened. This helps avoid transferring conclusions between different substances and diseases. Full TB-500 profile also covers uncertainties, product quality and anti-doping rules.
Where does this information come from?
Show sources and how they were checked
- FDA: ocena TB-500 dla komisji PCAC
US regulator · materials for 23–24 July 2026 · sections on identity, studies, safety and recommendations. Accessed: 2 November 2026.
- RGN-259: a study of full-length thymosin beta-4 in corneal disease
Small randomised study · 29.12.2022 · abstract and available methods sections, not the full text · DOI: 10.3390/ijms24010554. Accessed: 02.11.2026.
- Delcourt et al.: analysis of TB500/TB1000 and SGF1000 products
Product composition study · online 23 December 2022, 2023 issue · abstract reviewed · DOI: 10.1002/dta.3421. Accessed: 2 November 2026.
- HHS: draft policy and appendices concerning peptides
US document · October 2026 · policy and sections concerning the substances discussed. Accessed: 2 November 2026.