TB-500 and Thymosin Beta-4 are constantly confused, and for good reason: TB-500 is based on a fragment of Thymosin Beta-4, the natural actin-regulating protein involved in cell migration and tissue repair. But they are not identical — TB-500 is a synthetic peptide representing an active region, while Thymosin Beta-4 is the full protein being studied as a drug candidate.
At a glance
| TB-500 | Thymosin Beta-4 | |
|---|---|---|
| What it is | Synthetic fragment/analog of TB4's active region | The full natural 43-amino-acid protein |
| Studied for | Soft-tissue repair, cell migration | Tissue repair, eye and wound healing |
| Development | Research chemical | Investigational (e.g. studied as eye-drop drug candidate) |
| FDA status | Not approved | Not approved |
| Evidence | Largely animal data | Animal data plus some clinical trials |
| Sport status | Banned (WADA) | Banned (WADA) |
The bottom line
Bottom line: Think of Thymosin Beta-4 as the full natural protein and TB-500 as a synthetic stand-in for its active part. Thymosin Beta-4 itself has been taken further into formal clinical research (including ophthalmic trials), while TB-500 remains a research chemical supported mostly by animal work. Neither is approved, and both are banned in sport.
Frequently asked questions
Is TB-500 the same as Thymosin Beta-4?
Not exactly. TB-500 is a synthetic peptide based on an active fragment of Thymosin Beta-4, the natural protein. They are closely related but not identical, and the terms are often used loosely and interchangeably online.
Which one has more human evidence?
Thymosin Beta-4 (the full protein) has been studied in some formal clinical trials, including for eye conditions, whereas TB-500 rests mostly on animal data. Neither is FDA-approved.
Are they banned in sport?
Yes. Both are prohibited at all times under the World Anti-Doping Agency code, and neither is an approved medicine for general use.
References
Combined peer-reviewed sources from both peptide guides. Inclusion is not endorsement.
- Philp D, Kleinman HK. Animal studies with thymosin beta-4, a multifunctional tissue repair and regeneration peptide. Ann N Y Acad Sci. 2010. Peer-reviewed study
- Malinda KM, Sidhu GS, Mani H, et al. Thymosin beta4 accelerates wound healing. J Invest Dermatol. 1999. Peer-reviewed study
- Rahaman KA, Muresan AR, Min H, et al. Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro. J Chromatogr B Analyt Technol Biomed Life Sci. 2024. Peer-reviewed study
- Ho EN, Kwok WH, Lau MY, et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin β₄, in equine urine and plasma by liquid chromatography-mass spectrometry. J Chromatogr A. 2012. Peer-reviewed study
- Judák P, Van Eenoo P, Deventer K. Adsorption effects of the doping relevant peptides Insulin Lispro, Synachten, TB-500 and GHRP 5. Anal Biochem. 2017. Peer-reviewed study
- Esposito S, Deventer K, Goeman J, et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential. Drug Test Anal. 2012. Peer-reviewed study
- Goldstein AL, Hannappel E, Kleinman HK. Thymosin beta-4: actin-sequestering protein moonlights to repair injured tissues. Trends Mol Med. 2005. Peer-reviewed study
- Sosne G, Ousler GW. Thymosin beta-4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial. Clin Ophthalmol. 2015. Peer-reviewed study
- Sosne G, Qiu P, Goldstein AL, Wheater M. Biological activities of thymosin beta-4 defined by active sites in short peptide sequences. FASEB J. 2010. Peer-reviewed study
- Bock-Marquette I, Maar K, Maar S, et al. Thymosin beta-4 denotes new directions towards developing prosperous anti-aging regenerative therapies. Int Immunopharmacol. 2023. Peer-reviewed study
- Zeng PM, Sun XY, Li Y, et al. Thymosin beta 4 as an Alzheimer disease intervention target identified using human brain organoids. Stem Cell Reports. 2025. Peer-reviewed study
- Sosne G. Thymosin beta 4 and the eye: the journey from bench to bedside. Expert Opin Biol Ther. 2018. Peer-reviewed study