Thymosin Beta-4
Thymosin beta-4 is a 43-amino-acid peptide the body makes. What it does, how it has been studied as a medicine, what trials show, and how it differs from TB-500 products.
Content last updated . This page has not been medically reviewed.
Overview
Thymosin beta-4 is a naturally occurring peptide of 43 amino acids. It is found in many cell types and in body fluids including blood, saliva, tears and wound fluid. [1][2] Researchers have tested synthetic or recombinant versions as drug candidates, mostly as eye drops. No thymosin beta-4 medicine was found approved in the sources read. This page is education only and gives no amounts, sourcing or use instructions.What it is, and what it is not
- Endogenous molecule: thymosin beta-4 is made in the body. It was first isolated from calf thymus and was originally proposed to be a thymic hormone. [1]
- Test-drug versions: studies use synthetic or recombinant thymosin beta-4, for example an eye-drop solution called RGN-259 in dry eye trials. [3]
- A different thing: "TB-500" is a seven-amino-acid fragment of thymosin beta-4 (residues 17 to 23), not the full molecule. [1] See the TB-500 naming explainer and thymosin beta-4 vs TB-500.
Proposed biology
Thymosin beta-4 is described as a G-actin sequestering peptide (actin is a structural protein inside cells). In mouse heart studies it was reported to promote heart cell migration and survival. [4] A 2015 review lists proposed roles in tissue repair and says wider potential uses, such as kidney and liver disease or bone and ligament repair, are based on animal studies. [5] Label for these: preclinical.Human research by use
| Use and form | Design and size | What was reported | Label |
|---|---|---|---|
| Dry eye, eye drops (phase 2) | Randomized, 72 people | Neither primary endpoint differed significantly from placebo; several secondary measures did [3] | mixed |
| Severe dry eye, eye drops (phase 2) | Randomized, 9 people | Significant differences on several signs and symptoms; authors called it small [6] | promising but limited |
| Nonhealing corneal defects, eye drops | 9 compassionate-use patients, no comparator | Six with geographic defects healed markedly; three did not change [7] | insufficient evidence |
| Healthy volunteers, intravenous | Randomized, placebo-controlled, 40 people | Mild or moderate infrequent adverse events; no serious events (safety only) [8] | not a test of benefit |
| Dry eye, phase 3 (ARISE-2, ARISE-3) | Randomized, 601 and 700 people | Registered as completed with results posted on the registry; efficacy results not summarized here [9][10] | not assessed here |
| Heart attack, intravenous recombinant form (phase 2) | Randomized, 62 people | Registered as completed; no published results found [11] | Proper evidence not found |
Other registered thymosin beta-4 trials include withdrawn and terminated records (for example a corneal wound trial terminated for slow recruitment), which is part of the picture: not every registered study reports. [12]
Funding: the phase 3 dry eye trials list the product developer, ReGenTree, as sponsor. [10] Check the original papers for conflict statements.
Related guides
Peptide safety and adverse events, how to evaluate peptide claims and peptides and wound healing.Frequently asked questions
What is thymosin beta-4?
A 43-amino-acid peptide made naturally in the body and found in tears, blood and other fluids. [1]
Is thymosin beta-4 an approved medicine?
No approved thymosin beta-4 medicine was found in the sources read. Eye-drop forms have been in phase 3 trials. [10]
Does it work for dry eye?
Results are mixed: a 72-person phase 2 trial missed its primary endpoints, while a 9-person trial reported benefits. [3][6]
Is it allowed in sport?
No. WADA's 2026 list prohibits thymosin-beta-4 and its derivatives at all times. [13]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: preclinical (cells or animals only), promising but limited, mixed, insufficient evidence and Proper evidence not found. "Biomarker" results (a lab value) are not the same as a clinical outcome (how a person feels or functions).
Safety
In the healthy-volunteer study, adverse events were infrequent and mild or moderate. [8] In the severe dry eye and phase 2 eye studies, drops were reported well tolerated. [6][3] These are small, short studies of specific products. They do not describe the safety of injected products sold online, and they cannot establish long-term or cancer-related safety. Proper evidence not found for pregnancy, children, or people with liver, kidney or heart disease.
Regulatory and sport status (read 2026-10-22)
Laws change; this is not legal advice. WADA's 2026 list prohibits thymosin-beta-4 and its derivatives at all times. [13] In the United States, FDA reviewed only the TB-500 fragment for compounding, not full-length thymosin beta-4. [14] No approval of any thymosin beta-4 drug was found in the sources read; other jurisdictions: not verified.
References
- U.S. Food and Drug Administration. FDA Briefing Document: TB-500-related bulk drug substances, Pharmacy Compounding Advisory Committee, July 23-24, 2026. Read 2026-10-22.
- Sosne G, Berger EA. Thymosin beta 4: a potential novel adjunct treatment for bacterial keratitis. Int Immunopharmacol 2023. PubMed. Read 2026-10-22.
- Sosne G, Ousler GW. Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial using the controlled adverse environment model. Clin Ophthalmol 2015. PubMed. Read 2026-10-22.
- Bock-Marquette I et al. Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature 2004. PubMed. Read 2026-10-22.
- Goldstein AL, Kleinman HK. Advances in the basic and clinical applications of thymosin β4. Expert Opin Biol Ther 2015. PubMed. Read 2026-10-22.
- Sosne G, Dunn SP, Kim C. Thymosin beta 4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea 2015. PubMed. Read 2026-10-22.
- Dunn SP et al. Treatment of chronic nonhealing neurotrophic corneal epithelial defects with thymosin beta4. Ann N Y Acad Sci 2010. PubMed. Read 2026-10-22.
- Ruff D et al. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers. Ann N Y Acad Sci 2010. PubMed. Read 2026-10-22.
- ClinicalTrials.gov. NCT02974907 ARISE-2, RGN-259 for dry eye; ReGenTree. Read 2026-10-22.
- ClinicalTrials.gov. NCT03937882 ARISE-3, RGN-259 for dry eye; ReGenTree. Read 2026-10-22.
- ClinicalTrials.gov. NCT05485818 Thymosin beta 4 in acute myocardial infarction; Beijing Northland Biotech. Read 2026-10-22.
- ClinicalTrials.gov. NCT00598871 Thymosin beta 4 for corneal wounds; ReGenTree. Read 2026-10-22.
- World Anti-Doping Agency. 2026 Prohibited List (in force 1 January 2026; the page says each new list is published in October, and the 2027 list was not read). Read 2026-10-22.
- U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (content current as of 04/22/2026). Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.