Is TB-500 (Thymosin Beta-4) an approved drug?

No. TB-500 / thymosin beta-4 is sold strictly as a research-use-only material and is not an approved drug for humans or animals in any jurisdiction. It has been studied in Phase 2 topical clinical trials but no product has received marketing approval, and it is not intended for human or veterinary use.

Is TB-500 the same as full-length Thymosin beta-4?

Not always. Full-length thymosin beta-4 is a 43-amino-acid peptide (PubChem CID 45382195, CAS 77591-33-4). Some products marketed as 'TB-500' are instead the shorter actin-binding fragment (Ac-LKKTETQ). Researchers should confirm the exact sequence and identity for any material rather than assuming the two are interchangeable.

What does the research literature report about thymosin beta-4?

In cell and animal models, researchers reported that Tβ4 sequesters G-actin and is associated with accelerated wound reepithelialization, angiogenesis, and collagen deposition. Controlled Phase 2 human trials of topical formulations reported improvement in severe dry eye and a mid-dose signal in venous stasis ulcers. These are research findings; no clinical effect is established for systemic use.

What dosing has been used in studies?

Published regimens are research protocols, not usage directions: a 0.1% topical ophthalmic solution dosed 6 times daily for 28 days in a Phase 2 dry-eye trial; 2–18 mg/kg intraperitoneally in a rat stroke dose-response study (calculated optimum ~3.75 mg/kg); and single ascending IV doses of 42–1260 mg in a Phase 1 human pharmacokinetic study, where plasma half-life was ~1–2 hours.

TB-500 (Thymosin Beta-4) Dosage, Half-Life & Research

TB-500 is the research label most commonly applied to Thymosin beta-4 (Tβ4), a naturally occurring 43-amino-acid peptide that is the major actin-sequestering molecule in mammalian cells.¹ It is sold in Canada strictly as a research-use-only material and is not an approved drug for humans or animals in any jurisdiction. Note that some commercial “TB-500” products are sold as the shorter actin-binding fragment (Ac-LKKTETQ) rather than full-length Tβ4; the chemical identity below corresponds to full-length thymosin beta-4 (PubChem CID 45382195).⁵

Researchers have studied Tβ4 in wound-healing, corneal, cardiac, and neurological injury models, and it has advanced into a small number of Phase 2 human ophthalmic and dermal trials.²³ Evidence is graded B: animal and in-vitro data are extensive and several controlled human trials exist, but no indication has been approved and the systemic injectable use discussed in fitness contexts has not been validated in humans.

Structure

Sequence & identity

Ac-SerAspLysProAspMetAlaGluIleGluLysPheAspLysSerLysLeuLysLysThrGluThrGlnGluLysAsnProLeuProSerLysGluThrIleGluGlnGluLysGlnAlaGlyGluSer

Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES · C₂₁₂H₃₅₀N₅₆O₇₈S · 4963 g/mol

Identity per PubChem CID 45382195: InChIKey UGPMCIBIHRSCBV-UHFFFAOYSA-N, formula C₂₁₂H₃₅₀N₅₆O₇₈S, average mass ≈4963 g/mol; CAS 77591-33-4.⁵⁶

What the research shows

Mechanisms studied

Researchers report that Tβ4 binds and sequesters monomeric G-actin in a 1:1 complex, regulating actin polymerization and thereby cell motility.¹ Beyond this intracellular role, reviewers describe extracellular actions in which Tβ4 promotes endothelial cell migration and angiogenesis, acts as a chemoattractant for keratinocytes and other cells, and modulates inflammation in injury models.¹⁴ In dermal wound studies, investigators observed increased reepithelialization, collagen deposition, and new vessel formation when Tβ4 was applied to the wound bed.⁴ These mechanisms are characterized in cell and animal systems; the framing here reflects what researchers reported rather than any established clinical effect.

Reported in studies

Dosing in the research literature

The figures below summarise regimens as reported in published research — they are not recommendations or directions for use.

Source / model	Regimen reported	Notes
Malinda et al., J Invest Dermatol 1999 (rat full-thickness wound model)	Tβ4 applied topically or intraperitoneally to full-thickness punch wounds in rats; in cell assays keratinocyte migration was stimulated by as little as 10 pg Tβ4.⁴	Animal/in-vitro study. Researchers observed reepithelialization increased ~42% at day 4 and up to ~61% at day 7 versus saline controls. Not a human dosing guide.
Sosne et al., Cornea 2015 (Phase 2, severe dry eye)	0.1% Tβ4 ophthalmic solution (RGN-259), one drop 6 times daily for 28 days.²	Randomized, double-masked, placebo-controlled human trial. Topical ocular only. Reported reduced ocular discomfort and corneal staining vs vehicle; well tolerated. Not a systemic regimen.
Morris et al., J Neurol Sci 2014 (rat embolic stroke dose-response)	2, 12, or 18 mg/kg intraperitoneally starting 24 h post-injury, repeated every 3 days for four additional doses.⁷	Animal study. Neurological outcome improved at 2 and 12 mg/kg (calculated optimum ≈3.75 mg/kg); 18 mg/kg showed no benefit. Rodent-only; does not translate to a human dose.
Ruff et al., Ann N Y Acad Sci 2010 (Phase 1 IV pharmacokinetics, healthy volunteers)	Single ascending IV doses of 42, 140, 420, or 1260 mg per subject in healthy volunteers.⁸	Reported plasma half-life rose with dose (~0.95 h at 42 mg to ~2.1 h at 1260 mg). Reported as safe and well tolerated with no dose-limiting toxicity over the 42–1260 mg range; these are research administrations, not approved or recommended use.

Research use only. Peptigo products are sold to qualified researchers for laboratory use. This information summarises published research for reference and is not medical advice, a dosing recommendation, or directions for human or animal use.

Reported in studies

Effects observed in research

In animal and in-vitro models, studies reported that Tβ4 accelerated dermal wound closure and reepithelialization, increased angiogenesis and collagen deposition, and acted as a chemoattractant for keratinocytes and endothelial cells.¹⁴ In rodent stroke and traumatic-brain-injury models, researchers observed improved neurological outcomes within a defined dose window.⁷ In human ophthalmology, a Phase 2 trial reported that a topical 0.1% formulation significantly reduced signs and symptoms of severe dry eye versus vehicle.² In a European Phase 2 program of a topical gel (RGN-137) in venous stasis ulcers, the sponsor reported that the mid-dose appeared the most active of three doses and that the agent was well tolerated at all dose levels.³⁹ No effect has been established for the systemic “recovery/healing” uses commonly discussed in fitness contexts, and Tβ4 has no approved human indication.

Honest assessment

Strength of evidence

Grade B

Grade B. The mechanistic and preclinical literature is large and consistent across dermal, corneal, cardiac, and neurological injury models, and several controlled human trials exist — notably a Phase 2 ophthalmic (dry eye) trial and a Phase 2 dermal (venous ulcer) program using topical formulations.²⁹ However, no thymosin beta-4 product has received marketing approval for any indication, and the systemic injectable use most associated with the “TB-500” label has not been validated in adequately powered human trials. Reported plasma half-life is short (≈1–2 h).⁸ Commercial “TB-500” may be either full-length Tβ4 or a shorter fragment, so identity should not be assumed. This material is research-use-only.

Handling

Reconstitution & storage

Reconstitute with bacteriostatic water for laboratory handling. Store lyophilised material frozen and reconstituted material refrigerated. Use Peptigo’s reconstitution calculator and storage cheat sheet for working figures.

References

Goldstein AL, Hannappel E, Kleinman HK. Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues. Trends Mol Med. 2005;11(9):421-429. doi:10.1016/j.molmed.2005.07.004. https://pubmed.ncbi.nlm.nih.gov/16099219/
Sosne G, Dunn SP, Kim C. Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. 2015;34(5):491-496. doi:10.1097/ICO.0000000000000379. https://pubmed.ncbi.nlm.nih.gov/25826322/
Guarnera G, DeRosa A, Camerini R. Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement on healing. Ann N Y Acad Sci. 2007;1112:407-412. doi:10.1196/annals.1415.045. https://pubmed.ncbi.nlm.nih.gov/17495250/
Malinda KM, Sidhu GS, Mani H, Banaudha K, Maheshwari RK, Goldstein AL, Kleinman HK. Thymosin beta4 accelerates wound healing. J Invest Dermatol. 1999;113(3):364-368. doi:10.1046/j.1523-1747.1999.00708.x. https://pubmed.ncbi.nlm.nih.gov/10469335/
National Center for Biotechnology Information. PubChem Compound Summary for CID 45382195, Thymosin beta-4. https://pubchem.ncbi.nlm.nih.gov/compound/45382195
Thymosin beta 4, CAS 77591-33-4. ChemicalBook. https://www.chemicalbook.com/ChemicalProductProperty_EN_CB4409683.htm
Morris DC, Cui Y, Cheung WL, Lu M, Zhang L, Zhang ZG, Chopp M. A dose-response study of thymosin β4 for the treatment of acute stroke. J Neurol Sci. 2014;345(1-2):61-67. doi:10.1016/j.jns.2014.07.006. https://pmc.ncbi.nlm.nih.gov/articles/PMC4177939/
Ruff D, Crockford D, Girardi G, Zhang Y. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin β4 in healthy volunteers. Ann N Y Acad Sci. 2010;1194:223-229. doi:10.1111/j.1749-6632.2010.05474.x. https://pubmed.ncbi.nlm.nih.gov/20536472/
RegeneRx Biopharmaceuticals. RegeneRx reports Phase II venous stasis ulcer trial results (RGN-137 topical gel); mid-dose most active, well tolerated at all dose levels. March 26, 2009. https://www.fiercebiotech.com/biotech/regenerx-reports-phase-ii-venous-stasis-trial-results

Written by the Peptigo Research Team · scientifically reviewed by Peter, Peptigo Research Team · Last reviewed June 2026. We cite primary literature and flag where evidence is limited. Our sourcing & RUO policy →