Thymosin beta-4 dosage

What Thymosin beta-4 is

Thymosin beta-4 is a naturally occurring 43-amino-acid, N-acetylated actin-binding protein that is under clinical investigation (for example as the RGN-259 eye drop) and is distinct from the seven-residue TB-500 fragment.

Tβ4 binds monomeric G-actin and inhibits its polymerization; in resting human neutrophils it was reported to be the major G-actin-sequestering protein, present at roughly 149 µM in the cytoplasm ^1,2. Proposed extracellular actions Cardiac cells (mice and cultured cells): Tβ4 was reported to form a complex with PINCH and integrin-linked kinase, activating Akt, and to be associated with cardiomyocyte migration and… How it works →

Doses given in human trials

• In SEER-1 (NCT02600429), people with neurotrophic keratopathy received 0.1% RGN-259 or placebo eye drops five times a day for 4 weeks ^10,20.
• In ARISE-3 (NCT03937882), adults with dry eye received RGN-259 or placebo eye drops four times a day for 14 days ^11.
• In a phase 2 severe dry-eye trial (NCT01393132), 0.1% RGN-259 or vehicle was instilled 6 times daily for 28 days ^9.
• In a phase 1 study, healthy volunteers received single intravenous doses of 42, 140, 420 or 1260 mg synthetic Tβ4 or placebo, then the same dose daily for 14 days ^6.
• In the NL005 phase IIb myocardial infarction study (NCT05984134), arms received recombinant human Tβ4 intravenously at 0.5 or 1.0 µg/kg per the arm descriptions, or placebo, for 7 days after PCI ^14.

How long did human studies run?

No human study durations are recorded for Thymosin beta-4.

Side effects reported in studies

• Any non-serious adverse event (registry tally)
  47 of 350 RGN-259 versus 31 of 349 placebo; no serious adverse events in either arm · Adults with dry eye, ARISE-3 (NCT03937882) ¹¹
• Serious adverse events (registry tally)
  3 of 299 RGN-259 versus 2 of 302 placebo · Adults with dry eye, ARISE-2 (NCT02974907) ¹²
• Adverse events after intravenous dosing
  Described as infrequent; no serious events · 40 healthy volunteers, phase 1 ⁶

Supplies and handling

• Lyophilized vial
  Sealed vial with the freeze-dried cake. Check the label, lot and the certificate of analysis before opening.
• Sterile diluent
  The diluent named on the product documentation. Bacteriostatic water contains benzyl alcohol; sterile water does not.
• Graduated syringes
  Sized to the volume being measured. U-100 insulin syringes are graduated in units where 100 units = 1 mL.
• Alcohol prep pads
  For wiping vial stoppers before each puncture.
• Nitrile gloves
  Clean gloves for aseptic handling.
• Sharps container
  Puncture-resistant container for used needles.

Storage

Follow the documentation for the specific material; lyophilized peptides and proteins are generally kept dry and protected from heat, light and moisture.

• Lyophilized (unmixed) vials: typically stored cold and dry, away from light, as the documentation directs. Many are stable longer frozen.
• Reconstituted vials: typically refrigerated (about 2–8 °C), protected from light and not frozen.
• Bacteriostatic water contains benzyl alcohol, which inhibits bacterial growth in multi-use vials; sterile water has no preservative.

Handling mistakes and troubleshooting

Added the wrong volume of diluent

The concentration changes, not the amount of compound in the vial. Recalculate with the volume actually added and relabel the vial.

Shook the vial and it foamed

Let it settle in the refrigerator. Foam is a sign of agitation; some peptides aggregate when shaken. Note it on the label.

The solution is cloudy or has particles

Do not use it. Cloudiness can indicate incomplete dissolution, contamination or degradation. Record the lot and contact the supplier with the certificate of analysis.

The powder cake looks melted or shrunken before reconstitution

This can indicate the vial was exposed to heat or moisture. Record the lot and condition on arrival.

Liquid sprayed back when the needle was removed

Pressure built up in the vial. Withdraw a small volume of air while adding diluent to keep pressure neutral.

Regulatory status

Status

Not FDA-approved; no Drugs@FDA application was located as of 2026-10-24 ^17. The RGN-259 eye drop has completed phase 3 dry-eye trials and a second neurotrophic keratopathy phase 3 trial (SEER-2) was listed as recruiting ^11,12,19.

United States (FDA)

No FDA-approved thymosin beta-4 product was located in Drugs@FDA as of 2026-10-24 ^17. FDA's compounding safety-risk page (current as of April 22, 2026) addresses the TB-500 fragment, not the full-length protein ^15.

Sport (WADA)

The 2026 Prohibited List names 'Thymosin-β4 and its derivatives e.g. TB-500' under S2.3 (growth factors and growth factor modulators); S2 substances are prohibited at all times and are non-Specified Substances ^16.

Status varies by country and changes over time. How we describe regulatory status.

Thymosin beta-4 compared with related compounds

Frequently asked questions

References

1. UniProtKB P62328 (TYB4_HUMAN): Thymosin beta-4 UniProt. 2026
2. Thymosin beta 4 sequesters the majority of G-actin in resting human polymorphonuclear leukocytes J Cell Biol. 1992
3. Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair Nature. 2004
4. Thymosin beta4 induces adult epicardial progenitor mobilization and neovascularization Nature. 2007
5. Thymosin beta 4 is dispensable for murine cardiac development and function Circ Res. 2012
6. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers Ann N Y Acad Sci. 2010
7. A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin beta4 in healthy Chinese volunteers J Cell Mol Med. 2021
8. Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial conducted using the controlled adverse environment (CAE) model Clin Ophthalmol. 2015
9. Thymosin beta4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial Cornea. 2015
10. 0.1% RGN-259 (Thymosin beta4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial Int J Mol Sci. 2022
11. Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-3 (NCT03937882) ClinicalTrials.gov. 2026
12. Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-2 (NCT02974907) ClinicalTrials.gov. 2026
13. A Study of the Safety and Efficacy of Injectable Thymosin Beta 4 for Treating Acute Myocardial Infarction (NCT01311518) ClinicalTrials.gov. 2026
14. Efficacy and Safety Study of Thymosin Beta 4 in Patients With Acute Myocardial Infarction (NL005 phase IIb; NCT05984134) ClinicalTrials.gov. 2026
15. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (content current as of 04/22/2026) FDA. 2026
16. Tractatenblad 2026 Nr. 25: Anti-doping convention (ETS No. 135), amendment to the appendix - The 2026 Prohibited List, World Anti-Doping Code (English text; entry into force 1 January 2026) Tractatenblad van het Koninkrijk der Nederlanden (official government publication). 2026
17. openFDA Drugs@FDA query for 'thymosin' (no matching applications) FDA (openFDA Drugs@FDA). 2026
18. PubChem compound record for thymosin beta 4 (CID 45382195) PubChem. 2026
19. Assessment of the Safety and Efficacy of 0.1% RGN-259 Ophthalmic Solution for the Treatment of NK: SEER-2 (NCT05555589) ClinicalTrials.gov. 2026
20. Assessment of the Safety and Efficacy Study of RGN-259 Ophthalmic Solutions for Neurotrophic Keratopathy: SEER-1 (NCT02600429) ClinicalTrials.gov. 2026