Skip to content
The Peptide Effect
phase 2Healing & Recovery

Thymosin Beta-4

Also known as: Tβ4, TB4, Thymosin β4, Full-length TB-500 precursor

Thymosin Beta-4 is a 43-amino acid peptide and the primary intracellular G-actin sequestering protein in mammalian cells. While often confused with TB-500 (a synthetic fragment), the full-length Thymosin Beta-4 molecule has distinct and broader biological activity, including cardiac repair and corneal healing. It has advanced to Phase 2 clinical trials for dry eye disease and cardiac regeneration.

Key Facts

Mechanism
Thymosin Beta-4 functions as the main G-actin sequestering peptide in the cytoplasm, regulating actin polymerization and thus controlling cell migration, adhesion, and tissue repair. It promotes angiogenesis, reduces inflammatory cytokines, inhibits apoptosis, and upregulates anti-inflammatory genes. The full-length molecule (unlike the TB-500 fragment) has additional activity in cardiac progenitor cell recruitment and optic nerve axon regeneration. It is released from platelets upon injury, where it acts as a key mediator of the wound healing cascade.
Research Status
phase 2
Half-Life
~1 hour
Molecular Formula
C₂₁₂H₃₅₀N₅₆O₇₈S
Primary Use
Healing & Recovery
Table of Contents

Benefits

  • Cardiac repair after myocardial infarction — activates cardiac progenitor cellsmoderate
  • Dry eye treatment — RegeneRx Phase 2 trials showed significant improvement in corneal healingmoderate
  • Promotes wound healing by enhancing cell migration and angiogenesisstrong
  • Potent anti-inflammatory effects via downregulation of NF-κB and inflammatory cytokinesmoderate
  • Optic nerve and neuronal regeneration potential — promotes axon regrowth in preclinical studiespreliminary
  • Reduces fibrosis and scar formation during tissue repairpreliminary

Dosage Protocols

RouteDosage RangeFrequencyNotes
Subcutaneous injection1.5–6 mg2× weeklyStandard healing protocol; loading phase may use higher end for 2–4 weeks
Topical (ophthalmic)0.1% eye drops (RGN-259)2–4× dailyClinical trial dose for dry eye disease (RegeneRx protocol)
Subcutaneous injection (intensive)3–6 mgDaily for 2 weeks, then 2× weeklyPost-injury or post-surgical loading protocol; taper to maintenance after initial phase

Medical disclaimer

Dosage information is provided for educational reference only. Always follow your prescriber's instructions and consult a qualified healthcare provider before starting any peptide protocol.

Side Effects

  • Injection site irritation, redness, or mild swellingcommon
  • Temporary fatigue or malaise following dosingcommon
  • Headacherare
  • Mild nausea (usually resolves within hours)rare
  • Theoretical concern of promoting tumor growth due to angiogenic and cell migration properties (not observed in trials)serious

Explore next

Frequently Asked Questions

Is Thymosin Beta-4 the same thing as TB-500?
No, though they are closely related. TB-500 is a synthetic peptide corresponding to the active region (amino acids 17-23) of full-length Thymosin Beta-4. The full 43-amino acid Thymosin Beta-4 has the same tissue repair activity but also demonstrates cardiac progenitor cell activation and optic nerve regeneration that the shorter TB-500 fragment does not. TB-500 is more commercially available and less expensive, which is why it is more commonly used.
What are the cardiac applications of Thymosin Beta-4?
Thymosin Beta-4 has been studied for cardiac repair following myocardial infarction (heart attack). It activates epicardial progenitor cells that can differentiate into new cardiomyocytes, promotes coronary vessel growth, and reduces scar tissue formation in damaged heart muscle. These effects have been demonstrated in animal models and early-phase clinical trials. This cardiac regeneration activity is unique to the full-length molecule and not seen with TB-500.
What is the status of the dry eye clinical trials?
RegeneRx Biopharmaceuticals developed RGN-259, a sterile eye drop containing 0.1% Thymosin Beta-4, for dry eye disease. Phase 2 clinical trials showed statistically significant improvement in both symptoms and signs of dry eye compared to placebo. The peptide promotes corneal epithelial healing and reduces ocular surface inflammation. As of 2024, the program is seeking partners for Phase 3 trials.
Is there a regulatory pathway for Thymosin Beta-4?
Yes. Thymosin Beta-4 has a clearer regulatory path than most research peptides because of the RegeneRx clinical trial program. RGN-259 (the ophthalmic formulation) has completed Phase 2 trials with FDA oversight. The injectable form is earlier in development. This distinguishes Thymosin Beta-4 from purely research-stage peptides — it has actual IND (Investigational New Drug) applications on file with the FDA.
Can Thymosin Beta-4 help with nerve damage?
Preclinical research shows Thymosin Beta-4 can promote optic nerve axon regeneration and support neuronal survival after injury. It upregulates genes involved in neurite outgrowth and reduces inflammation in neural tissue. While these results are promising, they remain in the preclinical stage. Clinical trials for neurological applications have not yet begun, so nerve repair applications should be considered experimental.

References

  1. 1
    Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair(2004)PubMed ↗
  2. 2
    Thymosin β4 promotes corneal wound healing and modulates inflammatory mediators in vivo(2010)PubMed ↗
  3. 3
    Thymosin beta 4: actin sequestering protein and beyond, with implications for tissue regeneration(2012)PubMed ↗
  4. 4
    Phase 2 clinical trial results of RGN-259 (thymosin β4) ophthalmic solution for dry eye(2018)PubMed ↗

Last updated: 2026-02-14