Compounds / Thymosin Beta-4

Thymosin Beta-4

Also known as: Tβ4, TB4, TMSB4X gene product

Early clinical Not FDA-approved Category: Repair and Recovery

The compounds described in this library are research-use-labeled chemicals and are not FDA-approved for human use. This content is factual scientific reference drawn from published literature. It is not medical, dosing, or purchasing advice. VialReport does not sell, supply, or distribute any compound.

Short summary

A naturally occurring 43-amino-acid peptide expressed in most cell types, and a major intracellular G-actin-sequestering peptide. It is the full-length parent molecule that the much shorter TB-500 fragment derives from, and it is the molecule that much of the clinical evidence invoked in this market was actually generated with.

Dive deeper

Origin and Development

First isolated from the thymus in the 1960s during research on thymic hormones, and subsequently found to be expressed almost ubiquitously rather than being thymus-specific. Encoded by the TMSB4X gene.

Mechanism as Understood in the Literature

The dominant described function is actin sequestration: binding G-actin monomers and regulating the equilibrium between free and polymerised actin, which underlies cell migration and cytoskeletal reorganization. Beyond that, the literature describes distinct activities mapped to different regions of the molecule (peptide, not protein). The N-terminal Ac-SDKP fragment has independent antifibrotic and haematopoietic activity, and residues 1 to 15 have been associated with anti-apoptotic effects. The actin-binding region (residues 17 to 23) is the part that TB-500 corresponds to.

Research Status

Considerably better characterized than the fragment sold as TB-500. Published work includes dermal wound healing, cardiac repair following myocardial infarction, and a clinical program in ophthalmology (RGN-259) for neurotrophic keratopathy and dry eye. A Phase 1 safety study has been published. Critically, this literature used pharmaceutical-grade full-length recombinant Tβ4, not the fragment sold in research markets. Claims about the clinical literature are stated here only as far as the evidence defensibly supports.

Regulatory status

Not FDA-approved for any indication. Clinical development in ophthalmology has proceeded through trials without resulting in approval to date. Prohibited in competitive sport under World Anti-Doping Agency rules.

Commonly Confused With

This is the single most important distinction in this library. Thymosin Beta-4 and TB-500 are routinely sold and labeled as the same thing. They are not. Tβ4 is 43 amino acids at roughly 4963 Da; TB-500 is a short fragment at roughly 889 Da. The clinical evidence people cite when buying TB-500 was generated with this molecule, not with the fragment. Also distinct from Thymosin Alpha-1, an unrelated peptide with immune-modulating activity that shares only the thymic naming convention.

How This Compound Is Marketed

Vendor marketing for this compound typically references tissue repair, wound healing, and recovery, frequently sold under the TB-500 name. VialReport does not evaluate or endorse these claims. See Research Status above for what the published literature actually establishes.

Analytical Profile

43 amino acids, molecular weight approximately 4963 Da. The mass difference from TB-500 is roughly fivefold and unambiguous by mass spectrometry, provided the reference standards and molecular forms are correctly defined. Retention-time comparison against the wrong reference standard would not catch a substitution. Note that intact mass supports molecular identity but does not by itself establish sequence, disulfide topology, or folding.

Stability and Handling

Supplied lyophilized. Larger than the fragment and correspondingly more sensitive to handling once reconstituted. Stability depends on molecular form, formulation, container closure, and reconstitution conditions.

Key Literature

  1. 01 Malinda KM, et al. Thymosin beta-4 accelerates wound healing. J Invest Dermatol. 1999;113(3):364-368.
  2. 02 Bock-Marquette I, et al. Thymosin beta-4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature. 2004;432:466-472.
  3. 03 Xing Y, et al. Progress on the function and application of thymosin β4. Front Endocrinol. 2021;12:767785.
  4. 04 Philp D, et al. Thymosin beta-4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair. FASEB J. 2004;18(2):385-387.

VialReport publishes factual reference information and independent test data. Nothing here is medical, dosing, or purchasing advice.

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