Actin-binding peptide · research peptide

TB-500 (Thymosin β-4 Fragment)

Studied for: tissue repair, cell migration, angiogenesis, wound healing (preclinical)

TB-500 is a commercial research-chemical designation for a synthetic peptide derived from thymosin β-4, a 43-amino-acid actin-binding protein studied for cell migration, angiogenesis, and tissue repair. It is not FDA-approved in any formulation and is prohibited at all times in sport by WADA. This page is an educational reference — it does not recommend doses, does not constitute a protocol, and is not medical advice.

Class
Actin-binding peptide
Parent protein
Thymosin β-4 (Tβ4) — 43 AA
Core activity region
Residues 17–23 for migration[1]
Plasma half-life (animal)
< ~2 hours[2]
Typical reconstitution solvent
Bacteriostatic water (0.9% benzyl alcohol)
Reconstituted storage
2–8 °C refrigerated
FDA status
Not approved
Sport status
WADA-prohibited (all times)
Educational reference only. TB-500 has no approved human clinical use. This page summarizes published preclinical research on thymosin β-4 and documents the reconstitution math for lyophilized research vials. It does not recommend a dose, an indication, or a source.

Last reviewed April 22, 2026 by the Enhanced Health Editorial Team. Reviewed for source alignment, FDA-status language, and medical-claim boundaries. See the editorial policy.

What TB-500 is

Thymosin β-4 (Tβ4) is a naturally occurring 43-amino-acid intracellular protein that sequesters G-actin and is one of the most abundant polypeptides in eukaryotic cells. It plays a role in regulating actin dynamics, cell motility, wound healing, angiogenesis, and inflammation.[1] "TB-500" is a label used by research-chemical vendors for a synthetic preparation that in published work is typically described either as full-length thymosin β-4 or as the 17–23 amino-acid fragment that retains the actin-binding and cell-migration activity.[3]

Functional studies have mapped distinct activities to distinct regions of the parent protein: residues 1–4 (anti-inflammatory), 1–15 (anti-apoptotic and cytoprotective), and 17–23 (cell migration, actin binding, dermal wound healing, angiogenesis, and hair growth).[1]

Mechanism

  • G-actin sequestration. Thymosin β-4 binds monomeric (G) actin, regulating the pool available for filament (F) assembly. Profilin-mediated dissociation of the G-actin–Tβ4 complex then liberates actin for polymerization — supporting the cytoskeletal reorganization required for cell migration.[3]
  • ILK–Akt2–MMP axis. Tβ4 has been reported to bind integrin-linked kinase in lamellipodia, activating Akt2 and increasing metalloproteinase production involved in tissue remodeling during wound healing.[1]
  • Angiogenesis and repair. Preclinical work has described promotion of angiogenesis, wound re-epithelialization, and reduced scar formation in dermal, corneal, and cardiac injury models.[1][4]

Pharmacokinetics

  • Plasma half-life. Animal pharmacokinetic data indicate a short plasma half-life (< ~2 hours) due to rapid proteolytic degradation.[2]
  • Tissue activity. Effects in preclinical wound and cardiac models persist beyond the plasma window, likely reflecting local uptake and slow turnover at sites of injury.
  • Human PK. No peer-reviewed human pharmacokinetic study of the research-chemical TB-500 product is available. Claims of long subcutaneous half-lives for research-chemical TB-500 are not supported by published data.

Storage and stability

  • Lyophilized powder. Store sealed per the supplier's certificate of analysis — typically refrigerated at 2–8 °C or frozen at −20 °C.
  • After reconstitution. Store refrigerated at 2–8 °C. Bacteriostatic water (0.9% benzyl alcohol) is preferred when multi-draw use is planned; sterile water is used for single-draw preparations.
  • Handling. Swirl to mix — do not shake vigorously. Avoid freeze–thaw cycles. Discard cloudy or discolored solutions.

Reconstitution math

Math only — no dose recommendation. The concentration after reconstitution determines how many insulin-syringe units equal a given mcg or mg amount.

Example 1 · 5 mg vial + 2 mL bac water concentration = 5 mg / 2 mL = 2.5 mg/mL = 2500 mcg/mL
1 unit = 0.01 mL = 25 mcg
→ 500 mcg = 20 units
→ 1 mg = 40 units
→ 2 mg = 80 units
→ 2.5 mg = 100 units (full syringe)
Example 2 · 10 mg vial + 2 mL bac water concentration = 10 mg / 2 mL = 5 mg/mL = 5000 mcg/mL
1 unit = 0.01 mL = 50 mcg
→ 500 mcg = 10 units
→ 1 mg = 20 units
→ 2 mg = 40 units
→ 5 mg = 100 units (full syringe)
Example 3 · 5 mg vial + 5 mL bac water concentration = 5 mg / 5 mL = 1 mg/mL = 1000 mcg/mL
1 unit = 0.01 mL = 10 mcg
→ 500 mcg = 50 units
→ 1 mg = 100 units (full syringe)

Frequently asked questions

What is TB-500?

A commercial research-chemical designation for a synthetic preparation of thymosin β-4 or its 17–23 residue actin-binding fragment. Not FDA-approved. WADA-prohibited.[1]

What does it do?

Binds G-actin and regulates the pool available for filament assembly, supporting cell migration and tissue repair signaling. Also engages ILK–Akt2–MMP pathway in preclinical work.[1][3]

What is the half-life?

Animal data: < 2 hours plasma half-life. No peer-reviewed human PK for the research-chemical product.[2]

How do I reconstitute a 5 mg vial?

Typical: 5 mg + 2 mL bacteriostatic water = 2.5 mg/mL → 1 unit = 25 mcg, 1 mg = 40 units. Using 3 mL or 5 mL changes the ratio proportionally.

Is TB-500 FDA-approved?

No. Thymosin β-4 has been in earlier-phase human studies (e.g., dry eye) but no approved human product exists. TB-500 as sold by research vendors is not a regulated drug product.

How is it stored after reconstitution?

Refrigerated at 2–8 °C. Bacteriostatic water for multi-draw use; sterile water for single-draw. Avoid freeze–thaw and vigorous shaking.

Primary references

  1. Xing Y, Ye Y, Zuo H, Li Y. Progress on the function and application of thymosin β4. Front Endocrinol (Lausanne), 2021;12:767785 (PMC8724243). PMC8724243
  2. Goldstein AL, Hannappel E, Sosne G, Kleinman HK. Thymosin β4: a multi-functional regenerative peptide — basic properties and clinical applications. Expert Opin Biol Ther, 2012;12:37–51 (PubMed 22074294). PubMed 22074294
  3. Philp D, Huff T, Gho YS, Hannappel E, Kleinman HK. The actin binding site on thymosin β4 promotes angiogenesis. FASEB J, 2003;17:2103–2105 (PubMed 14500546). PubMed 14500546
  4. Malinda KM, Sidhu GS, Mani H, Banaudha K, et al. Thymosin β4 accelerates wound healing. J Invest Dermatol, 1999;113:364–368 (PubMed 10469335). PubMed 10469335

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