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Actin-sequestering peptide

Thymosin beta-4

Thymosin beta-4 is a naturally occurring 43-amino-acid peptide and the principal actin-sequestering molecule in many cell types. The research compound TB-500 is derived from an active region of this larger peptide.

By The Peptides Codex Editorial TeamIndividual review date not recorded

Page data last changed: . Chemistry registry snapshot: . Registry refreshes and identity assessments are separate from scientific content review.

Length
43 aa
Class
Actin-sequestering peptide
Function
Regulates actin polymerization within cells
Context
Investigational research peptide; not authorized by Health Canada

The full 43-residue peptide behind the widely discussed TB-500 fragment.

Also known as: TB4 · Tβ4

Part of the Repair & recovery peptides cluster

Overview

Thymosin beta-4 is a naturally occurring 43-amino-acid peptide and the principal actin-sequestering molecule in many cell types. The research compound TB-500 is derived from an active region of this larger peptide. Thymosin beta-4 is investigational and not authorized by Health Canada; this page is educational only.

Source & context

Biological / chemical source: Naturally occurring 43-residue intracellular peptide

Primary research or clinical context: Investigational research peptide; not authorized by Health Canada

Actin regulation

Thymosin beta-4 (SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES) binds monomeric G-actin and holds it in reserve, buffering the balance between free actin and filaments. This role in cytoskeletal dynamics underlies its study in cell motility, and it is why the peptide is examined in tissue-repair research.

Relationship to TB-500 and status

TB-500 corresponds to an active fragment associated with thymosin beta-4 rather than the whole peptide, which is why the two names are often confused. Thymosin beta-4 itself is an investigational research compound, not an approved drug in Canada. This summary is educational and makes no therapeutic claims.

Sequence

One-letter sequence commonly cited for Thymosin beta-4 (educational; isoforms and modifications may differ):

SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES

SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES

Thymosin beta-443 aa · C212H350N56O78S · ≈ 4,963 DaPEPTIDESCODEX.COMN-terminus →→ C-terminusS1D−2K+3P4D−5M6A7E−8I9E−10K+11F12D−13K+14S15K+16L17K+18K+19T20E−21T22Q23E−24K+25N26P27L28P29S30K+31E−32T33I34E−35Q36E−37K+38Q39A40G41E−42S43nonpolarpolaracidicbasicGly / Pronon-canonical (X)Hydropathy (Kyte–Doolittle): ▮ hydrophobic (cyan) / ▮ hydrophilic (rose) · Side-chain charge at pH 7: + / −
Thymosin beta-4 — Structure cardDownload SVG
S1D2K3P4D5M6A7E8I9E10K11F12D13K14S15K16L17K18K19T20E21T22Q23E24K25N26P27L28P29S30K31E32T33I34E35Q36E37K38Q39A40G41E42S43
Helical wheel projection

Residues plotted ~100° apart around an α-helix — clustering of one color reveals an amphipathic face.

Analyze sequences in the playground →

Structure & chemistry

Molecular identity & reference confidence

Source-supported reference

Reference values are taken from the cited molecular record or curated profile. A database match is not independent laboratory verification; modifications, counter-ions, and formulations can change the measured mass.

Molecular form
Thymosin beta-4 (source record; form not independently established)
Species
Not established by this molecular identity audit
Termini (N / C)
Not specified / Not specified

Average reference mass

Reference policy updated: 2026-10-05

Molecular formula
C212H350N56O78S
Average reference mass
≈ 4,963
Identifiers

Chemistry values: PubChem · fetched 2026-10-01.

Clinical development snapshot

ClinicalTrials.gov lists 18 registered studies with “Thymosin beta-4” as an intervention (snapshot 2026-09-06). A registry footprint is not evidence of efficacy or approval.

Registered studies
18
Highest phase reached
Phase 3
Active in latest 100
3
Most recent update
2026-08-28
Most recently updated studies
NCTTitlePhaseStatusUpdated
NCT03937882Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-3Phase 3completed2026-08-28
NCT07586865Recombinant Human Thymosin Beta 4 for Injection(NL005) for Acute Myocardial InfarctionPhase 2not yet recruiting2026-05-14
NCT07487363TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable ASCVDPhase 2recruiting2026-03-23
NCT05555589Assessment of the Safety and Efficacy of 0.1% RGN-259 Ophthalmic Solution for the Treatment of NK: SEER-2Phase 3recruiting2025-12-23
NCT05984134Efficacy and Safety Study of Thymosin Beta 4 in Patients With Acute Myocardial InfarctionPhase 2completed2024-06-21
NCT05485818Safety and Efficacy Study of Thymosin Beta 4 in Patients With Acute Myocardial Infarction.InfarctionPhase 2completed2022-08-03
See all on ClinicalTrials.gov →
Concentration math

Thymosin beta-4 — reconstitution calculator

Enter how much peptide is in the vial and how much diluent (e.g. bacteriostatic water) is added. The tool returns the resulting solution concentration — and, for any amount you type, the volume it corresponds to. This is educational arithmetic, not a dosing recommendation.

Reference form: Thymosin beta-4 (source record; form not independently established)Average reference mass: 4,963 Da

Syringe graduation
Solution concentration
5 mg/mL5,000 mcg/mL
mcg

Enter an amount to see the volume it corresponds to.

Educational concentration mathematics only. This tool does not recommend a dose, amount, or protocol, and nothing here is medical advice. Many peptides are not authorized by Health Canada for human use — see our reconstitution and bacteriostatic-water guides for context.

Open the Thymosin beta-4 calculator on its own page →

FAQ about Thymosin beta-4

What is Thymosin beta-4?+

Thymosin beta-4 is a naturally occurring 43-amino-acid peptide and the principal actin-sequestering molecule in many cell types. The research compound TB-500 is derived from an active region of this larger peptide. Thymosin beta-4 is investigational and not authorized by Health Canada; this page is educational only.

What Canadian product status is recorded for Thymosin beta-4?+

Canadian product status for Thymosin beta-4 has not been verified in this profile. No verified record here does not mean no authorization exists. Status depends on the product, formulation and use; consult Health Canada's product records.

What is the typical length of Thymosin beta-4?+

Thymosin beta-4 is commonly described as approximately 43 amino acids (Actin-sequestering peptide).

Related peptides

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References & further reading

  1. 1.Tan et al. (2018). Sources of variability in quantifying circulating thymosin beta-4: literature review and recommendations. Expert Opin Biol Ther
  2. 2.Gao et al. (2015). Thymosin Beta-4 Induces Mouse Hair Growth. PLoS One
  3. 3.Zhang et al. (2025). Enhancing fat graft survival: thymosin beta-4 facilitates mitochondrial transfer from ADSCs via tunneling nanotubes by upregulating the Rac/F-actin pathway. Free Radic Biol Med
  4. 4.Lin et al. (2023). Thymosin beta-4 participate in antibacterial immunity and wound healing in black tiger shrimp, Penaeus monodon. Fish Shellfish Immunol
  5. 5.Smart et al. (2007). Thymosin beta-4 is essential for coronary vessel development and promotes neovascularization via adult epicardium. Ann N Y Acad Sci
  6. 6.Liang et al. (2026). Decidualization-empowered ECM hydrogel integrating sustained Tβ4 release drives endometrial regeneration in intrauterine adhesions. Nat Commun
  7. 7.PubChem — compound summary for Thymosin beta-4 (CID 45382195)
  8. 8.Wikipedia — Thymosin beta-4
Disclaimer: Educational content only. Not medical advice. Not instructions for human use. Research peptides and unapproved products may be restricted or illegal to market for human consumption in your jurisdiction. Consult qualified professionals and applicable law.
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