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No. 003 · Repair · Recovery Peptide

Thymosin Beta-4

Tβ4TMSB4XRGN-259RGN-137Timbetasin

A Tier A · Controlled human trials how tiers work →
  • Not FDA approved
  • WADA ✗ S2
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no sequence C212H350N56O78S
S O O O O O H O O O O O O O O O O O O H O O H O O H O H O O H O O O O O O H O O H O O O O O O O O H O H O H O O O O H O O O O O O O O H O O O H O O O O O O O O O O O H O H O O O O O H O O H O H O N N N H N H N H N H N H N N 2 H N H N H N H N H N 2 H N 2 H N H N H N H N H N 2 H N H N H N H N H N 2 H N H N H N H N H N H N H N H N H N H N H N H N 2 H N H N H N 2 H N H N H N 2 H N H N 2 H N H N 2 H N H N H N H N 2 H N 2 H N H N 2 H N H N H

2D structure from PubChem CID 16132341 (Timbetasin), matched by exact name. Hydrogens on carbon are implied.

Thymosin Beta-4 (no defined sequence)

No sequence on file. We only draw fingerprints from published sequences — this ring motif is a placeholder, never a guessed sequence.

01

Quick answers

What is Thymosin Beta-4?
The full-length naturally occurring protein from which TB-500 is derived.
How strong is the evidence for Thymosin Beta-4?
Tier A (controlled human trials) on the peptidemeta evidence scale. Randomized, placebo-controlled phase 2/3 trials have been run in humans (RGN-259 eye drops for dry eye and neurotrophic keratopathy; RGN-137 for chronic wounds); not approved.
Is Thymosin Beta-4 FDA-approved?
No. Thymosin Beta-4 is not approved by the FDA for any use.
Is Thymosin Beta-4 banned in sport?
Yes. Thymosin Beta-4 is prohibited in sport by the World Anti-Doping Agency under S2 (peptide hormones, growth factors, related substances and mimetics).
How does Thymosin Beta-4 work?
Thymosin beta-4 is a 43-amino-acid actin-sequestering protein that regulates cell motility by modulating actin polymerization. It promotes tissue repair through activation of integrin-linked kinase (ILK) and Akt survival pathways, while also suppressing inflammatory cytokines and promoting stem cell recruitment.
What is known about the safety of Thymosin Beta-4?
Phase II clinical trial data suggest acceptable safety. Naturally occurring in most human tissues.

Last reviewed · editorial policy · markdown

02

Evidence

  1. D In vitro
  2. C Animal
  3. B Human pilot
  4. A RCT
  5. S Approved

TIER A — At least one published randomized controlled trial in humans.

Randomized, placebo-controlled phase 2/3 trials have been run in humans (RGN-259 eye drops for dry eye and neurotrophic keratopathy; RGN-137 for chronic wounds); not approved.

Tiers rate the strength of published evidence — not effectiveness, safety, or a recommendation.

03

At a glance

Discovered
1981 Isolated from calf thymus (thymosin fraction 5) by Goldstein and colleagues.
Routes studied
Subcutaneous, Intramuscular Routes used in published research
FDA
Not approved
WADA
Prohibited · S2 Peptide hormones, growth factors, related substances and mimetics
04

Overview

The full-length naturally occurring protein from which TB-500 is derived. It plays a critical role in cell migration, wound healing, and anti-inflammatory processes throughout the body.

Research status Phase II clinical trials for cardiac repair; well-established preclinical safety profile

05

Mechanism

Thymosin beta-4 is a 43-amino-acid actin-sequestering protein that regulates cell motility by modulating actin polymerization. It promotes tissue repair through activation of integrin-linked kinase (ILK) and Akt survival pathways, while also suppressing inflammatory cytokines and promoting stem cell recruitment.

06

Effects reported in research

Reported outcomes, not promises. Some come from controlled human trials; others may be from smaller or preclinical studies — check the studies below.

  • Comprehensive tissue regeneration
  • Anti-inflammatory signaling
  • Cardiac tissue protection
  • Stem cell differentiation support
07

Safety & unknowns

Phase II clinical trial data suggest acceptable safety. Naturally occurring in most human tissues. Theoretical concern about promoting existing malignancies through angiogenesis. Not FDA-approved for therapeutic use.

Unknowns. Trial safety data apply to the populations, formulations and conditions studied.

Informational only — not medical advice. peptidemeta publishes no dosing, protocols, or sourcing. Talk to a qualified clinician about any treatment decision.

08

Studies [0]

No studies cited for this entry yet.

10

Status sources

Sources behind the tier, regulatory status, sequence and dates on this page.

11

Cite this entry

$ cite --format=apa

peptidemeta. (2026). Thymosin Beta-4. In peptidemeta: The peptide library, ranked by evidence. Retrieved November 8, 2026, from https://peptidemeta.com/p/thymosin-beta-4/

$ cite --format=bibtex 
@misc{peptidemeta-thymosin-beta-4,
  title = {Thymosin Beta-4},
  author = {{peptidemeta}},
  year = {2026},
  howpublished = {\url{https://peptidemeta.com/p/thymosin-beta-4/}},
  note = {Accessed 2026-11-08}
}

Accessed date reflects when you opened this page. Cite primary studies for scientific claims.

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