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Not FDA-approved

Bones & muscles

Thymosin beta-4

Also called Tβ4

EvidenceLow research
ClassActin-regulating peptide

Thymosin beta-4 is a natural tissue-repair peptide sold as a research peptide. See how it works, what human data exist, and its FDA status today.

Reviewed by
William Maish, MD MBA MPH, Clinical Product Lead
Published
April 18, 2026
Last updated
October 5, 2026

Key takeaway

Thymosin beta-4 is a naturally occurring tissue-repair peptide involved in cell movement and healing, sold on the "research peptide" market for recovery. Its animal data are extensive, but human data are thin. In a Phase III trial in neurotrophic keratopathy, eye drops healed the corneal defect at 4 weeks in 6 of 10 treated patients versus 1 of 8 on placebo (p = 0.0656). It is banned in sport and is not FDA-approved.

At a glance

FDA statusNot FDA-approved, sold in the wellness/gray market
What it isNaturally occurring actin-regulating peptide involved in cell migration and tissue repair
ResearchHuman data limited to small early trials and Phase III eye-drop trials
SportProhibited by WADA at all times
Evidence strengthLow research

What is thymosin beta-4?

Thymosin beta-4 is a small, naturally occurring 43-amino acid peptide found in most cells and body fluids, released at sites of injury by platelets and immune cells. It plays a role in cell movement and tissue repair. It is sold through wellness and "research peptide" channels for recovery and healing, and it is not an approved medicine. (A marketed fragment of this peptide, TB-500, is catalogued separately.)

How does it work?

Thymosin beta-4 binds a cell-structure protein called actin and promotes:

  • Cell migration
  • The mobilization of stem and progenitor cells
  • New blood-vessel formation
  • Reduced inflammation and scarring

This mechanism is well characterized in laboratory and animal models of wound, eye, heart, and nervous-system repair. This describes the proposed mechanism, separate from demonstrated benefit in people.

Is it FDA-approved?

No. Thymosin beta-4 is not approved by the FDA, and it is not available through Superpower. In sport, it is prohibited at all times under the growth-factor section of the WADA list. The 2026 FDA compounding advisory meetings reviewed its marketed fragment TB-500, not the full-length peptide.

What does the research show?

The animal and laboratory base is large, but human data are limited. According to PubMed, human experience is confined to small or early trials, such as a review of its regenerative properties1 and a randomized dose-escalation venous-ulcer study2 assessing safety and tolerability, plus eye-drop trials that reached Phase III in dry eye3. No pivotal trial has established efficacy for a general recovery or wellness use, so its marketed benefit is unproven in people. In the Phase III neurotrophic keratopathy trial4, the results were:

ArmComplete healing at 4 weeks
Treated patients6 of 10
Placebo1 of 8

The difference (p = 0.0656) was a trend short of the usual significance cutoff.

More for bones & muscles

Sources: a review of thymosin beta-4's regenerative properties (Goldstein et al., Expert Opinion on Biological Therapy, 2012, DOI: 10.1517/14712598.2012.6347931) and a venous-ulcer study (Guarnera et al., Annals of the New York Academy of Sciences, 2007, DOI: 10.1196/annals.1415.0032), indexed on PubMed; and the WADA Prohibited List. This document is educational, is not medical advice or a health claim, and is not an offer to sell any product.