Bones & muscles Actin-regulating peptide
Thymosin beta-4
Regulatory status
Status at a glance
503A compounding status
Not nominated
We found no pending nomination for the 503A bulks list. Unless the substance has another legal pathway (for example, a USP monograph or use in an FDA-approved drug), 503A pharmacies generally may not compound with it.
- FDA approval
- Not FDA-approved for any use
- 503B outsourcing
- Not determined
- Anti-doping (WADA)
- On the WADA Prohibited List
- DEA schedule
- Not a controlled substance
About peptide status
Most peptides discussed here are not FDA-approved for any use, and products labeled “research use only” are not for human use. Removal from Category 2 does not authorize compounding. PCAC votes are non-binding recommendations; FDA and HHS make the final decisions.
This is not medical or legal advice, and we do not publish dosing, sourcing or reconstitution information. Talk with a licensed clinician before using any peptide.
If you think you are having a medical emergency, call 911.
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 status
- Not FDA-approved, sold in the wellness/gray market
- What it is
- Naturally occurring actin-regulating peptide involved in cell migration and tissue repair
- Research
- Human data limited to small early trials and Phase III eye-drop trials
- Sport
- Prohibited by WADA at all times
- Evidence strength
- Low research
Summary
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.
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?
Safety note
Status: Not FDA-approved, sold in the wellness/gray market
Category: Wellness and performance · Primary body area: Bones & muscles
No. Thymosin beta-4 is not approved by the FDA, and it is not an FDA-approved product. 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?
Editor’s note
Evidence strength: Low research
There is a strong mechanism and preclinical base, but human data are limited to small early trials and eye-drop trials, with no efficacy established for the marketed recovery or wellness use.
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 properties and a randomized dose-escalation venous-ulcer study assessing safety and tolerability, plus eye-drop trials that reached Phase III in dry eye. 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 trial, the results were:
| Arm | Complete healing at 4 weeks |
|---|---|
| Treated patients | 6 of 10 |
| Placebo | 1 of 8 |
The difference (p = 0.0656) was a trend short of the usual significance cutoff.
Sources: a review of thymosin beta-4's regenerative properties (Goldstein et al., Expert Opinion on Biological Therapy, 2012, DOI: 10.1517/14712598.2012.634793) and a venous-ulcer study (Guarnera et al., Annals of the New York Academy of Sciences, 2007, DOI: 10.1196/annals.1415.003), 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.
Registered human trials
0 registered human trials on ClinicalTrials.gov that we reviewed
Sources
- [1]
- [2]
- [3]
- ClinicalTrials.gov NCT03937882
- [4]
- [5]
- [6]
- [7]
- PMID 41229390
- [8]
- [9]
Phase III trial in neurotrophic keratopathy
- ClinicalTrials.gov NCT05555589
- [10]
- [11]
- [12]
- [13]
- [14]
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