VialOwlLibrary / Repair and recovery
Thymosin beta-4
Also known as Tβ4, RGN-259 (eye drops), RGN-137 (gel)
Failed trials
Naturally occurring 43 amino acid peptide involved in cell movement and tissue repair. Eye drop versions were tested in phase 2 and 3 trials for dry eye and neurotrophic keratopathy with mixed results, including missed primary endpoints.
Not an approved medicine. Thymosin beta-4 is not an approved medicine for this use in Australia or the United States. This page summarises published research for information only. It is not a recommendation to use Thymosin beta-4, and VialOwl does not sell or supply it.
Background
Naturally occurring 43 amino acid peptide found in most cells, first isolated from calf thymus extracts by Allan Goldstein's group. RegeneRx developed eye drop (RGN-259) and gel (RGN-137) versions for clinical trials.
How it is thought to work
It is the main protein that holds actin, the building block of cell scaffolding, in reserve. Released after injury, it helps cells move, supports new blood vessels and reduces inflammation and scarring in animal studies.
What is claimed, and the evidence
| Claim | Evidence | Notes |
|---|---|---|
| Heals corneal defects in neurotrophic keratopathy (eye drops) | Human trials | Phase 3 trial of 18 patients: complete healing in 6 of 10 versus 1 of 8, missing statistical significance on the main endpoint. |
| Relieves dry eye (eye drops) | Human trials Not supported | Phase 2 trial missed both primary endpoints; some secondary measures improved. |
| Heals skin wounds and ulcers | Small human studies | Early phase trials with a topical gel; not approved. |
| Repairs heart muscle after heart attack | Animal studies only | Animal studies only. |
| Speeds recovery from sports injuries when injected | No published evidence | Marketed online; no human trials of injected use for injury. |
Side effects
| Effect | How often | Notes |
|---|---|---|
| No significant adverse effects in eye drop trials | Frequency unknown | The published eye trials report no significant safety issues, but they were small and used eye drops, not injections. |
| Unknown risks with injection Serious | Frequency unknown | No published human safety data for injected use; theoretical concern about promoting growth of existing tumours because it supports cell migration and blood vessel growth. |
Warnings
- Not approved anywhere; eye drop trials had mixed results with missed primary endpoints.
- In Australia it is Schedule 4 with Appendix D possession controls.
- Unapproved products are not made to medicine standards and may be contaminated, underdosed, overdosed or contain a different substance from the label; the TGA warns that injected unapproved peptides carry risks including contamination, infection and local tissue damage.
Regulatory status
- Australia
- Not included on the ARTG (unapproved). Schedule 4 (Prescription Only Medicine) in the Poisons Standard, also listed in Appendix D clause 5 (possession without authority is illegal).
- United States
- Not FDA approved. Eye drop (RGN-259) and topical versions have been studied in FDA regulated trials.
Sources
- 0.1% RGN-259 (Thymosin beta 4) Ophthalmic Solution in Neurotrophic Keratopathy: phase III trial
- Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, phase II clinical trial
- Thymosin beta 4: a multi-functional regenerative peptide. Basic properties and clinical applications
- Advances in the basic and clinical applications of thymosin beta 4
- TGA: Understanding your responsibilities when importing, compounding and supplying unapproved peptide products
- Poisons Standard June 2026 (Federal Register of Legislation)
Also in Repair and recovery
From the VialOwl library, reviewed 26 September 2026. For education and general information. It is not medical advice and not a recommendation to use Thymosin beta-4.