Overview
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In plain language
Thymosin beta-4 is a natural protein of 43 amino acids found in nearly every cell. It holds on to actin, a building block that cells use to move and change shape.
In animals, it has been studied for wound healing, heart repair and eye injuries. Eye-drop versions have been tested in human trials with mixed results. It is not a general FDA-approved injectable medicine.
For students
Thymosin beta-4 (Tβ4, about 4,963 Da) is the main G-actin-sequestering protein in mammalian cells. Its N-terminus is acetylated. It was first isolated from thymosin fraction 5, a calf thymus extract, though it is not thymus-specific.
Proposed repair-related actions include promoting cell migration, angiogenesis and reduced inflammation. Its N-terminal fragment, Ac-SDKP, has separate anti-fibrotic activity and is degraded by ACE.
For researchers and instructors
Human evidence. Trials of Tβ4 eye drops (RGN-259) for neurotrophic keratopathy and dry eye showed some signals but missed several primary endpoints. Topical and injectable trials for wounds and heart attack were small.
Fragments. TB-500 and other short fragments do not inherit Tβ4's evidence base.
Regulatory. Status depends on formulation and jurisdiction; not a general FDA-approved injectable therapy.
Molecular identity
- Amino acids
- 43
- Molecular weight
- ~4,963.4 Da
- Formula
- Form-dependent; verify
- Sequence
- Full-length 43-residue thymosin β4
Origin and history
In the 1960s Allan Goldstein and Abraham White at the Albert Einstein College of Medicine extracted a mixture of hormone-like substances from the thymus, called thymosin fraction 5. Goldstein spent the following decades separating it into individual peptides.
Thymosin beta-4 was isolated and sequenced in 1981. A decade later, in 1991, Daniel Safer and colleagues found its main job: it holds onto actin monomers inside cells, controlling how cells build their internal skeleton and move. That link to cell migration led to research on wound, eye and heart repair, including RegeneRx’s eye-drop trials. It is not an approved drug.
Key people
- Allan L. GoldsteinDiscovered the thymosins
- Abraham WhiteCo-discoverer of thymosin
- Daniel SaferIdentified it as the main actin-sequestering peptide
Timeline
- 1966
Thymosin first described
- 1981
Thymosin beta-4 isolated and sequenced
- 1991
Shown to be the main actin-sequestering molecule in cells
- 2010s
Eye-drop trials for dry eye and corneal damage
See every peptide on one history timeline.
Human evidence
Human research has explored specific topical/ophthalmic formulations; results cannot be generalized to TB-500 products.
Study design, enrollment, endpoints, outcomes and limitations must be assessed individually; registration is not proof of efficacy.
Explore the literature for Thymosin beta-4 and distinguish in-vitro, animal, and human findings.
Safety and regulatory status
See every compound on the regulatory tracker.
Regulatory status depends on formulation and jurisdiction; not a general FDA-approved injectable therapy.
Long-term risks, formulation differences, and human safety evidence require careful review. Educational content only; not medical advice.
Sources
- Primary scientific source
- PubMed: Low Hu Goldstein 1981 thymosin beta 4
- ClinicalTrials.gov search: Thymosin beta-4
Hernandez Gener, E. (2026, November 7). Thymosin beta-4: molecular data, research history and evidence. VALREXA Biosciences. https://valrexa.com/peptides/thymosin-beta-4.html
APA style · Last reviewed November 7, 2026 · Our editorial standardsLast reviewed November 7, 2026. Trial and regulatory status can change; confirm in the linked registries. This profile is educational and is not medical advice, a treatment recommendation, or dosing or sourcing guidance. Report an error · Corrections policy