3 min read
Apr 2, 2026
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Thymosin beta-4 (Tβ4) is a peptide produced in most tissues of the body (except red blood cells). It was initially discovered to bind to actin, which is part of the cytoskeleton, and influence cell migration for wound healing.[ref]
What is a peptide?
Before we go any further, I want to explain that a peptide is a broad term for a class of molecules made up of a short chain of amino acids. Longer chains of amino acids (usually more than 50–100) are called proteins. Peptides are created by the body, usually through chopping up proteins, and peptides are naturally found in food. Peptides are also produced as medications or research chemicals.
Endogenous (in the body) production of thymosin beta 4 (Tβ4):
Thymosin beta-4 contains 43 amino acids. It is encoded by the TMSB4X gene as a longer protein and cleaved to the 43 amino acid peptide. In the fetus, it is important for development. Researchers have found that levels of thymosin beta 4 in newborns are about 20 times higher than in adults. It plays an integral role in fetal development.[ref]
Thymosin beta 4 is found throughout the body in all tissues, including in the nervous system, where it plays a role in the development of the brain and helps to promote neuronal survival.[ref][ref] In the lungs, thymosin beta 4 plays a protective role against damage and is anti-fibrotic.[ref] In the eyes, Tβ4 is essential in ocular repair.[ref]
However, overexpression of TB4 in cancerous cells may be a negative factor and help the tumor to survive.[ref[ref] In cancerous tumors, there is an increase in Tβ4 for certain types of cancer. Tβ4 helps to promote angiogenesis, or the formation of new blood vessels needed by fast-growing tumors. It is also thought that Tβ4 may increase cell migration, which could increase metastasis.[ref] For example, thyroid cancers often have higher TMSB4X expression.[ref]
Clinical trials with TB4 peptide supplements:
Thymosin beta 4 is available as a full-length peptide that is usually injected or as a fragment of the peptide that is available orally. Note that TB-500 and TB4 Frag are sold as wellness products and not as an FDA-approved therapeutic drug in the US.
Recombinant human thymosin: A phase I clinical trial assessed the safety of multiple doses of injectable recombinant human thymosin in healthy adults. The results showed no toxicities or serious adverse events.[ref]
Synthetic thymosin beta 4: A phase I safety trial using synthetic thymosin beta 4 at doses from 42 to 1260 mg for 14 days showed no toxicity or serious adverse events.[ref]
Venous ulcers: Wounds that don’t heal, such as venous ulcers, are a significant problem in older patients with limited mobility. A clinical trial found that thymosin beta 4 applied topically helped to accelerate wound healing.[ref] Other studies show that it accelerates wound healing by up to a month faster than without TB4.[ref]
Dry eyes: Eye drops containing thymosin beta 4 were trialed in a “multicenter, randomized, double-masked, placebo-controlled 56-day phase 2 clinical trial including a 28-day follow-up at 2 US sites”. The results showed that the Tβ4 eye drops improved ocular discomfort and increased tear volume compared to placebo.[ref]
Bacterial eye infection: Using Tβ4 along with an antibiotic improved the healing of infections in the cornea.[ref]
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This is just a short excerpt from my in-depth article on Thymosin Beta 4. Click here to read my full article
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