Is TB-500 the same as thymosin beta-4?

Not exactly. Thymosin beta-4 is a natural 43-amino-acid protein, while TB-500 usually refers to a synthetic 7-amino-acid fragment of it, though some products under that name are the full protein.

Has TB-500 been tested in humans?

Not in published clinical trials. Full-length thymosin beta-4 has been tested in small human trials for skin wounds and eye conditions, with mixed results.

No. Despite the thymosin name, thymosin beta-4 is not considered a thymus hormone. It is a protein found inside most cells that helps manage actin.

What is TB-500 researched for?

Most research is on thymosin beta-4, which has been studied for wound healing, heart repair after injury, eye surface healing, brain injury and hair growth, mostly in animals.

TB-500 Peptide: What It Is, How It Works, Research and Side Effects

What is TB-500?

TB-500 is a name used for a synthetic peptide linked to thymosin beta-4. Thymosin beta-4 is a natural protein of 43 amino acids. It was first isolated from thymus tissue, which is how it got its name, but it is not considered a thymus hormone today. It is found in almost all cells, with especially high levels in platelets and white blood cells.

The name TB-500 is used loosely. In laboratory analyses it usually refers to a short synthetic peptide matching amino acids 17 to 23 of thymosin beta-4, the part that binds actin, often with an acetyl group added at one end. Some products sold as TB-500 are instead the full-length protein. Because labels are often unclear, it can be hard to know which molecule a given source means.

How does TB-500 work?

Thymosin beta-4 binds to single units of actin, the protein cells use to build their internal scaffolding and to move. By holding actin units in reserve, it helps cells control when they build or break down that scaffolding. In lab and animal studies, this was linked to cells migrating more readily toward injured areas, more new blood vessel growth and lower levels of some inflammatory signals.

The short TB-500 fragment contains the actin-binding segment, so it is assumed to share some of these effects. A small amount of lab work suggests this segment alone can promote blood vessel cell migration. Whether the fragment behaves like the whole protein in people has not been shown, so most mechanism claims about TB-500 are borrowed from thymosin beta-4 research.

What has research looked at?

Skin wounds: In rat and mouse studies, thymosin beta-4 applied to the skin or injected was reported to speed wound closure. Small human trials of a thymosin beta-4 gel tested it on chronic skin ulcers, with limited and mixed results.
Heart: In mouse studies of heart attack, researchers reported that thymosin beta-4 improved heart cell survival and heart function. These results have not been shown in human patients.
Eye surface: Thymosin beta-4 eye drops have been tested in human trials for dry eye and a rare corneal healing disorder. Results were mixed, with some measures improving and others not.
Brain and nerves: Rat studies of traumatic brain injury and stroke reported better recovery of function in treated animals. These are early findings.
Hair: Rodent studies reported that thymosin beta-4 activated hair follicle stem cells and sped hair growth. Human data are lacking.
Muscle and tendon: This is the most common reason TB-500 is discussed online, yet controlled studies of TB-500 for muscle or tendon injury in people have not been published.

Nearly all of this evidence is for full-length thymosin beta-4, not the TB-500 fragment. Even for thymosin beta-4, human trials have been small and mostly focused on skin and eyes. For TB-500 as usually sold, there are no published human trials.

TB-500 vs thymosin beta-4

Online, TB-500 and thymosin beta-4 are often used as if they were the same thing. They are not. Thymosin beta-4 is the full 43-amino-acid protein made in the body and tested in human trials. TB-500 usually means a 7-amino-acid lab-made fragment of it. Other fragments exist too. The first four amino acids form a separate small peptide, called Ac-SDKP, that has been studied for anti-fibrotic and anti-inflammatory effects. Research on one form should not be assumed to apply to another.

Side effects and cautions

In small human trials, thymosin beta-4 given as a gel, as eye drops and, in an early safety study, by infusion was generally reported to be well tolerated. There are no comparable human safety data for the TB-500 fragment. Effects people report online, such as irritation where it was injected, tiredness or headache, are anecdotal. Anyone with health questions should talk to a qualified clinician.

Cancer history: Higher thymosin beta-4 levels have been linked with growth and spread in some tumor types in lab studies. That is a theoretical concern for people with current or past cancer.
Unclear identity: Products called TB-500 may be the fragment or the full protein, and purity can vary, so studies may not match what a product contains.
Long-term effects: No study has followed people using TB-500 over time.
Pregnancy and breastfeeding: There are no safety data.