PeptideSearch

Thymosin Beta-4

Tested in people

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It has been tested in people, but it is not an approved medicine. The studies are usually small.

Compiled and reviewed by the PeptideSearch Editorial Team · Status checked 2026-08-04

Also called TB4 / Tβ4 / Timbetasin / RGN-259

The full-length natural protein that TB-500 is a fragment of. This version has been tested in people for eye and wound conditions.

TB-500 is a seven-amino-acid fragment of this protein, sold as a research chemical. Research on the fragment is far thinner than on the protein itself: see what the research shows on TB-500.

Watch: what the research shows

Thymosin Beta-4: What The Research Actually Shows

Nine studies in people — two never gave anyone the protein. None of the seven that did were about tendons or muscle.

Official status: Not nominated for 503A compounding · Checked 2026-08-04

Can a doctor prescribe this?

Small pharmacy (503A)
Never put forward to FDA
Large outsourcing facility (503B)
Never put forward to FDA

Not approved. Worth noting: human trial results for full-length Thymosin Beta-4 do not automatically apply to the shorter TB-500 fragment.

503A is a pharmacy making a single prescription for one patient. 503B is a facility making batches. They are governed by separate lists. Where a category is shown, it is a position on the FDA's list of substances that have been put forward and are still being worked through — not the final list, which is set by rulemaking. Category 1 means the FDA does not plan to act against a pharmacy that makes it while the review runs.

Lab suppliers we list: 3

Doses used in research

Taken word for word from the studies and trials listed on this page. This is not a recommendation and not a dose for anyone to take.

This is a sample, not the whole literature.

About 4,000 papers mentioning this compound have been published. We show a selected sample of 53 of them, not the full literature. How we choose them · count checked 2026-08-23

Spot an error? corrections@peptidesearch.org

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