TB-500 upregulates the cell-building protein actin, a key component of cell structure and movement, while blocking actin polymerization. It has also been shown to promote angiogenesis, likely through the Notch signaling pathway.

TB-500 is the synthetic version of a natural compound called thymosin-beta-4. It is a research chemical that has been used in both test-tube and animal studies, along with a small number of human trials, having been found to promote wound healing, muscle repair, joint and tissue strength, and endothelial health.

The primary function of thymosin beta-4 is in cell repair and regeneration. It exhibits most of its actions through the sequestering of actin, which — in the simplest of terms — means that it keeps actin in place. In the event of an injury, thymosin beta-4 would sequester actin at the site of the injury, signaling a cascade of other reactions to occur.

Because actin is a key component of connective tissue, this actin-sequestering action of thymosin-beta 4 helps promote connective tissue healing and regeneration. This activity also signals for the body to begin migrating other stem or progenitor cells to the site where repair is needed. Thymosin beta 4 helps those cells to differentiate into, for example, myocytes (muscle cells), epithelial cells, or other connective or vascular cells to repair the area and rebuild the tissue