Thymosin α1

Zadaxin

Thymosin alpha-1 (Tα1) is a naturally occurring 28-amino-acid peptide cleaved from prothymosin α and secreted by thymic epithelial cells. It plays a role in T-cell maturation and immune regulation. Synthetic Tα1 (marketed as Zadaxin) has been approved as an immunomodulator in over 30 countries (including China, Italy, Argentina, Mexico) for the treatment of chronic hepatitis B and C, and is used as an adjunct in HIV, malignancy, and vaccine-enhancement protocols. It is not FDA-approved in the United States; US use is restricted to research and compounding. Mechanism of action centers on enhancement of T-helper-1 (Th1) cytokine production (IL-2, IFN-γ) and upregulation of Toll-like receptor signaling in dendritic cells. Clinical evidence is strongest for hepatitis treatment where Tα1 has been used in combination with interferon.